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the optical observations of ic-4 supernova (sn) 2016coi/asassn-16fp, from ∼2 to ∼450 d after explosion, are presented along with analysis of its physical properties. the sn shows the broad lines associated with sne ic-3/4 but with a key difference. the early spectra display a strong absorption feature at ∼5400 å which is not seen in other sne ic-3/4 at this epoch. this feature has been attributed to he i in the literature. spectral modelling of the sn in the early photospheric phase suggests the presence of residual he in a c/o dominated shell. however, the behaviour of the he i lines is unusual when compared with he-rich sne, showing relatively low velocities and weakening rather than strengthening over time. the sn is found to rise to peak ∼16 d after core-collapse reaching a bolometric luminosity of lp∼3 × 1042 erg s-1. spectral models, including the nebular epoch, show that the sn ejected 2.5-4 m⊙ of material, with ∼1.5 m⊙ below 5000 km s-1, and with a kinetic energy of (4.5-7) × 1051 erg. the explosion synthesized ∼0.14 m⊙ of 56ni. there are significant uncertainties in e(b - v)host and the distance, however, which will affect lp and mni. sn 2016coi exploded in a host similar to the large magellanic cloud (lmc) and away from star-forming regions. the properties of the sn and the host-galaxy suggest that the progenitor had mzams of 23-28 m⊙ and was stripped almost entirely down to its c/o core at explosion. | sn 2016coi/asassn-16fp: an example of residual helium in a typeic supernova? |
exoplanets have been observed around stars at all stages of stellar evolution, in many cases orbiting in configurations that will eventually lead to the planets being engulfed or consumed by their host stars, such as hot jupiters or ultrashort period planets. furthermore, objects such as polluted white dwarfs provide strong evidence that the consumption of planets by stars is a common phenomenon. this consumption causes several significant changes in the stellar properties, such as changes to the stellar spin, luminosity, chemical composition, or mass-loss processes. here, we explore this wide variety of effects for a comprehensive range of stellar and planetary masses and stages of stellar evolution, from the main sequence over red giants to white dwarfs. we determine that planet consumption can cause transient luminosity features that last on the order of centuries to millennia, and that the post-consumption stellar spins can often reach breakup speeds. furthermore, stellar mass loss can be caused by this spin-up, as well as through surface grazing interactions, leading to to the formation of unusual planetary nebula shapes or collimated stellar gas ejections. our results highlight several observable stellar features by which the presence or previous existence of a planet around a given star can be deduced. this will provide future observational campaigns with the tools to better constrain exoplanet demographics, as well as planetary formation and evolution histories. | eating planets for lunch and dinner: signatures of planet consumption by evolving stars |
numerous superluminous supernovae (slsne) of type ic have been discovered and monitored in the last decade. the favored mechanism at their origin is a sustained power injection from a magnetar. this study presents non-local thermodynamic equilibrium (nlte) time-dependent radiative transfer simulations of various single carbon-rich wolf-rayet star explosions influenced by magnetars of diverse properties and covering from a few days to one or two years after explosion. nonthermal processes are treated; the magnetar-power deposition profile is prescribed; dynamical effects are ignored. in this context, the main influence of the magnetar power is to boost the internal energy of the ejecta on week-long time scales, enhancing the ejecta temperature and ionization, shifting the spectral energy distribution to the near-uv (even for the adopted solar metallicity), creating blue optical colors. varying the ejecta and magnetar properties introduces various stretches and shifts to the light curve (rise time, peak or nebular luminosity, light curve width). at maximum, all models show the presence of o ii and c ii lines in the optical, and more rarely o iii and c iii lines. non-thermal effects are found to be negligible during the high-brightness phase. after maximum, higher energy explosions are hotter and more ionized, and produce spectra that are optically bluer. clumping is a source of spectral diversity after maximum. clumping is essential to trigger ejecta recombination and yield the presence of o i, ca ii, and fe ii lines from a few weeks after maximum until nebular times. the uv and optical spectrum of gaia16apd at maximum or the nebular spectrum of lsq14an at +410 d are compatible with some models that assume no clumping. however, most observed slsne ic seem to require clumping from early post-maximum to nebular times (e.g., sn 2007bi at +46 and +367 d; gaia16apd at +43 d). | simulations of light curves and spectra for superluminous type ic supernovae powered by magnetars |
interpreting observations of distant galaxies in terms of constraints on physical parameters - such as stellar mass (m★), star formation rate (sfr) and dust optical depth ({hat{τ}v}) - requires spectral synthesis modelling. we analyse the reliability of these physical parameters as determined under commonly adopted `classical' assumptions: star formation histories assumed to be exponentially declining functions of time, a simple dust law and no emission-line contribution. improved modelling techniques and data quality now allow us to use a more sophisticated approach, including realistic star formation histories, combined with modern prescriptions for dust attenuation and nebular emission. we present a bayesian analysis of the spectra and multiwavelength photometry of 1048 galaxies from the 3d-hst survey in the redshift range 0.7 < z < 2.8 and in the stellar mass range 9 ≲ log (m★/m⊙) ≲ 12. we find that, using the classical spectral library, stellar masses are systematically overestimated (∼0.1 dex) and sfrs are systematically underestimated (∼0.6 dex) relative to our more sophisticated approach. we also find that the simultaneous fit of photometric fluxes and emission-line equivalent widths helps break a degeneracy between sfr and {hat{τ}v}, reducing the uncertainties on these parameters. finally, we show how the biases of classical approaches can affect the correlation between m★ and sfr for star-forming galaxies (the `star-formation main sequence'). we conclude that the normalization, slope and scatter of this relation strongly depend on the adopted approach and demonstrate that the classical, oversimplified approach cannot recover the true distribution of m★ and sfr. | on the importance of using appropriate spectral models to derive physical properties of galaxies at 0.7 < z < 2.8 |
we present extensive ultraviolet, optical, and near-infrared observations of the type iip supernova (sn iip) 2013ej in the nearby spiral galaxy m74. the multicolor light curves, spanning from ∼8-185 days after explosion, show that it has a higher peak luminosity (i.e., mv ∼ -17.83 mag at maximum light), a faster post-peak decline, and a shorter plateau phase (i.e., ∼50 days) compared to the normal type iip sn 1999em. the mass of 56ni is estimated as 0.02 ± 0.01 m⊙ from the radioactive tail of the bolometric light curve. the spectral evolution of sn 2013ej is similar to that of sn 2004et and sn 2007od, but shows a larger expansion velocity (i.e., vfe ii ∼ 4600 km s-1 at t ∼ 50 days) and broader line profiles. in the nebular phase, the emission of the hα line displays a double-peak structure, perhaps due to the asymmetric distribution of 56ni produced in the explosion. with the constraints from the main observables such as bolometric light curve, expansion velocity, and photospheric temperature of sn 2013ej, we performed hydrodynamical simulations of the explosion parameters, yielding the total explosion energy as ∼0.7× 1051 erg, the radius of the progenitor as ∼600 r⊙, and the ejected mass as ∼10.6 m⊙. these results suggest that sn 2013ej likely arose from a red supergiant with a mass of 12-13 m⊙ immediately before the explosion. | sn 2013ej in m74: a luminous and fast-declining type ii-p supernova |
we present optical photometric and spectroscopic observations of sn 2013ej. it is one of the brightest type ii supernovae (sne ii) exploded in a nearby (∼10 mpc) galaxy, ngc 628. the light-curve characteristics are similar to sne ii, but with a relatively shorter (∼85 days) and steeper (∼1.7 mag (100 days)-1 in v) plateau phase. the sn shows a large drop of 2.4 mag in v-band brightness during the plateau-to-nebular transition. the absolute ultraviolet (uv) light curves are identical to sn 2012aw, showing a similar uv-plateau trend extending up to 85 days. the radioactive 56ni mass estimated from the tail luminosity is 0.02 {m}⊙ , which is significantly lower than typical sne iip. the characteristics of spectral features and evolution of line velocities indicate that sn 2013ej is a type ii event. however, light-curve characteristics and some spectroscopic features provide strong support in classifying it as a type iil event. a detailed synow modeling of spectra indicates the presence of some high-velocity components in hα and hβ profiles, implying a possible ejecta-circumstellar medium interaction. the nebular phase spectrum shows an unusual notch in the hα emission, which may indicate bipolar distribution of 56ni. modeling of the bolometric light curve yields a progenitor mass of ∼14 {m}⊙and a radius of ∼450 {r}⊙ , with a total explosion energy of ∼ 2.3× {10}51 erg. | sn 2013ej: a type iil supernova with weak signs of interaction |
we investigate the properties of ∼7000 narrow-band selected galaxies with strong hβ+[o iii] and [o ii] nebular emission lines from the high-z emission-line survey between z ∼ 0.8 and 5.0. our sample covers a wide range in stellar mass (mstellar ∼ 107.5-12.0 m⊙), rest-frame equivalent widths (ewrest∼10-105 å), and line luminosities (lline ∼ 1040.5-43.2 erg s-1). we measure the hβ+[o iii]-selected stellar mass functions out to z ∼ 3.5 and find that both m⋆ and φ⋆ increases with cosmic time. the [o ii]-selected stellar mass functions show a constant m⋆ ≈ 1011.6 m⊙ and a strong, increasing evolution with cosmic time in φ⋆ in line with hα studies. we also investigate the evolution of the ewrest as a function of redshift with a fixed mass range (109.5-10.0 m⊙) and find an increasing trend best represented by (1 + z)3.81 ± 0.14 and (1 + z)2.72 ± 0.19 up to z ∼ 2 and ∼3 for hβ+[o iii] and [o ii] emitters, respectively. this is the first time that the ewrest evolution has been directly measured for hβ+[o iii] and [o ii] emitters up to these redshifts. there is evidence for a slower evolution for z > 2 in the hβ+[o iii] ewrest and a decreasing trend for z > 3 in the [o ii] ewrest evolution, which would imply low [o ii] ew at the highest redshifts and higher [o iii]/[o ii] line ratios. this suggests that the ionization parameter at higher redshift may be significantly higher than the local universe. our results set the stage for future near-ir space-based spectroscopic surveys to test our extrapolated predictions and also produce z > 5 measurements to constrain the high-z end of the ewrest and [o iii]/[o ii] evolution. | the nature of hβ+[o iii] and [o ii] emitters to z ∼ 5 with hizels: stellar mass functions and the evolution of ews |
we present a set of nonlocal thermodynamic equilibrium steady-state calculations of radiative transfer for one-year-old type ii supernovae (sne) starting from state-of-the-art explosion models computed with detailed nucleosynthesis. this grid covers single-star progenitors with initial masses between 9 and 29 m⊙, all evolved with the code kepler at solar metallicity and ignoring rotation. the [o i] λλ 6300, 6364 line flux generally grows with progenitor mass, and hα exhibits an equally strong and opposite trend. the [ca ii] λλ 7291, 7323 strength increases at low 56ni mass, at low explosion energy, or with clumping. this ca ii doublet, which forms primarily in the explosively produced si/s zones, depends little on the progenitor mass but may strengthen if ca+ dominates in the h-rich emitting zones or if ca is abundant in the o-rich zones. indeed, si-o shell merging prior to core collapse may boost the ca ii doublet at the expense of the o i doublet, and may thus mimic the metal line strengths of a lower-mass progenitor. we find that the 56ni bubble effect has a weak impact, probably because it is too weak to induce much of an ionization shift in the various emitting zones. our simulations compare favorably to observed sne ii, including sn 2008bk (e.g., the 9 m⊙ model), sn 2012aw (12 m⊙ model), sn 1987a (15 m⊙ model), or sn 2015bs (25 m⊙ model with no si-o shell merging). sne ii with narrow lines and a low 56ni mass are well matched by the weak explosion of 9-11 m⊙ progenitors. the nebular-phase spectra of standard sne ii can be explained with progenitors in the mass range 12-15 m⊙, with one notable exception for sn 2015bs. in the intermediate mass range, these mass estimates may increase by a few m⊙, with allowance for clumping of the o-rich material or co molecular cooling. | the explosion of 9-29 m⊙ stars as type ii supernovae: results from radiative-transfer modeling at one year after explosion |
we present new diagnostic tools for distinguishing supernova remnants (snrs) from h ii regions. up to now, sources with flux ratio [s ii]/h{α } higher than 0.4 have been considered as snrs. here, we present combinations of three or two line ratios as more effective tools for the separation of these two kinds of nebulae, depicting them as 3d surfaces or 2d lines. the diagnostics are based on photoionization and shock-excitation models (mappings iii) analysed with support vector machine (svm) models for classification. the line-ratio combination that gives the most efficient diagnostic is [o i]/h{α } - [o ii]/h{β } - [o iii]/h{β }. this method gives 98.95 per cent completeness in the snr selection and 1.20 per cent contamination. we also define the [o i]/h{α } snr selection criterion and measure its efficiency in comparison with other selection criteria. | a diagnostic tool for the identification of supernova remnants |
the ratio between the two stable isotopes of nitrogen, 14n and 15n, is well measured in the terrestrial atmosphere ( 272), and for the pre-solar nebula ( 441, deduced from the solar wind). interestingly, some pristine solar system materials show enrichments in 15n with respect to the pre-solar nebula value. however, it is not yet clear if and how these enrichments are linked to the past chemical history because we have only a limited number of measurements in dense star-forming regions. in this respect, dense cores, which are believed to be the precursors of clusters and also contain intermediate- and high-mass stars, are important targets because the solar system was probably born within a rich stellar cluster, and such clusters are formed in high-mass star-forming regions. the number of observations in such high-mass dense cores has remained limited so far. in this work, we show the results of iram-30 m observations of the j = 1-0 rotational transition of the molecules hcn and hnc and their 15n-bearing counterparts towards 27 intermediate- and high-mass dense cores that are divided almost equally into three evolutionary categories: high-mass starless cores, high-mass protostellar objects, and ultra-compact hii regions. we have also observed the dnc(2-1) rotational transition in order to search for a relation between the isotopic ratios d/h and 14n/15n. we derive average 14n/15n ratios of 359 ± 16 in hcn and of 438 ± 21 in hnc, with a dispersion of about 150-200. we find no trend of the 14n/15n ratio with evolutionary stage. this result agrees with what has been found for n2h+ and its isotopologues in the same sources, although the 14n/15n ratios from n2h+ show a higher dispersion than in hcn/hnc, and on average, their uncertainties are larger as well. moreover, we have found no correlation between d/h and 14n/15n in hnc. these findings indicate that (1) the chemical evolution does not seem to play a role in the fractionation of nitrogen, and that (2) the fractionation of hydrogen and nitrogen in these objects is not related. iram data used in the paper (fits) is only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/609/a129 | nitrogen and hydrogen fractionation in high-mass star-forming cores from observations of hcn and hnc |
aims: we present kinematic and photometric evidence for an accretion event in the halo of the cd galaxy m 87 in the last gyr.methods: using velocities for ~300 planetary nebulas (pns) in the m 87 halo, we identify a chevron-like substructure in the pn phase-space. we implement a probabilistic gaussian mixture model to identify pns that belong to the chevron. from analysis of deep v-band images of m 87, we find that the region with the highest density of chevron pns is a crown-shaped substructure in the light.results: we assign a total of npn,sub = 54 to the substructure, which extends over ~50 kpc along the major axis where we also observe radial variations of the ellipticity profile and a colour gradient. the substructure has highest surface brightness in a 20 kpc × 60 kpc region around 70 kpc in radius. in this region, the substructure causes an increase in surface brightness by ≳60%. the accretion event is consistent with a progenitor galaxy with a v-band luminosity of l = 2.8±1.0×109 l⊙ ,v, a colour of (b - v) = 0.76±0.05, and a stellar mass of m = 6.4±2.3×109 m⊙.conclusions: the accretion of this progenitor galaxy has caused an important modification of the outer halo of m 87 in the last gyr. this result provides strong evidence that the galaxy's cd halo is growing through the accretion of smaller galaxies as predicted by hierarchical galaxy evolution models. based on observations made with the vlt at paranal observatory under programme 088.b-0288(a) and 093.b-066(a), and with the subaru telescope under programme s10a-039. | the build-up of the cd halo of m 87: evidence for accretion in the last gyr |
we discuss the events that led to the giant eruption of eta carinae, and find that the mid-nineteenth century (in 1838-1843) giant mass-loss outburst has the characteristics of being produced by the merger event of a massive close binary, triggered by the gravitational interaction with a massive third companion star, which is the current binary companion in the eta carinae system. we come to this conclusion by a combination of theoretical arguments supported by computer simulations using the astrophysical multipurpose software environment. according to this model the ∼90 m⊙ present primary star of the highly eccentric eta carinae binary system is the product of this merger, and its ∼30 m⊙ companion originally was the third star in the system. in our model, the homunculus nebula was produced by an extremely enhanced stellar wind, energized by tidal energy dissipation prior to the merger, which enormously boosted the radiation-driven wind mass-loss. the current orbital plane is then aligned with the equatorial plane of the homunculus, and the symmetric lobes are roughly aligned with the argument of periastron of the current eta carina binary. the merger itself then occurred in 1838, which resulted in a massive asymmetric outflow in the equatorial plane of the homunculus. the 1843 outburst can in our model be attributed to the subsequent encounter when the companion star (once the outermost star in the triple system) plunges through the bloated envelope of the merger product, once when it passed periastron again. we predict that the system has an excess space velocity of order 50 km s-1 in the equatorial plane of the homunculus. our triple model gives a viable explanation for the high runaway velocities typically observed in lbvs. | was the nineteenth century giant eruption of eta carinae a merger event in a triple system? |
we present alma co(1-0) and co(3-2) observations of the brightest cluster galaxy (bcg) in the 2a 0335+096 galaxy cluster (z = 0.0346). the total molecular gas mass of 1.13 ± 0.15 × 109 m ⊙ is divided into two components: a nuclear region and a 7 kpc long dusty filament. the central molecular gas component accounts for 3.2 ± 0.4 × 108 m ⊙ of the total supply of cold gas. instead of forming a rotationally supported ring or disk, it is composed of two distinct, blueshifted clumps south of the nucleus and a series of low-significance redshifted clumps extending toward a nearby companion galaxy. the velocity of the redshifted clouds increases with radius to a value consistent with the companion galaxy, suggesting that an interaction between these galaxies <20 myr ago disrupted a pre-existing molecular gas reservoir within the bcg. most of the molecular gas, 7.8 ± 0.9 × 108 m ⊙, is located in the filament. the co emission is co-spatial with a 104 k emission-line nebula and soft x-rays from 0.5 kev gas, indicating that the molecular gas has cooled out of the intracluster medium over a period of 25-100 myr. the filament trails an x-ray cavity, suggesting that the gas has cooled from low-entropy gas that has been lifted out of the cluster core and become thermally unstable. we are unable to distinguish between inflow and outflow along the filament with the present data. cloud velocities along the filament are consistent with gravitational free-fall near the plane of the sky, although their increasing blueshifts with radius are consistent with outflow. | molecular gas along a bright hα filament in 2a 0335+096 revealed by alma |
we present near-infrared and optical spectroscopic observations of a sample of 450 and 850 μm-selected dusty star-forming galaxies (dsfgs) identified in a 400 arcmin2 area in the cosmos field. thirty-one sources of the 114 targets were spectroscopically confirmed at 0.2< z< 4, identified primarily in the near-infrared with keck mosfire and some in the optical with keck lris and deimos. the low rate of confirmation is attributable both to high rest-frame optical obscuration in our targets and limited sensitivity to certain redshift ranges. the median spectroscopic redshift is < {z}{spec}> =1.55+/- 0.14, comparable to < {z}{phot}> =1.50+/- 0.09 for the larger parent dsfg sample; the median stellar mass is ({4.9}-1.4+2.1)× {10}10 m {}⊙ , star formation rate is 160 ± 50 m {}⊙yr-1, and attenuation is {a}{{v}}=5.0+/- 0.4. the high-quality photometric redshifts available in the cosmos field allow us to test the robustness of photometric redshifts for dsfgs. we find a subset (11/31≈ 35%) of dsfgs with inaccurate ({{δ }}z/(1+z)> 0.2) or non-existent photometric redshifts; these have very distinct spectral energy distributions from the remaining dsfgs, suggesting a decoupling of highly obscured and unobscured components. we present a composite rest-frame 4300-7300 å spectrum for dsfgs, and find evidence of 200 ± 30 km s-1 gas outflows. nebular line emission for a subsample of our detections indicate that hard ionizing radiation fields are ubiquitous in high-z dsfgs, even more so than typical mass or uv-selected high-z galaxies. we also confirm the extreme level of dust obscuration in dsfgs, measuring very high balmer decrements and very high ratios of ir to uv and ir to hα luminosities. this work demonstrates the need to broaden the use of wide bandwidth technology in the millimeter to spectroscopically confirm larger samples of high-z dsfgs, as the difficulty in confirming such sources at optical/near-infrared wavelengths is exceedingly challenging given their obscuration. | near-infrared mosfire spectra of dusty star-forming galaxies at 0.2 < z < 4 |
the combination of precise radial velocities from multi-object spectroscopy and highly accurate proper motions from gaia dr2 opens up the possibility for detailed 3d kinematic studies of young star-forming regions and clusters. here, we perform such an analysis by combining gaia-eso survey spectroscopy with gaia astrometry for ∼900 members of the lagoon nebula cluster, ngc 6530. we measure the 3d velocity dispersion of the region to be 5.35^{+0.39}_{-0.34} km s-1, which is large enough to suggest the region is gravitationally unbound. the velocity ellipsoid is anisotropic, implying that the region is not sufficiently dynamically evolved to achieve isotropy, though the central part of ngc 6530 does exhibit velocity isotropy that suggests sufficient mixing has occurred in this denser part. we find strong evidence that the stellar population is expanding, though this is preferentially occurring in the declination direction and there is very little evidence for expansion in the right ascension direction. this argues against a simple radial expansion pattern, as predicted by models of residual gas expulsion. we discuss these findings in the context of cluster formation, evolution, and disruption theories. | the gaia-eso survey: asymmetric expansion of the lagoon nebula cluster ngc 6530 from ges and gaia dr2 |
argon, krypton, xenon, carbon, nitrogen, sulfur, and phosphorus have all been measured and found to be enriched by a quasi uniform factor in the 2-4 range, compared to their protosolar values, in the atmosphere of jupiter. to elucidate the origin of these volatile enrichments, we investigate the possibility of an inward drift of particles made of amorphous ice and adsorbed volatiles, and their ability to enrich in heavy elements the gas phase of the protosolar nebula, once they cross the amorphous-to-crystalline ice transition zone, following the original idea formulated by monga & desch. to do so, we use a simple accretion disk model coupled to modules depicting the radial evolution of icy particles and vapors, assuming growth, fragmentation, and crystallization of amorphous grains. we show that it is possible to accrete supersolar gas from the nebula onto proto-jupiter’s core to form its envelope, and allowing it to match the observed volatile enrichments. our calculations suggest that nebular gas, with a metallicity similar to that measured in jupiter, can be accreted by its envelope if the planet is formed in the ∼0.5-2 myr time range and in the 0.5-20 au distance range from the sun, depending on the adopted viscosity parameter of the disk. these values match a wide range of jupiter’s formation scenarios, including in situ formation and migration/formation models. | jupiter’s formation in the vicinity of the amorphous ice snowline |
we present an overview of sitelle, an imaging fourier transform spectrometer (ifts) available at the 3.6-m canada-france-hawaii telescope. sitelle is a michelson-type interferometer able to reconstruct the spectrum of every light source within its 11 arcmin field of view in filter-selected bands of the visible (350-900 nm). the spectral resolution can be adjusted up to r = 10 000 and the spatial resolution is seeing-limited and sampled at 0.32 arcsec pixel-1. we describe the design of the instrument as well as the data reduction and analysis process. to illustrate sitelle's capabilities, we present some of the data obtained during and since the 2015 august commissioning run. in particular, we demonstrate its ability to separate the components of the [o ii] λλ 3726,29 doublet in orion and to reach r = 9500 around hα; to detect diffuse emission at a level of 4 × 10-17 erg cm-2 s-1 arcsec-2; to obtain integrated spectra of stellar absorption lines in galaxies despite the well-known multiplex disadvantage of the ifts and to detect emission-line galaxies at different redshifts. | sitelle: an imaging fourier transform spectrometer for the canada-france-hawaii telescope |
we compute successfully the launching of two magnetic winds from two circumbinary disks formed after a common envelope event. the launching is produced by the increase of magnetic pressure due to the collapse of the disks. the collapse is due to internal torques produced by a weak poloidal magnetic field. the first wind can be described as a wide jet, with an average mass-loss rate of ~1.3 × 10-7 m⊙ yr-1 and a maximum radial velocity of ~230 km s-1. the outflow has a half-opening angle of ~20°. narrow jets are also formed intermittently with velocities up to 3000 km s-1, with mass-loss rates of ~6 × 10-12 m⊙ yr-1 during short periods of time. the second wind can be described as a wide x-wind, with an average mass-loss rate of ~1.68 × 10-7 m⊙ yr-1 and a velocity of ~30 km s-1. a narrow jet is also formed with a velocity of 250 km s-1 and a mass-loss rate of ~10-12 m⊙ yr-1. the computed jets are used to provide inflow boundary conditions for simulations of proto-planetary nebulae. the wide jet evolves into a molecular collimated outflow within a few astronomical units, producing proto-planetary nebulae with bipolar, elongated shapes, whose kinetic energies reach ~4 × 1045 erg at 1000 yr. similarities with observed features in w43a, oh 231.8+4.2, and hen 3-1475 are discussed. the computed wide x-wind produces proto-planetary nebulae with slower expansion velocities, bipolar and elliptical shapes, and possible starfish-type and quadrupolar morphology. | common envelope shaping of planetary nebulae. iii. the launching of jets in proto-planetary nebulae |
we present new photometric and spectroscopic observations of sn 2019yvq, a type ia supernova (sn ia) exhibiting several peculiar properties including an excess of uv/optical flux within days of explosion, a high si ii velocity, and a low peak luminosity. photometry near the time of first light places new constraints on the rapid rise of the uv/optical flux excess. a near-infrared spectrum at +173 days after maximum light places strict limits on the presence of h or he emission, effectively excluding the presence of a nearby nondegenerate star at the time of explosion. new optical spectra, acquired at +128 and +150 days after maximum light, confirm the presence of [ca ii] λ7300 and persistent ca ii nir triplet emission as sn 2019yvq transitions into the nebular phase. the lack of [o i] $\lambda 6300$ emission disfavors the violent merger of two c/o white dwarfs (wds) but the merger of a c/o wd with a he wd cannot be excluded. we compare our findings with several models in the literature postulated to explain the early flux excess including double-detonation explosions, 56ni mixing into the outer ejecta during ignition, and interaction with h- and he-deficient circumstellar material. each model may be able to explain both the early flux excess and the nebular [ca ii] emission, but none of the models can reconcile the high photospheric velocities with the low peak luminosity without introducing new discrepancies. | sn 2019yvq does not conform to sn ia explosion models |
we present the discovery and extensive follow-up observations of sn 2020jfo, a type iip supernova (sn) in the nearby (14.5 mpc) galaxy m 61. optical light curves (lcs) and spectra from the zwicky transient facility (ztf), complemented with data from swift/uvot and near-infrared photometry is presented. these were used to model the 350-day duration bolometric light curve, which exhibits a relatively short (∼65 days) plateau. this implies a moderate ejecta mass (∼5 m⊙) at the time of explosion, whereas the deduced amount of ejected radioactive nickel is ∼0.025 m⊙. an extensive series of spectroscopy is presented, including spectropolarimetric observations. the nebular spectra are dominated by hα, but also reveal emission lines from oxygen and calcium. comparisons to synthetic nebular spectra indicate an initial progenitor mass of ∼12 m⊙. we also note the presence of stable nickel in the nebular spectrum, and sn 2020jfo joins a small group of sne that have inferred super-solar ni/fe ratios. several years of prediscovery data were examined, but no signs of precursor activity were found. pre-explosion hubble space telescope imaging reveals a probable progenitor star, detected only in the reddest band (mf814w ≈ −5.8) and it is fainter than expected for stars in the 10−15 m⊙ range. there is thus some tension between the lc analysis, the nebular spectral modeling, and the pre-explosion imaging. to compare and contrast, we present two additional core-collapse sne monitored by the ztf, which also have nebular hα-dominated spectra. this illustrates how the absence or presence of an interaction with circumstellar material (csm) affect both the lcs and in particular the nebular spectra. type ii sn 2020amv has a lc powered by csm interaction, in particular after ∼40 days when the lc is bumpy and slowly evolving. the late-time spectra show strong hα emission with a structure suggesting emission from a thin, dense shell. the evolution of the complex three-horn line profile is reminiscent of that observed for sn 1998s. finally, sn 2020jfv has a poorly constrained early-time lc, but it is of interest because of the transition from a hydrogen-poor type iib to a type iin, where the nebular spectrum after the light-curve rebrightening is dominated by hα, although with an intermediate line width. full tables 2-4 are only available at the cds via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/655/a105 | the type ii supernova sn 2020jfo in m 61, implications for progenitor system, and explosion dynamics |
this work examines the relationships between the properties (flux ratios, full width at half-maximum velocities) of the [o i] λλ6300, 6364, [ca ii] λλ7291, 7323, and the ca ii near-infrared triplet, emission lines of a large sample of core-collapse supernovas (sne) and ca-rich transients (509 spectra of 86 transients, of which 10 transients are ca-rich events). line-flux ratios as a function of time were investigated with differences identified between the transient classes, in particular the type ii sne were found to have distinct line-flux ratios compared to stripped-envelope (se) sne. no correlation was found between the [ca ii]/[o i] flux ratios of se-sne and their ejecta masses and kinetic energies (as measured from light-curve modelling), suggesting that there may be a contribution from an additional power source in more luminous se-sne. we found that the mean characteristic width of the [ca ii] emission line is less than the [o i] emission line for all sn types, indicating that the [ca ii] emission typically originates from deeper in the ejecta than [o i]. this is in some tension with standard models for emission in type ii sne. the emission line properties of type ii sne were also compared to theoretical models and found to favour lower mass tracks (mzams< 15 m⊙), with no evidence found for significant mixing of 56ni into the h envelope nor ca mixed into the o shell. the flux ratios of some superluminous sne were found to be similar to those of se-sne when scaling to account for their longer rise times was applied (although we caution the sample size is small). | oxygen and calcium nebular emission line relationships in core-collapse supernovae and ca-rich transients |
studying the driving modes of turbulence is important for characterizing the impact of turbulence in various astrophysical environments. the driving mode of turbulence is parametrized by b, which relates the width of the gas density pdf to the turbulent mach number; b ≈ 1/3, 1, and 0.4 correspond to driving that is solenoidal, compressive, and a natural mixture of the two, respectively. in this work, we use high-resolution (sub-pc) alma 12co (j = 2-1), 13co (j = 2-1), and c18o (j = 2-1) observations of filamentary molecular clouds in the star-forming region n159e (the papillon nebula) in the large magellanic cloud (lmc) to provide the first measurement of turbulence driving parameter in an extragalactic region. we use a non-local thermodynamic equilibrium (nlte) analysis of the co isotopologues to construct a gas density pdf, which we find to be largely lognormal in shape with some intermittent features indicating deviations from lognormality. we find that the width of the lognormal part of the density pdf is comparable to the supersonic turbulent mach number, resulting in b ≈ 0.9. this implies that the driving mode of turbulence in n159e is primarily compressive. we speculate that the compressive turbulence could have been powered by gravo-turbulent fragmentation of the molecular gas, or due to compression powered by h i flows that led to the development of the molecular filaments observed by alma in the region. our analysis can be easily applied to study the nature of turbulence driving in resolved star-forming regions in the local as well as the high-redshift universe. | first extragalactic measurement of the turbulence driving parameter: alma observations of the star-forming region n159e in the large magellanic cloud |
context. the andromeda (m31) galaxy presents evidence of recent substantial mass accretion. this is unlike what has happened in the milky way, which has experienced a rather quiescent evolution.aims: we use oxygen and argon abundances for planetary nebulae (pne) with low internal extinction (progenitor ages of > 4.5 gyr) and high extinction (progenitor ages < 2.5 gyr), as well as those of the hii regions, to constrain the chemical enrichment and star formation efficiency in the thin and thicker discs of m31.methods: the argon element is produced in larger fractions by type ia supernovae compared to oxygen. we find that the mean log(o/ar) values of pne as a function of their argon abundances, 12 + log(ar/h), trace the interstellar medium (ism) conditions at the time of birth of the m31 disc pn progenitors. thus, the chemical enrichment and star formation efficiency information encoded in the [α/fe] versus [fe/h] distribution of stars is also imprinted in the oxygen-to-argon abundance ratio log(o/ar) versus argon abundance for the nebular emissions of the different stellar evolution phases. we propose using the log(o/ar) versus (12 + log(ar/h)) distribution of pne with different ages to constrain the star formation histories of the parent stellar populations in the thin and thicker m31 discs.results: for the inner m31 disc (rgc < 14 kpc), the chemical evolution model that reproduces the mean log(o/ar) values as a function of argon abundance for the high- and low-extinction pne requires a second infall of metal-poorer gas during a gas-rich (wet) satellite merger. this wet merger triggered the burst of star formation seen by the phat survey in the m31 disc, ∼3 gyr ago. a strong starburst is ongoing in the intermediate radial range (14 ≤ rgc ≤ 18 kpc). in the outer m31 disc (rgc > 18 kpc), the log(o/ar) versus argon abundance distribution of the younger high-extinction pne indicates that they too were formed in a burst, though mostly from the metal-poorer gas. present-day hii regions show a range of oxygen-to-argon ratios, which is indicative of spatial variations and consistent with a present-day rainfall of metal-poorer gas onto the disc with different degrees of mixing with the previously enriched ism.conclusions: we implement the use of the log(o/ar) versus argon abundance distribution for emission nebulae as a complement to the [α/fe] versus [fe/h] diagram for stars, and use it to constrain the star formation efficiency in the thin and thicker discs of m31. diagrams for m31 pne in different age ranges reveal that a secondary infall of gas affected the chemical evolution of the m31 thin disc. in m31, the thin disc is younger and less radially extended, formed stars at a higher star formation efficiency, and had a faster chemical enrichment timescale than the more extended thicker disc. both the thin and thicker discs in m31 reach similar high argon abundances (12 + log(ar/h)) ≃ 6.7. the chemical and structural properties of the thin and thicker discs in m31 are thus remarkably different from those determined for the milky way thin and thick discs. | the survey of planetary nebulae in andromeda (m31). v. chemical enrichment of the thin and thicker discs of andromeda: oxygen to argon abundance ratios for planetary nebulae and hii regions |
recently, intense emission from nebular c iii] and c iv emission lines have been observed in galaxies in the epoch of reionization (z > 6) and have been proposed as the prime way of measuring their redshift and studying their stellar populations. these galaxies might represent the best examples of cosmic reionizers, as suggested by recent low-z observations of lyman continuum emitting galaxies, but it is hard to directly study the production and escape of ionizing photons at such high redshifts. the eso spectroscopic public survey vandels offers the unique opportunity to find rare examples of such galaxies at cosmic noon (z ∼ 3), thanks to the ultra deep observations available. we have selected a sample of 39 galaxies showing c iv emission, whose origin (after a careful comparison to photoionization models) can be ascribed to star formation and not to active galactic nuclei. by using a multiwavelength approach, we determined their physical properties including metallicity and the ionization parameter and compared them to the properties of the parent population to understand what the ingredients are that could characterize the analogs of the cosmic reionizers. we find that c iv emitters are galaxies with high photon production efficiency and there are strong indications that they might also have a large escape fraction: given the visibility of c iv in the epoch of reionization, this could become the best tool to pinpoint the cosmic reioinzers. | insights into the reionization epoch from cosmic-noon-c iv emitters in the vandels survey |
context. while it is generally assumed that class ii sources evolve largely in isolation from their environment, many still lie close to molecular clouds and may continue to interact with them. this may result in late accretion of material onto the disk that can significantly influence disk processes and planet formation.aims: in order to systematically study late infall of gas onto disks, we identify candidate class ii sources in close vicinity to a reflection nebula (rn) that may be undergoing this process.methods: first we targeted class ii sources with known kilo-au scale gas structures - possibly due to late infall of material - and we searched for rne in their vicinity in optical and near-infrared images. second, we compiled a catalogue of class ii sources associated with rne and looked for the large-scale co structures in archival alma data. using the catalogues of protostars and rne, we also estimated the probability of class ii sources interacting with surrounding material.results: all of the sources with large-scale gas structures also exhibit some reflection nebulosity in their vicinity. similarly, at least five class ii objects associated with a prominent rne, and for which adequate alma observations are available, were found to have spirals or stream-like structures which may be due to late infall. we report the first detection of these structures around s cra.conclusions: our results suggest that a non-negligible fraction of class ii disks in nearby star-forming regions may be associated with rne and could therefore be undergoing late accretion of gas. surveys of rne and kilo-au scale gas structures around class ii sources will allow us to better understand the frequency and impact of late-infall phenomena. | reflections on nebulae around young stars. a systematic search for late-stage infall of material onto class ii disks |
there is significant astronomical interest around the intense mass loss that appears to take place in some massive stars immediately before core collapse. however, because it occurs too late, it has a negligible impact on the star's evolution or the final yields. these properties are then influenced instead by the longer term, quasi-steady, and relatively weak mass loss taking place during h and he burning. late-time observations of core-collapse supernovae (sne) interacting with the progenitor wind are one means of constraining this secular mass loss. here, we present radiative transfer calculations for a type ii sn from a standard red-supergiant (rsg) star explosion. at first, a reference model was computed without interaction power. a second model was then taken to assume a constant interaction power of 1040erg s−1 associated with a typical rsg progenitor wind mass-loss rate of 10−6 m⊙yr−1. we focused on the phase between 350 and 1000 d after explosion. we find that without interaction power, the ejecta are powered through radioactive decay, whose exponential decline produces an ever-fading sn. instead, with a constant interaction power of 1040 erg s−1, the spectrum morphs from decay powered at 350 d, with narrow lines forming in the inner metal-rich ejecta, to interaction powered at 1000 d, with broad boxy lines forming in the outer h-rich ejecta. intermediate times are characterized by a hybrid and complex spectrum made of overlapping narrow and broad lines. while interaction boosts primarily the flux in the ultraviolet, which remains largely unobserved today, a knee in the r-band light curve or a u-band boost are clear signatures of interaction at late times. the model predictions offer a favorable comparison with a number of type ii sne, including sn 2004et or sn 2017eaw at 500-1000 d after explosion. | the morphing of decay powered to interaction powered type ii supernova ejecta at nebular times |
signals, the star formation, ionized gas, and nebular abundances legacy survey, is a large observing programme designed to investigate massive star formation and h ii regions in a sample of local extended galaxies. the programme will use the imaging fourier transform spectrograph sitelle at the canada-france-hawaii telescope. over 355 h (54.7 nights) have been allocated beginning in fall 2018 for eight consecutive semesters. once completed, signals will provide a statistically reliable laboratory to investigate massive star formation, including over 50 000 resolved h ii regions: the largest, most complete, and homogeneous data base of spectroscopically and spatially resolved extragalactic h ii regions ever assembled. for each field observed, three datacubes covering the spectral bands of the filters sn1 (363-386 nm), sn2 (482-513 nm), and sn3 (647-685 nm) are gathered. the spectral resolution selected for each spectral band is 1000, 1000, and 5000, respectively. as defined, the project sample will facilitate the study of small-scale nebular physics and many other phenomena linked to star formation at a mean spatial resolution of ∼20 pc. this survey also has considerable legacy value for additional topics, including planetary nebulae, diffuse ionized gas, and supernova remnants. the purpose of this paper is to present a general outlook of the survey, notably the observing strategy, galaxy sample, and science requirements. | signals: i. survey description |
we present observations from the first light infrared test camera (flitecam) on board the stratospheric observatory for infrared astronomy, the spitzer infrared array camera (irac), and the spitzer infrared spectrograph sh mode in three well-known photodissociation regions, the reflection nebulae (rne) ngc 7023 and ngc 2023 and to the southeast of the orion bar, which are well suited to probe emission from polycyclic aromatic hydrocarbon molecules (pahs). we investigate the spatial behavior of the flitecam 3.3 μm filter as a proxy for the 3.3 μm pah band, the integrated 11.2 μm pah band, and the irac 8.0 μm filter as a proxy for the sum of the 7.7 and 8.6 μm pah bands. the resulting ratios of 11.2/3.3 and irac 8.0/11.2 provide an approximate measure of the average pah size and pah ionization, respectively. in both rne, we find that the relative pah ionization and the average pah size increase with decreasing distance to the illuminating source. the average pah sizes derived for ngc 2023 are greater than those found for ngc 7023 at all points. both results indicate that pah size is dependent on the radiation field intensity. these results provide additional evidence of a rich carbon-based chemistry driven by the photochemical evolution of the omnipresent pah molecules within the interstellar medium. in contrast, we did not detect a significant variation in the average pah size found in the region southeast of the orion bar and report a peculiar pah ionization radial profile. | tracing pah size in prominent nearby mid-infrared environments |
context. reconstructing the structure and history of young clusters is pivotal to understanding the mechanisms and timescales of early stellar evolution and planet formation. recent studies suggest that star clusters often exhibit a hierarchical structure, possibly resulting from several star formation episodes occurring sequentially rather than a monolithic cloud collapse.aims: we aim to explore the structure of the open cluster and star-forming region ngc 2264 ( 3 myr), which is one of the youngest, richest and most accessible star clusters in the local spiral arm of our galaxy; we link the spatial distribution of cluster members to other stellar properties such as age and evolutionary stage to probe the star formation history within the region.methods: we combined spectroscopic data obtained as part of the gaia-eso survey (ges) with multi-wavelength photometric data from the coordinated synoptic investigation of ngc 2264 (csi 2264) campaign. we examined a sample of 655 cluster members, with masses between 0.2 and 1.8 m⊙ and including both disk-bearing and disk-free young stars. we used teff estimates from ges and g,r,i photometry from csi 2264 to derive individual extinction and stellar parameters.results: we find a significant age spread of 4-5 myr among cluster members. disk-bearing objects are statistically associated with younger isochronal ages than disk-free sources. the cluster has a hierarchical structure, with two main blocks along its latitudinal extension. the northern half develops around the o-type binary star s mon; the southern half, close to the tip of the cone nebula, contains the most embedded regions of ngc 2264, populated mainly by objects with disks and ongoing accretion. the median ages of objects at different locations within the cluster, and the spatial distribution of disked and non-disked sources, suggest that star formation began in the north of the cluster, over 5 myr ago, and was ignited in its southern region a few myr later. star formation is likely still ongoing in the most embedded regions of the cluster, while the outer regions host a widespread population of more evolved objects; these may be the result of an earlier star formation episode followed by outward migration on timescales of a few myr. we find a detectable lag between the typical age of disk-bearing objects and that of accreting objects in the inner regions of ngc 2264: the first tend to be older than the second, but younger than disk-free sources at similar locations within the cluster. this supports earlier findings that the characteristic timescales of disk accretion are shorter than those of disk dispersal, and smaller than the average age of ngc 2264 (i.e., ≲3 myr). at the same time, we note that disks in the north of the cluster tend to be shorter-lived ( 2.5 myr) than elsewhere; this may reflect the impact of massive stars within the region (notably s mon), that trigger rapid disk dispersal.conclusions: our results, consistent with earlier studies on ngc 2264 and other young clusters, support the idea of a star formation process that takes place sequentially over a prolonged span in a given region. a complete understanding of the dynamics of formation and evolution of star clusters requires accurate astrometric and kinematic characterization of its population; significant advance in this field is foreseen in the upcoming years thanks to the ongoing gaia mission, coupled with extensive ground-based surveys like ges. full table b.1 is only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/609/a10 | the gaia-eso survey and csi 2264: substructures, disks, and sequential star formation in the young open cluster ngc 2264 |
aims: as a new approach to the study of resolved stellar populations in nearby galaxies, our goal is to demonstrate with a pilot study in ngc 300 that integral field spectroscopy with high spatial resolution and excellent seeing conditions reaches an unprecedented depth in severely crowded fields.methods: observations by muse with seven pointings in ngc 300 have resulted in data cubes that are analyzed in four ways: (1) point spread function-fitting 3d spectroscopy with pampelmuse, as already successfully pioneered in globular clusters, yields de-blended spectra of individually distinguishable stars, thus providing a complete inventory of blue and red supergiants, and asymptotic giant branch (agb) stars of type m and c. the technique is also applicable to emission line point sources and provides samples of planetary nebulae (pne) that are complete down to m5007 = 28. (2) pseudo-monochromatic images, created at the wavelengths of the most important emission lines and corrected for continuum light with the p3d visualization tool, provide maps of h ii regions, supernova remnants (snr), and the diffuse interstellar medium (ism) at a high level of sensitivity, where also faint point sources stand out and allow for the discovery of pne, wolf-rayet (wr) stars, etc. (3) the use of the p3d line-fitting tool yields emission line fluxes, surface brightness, and kinematic information for gaseous objects, corrected for absorption line profiles of the underlying stellar population in the case of hα. (4) visual inspection of the data cubes by browsing through the row-stacked spectra image in p3d is demonstrated to be efficient for data mining and the discovery of background galaxies and unusual objects.results: we present a catalog of luminous stars, rare stars such as wr, and other emission line stars, carbon stars, symbiotic star candidates, pne, h ii regions, snr, giant shells, peculiar diffuse and filamentary emission line objects, and background galaxies, along with their spectra.conclusions: the technique of crowded-field 3d spectroscopy, using the pampelmuse code, is capable of deblending individual bright stars, the unresolved background of faint stars, gaseous nebulae, and the diffuse component of the ism, resulting in unprecedented legacy value for observations of nearby galaxies with muse. based on observations obtained at the very large telescope (vlt) of the european southern observatory, paranal, chile (eso programme id 094.d-0116(a), 094.d-0116(b), 095.d-0173(a)).the full version of tables 6, 9 and the reduced dat-acube (fits file) are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/618/a3 | muse crowded field 3d spectroscopy in ngc 300. i. first results from central fields |
we present atacama large millimeter array co(3 - 2) and hco+(4 - 3) observations covering the central 1'5 × 1'5 region of the orion nebula cluster (onc). the unprecedented level of sensitivity (∼0.1 mjy beam-1) and angular resolution (∼0"09 ≈ 40 au) of these line observations enable us to search for gas-disk detections toward the known positions of submillimeter-detected dust disks in this region. we detect 23 disks in gas: 17 in co(3 - 2), 17 in hco+(4 - 3), and 11 in both lines. depending on where the sources are located in the onc, we see the line detections in emission, in absorption against the warm background, or in both emission and absorption. we spectrally resolve the gas with 0.5 km s-1 channels and find that the kinematics of most sources are consistent with keplerian rotation. we measure the distribution of gas-disk sizes and find typical radii of ∼50-200 au. as such, gas disks in the onc are compact in comparison with the gas disks seen in low-density star-forming regions. gas sizes are universally larger than the dust sizes. however, the gas and dust sizes are not strongly correlated. we find a positive correlation between gas size and distance from the massive star θ1 ori c, indicating that disks in the onc are influenced by photoionization. finally, we use the observed kinematics of the detected gas lines to model keplerian rotation and infer the masses of the central pre-main-sequence stars. our dynamically derived stellar masses are not consistent with the spectroscopically derived masses, and we discuss possible reasons for this discrepancy. | protoplanetary disks in the orion nebula cluster: gas-disk morphologies and kinematics as seen with alma |
common envelope (ce) evolution is a critical but still poorly understood progenitor phase of many high-energy astrophysical phenomena. although 3d global hydrodynamic ce simulations have become more common in recent years, those involving an asymptotic giant branch (agb) primary are scarce, due to the high computational cost from the larger dynamical range compared to red giant branch (rgb) primaries. but ce evolution with agb progenitors is desirable to simulate because such events are the likely progenitors of most bi-polar planetary nebulae (pne), and prominent observational testing grounds for ce physics. here we present a high-resolution global simulation of ce evolution involving an agb primary and 1-m⊙ secondary, evolved for 20 orbital revolutions. during the last 16 of these orbits, the envelope unbinds at an almost constant rate of about 0.1-0.2 m⊙ yr-1. if this rate were maintained, the envelope would be unbound in less than 10 yr. the dominant source of this unbinding is consistent with inspiral; we assess the influence of the ambient medium to be subdominant. we compare this run with a previous run that used an rgb phase primary evolved from the same 2-m⊙ main-sequence star to assess the influence of the evolutionary state of the primary. when scaled appropriately, the two runs are quite similar, but with some important differences. | common envelope evolution on the asymptotic giant branch: unbinding within a decade? |
star-forming galaxies with strong nebular and collisional emission lines are privileged target galaxies in forthcoming cosmological large galaxy redshift surveys. we use the cosmos2015 photometric catalogue to model galaxy spectral energy distributions and emission-line fluxes. we adopt an empirical but physically motivated model that uses information from the best-fitting spectral energy distribution of stellar continuum to each galaxy. the emission-line flux model is calibrated and validated against direct flux measurements in subsets of galaxies that have 3d-hst or zcosmos-bright spectra. we take a particular care in modelling dust attenuation such that our model can explain both hα and [o ii] observed fluxes at different redshifts. we find that a simple solution to this is to introduce a redshift evolution in the dust attenuation fraction parameter, f = estar(b - v)/egas(b - v), as f(z) = 0.44 + 0.2z. from this catalogue, we derive the hα and [o ii] luminosity functions up to redshifts of about 2.5 after carefully accounting for emission line flux and redshift errors. this allows us to make predictions for hα and [o ii] galaxy number counts in next-generation cosmological redshift surveys. our modelled emission lines and spectra in the cosmos2015 catalogue shall be useful to study the target selection for planned next-generation galaxy redshift surveys and we make them publicly available as 'el-cosmos' on the aspic data base. | the synthetic emission line cosmos catalogue: hα and [o ii] galaxy luminosity functions and counts at 0.3 < z < 2.5 |
we calculate the evolution of gas giant planets during the runaway gas accretion phase of formation, to understand how the luminosity of young giant planets depends on the accretion conditions. we construct steady-state envelope models, and run time-dependent simulations of accreting planets with the code modules for experiments in stellar astrophysics. we show that the evolution of the internal entropy depends on the contrast between the internal adiabat and the entropy of the accreted material, parametrized by the shock temperature t 0 and pressure p 0. at low temperatures ({t}0≲ 300-1000 {{k}}, depending on model parameters), the accreted material has a lower entropy than the interior. the convection zone extends to the surface and can drive a high luminosity, leading to rapid cooling and cold starts. for higher temperatures, the accreted material has a higher entropy than the interior, giving a radiative zone that stalls cooling. for {t}0≳ 2000 {{k}}, the surface-interior entropy contrast cannot be accommodated by the radiative envelope, and the accreted matter accumulates with high entropy, forming a hot start. the final state of the planet depends on the shock temperature, accretion rate, and starting entropy at the onset of runaway accretion. cold starts with l≲ 5× {10}-6 {l}⊙require low accretion rates and starting entropy, and the temperature of the accreting material needs to be maintained close to the nebula temperature. if instead the temperature is near the value required to radiate the accretion luminosity, 4π {r}2σ {t}04∼ ({gm}\dot{m}/r), as suggested by previous work on radiative shocks in the context of star formation, gas giant planets form in a hot start with l∼ {10}-4 {l}⊙ . | the evolution of gas giant entropy during formation by runaway accretion |
the star-forming region of the orion nebula (onc) is ideal to study the stellar dynamics of young stars in a clustered environment. using gaia dr2 we search for pre-main sequence stars with unusually high proper motions that may be representative of a dynamical ejection from unstable young triple systems or other close three-body encounters. we identify 26 candidate stars that are likely to have had such an encounter in the last 1 myr. nine of these stars could be traced back to the densest central-most region of the onc, the trapezium, while five others have likely interactions with other ob-type stars in the cluster. seven stars originate from other nearby populations within the orion complex that coincidentally scattered toward the onc. a definitive point of origin cannot be identified for the remaining sources. these observations shed light on the frequency of the ejection events in young clusters. | runaway young stars near the orion nebula |
ck vul is the remnant of an energetic eruption known as nova 1670 that is thought to be caused by a stellar merger. the remnant is composed of (1) a large hourglass nebula of recombining gas (of 71'' in size), very similar to some classical planetary and pre-planetary nebulae (ppne), and (2) a much smaller and cooler inner remnant that is prominent in millimeter-wave emission from molecules. we investigate the three-dimensional spatio-kinematic structure of both components. our analysis of the hourglass structure yields a revised distance to the object of >2.6 kpc, at least 3.7 times greater than previously assumed. at this distance, the stellar remnant has a bolometric luminosity >12 l⊙ and is surrounded by molecular material with a total mass >0.8 m⊙ (the latter value has a large systematic uncertainty). we also analyzed the architecture of the inner molecular nebula using alma observations of rotational emission lines obtained at subarcsecond resolution. we find that the distribution of neutral and ionized gas in the lobes can be reproduced by several nested and incomplete shells or jets with different velocity fields and varying orientations. the analysis indicates that the molecular remnant was created in several ejection episodes, possibly involving an interacting binary system. we calculated the linear momentum (≈1040 g cm s-1) and kinetic energy (≈1047 erg) of the ck vul outflows and find values that are within the limits typical for classical ppne. given the similarities of the ck vul outflows to ppne, we suggest there may be ck vul analogs among wrongly classified ppne with low intrinsic luminosities, especially among ppne with post-red-giant-branch central stars. two movies associated to fig. 4 are available at http://www.aanda.org | molecular remnant of nova 1670 (ck vulpeculae). ii. a three-dimensional view of the gas distribution and velocity field |
we present new hubble space telescope cosmic origins spectrograph far-ultraviolet (far-uv) spectroscopy and keck echellete optical spectroscopy of 11 ultraluminous infrared galaxies (ulirgs), a rare population of local galaxies experiencing massive gas inflows, extreme starbursts, and prominent outflows. we detect lyα emission from eight ulirgs and the companion to iras09583+4714. in contrast to the p cygni profiles often seen in galaxy spectra, the lyα profiles exhibit prominent, blueshifted emission out to doppler shifts exceeding -1000 km s-1 in three h ii-dominated and two agn-dominated ulirgs. to better understand the role of resonance scattering in shaping the lyα line profiles, we directly compare them to non-resonant emission lines in optical spectra. we find that the line wings are already present in the intrinsic nebular spectra, and scattering merely enhances the wings relative to the line core. the lyα attenuation (as measured in the cos aperture) ranges from that of the far-uv continuum to over 100 times more. a simple radiative transfer model suggests the lyα photons escape through cavities which have low column densities of neutral hydrogen and become optically thin to the lyman continuum in the most advanced mergers. we show that the properties of the highly blueshifted line wings on the lyα and optical emission-line profiles are consistent with emission from clumps of gas condensing out of a fast, hot wind. the luminosity of the lyα emission increases nonlinearly with the ulirg bolometric luminosity and represents about 0.1-1% of the radiative cooling from the hot winds in the h ii-dominated ulirgs. | the lyα line profiles of ultraluminous infrared galaxies: fast winds and lyman continuum leakage |
we report on the detection of a bright, short, structured x-ray burst coming from the supernova remnant rcw 103 on 2016 june 22 caught by the swift/burst alert telescope (bat) monitor, and on the follow-up campaign made with swift/x-ray telescope, swift/uv/optical telescope, and the optical/near-infrared (nir) gamma-ray burst optical and near-infrared detector. the characteristics of this flash, such as duration and spectral shape, are consistent with typical short bursts observed from soft gamma repeaters. the bat error circle at 68 per cent confidence range encloses the point-like x-ray source at the centre of the nebula, 1e 161348-5055. its nature has been long debated due to a periodicity of 6.67 h in x-rays, which could indicate either an extremely slow pulsating neutron star, or the orbital period of a very compact x-ray binary system. we found that 20 min before the bat trigger, the soft x-ray emission of 1e 161348-5055 was a factor of ∼100 higher than measured 2 yr earlier, indicating that an outburst had already started. by comparing the spectral and timing characteristics of the source in the 2 yr before the outburst and after the bat event, we find that, besides a change in luminosity and spectral shape, also the 6.67 h pulsed profile has significantly changed with a clear phase shift with respect to its low-flux profile. the uv/optical/nir observations did not reveal any counterpart at the position of 1e 161348-5055. based on these findings, we associate the bat burst with 1e 161348-5055, we classify it as a magnetar, and pinpoint the 6.67 h periodicity as the magnetar spin period. | evidence for the magnetar nature of 1e 161348-5055 in rcw 103 |
the primordial helium abundance yp is calculated using sulphur as metallicity tracer in the classical methodology (with yp as an extrapolation of y to zero metals). the calculated value, yp, s= 0.244 ± 0.006, is in good agreement with the estimate from the planck experiment, as well as, determinations in the literature using oxygen as the metallicity tracer. the chemical analysis includes the substraction of the nebular continuum and of the stellar continuum computed from simple stellar population synthesis grids. the s+2 content is measured from the near-infrared [ s iii]λ λ 9069,9532 lines, while an icf(s3 +) is proposed based on the ar3 +/ar2 + fraction. finally, we apply a multivariable linear regression using simultaneously oxygen, nitrogen, and sulphur abundances for the same sample to determine the primordial helium abundance resulting in yp - o, n, s = 0.245 ± 0.007. | primordial helium abundance determination using sulphur as metallicity tracer |
context. in the theory of pebble accretion, planets form by the subsequent accretion of solids (micron-sized dust and larger pebbles) and gas. the amount of nebular gas that a planet can bind is limited by its cooling rate, which is set by the opacity of its envelope. accreting dust and pebbles contribute to the envelope opacity and, thus, influence the outcome of planet formation.aims: our aim is to model the size evolution and opacity contribution of solids inside planetary envelopes. we then use the resultant opacity relations to study emergent trends in planet formation.methods: we design a model for the opacity of solids in planetary envelopes that accounts for the growth, fragmentation, and erosion of pebbles during their sedimentation. it also includes a separate dust component, which can be both replenished and swept up by encounters with pebbles, depending on the relative velocities. we formulate analytical expressions for the opacity of pebbles and dust and map out their trends as a function of depth, planet mass, distance, and accretion rate.results: the accretion of pebbles rather than planetesimals can produce fully convective envelopes, but only in lower-mass planets that reside in the outer disk or in those that are accreting pebbles at a high rate. in these conditions, pebble sizes are limited by fragmentation and erosion, allowing them to pile up in the envelope. at higher planetary masses or reduced accretion rates, a different regime applies, where the sizes of sedimenting pebbles are only limited by their rate of growth. the opacity in this growth-limited regime is much lower and declines steeply with depth and planet mass but is invariant with the pebble mass flux. our results imply that the opacity of a forming planet's envelope cannot be approximated by a value that is constant with either depth or planet mass. applying these results to the solar system, we argue that uranus and neptune could not have maintained a sufficiently high opacity to avoid runaway gas accretion unless they both experienced sufficiently rapid accretion of solids and formed late. | how planets grow by pebble accretion. iv. envelope opacity trends from sedimenting dust and pebbles |
we present optical photometry and spectroscopy of sn 2016iet (=gaia16bvd=ps17brq), an unprecedented type i supernova (sn i) at z = 0.0676 with no obvious analog in the existing literature. sn 2016iet exhibits a peculiar light curve, with two roughly equal brightness peaks (≈ -19 mag) separated by about 100 days, and a subsequent slow decline by about 5 mag in 650 rest-frame days. the spectra are dominated by strong emission lines of calcium and oxygen, with a width of only 3400 km s-1, superposed on a strong blue continuum in the first year. there is no clear evidence for hydrogen or helium associated with the sn at any phase. the nebular spectra exhibit a ratio of {l}[{ca{{ii}}]}/{l}[{{o}{{i}}]}≈ 4, much larger than for core-collapse sne and type i superluminous sne. we model the light curves with several potential energy sources: radioactive decay, a central engine, and ejecta-circumstellar medium (csm) interaction. regardless of the model, the inferred progenitor mass near the end of its life (i.e., the co core mass) is ≳55 m ⊙ and potentially up to 120 m ⊙, clearly placing the event in the regime of pulsational pair instability supernovae (ppisne) or pair instability supernovae (pisne). the models of csm interaction provide the most consistent explanation for the light curves and spectra, and require a csm mass of ≈35 m ⊙ ejected in the final decade before explosion. we further find that sn 2016iet is located at an unusually large projected offset (16.5 kpc, 4.3 effective radii) from its low-metallicity dwarf host galaxy (z ≈ 0.1 z ⊙, l ≈ 0.02 l *, m ≈ 108.5 m ⊙), supporting the interpretation of a ppisn/pisn explosion. in our final spectrum at a phase of about 770 rest-frame days we detect weak and narrow hα emission at the location of the sn, corresponding to a star formation rate of ≈3 × 10-4 m ⊙ yr-1, which is likely due to a dim underlying galaxy host or an h ii region. despite the overall consistency of the sn and its unusual environment with ppisne and pisne, we find that the inferred properties of sn 2016iet challenge existing models of such events. | sn 2016iet: the pulsational or pair instability explosion of a low-metallicity massive co core embedded in a dense hydrogen-poor circumstellar medium |
the javalambre-physics of the accelerating universe astrophysical survey (j-pas) is expected to map thousands of square degrees of the northern sky with 56 narrowband filters (spectral resolution of r ∼ 60) in the upcoming years. this resolution allows us to study emission line galaxies (elgs) with a minimum equivalent width of 10 å in the hα emission line for a median signal-to-noise ratio (s/n) of 5. this will make j-pas a very competitive and unbiased emission line survey compared to spectroscopic or narrowband surveys with fewer filters. the minijpas survey covered 1 deg2, and it used the same photometric system as j-pas, but the observations were carried out with the pathfinder j-pas camera. in this work, we identify and characterize the sample of elgs from minijpas with a redshift lower than 0.35, which is the limit to which the hα line can be observed with the j-pas filter system. using a method based on artificial neural networks, we detect the elg population and measure the equivalent width and flux of the hα, hβ, [o iii], and [n ii] emission lines. we explore the ionization mechanism using the diagrams [oiii]/hβ versus [nii]/hα (bpt) and ew(hα) versus [nii]/hα (whan). we identify 1787 elgs (83%) from the parent sample (2154 galaxies) in the aegis field. for the galaxies with reliable ew values that can be placed in the whan diagram (2000 galaxies in total), we obtained that 72.8 ± 0.4%, 17.7 ± 0.4%, and 9.4 ± 0.2% are star-forming (sf), active galactic nucleus (seyfert), and quiescent galaxies, respectively. the distribution of ew(hα) is well correlated with the bimodal color distribution of galaxies. based on the rest-frame (u − r)-stellar mass diagram, 94% of the blue galaxies are sf galaxies, and 97% of the red galaxies are liners or passive galaxies. the nebular extinction and star formation rate (sfr) were computed from the hα and hβ fluxes. we find that the star formation main sequence is described as log sfr [m⊙ yr−1] = 0.90−0.02+0.02 log m⋆[m⊙]−8.85−0.20+0.19 and has an intrinsic scatter of 0.20−0.01+0.01. the cosmic evolution of the sfr density (ρsfr) is derived at three redshift bins: 0 < z ≤ 0.15, 0.15 < z ≤ 0.25, and 0.25 < z ≤ 0.35, which agrees with previous results that were based on measurements of the hα emission line. however, we find an offset with respect to other estimates that were based on the star formation history obtained from fitting the spectral energy distribution of the stellar continuum. we discuss the origin of this discrepancy, which is probably a combination of several factors: the escape of ionizing photons, the sfr tracers, and dust attenuation, among others. | the minijpas survey: identification and characterization of the emission line galaxies down to z < 0.35 in the aegis field |
among the nearest most metal-poor starburst-dwarf galaxies known, sbs 0335-052e is the most luminous in integrated nebular he ii λ4686 emission. this makes it a unique target to test spectral synthesis models and spectral interpretation tools of the kind that will be used to interpret future rest-frame uv observations of primeval galaxies. previous attempts to reproduce its he ii λ4686 luminosity found that x-ray sources, shocks, and single wolf-rayet stars are not main contributors to the he ii-ionizing budget; and that only metal-free single rotating stars or binary stars with a top-heavy imf and an unphysically low metallicity can reproduce it. we present new uv (cos) and optical (muse) spectra that integrate the light of four super star clusters in sbs 0335-052e. nebular he ii, [c iii], c iii], c iv, and o iii] uv emission lines with equivalent widths between 1.7 and 5 å and a c iv λλ1548, 1551 p-cygni like profile are detected. recent extremely metal-poor shock + precursor models and binary models fail to reproduce the observed optical emission-line ratios. we use different sets of uv and optical observables to test models of constant star formation with single non-rotating stars that account for very massive stars as blueshifted o v λ1371 absorption is present. simultaneously fitting the fluxes of all high-ionization uv lines requires an unphysically low metallicity. fitting the p-cygni like + nebular components of c iv λλ1548, 1551 does not constrain the stellar metallicity and time since the beginning of star formation. we obtain 12+log(o/h) $\, = 7.45\pm 0.04$ and log(c/o) $\, = -0.45^{+0.03}_{-0.04}$ for the galaxy. model testing would benefit from higher spatial resolution uv and optical spectroscopy of the galaxy. | stars and gas in the most metal-poor galaxies - i. cos and muse observations of sbs 0335-052e |
the nebular circumstellar environments of cool evolved stars are known to harbour a rich morphological complexity of gaseous structures on different length scales. a large part of these density structures are thought to be brought about by the interaction of the stellar wind with a close companion. the s-type asymptotic giant branch (agb) star π1gruis, which has a known companion at ∼440 au and is thought to harbour a second, closer-by (< 10 au) companion, was observed with the atacama large millimeter/submillimeter array as part of the atomium large programme. in this work, the brightest co, sio, and hcn molecular line transitions are analysed. the continuum map shows two maxima, separated by 0.04″ (6 au). the co data unambiguously reveal that π1gru's circumstellar environment harbours an inclined, radially outflowing, equatorial density enhancement. it contains a spiral structure at an angle of ∼38 ± 3° with the line-of-sight. the hcn emission in the inner wind reveals a clockwise spiral, with a dynamical crossing time of the spiral arms consistent with a companion at a distance of 0.04″ from the agb star, which is in agreement with the position of the secondary continuum peak. the inner wind dynamics imply a large acceleration region, consistent with a beta-law power of ∼6. the co emission suggests that the spiral is approximately archimedean within 5″, beyond which this trend breaks down as the succession of the spiral arms becomes less periodic. the sio emission at scales smaller than 0.5″ exhibits signatures of gas in rotation, which is found to fit the expected behaviour of gas in the wind-companion interaction zone. an investigation of sio maser emission reveals what could be a stream of gas accelerating from the surface of the agb star to the companion. using these dynamics, we have tentatively derived an upper limit on the companion mass to be ∼1.1 m⊙. | atomium: a high-resolution view on the highly asymmetric wind of the agb star π1gruis. i. first detection of a new companion and its effect on the inner wind |
the nebular spectra of type ia supernovae (⪆100 d after explosion) consist mainly of emission lines from singly and doubly ionized fe-group nuclei. however, theoretical models for many scenarios predict that non-thermal ionization leads to multiply ionized species whose recombination photons ionize and deplete fe+, resulting in negligible [fe ii] emission. we investigate a method to determine the collisional excitation conditions from [fe ii] line ratios independently from the ionization state and find that it cannot be applied to highly ionized models due to the influence of recombination cascades on fe+ level populations. when the ionization state is artificially lowered, the line ratios (and excitation conditions) are too similar to distinguish between explosion scenarios. we investigate changes to the treatment of non-thermal energy deposition as a way to reconcile overionized theoretical models with observations and find that a simple work function approximation provides closer agreement with the data for sub-mch models than a detailed spencer-fano treatment with widely used cross-section data. to quantify the magnitude of additional heating processes that would be required to sufficiently reduce ionization from fast leptons, we artificially boost the rate of energy loss to free electrons. we find that the equivalent of as much as an eight times increase to the plasma loss rate would be needed to reconcile the sub-mch model with observed spectra. future studies could distinguish between reductions in the non-thermal ionization rates and increased recombination rates, such as by clumping. | modelling the ionization state of type ia supernovae in the nebular phase |
the gas pixel detector (gpd) is designed and developed for high-sensitivity astronomical x-ray polarimetry, which is a new window about to open in a few years. due to the small mass, low power, and compact geometry of the gpd, we propose a cubesat mission polarimeter light (polarlight) to demonstrate and test the technology directly in space. there is no optics but a collimator to constrain the field of view to 2.3 degrees. filled with pure dimethyl ether (dme) at 0.8 atm and sealed by a beryllium window of 100 μm thick, with a sensitive area of about 1.4 mm by 1.4 mm, polarlight allows us to observe the brightest x-ray sources on the sky, with a count rate of, e.g., ∼0.2 counts s- 1 from the crab nebula. the polarlight is 1u in size and mounted in a 6u cubesat, which was launched into a low earth sun-synchronous orbit on october 29, 2018, and is currently under test. more launches with improved designs are planned in 2019. these tests will help increase the technology readiness for future missions such as the enhanced x-ray timing and polarimetry (extp), better understand the orbital background, and may help constrain the physics with observations of the brightest objects. | polarlight: a cubesat x-ray polarimeter based on the gas pixel detector |
we used the space telescope imaging spectrograph on the hubble space telescope (hst) to observe the semiforbidden c iii] λλ1907, 1909 doublet emission in green pea galaxies at 0.13 ≤ z ≤ 0.3. we detect c iii] emission in 7/10 galaxies with c iii] equivalent widths (ews) that range from 2 to 10 å, confirming that c iii] emission is almost ubiquitous in low-mass, low-metallicity (12+log(o/h) < 8.4) galaxies that are characterized by strong optical [o iii] λ5007 emission. the composite uv spectrum shows evidence for the he ii λ1640 emission line and interstellar absorption features (e.g., c iv λλ1548, 1550, al iii λλ1854, 1862). we do not detect the o iii] λλ1661, 1666 emission with >3σ significance. the observed c iii] emission line strengths are consistent with the predictions from photoionization models that incorporate the effects of binary stellar evolution with young stellar ages ≤3-5 myr and high ionization parameters (log u > -2). the hard ionizing radiation from young massive stars and high nebular temperatures at low metallicities can account for the observed high ews of c iii] λ1909 and [o iii] λ5007 emission lines. some of the star-forming galaxies at high redshift and local blue compact dwarf galaxies show offsets from the ew(c iii]) versus ew([o iii]) model grids, indicating an additional contribution to the continuum emission from composite stellar populations or different c/o abundances, nebular temperatures, and electron densities than assumed in the photoionization models. the green pea galaxies do not show a significant correlation between the lyα and c iii] ews, and the observed scatter is likely due to the variations in the optical depth of lyα to the neutral gas. green pea galaxies are likely to be density-bounded, and we examined the dependence of c iii] emission on the lyman continuum optical depth. the potential lyc leaker galaxies in our sample have high c iii] ews that can only be reproduced by starburst ages as young as <3 myr and harder ionizing spectra than the nonleakers. among the galaxies with similar metallicities and ionization parameters, the c iii] ew appears to be stronger for those with higher optical depth to lyc, as expected from the photoionization models. there are various factors that affect the c iii] emission line strengths, and further investigation of a larger sample of c iii] emitters is necessary to calibrate the dependence of c iii] emission on the escape of lyc radiation and enable application of the c iii] diagnostics to galaxies in the reionization epoch. | the semiforbidden c iii] λ1909 emission in the rest-ultraviolet spectra of green pea galaxies |
recent integral field spectroscopic (ifs) surveys have revealed radial gradients in the optical spectral indices of post-starburst (psb) galaxies, which can be used to constrain their formation histories. we study the spectral indices of post-processed mock ifs datacubes of binary merger simulations, carefully matched to the properties of the manga ifs survey, with a variety of black hole (bh) feedback models, progenitor galaxies, orbits, and mass ratios. based on our simulation sample, we find that only major mergers on prograde-prograde or retrograde-prograde orbits in combination with a mechanical bh feedback model can form galaxies with weak enough ongoing star formation, and therefore absent h α emission, to be selected by traditional psb selection methods. we find strong fluctuations in nebular emission line strengths, even within the psb phase, suggesting that h α selected psbs are only a subsample of the underlying population. the global psb population can be more robustly identified using stellar continuum-based approaches. the difficulty in reproducing the very young psbs in simulations potentially indicates that new sub-resolution star formation recipes are required to properly model the process of star formation quenching. in our simulations, we find that the starburst peaks at the same time at all radii, but is stronger and more prolonged in the inner regions. this results in a strong time evolution in the radial gradients of the spectral indices that can be used to estimate the age of the starburst without reliance on detailed star formation histories from spectral synthesis models. | comparison of stellar populations in simulated and real post-starburst galaxies in manga |
we present a strong and weak lensing reconstruction of the massive cluster abell 2744, the first cluster for which deep hubble frontier fields (hff) images and spectroscopy from the grism lens-amplified survey from space (glass) are available. by performing a targeted search for emission lines in multiply imaged sources using the glass spectra, we obtain five high-confidence spectroscopic redshifts and two tentative ones. we confirm one strongly lensed system by detecting the same emission lines in all three multiple images. we also search for additional line emitters blindly and use the full glass spectroscopic catalog to test reliability of photometric redshifts for faint line emitters. we see a reasonable agreement between our photometric and spectroscopic redshift measurements, when including nebular emission in photometric redshift estimations. we introduce a stringent procedure to identify only secure multiple image sets based on colors, morphology, and spectroscopy. by combining 7 multiple image systems with secure spectroscopic redshifts (at 5 distinct redshift planes) with 18 multiple image systems with secure photometric redshifts, we reconstruct the gravitational potential of the cluster pixellated on an adaptive grid, using a total of 72 images. the resulting mass map is compared with a stellar mass map obtained from the deep spitzer frontier fields data to study the relative distribution of stars and dark matter in the cluster. we find that the stellar to total mass ratio varies substantially across the cluster field, suggesting that stars do not trace exactly the total mass in this interacting system. the maps of convergence, shear, and magnification are made available in the standard hff format. | the grism lens-amplified survey from space (glass). iv. mass reconstruction of the lensing cluster abell 2744 from frontier field imaging and glass spectroscopy |
context. model atmosphere analyses have been previously undertaken for both galactic and extragalactic b-type supergiants. by contrast, little attention has been given to a comparison of the properties of single supergiants and those that are members of multiple systems.aims: atmospheric parameters and nitrogen abundances have been estimated for all the b-type supergiants identified in the vlt-flames tarantula survey. these include both single targets and binary candidates. the results have been analysed to investigate the role of binarity in the evolutionary history of supergiants.methods: tlusty non-local thermodynamic equilibrium (lte) model atmosphere calculations have been used to determine atmospheric parameters and nitrogen abundances for 34 single and 18 binary supergiants. effective temperatures were deduced using the silicon balance technique, complemented by the helium ionisation in the hotter spectra. surface gravities were estimated using balmer line profiles and microturbulent velocities deduced using the silicon spectrum. nitrogen abundances or upper limits were estimated from the n ii spectrum. the effects of a flux contribution from an unseen secondary were considered for the binary sample.results: we present the first systematic study of the incidence of binarity for a sample of b-type supergiants across the theoretical terminal age main sequence (tams). to account for the distribution of effective temperatures of the b-type supergiants it may be necessary to extend the tams to lower temperatures. this is also consistent with the derived distribution of mass discrepancies, projected rotational velocities and nitrogen abundances, provided that stars cooler than this temperature are post-red supergiant objects. for all the supergiants in the tarantula and in a previous flames survey, the majority have small projected rotational velocities. the distribution peaks at about 50 km s-1 with 65% in the range 30 km s-1 ≤ vesini ≤ 60 km s-1. about ten per cent have larger vesini (≥100 km s-1), but surprisingly these show little or no nitrogen enhancement. all the cooler supergiants have low projected rotational velocities of ≤70 km s-1and high nitrogen abundance estimates, implying that either bi-stability braking or evolution on a blue loop may be important. additionally, there is a lack of cooler binaries, possibly reflecting the small sample sizes. single-star evolutionary models, which include rotation, can account for all of the nitrogen enhancement in both the single and binary samples. the detailed distribution of nitrogen abundances in the single and binary samples may be different, possibly reflecting differences in their evolutionary history.conclusions: the first comparative study of single and binary b-type supergiants has revealed that the main sequence may be significantly wider than previously assumed, extending to teff = 20 000 k. some marginal differences in single and binary atmospheric parameters and abundances have been identified, possibly implying non-standard evolution for some of the sample. this sample as a whole has implications for several aspects of our understanding of the evolutionary status of blue supergiants. tables 1, 4, 7 are available in electronic form at http://www.aanda.org | the vlt-flames tarantula survey. xix. b-type supergiants: atmospheric parameters and nitrogen abundances to investigate the role of binarity and the width of the main sequence |
we present an extended grid of multi-epoch 1d nonlocal thermodynamic equilibrium radiative transfer calculations for nebular-phase type ibc supernovae (sne) from he-star explosions. compared to our previous work, which was focused on a post-explosion epoch of 200 days, here we study the spectral evolution from 100 to about 450 days. we also augment the model set with progenitors that evolved without wind mass loss. models with the same final, pre-sn mass have similar yields and produce essentially the same emergent spectra. hence, the uncertain progenitor mass loss history compromises the inference of the initial, main sequence mass. this shortcoming does not affect type iib sne in which mass-loss has left a small residual h-rich envelope in the progenitor star at core collapse and, hence, an intact he core. however, our 1d models with a different pre-sn mass tend to yield widely different spectra, as seen through variations in the strong emission lines due to [n ii] λλ 6548, 6583, [o i] λλ 6300, 6364, [ca ii] λλ 7291, 7323, [ni ii] λ 7378, and the forest of fe ii lines below 5500 å. at the lower mass end, the ejecta are he-rich, and at 100 days, they cool through he i, n ii, ca ii, and fe ii lines, with n ii and fe ii dominating at 450 days. these models, associated with he giants, stand in conflict to observed sne ib, which typically lack strong n ii emission. instead, they may lead to sne ibn or, because of additional stripping by a companion star, ultra-stripped sne ic. in contrast, for higher pre-sn masses, the ejecta are progressively he poor and cool at 100 days through o i, ca ii, and fe ii lines, with o i and ca ii dominating at 450 days. non-uniform, aspherical, large-scale mixing is more likely to determine the sn type at intermediate pre-sn masses, rather than any compositional differences. variations in clumping and mixing, as well as departures from spherical symmetry would increase the spectral diversity, but also introduce additional degeneracies. more robust predictions from spectral modeling thus require that careful attention be paid to the initial conditions by incorporating the salient features of physically consistent 3d explosion models. | modeling of the nebular-phase spectral evolution of stripped-envelope supernovae. new grids from 100 to 450 days |
we present new spectroscopic observations of ly α (ly α) blob 2 (z ~ 3.1). we observed extended ly α emission in three distinct regions, where the highest ly α surface brightness (sb) centre is far away from the known continuum sources. we searched through the mosfire slits that cover the high ly α sb regions, but were unable to detect any significant nebular emission near the highest sb centre. we further mapped the flux ratio of the blue peak to the red peak and found it is anticorrelated with ly α sb with a power-law index of ~ -0.4. we used radiative transfer models with both multiphase, clumpy, and shell geometries and successfully reproduced the diverse ly α morphologies. we found that most spectra suggest outflow-dominated kinematics, while 4/15 spectra imply inflows. a significant correlation exists between parameter pairs, and the multiphase, clumpy model may alleviate previously reported discrepancies. we also modelled ly α spectra at different positions simultaneously and found that the variation of the inferred clump outflow velocities can be approximately explained by line-of-sight projection effects. our results support the 'central powering + scattering' scenario, i.e. the ly α photons are generated by a central powering source and then scatter with outflowing, multiphase h i gas while propagating outwards. the infalling of cool gas near the blob outskirts shapes the observed blue-dominated ly α profiles, but its energy contribution to the total ly α luminosity is less than 10 per cent, i.e. minor compared to the photoionization by star-forming galaxies and/or agns. | where outflows meet inflows: gas kinematics in ssa22 ly α blob 2 decoded by advanced radiative transfer modelling |
context. the andromeda (m 31) galaxy subtends nearly 100 square degrees on the sky. any study of its halo must therefore account for the severe contamination from the milky way halo stars whose surface density displays a steep gradient across the entire m 31 field of view.aims: our goal is to identify a population of stars firmly associated with the m 31 galaxy. planetary nebulae (pne) are one such population that are excellent tracers of light, chemistry, and motion in galaxies. we present a 16 square degree survey of the disc and inner halo of m 31 with the megacam wide-field imager at the cfht to identify pne, and characterise the luminosity-specific pn number and pn luminosity function (pnlf) in m 31.methods: pne were identified via automated detection techniques based on their bright [o iii] 5007 å emission and absence of a continuum. subsamples of the faint pne were independently confirmed by matching with resolved hubble space telescope sources from the panchromatic hubble andromeda treasury and spectroscopic follow-up observations with hectospec at the mmt.results: the current survey reaches two magnitudes fainter than the previous most sensitive survey. we thus identify 4289 pne, of which only 1099 were previously known. by comparing the pn number density with the surface brightness profile of m 31 out to ∼30 kpc along the minor axis, we find that the stellar population in the inner halo has a luminosity-specific pn number value that is seven times higher than that of the disc. we measure the luminosity function of the pn population and find a bright cut-off and a slope consistent with previous determinations. interestingly, it shows a significant rise at the faint end, present in all radial bins covered by the survey. this rise in the m 31 pnlf is much steeper than that observed for the magellanic clouds and milky way bulge.conclusions: the significant radial variation of the pn specific frequency value indicates that the stellar population at deprojected minor-axis radii larger than ∼10 kpc is different from that in the disc of m 31. the rise at the faint end of the pnlf is a property of the late phases of the stellar population. m 31 shows two major episodes of star formation and the rise at the faint end of the pnlf is possibly associated with the older stellar population. it may also be a result of varying opacity of the pne. based on observations obtained with megacam, a joint project of the cfht and cea/dapnia, at the canada-france-hawaii telescope (cfht), which is operated by the national research council (nrc) of canada, the institut national des sciences de l'univers of the centre national de la recherche scientifique (cnrs) of france, and the university of hawaii. the observations at the cfht were performed with care and respect from the summit of maunakea which is a significant cultural and historic site. | the survey of planetary nebulae in andromeda (m 31). i. imaging the disc and halo with megacam at the cfht |
1es 1959+650 is a bright tev high-frequency-peaked bl lac object exhibiting interesting features like "orphan" tev flares and broad emission in the high-energy regime that are difficult to interpret using conventional one-zone synchrotron self-compton (ssc) scenarios. we report the results from the major atmospheric gamma imaging cherenkov (magic) observations in 2016 along with the multi-wavelength data from the fermi large area telescope (lat) and swift instruments. magic observed 1es 1959+650 with different emission levels in the very-high-energy (vhe, e > 100 gev) γ-ray band during 2016. in the long-term data, the x-ray spectrum becomes harder with increasing flux and a hint of a similar trend is also visible in the vhe band. an exceptionally high vhe flux reaching ∼3 times the crab nebula flux was measured by magic on the 13 and 14 of june, and 1 july 2016 (the highest flux observed since 2002). during these flares, the high-energy peak of the spectral energy distribution (sed) lies in the vhe domain and extends up to several tev. the spectrum in the γ-ray (both fermi-lat and vhe bands) and the x-ray bands are quite hard. on 13 june and 1 july 2016, the source showed rapid variations in the vhe flux within timescales of less than an hour. a simple one-zone ssc model can describe the data during the flares requiring moderate to large values of the doppler factors (δ ≥ 30-60). alternatively, the high-energy peak of the sed can be explained by a purely hadronic model attributed to proton-synchrotron radiation with jet power ljet ∼ 1046 erg s-1 and under high values of the magnetic field strength (∼100 g) and maximum proton energy (∼few eev). mixed lepto-hadronic models require super-eddington values of the jet power. we conclude that it is difficult to get detectable neutrino emission from the source during the extreme vhe flaring period of 2016. | broadband characterisation of the very intense tev flares of the blazar 1es 1959+650 in 2016 |
the orion nebula cluster (onc) is the most massive region of active star formation within a kpc of the sun. using gaia dr3 parallaxes and proper motions, we examine the bulk motions of stars radially and tangentially relative to the cluster centre. we find an age gradient with distance to the stars in the onc, from 385 pc for the oldest stars, to 395 pc for the younger stars, indicating that the star-forming front is propagating into the cloud. we find an organized signature of rotation of the central cluster, but it is present only in stars younger than 2 myr. we also observe a net infall of young stars into the centre of the onc's deep gravitational potential well. the infalling sources lie preferentially along the filament; on the other hand, outflowing sources are distributed spherically around the cluster, and they have larger velocity dispersion. we further propose a solution to a long-standing question of why the onc shows a weak signature of expansion even though the cluster is likely bound: much of this expansion may be driven by unstable n-body interactions among stars, resulting in low-velocity ejections. though analysing signatures imprinted on stellar dynamics across different spatial scales, these observation shed new light on the signatures of formation and evolution of young clusters. | a gravitational and dynamical framework of star formation: the orion nebula |
we present observations of three core-collapse supernovae (ccsne) in elliptical hosts, detected by the zwicky transient facility bright transient survey (bts). sn 2019ape is a sn ic that exploded in the main body of a typical elliptical galaxy. its properties are consistent with an explosion of a regular sn ic progenitor. a secondary g-band light-curve peak could indicate interaction of the ejecta with circumstellar material (csm). an hα-emitting source at the explosion site suggests a residual local star formation origin. sn 2018fsh and sn 2020uik are sne ii which exploded in the outskirts of elliptical galaxies. sn 2020uik shows typical spectra for sne ii, while sn 2018fsh shows a boxy nebular hα profile, a signature of csm interaction. we combine these 3 sne with 7 events from the literature and analyze their hosts as a sample. we present multi-wavelength photometry of the hosts, and compare this to archival photometry of all bts hosts. using the spectroscopically complete bts, we conclude that $0.3{ \% }_{-0.1}^{+0.3}$ of all ccsne occur in elliptical galaxies. we derive star formation rates and stellar masses for the host galaxies and compare them to the properties of other sn hosts. we show that ccsne in ellipticals have larger physical separations from their hosts compared to sne ia in elliptical galaxies, and discuss implications for star-forming activity in elliptical galaxies. | less than 1% of core-collapse supernovae in the local universe occur in elliptical galaxies |
context. the presence of large ionised gaseous nebulae found around some ultraluminous x-ray sources (ulxs) provides the means to assess the mechanical and radiative feedback of the central source, and hence constrain the efficiency and impact on the surroundings of the super-eddington regime powering most of these sources. ngc 1313 x-1 is an archetypal ulx, reported to be surrounded by abnormally high [o i]λ6300/hα > 0.1 ratios, and for which high-resolution spectroscopy in x-rays has hinted at the presence of powerful outflows.aims: we report observations taken with the integral field unit multi-unit spectroscopic explorer (muse) mounted at the very large telescope of ngc 1313 x-1 in order to confirm the presence of a nebula inflated by the winds, investigate its main sources of ionisation and estimate the mechanical output of the source.methods: we investigated the morphology, kinematics, and sources of ionisation of the bubble through the study of the main nebular lines. we compared the main line ratios with spatially resolved baldwin-phillips-terlevich diagrams and with the prediction from radiative shock libraries, which allows us to differentiate regions excited by shocks from those excited by extreme ultraviolet and x-ray radiation.results: we detect a bubble of 452 × 266 pc in size, roughly centred around the ulx, which shows clear evidence of shock ionisation in the outer edges. we estimate shock velocities to be in the ≈160 − 180 km s−1 range based on the line ratios. this suggests that an average and continuous outflow power of ∼(2 − 4.5)×1040 erg s−1 over a timescale of (4.5 − 7.8)×105 yr is required to inflate the bubble. in the interior of the bubble and closer to the ulx we detect an extended (∼140 pc) x-ray ionised region. additionally, we detect two supernova remnants coincidentally close to the ulx bubble of which we also report age and explosion energy estimates.conclusions: the elongated morphology and the kinematics of the bubble strongly suggest that the bubble is being inflated by winds and/or jets emanating from the central source, supporting the presence of winds found through x-ray spectroscopy. the estimated mechanical power is comparable to or higher than the x-ray luminosity of the source, which provides additional evidence in support of ngc 1313 x-1 harbouring a super-eddington accretor. | muse spectroscopy of the ulx ngc 1313 x-1: a shock-ionised bubble, an x-ray photoionised nebula, and two supernova remnants |
the baldwin, philips, & terlevich diagram of [o iii]/hβ versus [n ii]/hα (hereafter n2-bpt) has long been used as a tool for classifying galaxies based on the dominant source of ionizing radiation. recent observations have demonstrated that galaxies at z ~ 2 reside offset from local galaxies in the n2-bpt space. in this paper, we conduct a series of controlled numerical experiments to understand the potential physical processes driving this offset. we model nebular line emission in a large sample of galaxies, taken from the simba cosmological hydrodynamic galaxy formation simulation, using the cloudy photoionization code to compute the nebular line luminosities from h ii regions. we find that the observed shift toward higher [o iii]/hβ and [n ii]/hα values at high redshift arises from sample selection: when we consider only the most massive galaxies m * ~ 1010-11 m ⊙, the offset naturally appears, due to their high metallicities. we predict that deeper observations that probe lower-mass galaxies will reveal galaxies that lie on a locus comparable to z ~ 0 observations. even when accounting for samples-selection effects, we find that there is a subtle mismatch between simulations and observations. to resolve this discrepancy, we investigate the impact of varying ionization parameters, h ii region densities, gas-phase abundance patterns, and increasing radiation field hardness on n2-bpt diagrams. we find that either decreasing the ionization parameter or increasing the n/o ratio of galaxies at fixed o/h can move galaxies along a self-similar arc in n2-bpt space that is occupied by high-redshift galaxies. | the bpt diagram in cosmological galaxy formation simulations: understanding the physics driving offsets at high redshift |
context. r aqr is a symbiotic binary system consisting of a mira variable, a hot companion with a spectacular jet outflow, and an extended emission line nebula. because of its proximity to the sun, this object has been studied in much detail with many types of high resolution imaging and interferometric techniques. we have used r aqr as test target for the visual camera subsystem zimpol, which is part of the new extreme adaptive optics (ao) instrument sphere at the very large telescope (vlt).aims: we describe sphere/zimpol test observations of the r aqr system taken in hα and other filters in order to demonstrate the exceptional performance of this high resolution instrument. we compare our observations with data from the hubble space telescope (hst) and illustrate the complementarity of the two instruments. we use our data for a detailed characterization of the inner jet region of r aqr.methods: we analyze the high resolution ≈ 25 mas images from sphere/zimpol and determine from the hα emission the position, size, geometric structure, and line fluxes of the jet source and the clouds in the innermost region <2'' (<400 au) of r aqr. the data are compared to simultaneous hst line filter observations. the hα fluxes and the measured sizes of the clouds yield hα emissivities for many clouds from which one can derive the mean density, mass, recombination time scale, and other cloud parameters.results: our hα data resolve for the first time the r aqr binary and we measure for the jet source a relative position 45 mas west (position angle -89.5°) of the mira. the central jet source is the strongest hα component with a flux of about 2.5 × 10-12 erg cm-2 s-1. north east and south west from the central source there are many clouds with very diverse structures. within 0.5'' (100 au) we see in the sw a string of bright clouds arranged in a zig-zag pattern and, further out, at 1''-2'', fainter and more extended bubbles. in the n and ne we see a bright, very elongated filamentary structure between 0.2''-0.7'' and faint perpendicular "wisps" further out. some jet clouds are also detected in the zimpol [o i] and he i filters, as well as in the hst-wfc3 line filters for hα, [o iii], [n ii], and [o i]. we determine jet cloud parameters and find a very well defined correlation ne ∝ r-1.3 between cloud density and distance to the central binary. densities are very high with typical values of ne ≈ 3 × 105 cm-3 for the "outer" clouds around 300 au, ne ≈ 3 × 106 cm-3 for the "inner" clouds around 50 au, and even higher for the central jet source. the high ne of the clouds implies short recombination or variability timescales of a year or shorter.conclusions: hα high resolution data provide a lot of diagnostic information for the ionized jet gas in r aqr. future hα observations will provide the orientation of the orbital plane of the binary and allow detailed hydrodynamical investigations of this jet outflow and its interaction with the wind of the red giant companion. the reduced hα image given in fig. 6 is only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/602/a53 | sphere/zimpol observations of the symbiotic system r aquarii. i. imaging of the stellar binary and the innermost jet clouds |
we present the final data release of the apex low-redshift legacy survey for molecular gas (allsmog), comprising co(2-1) emission line observations of 88 nearby, low-mass (108.5<m∗ [m⊙] < 1010) star-forming galaxies carried out with the 230 ghz apex-1 receiver on the apex telescope. the main goal of allsmog is to probe the molecular gas content of more typical and lower stellar mass galaxies than have been studied by previous co surveys. we also present iram 30 m observations of the co(1-0) and co(2-1) emission lines in nine galaxies aimed at increasing the m∗< 109m⊙ sample size. in this paper we describe the observations, data reduction and analysis methods and we present the final co spectra together with archival hi 21 cm line observations for the entire sample of 97 galaxies. at the sensitivity limit of allsmog, we register a total co detection rate of 47%. galaxies with higher m∗, sfr, nebular extinction (av), gas-phase metallicity (o/h), and hi gas mass have systematically higher co detection rates. in particular, the parameter according to which co detections and non-detections show the strongest statistical differences is the gas-phase metallicity, for any of the five metallicity calibrations examined in this work. we investigate scaling relations between the co(1-0) line luminosity (l'co(1-0)) and galaxy-averaged properties using allsmog and a sub-sample of cold gass for a total of 185 sources that probe the local main sequence (ms) of star-forming galaxies and its ± 0.3 dex intrinsic scatter from m∗ = 108.5m⊙ to m∗ = 1011m⊙. l'co(1-0) is most strongly correlated with the sfr, but the correlation with m∗ is closer to linear and almost comparably tight. the relation between l'co(1-0) and metallicity is the steepest one, although deeper co observations of galaxies with av< 0.5 mag may reveal an as much steep correlation with av. our results suggest that star-forming galaxies across more than two orders of magnitude in m∗ obey similar scaling relations between co luminosity and the galaxy properties examined in this work. besides sfr, the co luminosity is likely most fundamentally linked to m∗, although we note that stellar mass alone cannot explain all of the variation in co emission observed as a function of o/h and mhi. | the final data release of allsmog: a survey of co in typical local low-m∗ star-forming galaxies |
we study a sample of 16 type ia supernovae (sne ia) having both spectroscopic and photometric observations within 2-3 days after the first light. the early b - v colors of such a sample tend to show a continuous distribution. for objects with normal ejecta velocity (nv), the c ii λ6580 feature is always visible in the early spectra, while it is absent or very weak in the high-velocity (hv) counterpart. moreover, the velocities of the detached high-velocity features (hvfs) of the ca ii near-ir triplet (cair3) above the photosphere are found to be much higher in hv objects than in nv objects, with typical values exceeding 30,000 km s-1 at 2-3 days. we further analyze the relation between the velocity shift of late-time [fe ii] lines (v[fe ii]) and host galaxy mass. we find that all hv objects have redshifted v[fe ii], while nv objects have both blue- and redshifted v[fe ii]. it is interesting to point out that the objects with redshifted v[fe ii] are all located in massive galaxies, implying that hv and a portion of nv objects may have similar progenitor metallicities and explosion mechanisms. we propose that, with a geometric/projected effect, the he-detonation model may account for the similarity in birthplace environment and the differences seen in some sne ia, including b - v colors, c ii features, cair3 hvfs at early times, and v[fe ii] in the nebular phase. nevertheless, some features predicted by he-detonation simulation, such as the rapidly decreasing light curve, deviate from the observations, and some nv objects with blueshifted nebular v[fe ii] may involve other explosion mechanisms. | can the helium-detonation model explain the observed diversity of type ia supernovae? |
the earth and other rocky planets and planetesimals in the solar system formed through the mixing of materials from various radial locations in the solar nebula. this primordial material likely had a range of oxidation states as well as bulk compositions and volatile abundances. we investigate the oxygen fugacity produced by the outgassing of mixtures of solid meteoritic material, which approximate the primitive nebular materials. we find that the gas composition and oxygen fugacity of binary and ternary mixtures of meteoritic materials vary depending on the proportion of reduced versus oxidized material, and also find that mixtures using differentiated materials do not show the same oxygen fugacity trends as those using similarly reduced but undifferentiated materials. we also find that simply mixing the gases produced by individual meteoritic materials together does not correctly reproduce the gas composition or oxygen fugacity of the binary and ternary mixtures. we provide tabulated fits for the oxygen fugacities of all of the individual materials and binary mixtures that we investigate. these values may be useful in planetary formation models, models of volatile transport on planetesimals or meteorite parent bodies, or models of trace element partitioning during metal-silicate fractionation. | redox states of initial atmospheres outgassed on rocky planets and planetesimals |
the bright southern star l2 pup is a particularly prominent asymptotic giant branch (agb) star, located at a distance of only 64 pc. we report new adaptive optics observations of l2 pup at visible wavelengths with the sphere/zimpol instrument of the vlt that confirm the presence of the circumstellar dust disk discovered recently. this disk is seen almost almost edge-on at an inclination of 82◦. the signature of its three-dimensional structure is clearly observed in the map of the degree of linear polarization pl. we identify the inner rim of the disk through its polarimetric signature at a radius of 6 au from the agb star. the zimpol intensity images in the v and r bands also reveal a close-in secondary source at a projected separation of 2 au from the primary. identification of the spectral type of this companion is uncertain due to the strong reddening from the disk, but its photometry suggests that it is a late k giant with comparable mass to the agb star. we present refined physical parameters for the dust disk derived using the radmc-3d radiative transfer code. we also interpret the pl map using a simple polarization model to infer the three-dimensional structure of the envelope. interactions between the inner binary system and the disk apparently form spiral structures that propagate along the orthogonal axis to the disk to form streamers. two dust plumes propagating orthogonally to the disk are also detected. they originate in the inner stellar system and are possibly related to the interaction of the wind of the two stars with the material in the disk. based on the morphology of the envelope of l2 pup, we propose that this star is at an early stage in the formation of a bipolar planetary nebula. based on observations made with eso telescopes at paranal observatory, under eso science verification program 60.a-9367(a). | the dust disk and companion of the nearby agb star l2 puppis. sphere/zimpol polarimetric imaging at visible wavelengths |
we report the identification of extended lyα nebulae at z ≃ 3.3 in the hubble ultra deep field (hudf, ≃40 kpc × 80 kpc) and behind the hubble frontier field galaxy cluster macsj0416 (≃40 kpc), spatially associated with groups of star-forming galaxies. vlt/muse integral field spectroscopy reveals a complex structure with a spatially varying double-peaked lyα emission. overall, the spectral profiles of the two lyα nebulae are remarkably similar, both showing a prominent blue emission, more intense and slightly broader than the red peak. from the first nebula, located in the hudf, no x-ray emission has been detected, disfavouring the possible presence of active galactic nuclei. spectroscopic redshifts have been derived for 11 galaxies within 2 arcsec from the nebula and spanning the redshift range 1.037 < z < 5.97. the second nebula, behind macsj0416, shows three aligned star-forming galaxies plausibly associated with the emitting gas. in both systems, the associated galaxies reveal possible intense rest-frame-optical nebular emissions lines [o iii] λλ4959, 5007+hβ with equivalent widths as high as 1500 å rest frame and star formation rates ranging from a few to tens of solar masses per year. a possible scenario is that of a group of young, star-forming galaxies emitting ionizing radiation that induces lyα fluorescence, therefore revealing the kinematics of the surrounding gas. also lyα powered by star formation and/or cooling radiation may resemble the double-peaked spectral properties and the morphology observed here. if the intense blue emission is associated with inflowing gas, then we may be witnessing an early phase of galaxy or a proto-cluster (or group) formation. | illuminating gas inflows/outflows in the muse deepest fields: lyα nebulae around forming galaxies at z ≃ 3.3 |
a previous spectroscopic study identified the very massive o2 iii star vfts 16 in the tarantula nebula as a runaway star based on its peculiar line-of-sight velocity. we use the gaia dr2 catalog to measure the relative proper motion of vfts 16 and nearby bright stars to test if this star might have been ejected from the central cluster, r136, via dynamical ejection. we find that the position angle and magnitude of the relative proper motion (0.338±0.046 mas yr-1, or approximately 80±11 km s-1) of vfts 16 are consistent with ejection from r136 approximately 1.5±0.2 myr ago, very soon after the cluster was formed. there is some tension with the presumed age of vfts 16 that, from published stellar parameters, cannot be greater than 0.9+0.3-0.2 myr. older ages for this star would appear to be prohibited due to the absence of he i lines in its optical spectrum, since this sets a firm lower limit on its effective temperature. the dynamical constraints may imply an unusual evolutionary history for this object, perhaps indicating it is a merger product. gaia dr2 also confirms that another very massive star in the tarantula nebula, vfts 72 (alias bi 253; o2 iii-v(n)((f*)), is also a runaway on the basis of its proper motion as measured by gaia. while its tangential proper motion (0.392±0.062 mas yr-1 or 93±15 km s-1) would be consistent with dynamical ejection from r136 approximately 1 myr ago, its position angle is discrepant with this direction at the 2σ level. from their gaia dr2 proper motions we conclude that the two ∼100 m⊙ o2 stars, vfts 16 and vfts 72, are fast runaway stars, with space velocities of around 100 km s-1 relative to r136 and the local massive star population. the dynamics of vfts 16 are consistent with it having been ejected from r136, and this star therefore sets a robust lower limit on the age of the central cluster of ∼1.3 myr. | gaia dr2 reveals a very massive runaway star ejected from r136 |
nanosims c-, n-, and o-isotopic mapping of matrix in co3.0 chondrite dominion range (dom) 08006 revealed it to have in its matrix the highest abundance of presolar o-rich grains (257 +76/-96 ppm, 2σ) of any meteorite. it also has a matrix abundance of presolar sic of 35 (+25/-17, 2σ) ppm, similar to that seen across primitive chondrite classes. this provides additional support to bulk isotopic and petrologic evidence that dom 08006 is the most primitive known co meteorite. transmission electron microscopy of five presolar silicate grains revealed one to have a composite mineralogy similar to larger amoeboid olivine aggregates and consistent with equilibrium condensation, two non-stoichiometric amorphous grains, and two olivine grains, though one is identified as such solely based on its composition. we also found insoluble organic matter (iom) to be present primarily as sub-micron inclusions with ranges of c- and n-isotopic anomalies similar to those seen in primitive cr chondrites and interplanetary dust particles. in contrast to other primitive extraterrestrial materials, h isotopic imaging showed normal and homogeneous d/h. most likely, dom 08006 and other co chondrites accreted a similar complement of primitive and isotopically anomalous organic matter to that found in other chondrite classes and idps, but the very limited amount of thermal metamorphism experienced by dom 08006 has caused loss of d-rich organic moieties, while not substantially affecting either the molecular carriers of c and n anomalies or most inorganic phases in the meteorite. one c-rich grain that was highly depleted in 13c and 15n was identified; we propose it originated in the sun's parental molecular cloud. | high abundances of presolar grains and 15n-rich organic matter in co3.0 chondrite dominion range 08006 |
this paper compares parameters that characterize vegetation flexibility effects on flow resistance and drag. drag forces have been measured in a flume for simple cylindrical obstructions of the same shape and size but with different flexibility under several flow conditions. this data set is used to fit drag parameters and to relate their value to flexibility through the cauchy number. a formulation is presented where the drag coefficient is evaluated as a function of a new calibration velocity parameter which is related to the elastic modulus of the obstruction. while the use of a vogel exponent and reference velocity provides a similar response, the reference velocity when used is somewhat nebulous and appears to have a critical impact on the parameter and the drag force calculated. the proposed formulation for drag reduction is more consistently estimated for the range of flexibilities in this study. | drag force parameters of rigid and flexible vegetal elements |
we present a semi-empirical calibration between the metallicity (z) of seyfert 2 active galactic nuclei and the n2 = log([n ii]λ6584/h α) emission-line intensity ratio. this calibration was derived through the [o iii]λ5007/[o ii]λ3727 versus n2 diagram containing observational data and photoionization model results obtained with the cloudy code. the observational sample consists of 463 confirmed seyfert 2 nuclei (redshift z ≲ 0.4) taken from the sloan digital sky survey dr7 data set. the obtained z-n2 relation is valid for the range 0.3 ≲ (z/z_{⊙ }) ≲ 2.0 that corresponds to -0.7 ≲ (n2) ≲ 0.6. the effects of varying the ionization parameter (u), electron density and the slope of the spectral energy distribution on the z estimations are of the order of the uncertainty produced by the error measurements of n2. this result indicates the large reliability of our z -n2 calibration. a relation between u and the [o iii]/[o ii] line ratio, almost independent of other nebular parameter, was obtained. | chemical abundances of seyfert 2 agns - ii. n2 metallicity calibration based on sdss |
in this second paper in a series of papers based on the most-up-to-date catalogue of symbiotic stars (systs), we present a new approach for identifying and distinguishing systs from other h α emitters in photometric surveys using machine learning algorithms such as classification tree, linear discriminant analysis, and k-nearest neighbour. the motivation behind this work is to seek for possible colour indices in the regime of near- and mid-infrared covered by the 2mass and wise surveys. a number of diagnostic colour-colour diagrams are generated for all the known galactic systs and several classes of stellar objects that mimic systs such as planetary nebulae, post-agb, mira, single k and m giants, cataclysmic variables, be, aebe, yso, weak and classical t tauri stars, and wolf-rayet. the classification tree algorithm unveils that primarily j-h, w1-w4, and ks-w3, and secondarily, h-w2, w1-w2, and w3-w4 are ideal colour indices to identify systs. linear discriminant analysis method is also applied to determine the linear combination of 2mass and allwise magnitudes that better distinguish systs. the probability of a source being an syst is determined using the k-nearest neighbour method on the lda components. by applying our classification tree model to the list of candidate systs (paper i), the iphas list of candidate systs, and the dr2 vphas + catalogue, we find 125 (72 new candidates) sources that pass our criteria while we also recover 90 per cent of the known galactic systs. | a machine learning approach for identification and classification of symbiotic stars using 2mass and wise |
veritas is a ground-based gamma-ray instrument operating at the fred lawrence whipple observatory in southern arizona. with an array of four imaging atmospheric cherenkov telescopes (iacts), veritas is designed to measure gamma rays with energies from $\sim$ 85 gev up to > 30 tev. it has a sensitivity to detect a point source with a flux of 1$\%$ of the crab nebula flux within 25 hours. since its first light observation in 2007, veritas has continued its successful mission for over seven years with two major upgrades: the relocation of telescope 1 in 2009 and a camera upgrade in 2012. we present the performance of veritas and how it has improved with these upgrades. | performance of the veritas experiment |
we present x-ray spectral analysis of 20 point-like x-ray sources detected in chandra planetary nebula survey observations of 59 planetary nebulae (pne) in the solar neighborhood. most of these 20 detections are associated with luminous central stars within relatively young, compact nebulae. the vast majority of these point-like x-ray-emitting sources at pn cores display relatively "hard" (>=0.5 kev) x-ray emission components that are unlikely to be due to photospheric emission from the hot central stars (cspn). instead, we demonstrate that these sources are well modeled by optically thin thermal plasmas. from the plasma properties, we identify two classes of cspn x-ray emission: (1) high-temperature plasmas with x-ray luminosities, l x, that appear uncorrelated with the cspn bolometric luminosity, l bol and (2) lower-temperature plasmas with l x/l bol ~ 10-7. we suggest these two classes correspond to the physical processes of magnetically active binary companions and self-shocking stellar winds, respectively. in many cases this conclusion is supported by corroborative multiwavelength evidence for the wind and binary properties of the pn central stars. by thus honing in on the origins of x-ray emission from pn central stars, we enhance the ability of cspn x-ray sources to constrain models of pn shaping that invoke wind interactions and binarity. | the chandra planetary nebula survey (chanplans). iii. x-ray emission from the central stars of planetary nebulae |
we present the first direct image of the high-metallicity gas component in a planetary nebula (ngc 6778), taken with the osiris blue tunable filter centered on the o ii λ4649+50 å optical recombination lines (orls) at the 10.4 m gran telescopio canarias. we show that the emission of these faint o ii orls is concentrated in the central parts of the planetary nebula and is not spatially coincident either with emission coming from the bright [o iii] λ5007 å collisionally excited line (cel) or the bright hα recombination line. from monochromatic emission line maps taken with vimos at the 8.2 m very large telescope, we find that the spatial distribution of the emission from the auroral [o iii] λ4363 line resembles that of the o ii orls but differs from nebular [o iii] λ5007 cel distribution, implying a temperature gradient inside the planetary nebula. the centrally peaked distribution of the o ii emission and the differences with the [o iii] and h i emission profiles are consistent with the presence of an h-poor gas whose origin may be linked to the binarity of the central star. however, determination of the spatial distribution of the orls and cels in other pne and a comparison of their dynamics are needed to further constrain the geometry and ejection mechanism of the metal-rich (h-poor) component and hence, understand the origin of the abundance discrepancy problem in pne. | imaging the elusive h-poor gas in the high adf planetary nebula ngc 6778 |
parameterizing hypothetical violation of lorentz invariance at high energies using the framework of effective quantum field theory, we discuss its effect on the formation of atmospheric showers by very-high-energy gamma rays. in the scenario where lorentz invariance violation leads to a decrease of the photon velocity with energy the formation of the showers is suppressed compared to the lorentz invariant case. absence of such suppression in the high-energy part of spectrum of the crab nebula measured independently by hegra and h.e.s.s. collaborations is used to set lower bounds on the energy scale of lorentz invariance violation. these bounds are competitive with the strongest existing constraints obtained from timing of variable astrophysical sources and the absorption of tev photons on the extragalactic background light. they will be further improved by the next generation of multi-tev gamma-ray observatories. | constraints on violation of lorentz invariance from atmospheric showers initiated by multi-tev photons |
this is the first paper of a series dedicated to nebular physics and the chemical evolution of nearby galaxies by investigating large samples of h ii regions with the canada-france-hawaii telescope imaging spectrograph sitelle (spectro-imageur à transformée de fourier pour l'étude en long et en large des raies d'émission). we present a technique adapted to imaging spectroscopy to identify and extract parameters from 4285 h ii region candidates found in the disc of ngc 628. using both the spatial and spectral capabilities of sitelle, our technique enables the extraction of the position, dust extinction, velocity, h α profile, diffuse ionized gas (dig) background, luminosity, size, morphological type, and the emission-line fluxes for individual spaxels and the integrated spectrum for each region. we have produced a well-sampled h ii region luminosity function and studied its variation with galactocentric radius and level of the dig background. we found a slope α of -1.12 ± 0.03 with no evidence of a break at high luminosity. based on the width of the region profile, bright regions are rather compact, while faint regions are seen over a wide range of sizes. the radius function reveals a slope of -1.81 ± 0.02. bpt diagrams of the individual spaxels and integrated line ratios confirm that most detections are h ii regions. also, maps of the line ratios show complex variations of the ionization conditions within h ii regions. all this information is compiled in a new catalogue for h ii regions. the objective of this data base is to provide a complete sample which will be used to study the whole parameter space covered by the physical conditions in active star-forming regions. | ngc628 with sitelle: i. imaging spectroscopy of 4285 h ii region candidates |
recently, three stellar sequences separated in age by about 1 myr were discovered in the orion nebula cluster (onc; beccari et al. 2017). kroupa et al. (2018) suggest that such small dense subpopulations eject all their ob stars via the decay of unstable few-body systems such that the gas can recombine and form new stars. this explains the multisequence phenomenon without introducing an extra mechanism into star formation theory. in this work, we apply the recently updated primordial binary distribution model (belloni et al. 2017; implemented here in a new version of mcluster) and perform a large set of direct n-body simulations to investigate the feasibility of this dynamical scenario. our results suggest that if 3-4 ob stars in the onc formed primordially mass-segregated in the cluster centre with a maximum separation of about 0.003 pc, all ob stars have a high chance ({≈}50{-}70 {{ per cent}}) to escape from the centre and do not come back within 1 myr and the dynamical ejection scenario is a viable channel to form short-age-interval multipopulation sequences as observed in the onc. this is also consistent with self-regulated star formation. | complete ejection of ob stars from very young star clusters and the formation of multiple populations |
the fractionation of nitrogen (n) in star-forming regions is a poorly understood process. to put more stringent observational constraints on the n-fractionation, we have observed with the iram-30-m telescope a large sample of 66 cores in massive star-forming regions. we targeted the (1-0) rotational transition of hn13c, hc15n, h13cn and hc15n, and derived the 14n/15n ratio for both hcn and hnc. we have completed this sample with that already observed by colzi et al., and thus analysed a total sample of 87 sources. the 14n/15n ratios are distributed around the proto-solar nebula value with a lower limit near the ta value (∼272). we have also derived the 14n/15n ratio as a function of the galactocentric distance and deduced a linear trend based on unprecedented statistics. the galactocentric dependences that we have found are consistent, in the slope, with past works but we have found a new local 14n/15n value of ∼400, i.e. closer to the prosolar nebula value. a second analysis was done, and a parabolic galactocentric trend was found. comparison with galactic chemical evolution models shows that the slope until 8 kpc is consistent with the linear analysis, while the flattening trend above 8 kpc is well reproduced by the parabolic analysis. | nitrogen fractionation in high-mass star-forming cores across the galaxy |
we apply novel survival analysis techniques to investigate the relationship between a number of the properties of galaxies and their atomic (m h i ) and molecular ({m}{{{h}}2}) gas mass, with the aim of devising efficient, effective empirical estimators of the cold gas content in galaxies that can be applied to large optical galaxy surveys. we find that dust attenuation, av , of both the continuum and nebular emission, shows significant partial correlations with {m}{{{h}}2}, after controlling for the effect of star formation rate (sfr). the partial correlation between avand m h i , however, is weak. this is expected because in poorly dust-shielded regions molecular hydrogen is dissociated by far-ultraviolet photons. we also find that the stellar half-light radius, r 50, shows significant partial correlations with both {m}{{{h}}2} and m h i . this hints at the importance of environment (e.g., galactocentric distance) on the gas content of galaxies and the interplay between gas and sfr. we fit multiple regression to summarize the median, mean, and the 0.15/0.85 quantile multivariate relationships among {m}{{{h}}2}, av , metallicity, and/or r 50. a linear combination of avand metallicity (inferred from stellar mass) or avand r 50, can estimate molecular gas masses within ∼2.5-3 times the observed masses. if sfr is used in addition, {m}{{{h}}2} can be predicted to within a factor ≲2. in this case, avand r 50 are the two best secondary parameters that improve the primary relation between {m}{{{h}}2} and sfr. likewise, m h ican be predicted to within a factor ≲3 using r 50 and sfr. | dirt-cheap gas scaling relations: using dust absorption, metallicity, and galaxy size to predict gas masses for large samples of galaxies |
the final steps of the evolution of massive stars leading to a supernova explosion, in particular the mass-loss mechanism, is an important open problem in astrophysics. stripped-envelope supernovae (sesne) are explosions of massive stars where a large amount of the outer envelope has been stripped away before the explosion: types iib, ib and ic in order of increasing degree of envelope stripping1-3. in this work, an analysis of late-time nebular spectra of sesne is presented. the results show that the progenitors of sne iib and ib are indistinguishable except for the residual amount of the h-rich envelope. the progenitors of sne ic are distinctly different in the nature of the carbon-oxygen (c+o) core, which is interpreted to be more massive than in sne iib and ib. these findings strongly suggest that different mechanisms are responsible for the removal of the outer h-rich envelope and the deeper he-rich layer. | a hybrid envelope-stripping mechanism for massive stars from supernova nebular spectroscopy |
high-energy astrophysical systems frequently contain collision-less relativistic plasmas that are heated by turbulent cascades and cooled by emission of radiation. understanding the nature of this radiative turbulence is a frontier of extreme plasma astrophysics. in this paper, we use particle-in-cell simulations to study the effects of external inverse compton radiation on turbulence driven in an optically thin, relativistic pair plasma. we focus on the statistical steady state (where injected energy is balanced by radiated energy) and perform a parameter scan spanning from low magnetization to high magnetization (0.04 ≲ σ ≲ 11). we demonstrate that the global particle energy distributions are quasi-thermal in all simulations, with only a modest population of non-thermal energetic particles (extending the tail by a factor of ∼2). this indicates that non-thermal particle acceleration (observed in similar non-radiative simulations) is quenched by strong radiative cooling. the quasi-thermal energy distributions are well fit by analytic models in which stochastic particle acceleration (due to, e.g. second-order fermi mechanism or gyroresonant interactions) is balanced by the radiation reaction force. despite the efficient thermalization of the plasma, non-thermal energetic particles do make a conspicuous appearance in the anisotropy of the global momentum distribution as highly variable, intermittent beams (for high magnetization cases). the beamed high-energy particles are spatially coincident with intermittent current sheets, suggesting that localized magnetic reconnection may be a mechanism for kinetic beaming. this beaming phenomenon may explain rapid flares observed in various astrophysical systems (such as blazar jets, the crab nebula, and sagittarius a*). | kinetic turbulence in shining pair plasma: intermittent beaming and thermalization by radiative cooling |
a very small fraction of (runaway) massive stars have masses exceeding 60-70 m_{⊙} and are predicted to evolve as luminous blue variable and wolf-rayet stars before ending their lives as core-collapse supernovae. our 2d axisymmetric hydrodynamical simulations explore how a fast wind (2000 km s^{-1}) and high mass-loss rate (10^{-5} m_{⊙} yr^{-1}) can impact the morphology of the circumstellar medium. it is shaped as 100 pc-scale wind nebula that can be pierced by the driving star when it supersonically moves with velocity 20-40 km s^{-1} through the interstellar medium (ism) in the galactic plane. the motion of such runaway stars displaces the position of the supernova explosion out of their bow shock nebula, imposing asymmetries to the eventual shock wave expansion and engendering cygnus-loop-like supernova remnants. we conclude that the size (up to more than 200 pc) of the filamentary wind cavity in which the chemically enriched supernova ejecta expand, mixing efficiently the wind and ism materials by at least 10{{ per cent}} in number density, can be used as a tracer of the runaway nature of the very massive progenitors of such 0.1 myr old remnants. our results motivate further observational campaigns devoted to the bow shock of the very massive stars bd+43°3654 and to the close surroundings of the synchrotron-emitting wolf-rayet shell g2.4+1.4. | wind nebulae and supernova remnants of very massive stars |
recent spitzer/infrared array camera (irac) photometric observations have revealed that rest-frame optical emission lines contribute significantly to the broad-band fluxes of high-redshift galaxies. specifically, in the narrow redshift range z ∼ 5.1-5.4 the [3.6]-[4.5] colour is expected to be very red, due to contamination of the 4.5 μm band by the dominant hα line, while the 3.6 μm filter is free of nebular emission lines. we take advantage of new reductions of deep spitzer/irac imaging over the great observatories origins deep survey-north+south fields (labbé et al. 2015) to obtain a clean measurement of the mean hα equivalent width (ew) from the [3.6]-[4.5] colour in the redshift range z = 5.1-5.4. the selected sources either have measured spectroscopic redshifts (13 sources) or lie very confidently in the redshift range z = 5.1-5.4 based on the photometric redshift likelihood intervals (11 sources). our zphot = 5.1-5.4 sample and zspec = 5.10-5.40 spectroscopic sample have a mean [3.6]-[4.5] colour of 0.31 ± 0.05 and 0.35 ± 0.07 mag, implying a rest-frame ew (hα+[n ii]+[s ii]) of 665 ± 53 and 707 ± 74 å, respectively, for sources in these samples. these values are consistent albeit slightly higher than derived by stark et al. at z ∼ 4, suggesting an evolution to higher values of the hα+[n ii]+[s ii] ew at z > 2. using the 3.6 μm band, which is free of emission line contamination, we perform robust spectral energy distribution fitting and find a median specific star formation rate of ssfr = 17_{-5}^{+2} gyr-1, 7_{-2}^{+1}× higher than at z ∼ 2. we find no strong correlation (<2σ) between the hα+[n ii]+[s ii] ew and the stellar mass of sources. before the advent of jwst, improvements in these results will come through an expansion of current spectroscopic samples and deeper spitzer/irac measurements. | mean hα+[n ii]+[s ii] ew inferred for star-forming galaxies atz ∼ 5.1-5.4 using high-qualityspitzer/irac photometry |
an analysis of the type ic supernova (sn) 2004aw is performed by means of models of the photospheric and nebular spectra and of the bolometric light curve. sn 2004aw is shown not to be 'broad-lined', contrary to previous claims, but rather a 'fast-lined' sn ic. the spectral resemblance to the narrow-lined type ic sn 1994i, combined with the strong nebular [o i] emission and the broad light curve, points to a moderately energetic explosion of a massive c+o star. the ejected 56ni mass is ≈0.20 m⊙. the ejecta mass as constrained by the models is ∼3-5 m⊙, while the kinetic energy is estimated as ek ∼3-6 × 1051 erg. the ratio ek/m⊙, the specific energy that influences the shape of the spectrum, is therefore ≈1. the corresponding zero-age main-sequence mass of the progenitor star may have been ∼23-28 m⊙. tests show that a flatter outer density structure may have caused a broad-lined spectrum at epochs before those observed without affecting the later epochs when data are available, implying that our estimate of ek is a lower limit. sn 2004aw may have been powered by either a collapsar or a magnetar, both of which have been proposed for gamma-ray burst sne. evidence for this is seen in the innermost layers, which appear to be highly aspherical as suggested by the nebular line profiles. however, any engine was not extremely powerful, as the outer ejecta are more consistent with a spherical explosion and no gamma-ray burst was detected in coincidence with sn 2004aw. | modelling the type ic sn 2004aw: a moderately energetic explosion of a massive c+o star without a grb |
the importance of long-period binaries for the formation and evolution of planetary nebulae is still rather poorly understood, which in part is due to the lack of central star systems that are known to comprise such long-period binaries. here, we report on the latest results from the on-going mercator-hermes survey for variability in the central stars of planetary nebulae. we present a study of the central stars of ngc 1514, bd+30°623, the spectrum of which shows features associated with a hot nebular progenitor as well as a possible a-type companion. cross-correlation of high-resolution hermes spectra against synthetic spectra shows the system to be a highly eccentric (e 0.5) double-lined binary with a period of 3300 days. previous studies indicated that the cool component might be a horizontal branch star of mass 0.55 m⊙, but the observed radial velocity amplitudes rule out such a low mass. if we assume that the nebular symmetry axis and binary orbital plane are perpendicular, then the data are more consistent with a post-main-sequence star ascending towards the giant branch. we also present the continued monitoring of the central star of lotr 5, hd 112313, which has now completed one full cycle, allowing the orbital period (p 2700 days) and eccentricity (e 0.3) to be derived. to date, the orbital periods of bd+30°623 and hd 112313 are the longest to have been measured spectroscopically in the central stars of planetary nebulae. furthermore, these systems, along with bd+33°2642, comprise the only spectroscopic wide-binary central stars currently known. based on observations made with the mercator telescope, operated on the island of la palma by the flemish community, at the spanish observatorio del roque de los muchachos of the instituto de astrofísica de canarias.the radial velocity data for both objects are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/600/l9 | the long-period binary central stars of the planetary nebulae ngc 1514 and lotr 5 |
we use the pyneb 1.1.16 python package to evaluate the atomic datasets available for the spectral modeling of [fe ii] and [fe iii], which list level energies, a-values, and effective collision strengths. most datasets are reconstructed from the sources, and new ones are incorporated to be compared with observed and measured benchmarks. for [fe iii], we arrive at conclusive results that allow us to select the default datasets, while for [fe ii], the conspicuous temperature dependency on the collisional data becomes a deterrent. this dependency is mainly due to the singularly low critical density of the 3d7a4f9/2 metastable level that strongly depends on both the radiative and collisional data, although the level populating by fluorescence pumping from the stellar continuum cannot be ruled out. a new version of pyneb (1.1.17) is released containing the evaluated datasets. | atomic data assessment with pyneb: radiative and electron impact excitation rates for [fe ii] and [fe iii] |
we obtain a magnitude-limited sample of andromeda (m 31) disc pne with chemical abundance estimated through the direct detection of the [o iii] 4363 å line. this leads to 205 and 200 pne with oxygen and argon abundances, respectively. we find that high- and low-extinction m 31 disc pne have statistically distinct argon and oxygen abundance distributions. in the radial range of 2-30 kpc, the older low-extinction disc pne are metal-poorer on average with a slightly positive radial oxygen abundance gradient (0.006 ± 0.003 dex kpc-1) and slightly negative for argon (-0.005 ± 0.003 dex kpc-1), while the younger high-extinction disc pne are metal-richer on average with steeper radial abundance gradients for both oxygen (-0.013 ± 0.006 dex kpc-1) and argon (-0.018 ± 0.006 dex kpc-1), similar to the gradients computed for the m 31 h ii regions. the m 31 disc abundance gradients are consistent with values computed from major merger simulations, with the majority of the low-extinction pne being the older pre-merger disc stars in the thicker disc, and the majority of the high-extinction pne being younger stars in the thin disc, formed during and after the merger event. the chemical abundance of the m 31 thicker disc has been radially homogenized because of the major merger. accounting for disc scale lengths, the positive radial oxygen abundance gradient of the m 31 thicker disc is in sharp contrast to the negative one of the mw thick disc. however, the thin discs of the mw and m 31 have remarkably similar negative oxygen abundance gradients. | the survey of planetary nebulae in andromeda (m31) - iv. radial oxygen and argon abundance gradients of the thin and thicker disc |
we present and discuss the optical spectrophotometric observations of the nearby (z = 0.087) type i superluminous supernova (slsn i) sn 2017gci, whose peak k-corrected absolute magnitude reaches mg = -21.5 mag. its photometric and spectroscopic evolution includes features of both slow- and of fast-evolving slsn i, thus favoring a continuum distribution between the two slsn-i subclasses. in particular, similarly to other slsne i, the multiband light curves (lcs) of sn 2017gci show two re-brightenings at about 103 and 142 d after the maximum light. interestingly, this broadly agrees with a broad emission feature emerging around 6520 å after ~51 d from the maximum light, which is followed by a sharp knee in the lc. if we interpret this feature as hα, this could support the fact that the bumps are the signature of late interactions of the ejecta with a (hydrogen-rich) circumstellar material. then we fitted magnetar- and csm-interaction-powered synthetic lcs on to the bolometric one of sn 2017gci. in the magnetar case, the fit suggests a polar magnetic field bp ≃ 6 × 1014 g, an initial period of the magnetar pinitial ≃ 2.8 ms, an ejecta mass $m_{\rm ejecta}\simeq 9\, \mathrm{m}_\odot $ and an ejecta opacity $\kappa \simeq 0.08\, \mathrm{cm}^{2}\, \rm{g}^{-1}$. a csm-interaction scenario would imply a csm mass $\simeq 5\, \mathrm{m}_\odot $ and an ejecta mass $\simeq 12\, \mathrm{m}_\odot $. finally, the nebular spectrum of phase + 187 d was modeled, deriving a mass of $\sim 10\, {\rm m}_\odot$ for the ejecta. our models suggest that either a magnetar or csm interaction might be the power sources for sn 2017gci and that its progenitor was a massive ($40\, {\rm m}_\odot$) star. | sn 2017gci: a nearby type i superluminous supernova with a bumpy tail |
context. stellar feedback is one of the fundamental factors regulating the evolution of galaxies. however, we still do not have access to strong observational constraints on the relative importance of the different feedback mechanisms (e.g. radiation, ionised gas pressure, stellar winds) in driving h ii region evolution and molecular cloud disruption. to quantify and compare the different feedback mechanisms, the size of an h ii region is crucial, whereas samples of well-resolved h ii regions are scarce.aims: we constrain the relative importance of the various feedback mechanisms from young massive star populations by resolving h ii regions across the disk of the nearby star-forming galaxy ngc 1672.methods: we combined measurements of ionised gas nebular lines obtained by phangs-muse, with high-resolution (psf fwhm ∼ 0.1″; ∼10 pc) imaging from hubble space telescope (hst) in both the narrow-band hα and broad-band (nuv, u, b, v, i) filters. we identified a sample of 40 isolated, compact h ii regions in the hst hα image. we measured the sizes of these h ii regions, which were previously unresolved in seeing-limited ground-based observations. in addition, we identified the ionisation source(s) for each h ii region from catalogues produced as part of the phangs-hst survey. in doing so, we were able to link young stellar populations with the properties of their surrounding h ii regions.results: the hst observations allowed us to resolve all 40 regions, with radii between 5 and 40 pc. the h ii regions investigated here are mildly dominated by thermal or wind pressure, yet their elevation above the radiation pressure is within the expected uncertainty range. we see that radiation pressure provides a substantially higher contribution to the total pressure than previously found in the literature over similar size scales. in general, we find higher pressures within more compact h ii regions, which is driven by the inherent size scaling relations of each pressure term, albeit with significant scatter introduced by the variation in the stellar population properties (e.g. luminosity, mass, age, metallicity).conclusions: for nearby galaxies, the combination of muse/vlt observations with stellar population and resolved hα observations from hst provides a promising approach that could yield the statistics required to map out how the importance of different stellar feedback mechanisms evolve over the lifetime of a h ii region. | linking stellar populations to h ii regions across nearby galaxies. i. constraining pre-supernova feedback from young clusters in ngc 1672 |
context. anomalies in the abundance measurements of short lived radionuclides in meteorites indicate that the protosolar nebulae was irradiated by a large number of energetic particles (e ≳ 10 mev). the particle flux of the contemporary sun cannot explain these anomalies. however, similar to t tauri stars the young sun was more active and probably produced enough high energy particles to explain those anomalies.aims: we aim to study the interaction of stellar energetic particles with the gas component of the disk (i.e. ionization of molecular hydrogen) and identify possible observational tracers of this interaction.methods: we used a 2d radiation thermo-chemical protoplanetary disk code to model a disk representative for t tauri stars. we used a particle energy distribution derived from solar flare observations and an enhanced stellar particle flux proposed for t tauri stars. for this particle spectrum we calculated the stellar particle ionization rate throughout the disk with an accurate particle transport model. we studied the impact of stellar particles for models with varying x-ray and cosmic-ray ionization rates.results: we find that stellar particle ionization has a significant impact on the abundances of the common disk ionization tracers hco+ and n2h+, especially in models with low cosmic-ray ionization rates (e.g. 10-19 s-1 for molecular hydrogen). in contrast to cosmic rays and x-rays, stellar particles cannot reach the midplane of the disk. therefore molecular ions residing in the disk surface layers are more affected by stellar particle ionization than molecular ions tracing the cold layers and midplane of the disk.conclusions: spatially resolved observations of molecular ions tracing different vertical layers of the disk allow to disentangle the contribution of stellar particle ionization from other competing ionization sources. modelling such observations with a model like the one presented here allows to constrain the stellar particle flux in disks around t tauri stars. | stellar energetic particle ionization in protoplanetary disks around t tauri stars |
cedrela species occur within the tropical montane cloud forest (tmcf) and rainforest in north america (mexico), central and south america. we assessed the hypothesis that functional xylem hydraulic architecture might be influenced by specific climatic variations. we investigated the effect of climate on tree-ring width and vessel traits (diameter, vessel density, vulnerability index and hydraulic diameter) of three relict-endemic and threatened cedrela species (cedrela fissilis, c. nebulosa and c. angustifolia) inhabiting peruvian tropical andean cloud forests. all cedrela species showed a significant reduction in radial growth and adjusted vessel trait linked with temperature, precipitation, and evapotranspiration. ring-width and vessel traits showed adaptation within cedrela species, crucial to understanding a rough indication of the plant's ability to withstand drought-induced embolism or cavitation. our results provide evidence for hydraulic mechanisms that determine specific wood anatomical functionality to climatic variation and drought responses. therefore, changing the frequency or intensity of future drought events might exceed the adaptive limits of tmcf tree species, resulting in a substantial reduction of hydraulic functionality in peruvian cedrela species. | plastic adjustments in xylem vessel traits to drought events in three cedrela species from peruvian tropical andean forests |
we have used the tidal equations of zahn to determine the maximum orbital distance at which companions are brought into roche lobe contact with their giant primary, when the primary expands during the giant phases. this is a key step when determining the rates of interaction between giants and their companions. our stellar structure calculations are presented as maximum radii reached during the red and asymptotic giant branch (rgb and agb, respectively) stages of evolution for masses between 0.8 and 4.0 m⊙ (z = 0.001-0.04) and compared with other models to gauge the uncertainty on radii deriving from details of these calculations. we find overall tidal capture distances that are typically 1-4 times the maximum radial extent of the giant star, where companions are in the mass range from 1 mj to a mass slightly smaller than the mass of the primary. we find that only companions at initial orbital separations between ∼320 and ∼630 r⊙ will be typically captured into a roche lobe-filling interaction or a common envelope on the agb. comparing these limits with the period distribution for binaries that will make planetary nebula (pn), we deduce that in the standard scenario where all ∼1-8 m⊙ stars make a pn, at most 2.5 per cent of all pn should have a post-common envelope central star binary, at odds with the observational lower limit of 15-20 per cent. the observed overabundance of post-interaction central stars of pn cannot be easily explained considering the uncertainties. we examine a range of explanations for this discrepancy. | the effect of tides on the population of pn from interacting binaries |
we present a study of hen 2-155 and hen 2-161, two planetary nebulae which bear striking morphological similarities to other planetary nebulae known to host close-binary central stars. both central stars are revealed to be photometric variables while spectroscopic observations confirm that hen 2-155 is host to a double-eclipsing, post-common-envelope system with an orbital period of 3h33m making it one of the shortest period binary central stars known. the observations of hen 2-161 are found to be consistent with a post-common-envelope binary of period ~1 day. a detailed model of the central star of hen 2-155 is produced, showing the nebular progenitor to be a hot, post-agb remnant of approximately 0.62 m⊙, consistent with the age of the nebula, and the secondary star to be an m dwarf whose radius is almost twice the expected zero age main sequence radius for its mass. in spite of the small numbers, all main-sequence companions, of planetary nebulae central stars, to have had their masses and radii constrained by both photometric and spectroscopic observations have also been found to display this "inflation". the cause of the "inflation" is uncertain but is probably related to rapid accretion, immediately before the recent common-envelope phase, to which the star has not yet thermally adjusted. the chemical composition of both nebulae is also analysed, showing both to display elevated abundance discrepancy factors. this strengthens the link between elevated abundance discrepancy factors and close binarity in the nebular progenitor. full tables 2-5, and 7 are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/580/a19 | the post-common envelope central stars of the planetary nebulae henize 2-155 and henize 2-161 |
understanding the relationships between and among chondritic components of various chondrite groups is of prime importance for deciphering the dynamics of material transport and planetary accretion in the early solar system. here we obtain insights into these processes and the reservoirs present by investigating the nucleosynthetic ti isotopic signatures of individual ca,al-rich inclusions (cais) and na-al-rich chondrules from ordinary and co chondrites. this specific type of chondrule is of interest as it is thought to have incorporated refractory, cai-like material as precursors. our data show that cais from ordinary and co chondrites exhibit 50ti excesses that are indistinguishable from cv cais, and thus indicate a common source reservoir for refractory inclusions in ordinary, co, and cv chondrites. na-al-rich chondrules from co chondrites also show 50ti excesses, indicating the presence of cais from this reservoir in the precursor materials of co chondrules. in contrast, na-al-rich chondrules from ordinary chondrites show no 50ti excesses and are indistinguishable from the bulk values for ordinary chondrites. thus, known cais cannot have been the refractory precursor of the na-al-rich chondrules in ordinary chondrites. consequently, within the accretion region of the ordinary chondrites, two different types of refractory components must have existed: (1) a 50ti-enriched refractory component that is present as cais and either arrived at the accretion region of the ordinary chondrites after chondrule formation, or was only present in insignificant amounts, and (2) another type of refractory material without a 50ti excess, which was involved as precursor in the chondrule formation process. our data thus imply that refractory components with condensation signatures must have formed in at least two isotopically distinct nebular regions. these may be related to non-carbonaceous and carbonaceous source regions, that is, the inner and outer solar system, divided by the early formation of jupiter. | ti isotopic evidence for a non-cai refractory component in the inner solar system |
we report the detection of co(j=2-1) coincident with the super star cluster (ssc) mrk 71-a in the nearby green pea analog galaxy, ngc 2366. our observations with the northern extended millimeter array reveal a compact, ∼7 pc, molecular cloud whose mass ({10}5 {m}⊙ ) is similar to that of the ssc, consistent with a high star formation efficiency, on the order of 0.5. there are two spatially distinct components separated by 11 {km} {{{s}}}-1. if expanding, these could be due to momentum-driven stellar wind feedback. alternatively, we may be seeing remnants of the infalling, colliding clouds responsible for triggering the ssc formation. the kinematics are also consistent with a virialized system. these extreme, high-density, star-forming conditions inhibit energy-driven feedback; the co-spatial existence of a massive, molecular cloud with the ssc supports this scenario, and we quantitatively confirm that any wind-driven feedback in mrk 71-a is momentum-driven, rather than energy-driven. since mrk 71-a is a candidate lyman continuum emitter, this implies that energy-driven superwinds may not be a necessary condition for the escape of ionizing radiation. in addition, the detection of nebular continuum emission yields an accurate astrometric position for the mrk 71-a. we also detect four other massive molecular clouds in this giant star-forming complex. | dense co in mrk 71-a: superwind suppressed in a young super star cluster |
we perform a comprehensive analysis of the redshift evolution of the rest-uv spectra of star-forming galaxies out to z ∼ 5. we combine new z ∼ 5 measurements of h i ly α and low- and high-ionization interstellar metal absorption features with comparable measurements at z ∼ 2-4. we measure the equivalent widths of interstellar absorption features using stacked spectra in bins of ly α equivalent width, performing corrections to ly α strengths based on a model for the transmission of the intergalactic medium. we find a strong correlation between decreasing low-ionization absorption strength and increasing ly α emission strength over the redshift range z ∼ 2-5, suggesting that both of these quantities are fundamentally linked to neutral gas covering fraction. at the highest ly α equivalent widths, we observe evolution at z ∼ 5 towards greater ly α emission strength at fixed low-ionization absorption strength. if we interpret the non-evolving relationship of ly α emission strength and low-ionization line strength at z ∼ 2-4 as primarily reflecting the radiative transfer of ly α photons, this evolution at z ∼ 5 suggests a higher intrinsic production rate of ly α photons than at lower redshift. our conclusion is supported by the joint evolution of the relationships among ly α emission strength, interstellar absorption strength, and dust reddening. we perform additional analysis in bins of stellar mass, star formation rate, uv luminosity, and age, examining how the relationships between galaxy properties and ly α emission evolve towards higher redshift. we conclude that increasing intrinsic ly α photon production and strong detection of nebular c iv emission (signalling lower metallicity) at z ∼ 5 indicate an elevated ionized photon production efficiency (ξion). | the redshift evolution of rest-uv spectroscopic properties to z ∼ 5 |
we revisit previous suggestions that the heating provided by the winds of dying low-mass stars plays an important role in preventing star formation in quiescent galaxies. at the end of their asymptotic giant branch phase, intermediate and low-mass stars eject their envelopes rapidly in a super-wind phase, usually giving rise to planetary nebulae. in spheroidal galaxies with high stellar velocity dispersions, the interaction of these ejected envelopes with the ambient diffuse gas can lead to significant, isotropic and steady-state heating that scales as \dot{m}*σ*2. we show that cooling of the central regions of the hot diffuse halo gas can be delayed for a hubble time for halos more massive than ∼ {{10}12.5} {{m}⊙ } at 0\lt z\lt 2, although stellar heating alone is unlikely to forestall cooling in the most massive clusters at z = 0. this mechanism provides a natural explanation for the strong trend of galaxy quiescence with stellar surface density and velocity dispersion. in addition, since the ejected material will thermalize to kt ∼ σ *2, this mechanism provides an explanation for the observed similarity between the central temperature of the hot diffuse gas and σ *2, a result that is not trivial in light of the short inferred cooling times of the hot gas. the main uncertainty in this analysis is the ultimate fate of the stellar ejecta. preventing accumulation of the ejecta in the central regions may require energy input from another source, such as type ia supernovae. detailed simulations of the interaction of the stellar wind with the ambient gas are required to better quantify the net effect of agb heating. | preventing star formation in early-type galaxies with late-time stellar heating |
distance uncertainties plague our understanding of the physical scales relevant to the physics of star formation in extragalactic studies. the planetary nebulae luminosity function (pnlf) is one of very few techniques that can provide distance estimates to within ∼10% however, it requires a planetary nebula (pn) sample that is uncontaminated by other ionizing sources. we employ optical integral field unit spectroscopy using the multi-unit spectroscopic explorer on the very large telescope to measure [o iii] line fluxes for sources unresolved on 50 pc scales within the central star-forming galaxy disk of ngc 628. we use diagnostic line ratios to identify 62 pne, 30 supernova remnants, and 87 h ii regions within our fields. using the 36 brightest pne, we determine a new pnlf distance modulus of {29.91}-0.13+0.08 mag (9.59{}-0.57+0.35 mpc), which is in good agreement with literature values, but significantly larger than the previously reported pnlf distance. we are able to explain the discrepancy and recover the previous result when we reintroduce snr contaminants to our sample. this demonstrates the power of full spectral information over narrowband imaging in isolating pne. given our limited spatial coverage within the galaxy, we show that this technique can be used to refine distance estimates, even when ifu observations cover only a fraction of a galaxy disk. | a revised planetary nebula luminosity function distance to ngc 628 using muse |
using three independent directions, we estimate that the fraction of type ia supernovae (sne ia) exploding inside planetary nebulae (pne), termed snips, is at least ∼20 per cent. our three directions are: (i) taking the variable sodium absorption lines in some sne ia to originate in massive circum-stellar matter (csm), as has been claimed recently, we use the results of sternberg et al. to imply that ≳ 20 per cent of sne ia occur inside a pn (or a pn descendant), hence classify them as snips. (ii) we next use results that show that whenever there are hydrogen lines in sne ia, the hydrogen mass in the csm is large, ≳ 1 m⊙, hence the explosion is a snip. we make the simplest assumption that the probability for explosion is constant in time for up to about 105 yr after the merger of the core with the white dwarf (wd) in the core-degenerate scenario. the result is that at least a few tens of per cent of sne ia may have an snip origin. (iii) we examine the x-ray morphologies of 13 well-resolved close-by type ia sn remnants (snrs) and derive a crude upper limit, according to which 10-30 per cent of all snrs ia possess opposite ear-like features, which we take as evidence of snip origin. our results, together with several other recent results, lead us to conclude that the two scenarios contributing most to sne ia are the core-degenerate and the double-degenerate scenarios. together these two account for >95 per cent of all sne ia. | the fraction of type ia supernovae exploding inside planetary nebulae (snips) |
we present observations of a peculiar hydrogen- and helium-poor stripped-envelope (se) supernova (sn) 2020wnt, primarily in the optical and near-infrared (near-ir). its peak absolute bolometric magnitude of -20.9 mag (l bol, peak = (6.8 ± 0.3) × 1043 erg s-1) and a rise time of 69 days are reminiscent of hydrogen-poor superluminous sne (slsne i), luminous transients potentially powered by spinning-down magnetars. before the main peak, there is a brief peak lasting <10 days post explosion, likely caused by interaction with circumstellar medium (csm) ejected ~years before the sn explosion. the optical spectra near peak lack a hot continuum and o ii absorptions, which are signs of heating from a central engine; they quantitatively resemble those of radioactivity-powered hydrogen/helium-poor type ic sesne. at ~1 yr after peak, nebular spectra reveal a blue pseudo-continuum and narrow o i recombination lines associated with magnetar heating. radio observations rule out strong csm interactions as the dominant energy source at +266 days post peak. near-ir observations at +200-300 days reveal carbon monoxide and dust formation, which causes a dramatic optical light-curve dip. pair-instability explosion models predict slow light curve and spectral features incompatible with observations. sn 2020wnt is best explained as a magnetar-powered core-collapse explosion of a 28 m ⊙ pre-sn star. the explosion kinetic energy is significantly larger than the magnetar energy at peak, effectively concealing the magnetar-heated inner ejecta until well after peak. sn 2020wnt falls into a continuum between normal sne ic and slsne i, and demonstrates that optical spectra at peak alone cannot rule out the presence of a central engine. | supernova 2020wnt: an atypical superluminous supernova with a hidden central engine |
sn 2014j in m 82 is the closest type ia supernova (sn ia) in decades. the proximity allows for detailed studies of supernova physics and provides insights into the circumstellar and interstellar environment. in this work, we analyse spitzer mid-infrared (mid-ir) data of sn 2014j in the 3.6 and 4.5 μm wavelength range, together with several other nearby and well-studied sne ia. we compile the first composite mid-ir light-curve templates from our sample of sne ia, spanning the range from before peak brightness well into the nebular phase. our observations indicate that sne ia form a very homogeneous class of objects at these wavelengths. using the low-reddening supernovae for comparison, we constrain possible thermal emission from circumstellar dust around the highly reddened sn 2014j. we also study sne 2006x and 2007le, where the presence of matter in the circumstellar environment has been suggested. no significant mid-ir excess is detected, allowing us to place upper limits on the amount of pre-existing dust in the circumstellar environment. for sn 2014j, mdust ≲ 10- 5 m⊙ within rdust ∼ 1017 cm, which is insufficient to account for the observed extinction. similar limits are obtained for sne 2006x and 2007le. | spitzer observations of sn 2014j and properties of mid-ir emission in type ia supernovae |
collisions that induce melting and vaporization can have a substantial effect on the thermal and geochemical evolution of planets. however, the thermodynamics of major minerals are not well known at the extreme conditions attained during planet formation. we obtained new data at the sandia z machine and use published thermodynamic data for the major mineral forsterite (mg2sio4) to calculate the specific entropy in the liquid region of the principal hugoniot. we use our calculated specific entropy of shocked forsterite, and revised entropies for shocked silica, to determine the critical impact velocities for melting or vaporization upon decompression from the shocked state to 1 bar and the triple points, which are near the pressures of the solar nebula. we also demonstrate the importance of the initial temperature on the criteria for vaporization. applying these results to n-body simulations of terrestrial planet formation, we find that up to 20% to 40% of the total system mass is processed through collisions with velocities that exceed the criteria for incipient vaporization at the triple point. vaporizing collisions between small bodies are an important component of terrestrial planet formation. | silicate melting and vaporization during rocky planet formation |
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