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we measure the balmer decrements of 23 of the brightest planetary nebulae (pne) in the inner bulge (r ≲ 3‧) of m31 and deredden the bright end of the region’s [o iii] λ5007 pn luminosity function. we show that the most luminous pne produce ≳1200 l ⊙ of power in their [o iii] λ5007 line, implying central star luminosities of at least ∼11,000 l ⊙. even with the most recent accelerated-evolution post-agb models, such luminosities require central star masses in excess of 0.66 m ⊙ and main-sequence progenitors of at least ∼2.5 m ⊙. since m31's bulge has very few intermediate-age stars, we conclude that conventional single-star evolution cannot be responsible for these extremely luminous objects. we also present the circumstellar extinctions for the region’s bright pne and demonstrate that the distribution is similar to that found for pne in the large magellanic cloud, with a median value of a 5007 = 0.71. finally, we compare our results to extinction measurements made for pne in the e6 elliptical ngc 4697 and the interacting lenticular ngc 5128. we show that such extinctions are not unusual and that the existence of very high-mass pn central stars is a general feature of old stellar populations. our results suggest that single-star population synthesis models significantly underestimate the maximum luminosities and total integrated light of agb stars. | the true luminosities of planetary nebulae in m31's bulge: massive central stars from an old stellar population |
astrophysical jets are collimated, high-speed outflows observed to be natural features of celestial objects that spin and accrete matter. from protoplanetary nebula and young stellar objects to active galactic nuclei, common features suggest that universal mechanisms may lead to the remarkable straightness observed in many jets. here we report observations from a new astrophysically relevant laboratory plasma jet experiment demonstrating the formation of long-lived, collimated, high aspect-ratio jets. the magnetized jets have strong helical shear flows and remain stable to instabilities over many growth times. these observations corroborate theoretical predictions that strong helical shear flows can stabilize current-driven instabilities in magnetically confined plasmas, solar prominences, and magnetically driven astrophysical jets in nature. | helical shear-flow stabilization of an astrophysically relevant laboratory plasma jet |
g21.5-0.9 is a plerionic supernova remnant (snr) used as a calibration target for the chandra x-ray telescope. the first observations found an extended halo surrounding the bright central pulsar wind nebula (pwn). a 2005 study discovered that this halo is limb-brightened and suggested the halo to be the missing snr shell. in 2010, the spectrum of the limb-brightened shell was found to be dominated by non-thermal x-rays. in this study, we combine 15 yr of chandra observations comprising over 1 ms of exposure time (796.1 ks with the advanced ccd imaging spectrometer and 306.1 ks with the high-resolution camera) to provide the deepest-to-date imaging and spectroscopic study. the emission from the limb is primarily non-thermal and is described by a power-law model with a photon index γ = 2.22 (2.04-2.34), plus a weak thermal component characterized by a temperature kt = 0.37 (0.20-0.64) kev and a low-ionization time-scale of net < 2.95 × 1010 cm-3 s. the northern knot located in the halo is best fitted with a two-component power-law + non-equilibrium ionization thermal model characterized by a temperature of 0.14 kev and an enhanced abundance of silicon, confirming its nature as ejecta. we revisit the spatially resolved spectral study of the pwn and find that its radial spectral profile can be explained by diffusion models. the best-fitting diffusion coefficient is d ∼ 2.1× 10^{27}cm^2 s^{-1} assuming a magnetic field b = 130 μg, which is consistent with recent 3d mhd simulation results. | the deepest chandra x-ray study of the plerionic supernova remnant g21.5-0.9 |
we have used existing optical emission and absorption lines, [c ii] emission lines, and h i absorption lines to create a new model for a central column of material near the trapezium region of the orion nebula. this was necessary because recent high spectral resolution spectra of optical emission lines and imaging spectra in the [c ii] 158 μm line have shown that there are new velocity systems associated with the foreground veil and the material lying between θ 1 ori c and the main ionization front of the nebula. when a family of models generated with the spectral synthesis code cloudy were compared with the surface brightness of the emission lines and strengths of the veil absorption lines seen in the trapezium stars, distances from θ 1 ori c were derived, with the closest, highest ionization layer being 1.3 pc. the line-of-sight distance of this layer is comparable with the size of the inner huygens region in the plane of the sky. these layers are all blueshifted with respect to the orion nebula cluster of stars, probably because of the pressure of a hot central bubble created by θ 1 ori c's stellar wind. we find velocity components that are ascribed to both sides of this bubble. our analysis shows that the foreground [c ii] 158 μm emission is part of a previously identified layer that forms a portion of a recently discovered expanding shell of material covering most of the larger extended orion nebula. | the structure of the orion nebula in the direction of θ 1 ori c |
context. m 105 (ngc 3379) is an early-type galaxy in the leo i group. the leo i group is the nearest group that contains all main galaxy types and can thus be used as a benchmark to study the properties of the intra-group light (igl) in low-mass groups.aims: we present a photometric survey of planetary nebulae (pne) in the extended halo of the galaxy to characterise its pn populations and investigate the presence of an extended pn population associated with the intra-group light.methods: we use pne as discrete stellar tracers of the diffuse light around m 105. these pne were identified on the basis of their bright [o iii]5007 å emission and the absence of a broad-band continuum using automated detection techniques. we compare the pn number density profile with the galaxy surface-brightness profile decomposed into metallicity components using published photometry of the hubble space telescope in two halo fields.results: we identify 226 pne candidates within a limiting magnitude of m5007, lim = 28.1 from our subaru-suprimecam imaging, covering 67.6 kpc (23 effective radii) along the major axis of m 105 and the halos of ngc 3384 and ngc 3398. we find an excess of pne at large radii compared to the stellar surface brightness profile from broad-band surveys. this excess is related to a variation in the luminosity-specific pn number α with radius. the α-parameter value of the extended halo is more than seven times higher than that of the inner halo. we also measure an increase in the slope of the pn luminosity function at fainter magnitudes with radius.conclusions: we infer that the radial variation of the pn population properties is due to a diffuse population of metal-poor stars ([m/h] < -1.0) following an exponential profile, in addition to the m 105 halo. the spatial coincidence between the number density profile of these metal-poor stars and the increase in the α-parameter value with radius establishes the missing link between metallicity and the post-asymptotic giant branch phases of stellar evolution. we estimate that the total bolometric luminosity associated with the exponential igl population is 2.04 × 109 l⊙ as a lower limit. the lower limit on the igl fraction is thus 3.8%. this work sets the stage for kinematic studies of the igl in low-mass groups. based on data collected at subaru telescope, which is operated by the national astronomical observatory of japan under programme s14a-006 and with the william herschel telescope operated on the island of la palma by the isaac newton group of telescopes in the spanish observatorio del roque de los muchachos of the instituto de astrofísica de canarias. | the halo of m 105 and its group environment as traced by planetary nebula populations. i. wide-field photometric survey of planetary nebulae in the leo i group |
it is believed that an isolated pulsar loses its rotational energy mainly through a relativistic wind consisting of electrons, positrons and possibly poynting flux1-3. as it expands, this wind may eventually be terminated by a shock, where particles can be accelerated to energies of x-ray synchrotron emission, and a pulsar wind nebula (pwn) is usually detectable surrounding a young energetic pulsar1-3. however, the nature and/or energetics of these physical processes remain very uncertain, largely because they typically cannot be studied in a time-resolved fashion. here we show that the x-ray pwn around the young pulsar psr b0540-69 brightens gradually up to 32 ± 8% over the mean previous flux, after a sudden change in the spin-down rate of 36% in december 2011. this spin-down-rate transition has very different properties from a traditional pulsar glitch4. no evidence is seen for any change in the pulsed x-ray emission. we conclude that the spin-down-rate transition results from a sudden change in the pulsar magnetosphere that increases the pulsar wind power and hence the pwn x-ray emission. the x-ray light curve of the pwn suggests a mean lifetime of the particles of 397 ± 374 d, corresponding to a magnetic field strength of 0.7 8-0.28+4.50mg ? in the pwn. | the brightening of the pulsar wind nebula of psr b0540-69 after its spin-down-rate transition |
the well-studied carbon star, v hya, showing evidence for high-speed, collimated outflows and dense equatorial structures, is a key object in the study of the poorly understood transition of agb stars into aspherical planetary nebulae. using the space telescope imaging spectrograph instrument on board the hubble space telescope, we have obtained high spatial-resolution long-slit optical spectra of v hya that show high-velocity emission in [s ii] and [fe ii] lines. our data set, spanning three epochs spaced apart by a year during each of two periods (in 2002-2004 and 2011-2013), shows that v hya ejects high-speed (∼200-250 {km} {{{s}}}-1) bullets once every ∼8.5 years. the ejection axis flip-flops around a roughly eastern direction, both in and perpendicular to the sky-plane, and the radial velocities of the ejecta also vary in concert between low and high values. we propose a model in which the bullet ejection is associated with the periastron passage of a binary companion in an eccentric orbit around v hya with an orbital period of ∼8.5 years. the flip-flop phenomenon is likely the result of collimated ejection from an accretion disk (produced by gravitational capture of material from the primary) that is warped and precessing, and/or that has a magnetic field that is misaligned with that of the companion or the primary star. we show how a previously observed 17 year period in v hya’s light-cycle can also be explained in our model. additionally, we describe how the model proposed here can be extended to account for multipolar nebulae. | high-speed bullet ejections during the agb-to-planetary nebula transition: hst observations of the carbon star, v hydrae |
the recurrent nova t crb has entered in 2015 a phase of unprecedented high activity. to trace something equivalent, it is necessary to go back to 1938, before the last nova eruption in 1946. the 2015 super-active state is characterized by: a large increase in the mean brightness (δb=0.72 mag over the underlying secular trend), vanishing of the orbital modulation from the b-band lightcurve, and appearance of strong and high ionization emission lines, on top of a nebular continuum that overwhelms at optical wavelengths the absorption spectrum of the m giant. among the emission lines, heii 4686 attains a flux in excess of hγ, the full set of oiii and niii lines involved in the bowen fluorescence mechanism are strong and varying in intensity in phase with heii 4686, and oiv and [nev] are present. a large increase in the radiation output from the hot source is responsible for a large expansion in the ionized fraction of the m giant wind. the wind is completely ionized in the direction to the observer. a high electron density is supported by the weakness of forbidden lines and by the large amplitude and short time scale of the reprocessing by the nebular material of the highly variable photo-ionization input from the hot source. during the super-active state the nebula is varying to and from ionization-bounded and density-bounded conditions, and the augmented irradiation of the cool giant has changed the spectral type of its side facing the wd from m3iii to m2iii, i.e. an increase of ∼80 k in effective temperature. | the 2015 super-active state of recurrent nova t crb and the long term evolution after the 1946 outburst |
we report on the first measurements of the isotopic ratio 14n/15n in n2h+ toward a statistically significant sample of high-mass star-forming cores. the sources belong to the three main evolutionary categories of the high-mass star formation process: high-mass starless cores, high-mass protostellar objects, and ultracompact h ii regions. simultaneous measurements of the 14n/15n ratio in cn have been made. the 14n/15n ratios derived from n2h+ show a large spread (from ∼180 up to ∼1300), while those derived from cn are in between the value measured in the terrestrial atmosphere (∼270) and that of the proto-solar nebula (∼440) for the large majority of the sources within the errors. however, this different spread might be due to the fact that the sources detected in the n2h+ isotopologues are more than those detected in the cn ones. the 14n/15n ratio does not change significantly with the source evolutionary stage, which indicates that time seems to be irrelevant for the fractionation of nitrogen. we also find a possible anticorrelation between the 14n/15n (as derived from n2h+) and the h/d isotopic ratios. this suggests that 15n enrichment could not be linked to the parameters that cause d enrichment, in agreement with the prediction by recent chemical models. these models, however, are not able to reproduce the observed large spread in 14n/15n, pointing out that some important routes of nitrogen fractionation could be still missing in the models. based on observations carried out with the iram-30 m telescope. iram is supported by insu/cnrs (france), mpg (germany), and ign (spain). | first measurements of 15n fractionation in n2h+ toward high-mass star-forming cores |
an investigation of the iras 16148-5011 region - a cluster at a distance of 3.6 kpc - is presented here, carried out using multiwavelength data in near-infrared (nir) from the 1.4 m infrared survey facility telescope, mid-infrared (mir) from the archival spitzer glimpse (galactic legacy infrared midplane survey extraordinaire) survey, far-infrared (fir) from the herschel archive, and low-frequency radio continuum observations at 1280 and 843 mhz from the giant metrewave radio telescope and molonglo survey archive, respectively. a combination of nir and mir data is used to identify 7 class i and 133 class ii sources in the region. spectral energy distribution (sed) analysis of selected sources reveals a 9.6 m⊙ high-mass source embedded in nebulosity. however, lyman continuum luminosity calculation using radio emission - which shows a compact h ii region - indicates the spectral type of the ionizing source to be earlier than b0-o9.5. free-free emission sed modelling yields the electron density as 138 cm-3, and thus the mass of the ionized hydrogen as ∼16.4 m⊙. thermal dust emission modelling, using the fir data from herschel and performing modified blackbody fits, helped us construct the temperature and column density maps of the region, which show peak values of 30 k and 3.3 × 1022 cm-2, respectively. the column density maps reveal an av > 20 mag extinction associated with the nebular emission, and weak filamentary structures connecting dense clumps. the clump associated with this iras object is found to have dimensions of ∼ 1.1 pc × 0.8 pc, and a mass of 1023 m⊙. | study of morphology and stellar content of the galactic h ii region iras 16148-5011 |
the detection of neutron(n)-capture elements in several planetary nebulae (pne) has provided a new means of investigating s-process nucleosynthesis in low-mass stars. however, a lack of atomic data has inhibited accurate trans-iron element abundance determinations in astrophysical nebulae. recently, photoionization (pi) and recombination data were determined for se and kr, the two most widely detected n-capture elements in nebular spectra. we have incorporated these new data into the photoionization code cloudy. to test the atomic data, numerical models were computed for 15 pne that exhibit emission lines from multiple kr ions. we found systematic discrepancies between the predicted and observed emission lines that are most likely caused by inaccurate pi and recombination data. these discrepancies were removed by adjusting the kr+-kr3+ pi cross sections within their cited uncertainties and the dielectronic recombination rate coefficients by slightly larger amounts. from grids of models spanning the physical conditions encountered in pne, we derive new, broadly applicable ionization correction factor (icf) formulae for calculating se and kr elemental abundances. the icfs were applied to our previous survey of near-infrared [kr iii] and [se iv] emission lines in 120 pne. the revised se and kr abundances are 0.1-0.3 dex lower than former estimates, with average values of [se/(o, ar)] = 0.12 ± 0.27 and [kr/(o, ar)] = 0.82 ± 0.29, but correlations previously found between their abundances and other nebular and stellar properties are unaffected. we also find a tendency for high-velocity pne that can be associated with the galactic thick disk to exhibit larger s-process enrichments than low-velocity pne belonging to the thin-disk population. | the abundances of light neutron-capture elements in planetary nebulae. iii. the impact of new atomic data on nebular selenium and krypton abundance determinations |
we identify [rb iv] 1.5973 and [cd iv] 1.7204 μm emission lines in high-resolution (r = 40,000) near-infrared spectra of the planetary nebulae (pne) ngc 7027 and ic 5117, obtained with the immersion grating infrared spectrometer (igrins) on the 2.7 m telescope at mcdonald observatory. we also identify [ge vi] 2.1930 μm in ngc 7027. alternate identifications for these features are ruled out based on the absence of other multiplet members and/or transitions with the same upper levels. ge, rb, and cd can be enriched in pne by s-process nucleosynthesis during the asymptotic giant branch stage of evolution. to determine ionic abundances, we calculate [rb iv] collision strengths and use approximations for those of [cd iv] and [ge vi]. our identification of [rb iv] 1.5973 μm is supported by the agreement between rb3+/h+ abundances found from this line and the 5759.55 å feature in ngc 7027. elemental rb, cd, and ge abundances are derived with ionization corrections based on similarities in ionization potential ranges between the detected ions and o and ne ionization states. our analysis indicates abundances 2-4 times solar for rb and cd in both nebulae. ge is subsolar in ngc 7027, but its abundance is uncertain due to the large and uncertain ionization correction. the general consistency of the measured relative s-process enrichments with predictions from models appropriate for these pne (2.0-2.5 m⊙, [fe/h] = -0.37) demonstrates the potential of using pn compositions to test s-process nucleosynthesis models. this paper includes data taken at the mcdonald observatory of the university of texas at austin. | discovery of rubidium, cadmium, and germanium emission lines in the near-infrared spectra of planetary nebulae |
we report the detection of near-ir h2 emission from the low-ionization structures (knots) in two planetary nebulae. the deepest ever high-angular-resolution h2 (1-0) s(1) at 2.122 μm, h2 (2-1) s(1) at 2.248 μm and brγ images of k 4-47 and ngc 7662, obtained using the near infrared imager and spectrometer (niri) at gemini-north, are analysed here. k 4-47 reveals a remarkable highly collimated bipolar structure not only in the optical but also in the molecular hydrogen emission. the h2 emission emanates from the walls of the bipolar outflows and also from the pair of knots at the tip of the outflows. the h2 (1-0) s(1)/(2-1) s(1) line ratio ranges from ∼7 to ∼10, suggesting the presence of shock interactions. our findings can be explained by the interaction of a jet/bullet ejected from the central star with the surrounding asymptotic giant branch material. the strongest h2 line, (1-0) s(1), is also detected in several low-ionization knots located at the periphery of the elliptical planetary nebula ngc 7662, but only four of these knots are detected in the h2 (2-1) s(1) line. these four knots exhibit an h2 line ratio between 2 and 3.5, which suggests that the emission is caused by the uv ionizing flux of the central star. our data confirm the presence of h2 gas in both fast- and slow-moving low-ionization knots, which has only been confirmed before in the nearby helix nebula and hu 1-2. overall, the low-ionization structures of planetary nebulae are found to have similar traits to photodissociation regions. | h2 in low-ionization structures of planetary nebulae |
dust plays a key role in the formation of planets and its emission also provides one of our most accessible views of protoplanetary discs. if set by radiative equilibrium with the central star, the temperature of dust in the disc plateaus at around 10-20 k in the outer regions. however, sufficiently nearby massive stars can heat the outer disc to substantially higher temperatures. in this paper, we study the radiative equilibrium temperature of discs in the presence of massive external sources and gauge the effect that it has on millimetre dust mass estimates. since millimetre grains are not entrained in any wind, we focus on geometrically simple 2d axisymmetric disc models using radiative transfer calculations with both the host star and an external source. recent surveys have searched for evidence of massive stars influencing disc evolution using disc properties as a function of projected separation. in assuming a disc temperature of 20 k for a disc a distance d from a strong radiation source, disc masses are overestimated by a factor that scales with d-1/2 interior to the separation that external heating becomes important. this could significantly alter dust mass estimates of discs in close proximity to θ1c in the orion nebular cluster (onc). we also make an initial assessment of the effect upon snow lines. within a parsec of an o star like θ1c a co snow line no longer exists, though the water snow line is virtually unaffected except for very close separations of $\le 0.01\,$ pc. | warm millimetre dust in protoplanetary discs near massive stars |
recent detection of exoplanets with earth-like insolation attracts growing interest in how common earth-like aqua planets are beyond the solar system. while terrestrial planets are often assumed to capture icy or water-rich planetesimals, a primordial atmosphere of nebular origin itself can produce water through oxidation of the atmospheric hydrogen with oxidizing minerals from incoming planetesimals or the magma ocean. thermodynamically, normal oxygen buffers produce water comparable in mole number equal to or more than hydrogen. thus, the primordial atmosphere would likely be highly enriched with water vapour; however, the primordial atmospheres have been always assumed to have the solar abundances. here we integrate the 1d structure of such an enriched atmosphere of sub-earths embedded in a protoplanetary disc around an m dwarf of 0.3 $\, \mathrm{m}_\odot$ and investigate the effects of water enrichment on the atmospheric properties with focus on water amount. we find that the well-mixed highly enriched atmosphere is more massive by a few orders of magnitude than the solar-abundance atmosphere, and that even a mars-mass planet can obtain water comparable to the present earth's oceans. although close-in mars-mass planets likely lose the captured water via disc dispersal and photoevaporation, these results suggest that there are more sub-earths with earth-like water contents than previously predicted. how much water terrestrial planets really obtain and retain against subsequent loss, however, depends on efficiencies of water production, mixing in the atmosphere and magma ocean, and photoevaporation, detailed investigation for which should be made in the future. | formation of aqua planets with water of nebular origin: effects of water enrichment on the structure and mass of captured atmospheres of terrestrial planets |
canis major ob1 (cma ob1) is a galactic stellar association with a very intriguing star-formation scenario. there are more than two dozen known star clusters in its line of sight, but it is not clear which ones are physically associated with cma ob1. we use a clustering code that employs five-dimensional data from the gaia dr2 catalogue to identify physical groups and obtain their astrometric parameters and, in addition, we use two different isochrone-fitting methods to estimate the ages of these groups. we find 15 stellar groups with distances between 570 and 1650 pc, including 10 previously known and five new open cluster candidates. four groups, precisely the youngest ones (< 20 myr), cma05, cma06, cma07, and cma08, are confirmed to be part of cma ob1. we find that cma08, a new cluster candidate, may be the progenitor cluster of runaway stars. cma06 coincides with the well-studied cma r1 star-forming region. while cma06 is still forming stars, due to the remaining material of the molecular cloud associated with the sh 2-262 nebula, cma05, cma07, and cma08 seem to be in more evolved stages of evolution, with no recent star-forming activity. the properties of these cma ob1 physical groups fit well in a monolithic scenario of star formation, with a common formation mechanism, and having suffered multiple episodes of star formation. this suggests that the hierarchical model alone, which explains the populations of other parts of the same association, is not sufficient to explain its whole formation history. | canis major ob1 stellar group contents revealed by gaia |
the crab nebula is a supernova remnant exhibiting a highly polarized synchrotron radiation at radio and millimetre wavelengths. it is the brightest source in the microwave sky with an extension of 7 by 5 arcmin, and is commonly used as a standard candle for any experiment which aims to measure the polarization of the sky. though its spectral energy distribution has been well characterized in total intensity, polarization data are still lacking at millimetre wavelengths. we report in this paper high resolution observations (18'' fwhm) of the crab nebula in total intensity and linear polarization at 150 ghz with the nika camera. nika, operated at the iram 30 m telescope from 2012 to 2015, is a camera made of lumped element kinetic inductance detectors (lekids) observing the sky at 150 and 260 ghz. from these observations we are able to reconstruct the spatial distribution of the polarization degree and angle of the crab nebula, which is found to be compatible with previous observations at lower and higher frequencies. averaging across the source and using other existing data sets we find that the crab nebula polarization angle is consistent with being constant over a wide range of frequencies with a value of - 87.7° ± 0.3 in galactic coordinates. we also present the first estimation of the crab nebula spectral energy distribution polarized flux in a wide frequency range: 30-353 ghz. assuming a single power law emission model we find that the polarization spectral index βpol = - 0.347 ± 0.026 is compatible with the intensity spectral index β = - 0.323 ± 0.001. | nika 150 ghz polarization observations of the crab nebula and its spectral energy distribution |
although fullerenes have long been hypothesized to occur in interstellar environments, they have only recently been unambiguously identified through spectroscopy1-4. c60, c70 and c60+ now constitute the largest molecular species individually identified in the interstellar medium. fullerenes have substantial proton affinities and it has been suggested that c60h+ is likely the most abundant interstellar analogue of c60 (ref. 5). we present here a laboratory infrared (ir) spectrum of gaseous c60h+. symmetry breaking in c60h+ produces an ir spectrum that is much richer than that of c60. the experimental spectrum is used to benchmark theoretical spectra indicating that the b3lyp density functional with the 6-311+g(d,p) basis set accurately reproduces the spectrum. comparison with ir emission spectra from two planetary nebulae, smp lmc56 and smc16, which have been associated with high c60? abundances, indicates that c60h+ is a plausible contributor to their ir emission. | the infrared spectrum of protonated buckminsterfullerene c60h+ |
in the hierarchical model of structure formation, giant elliptical galaxies form through merging processes within the highest density peaks known as protoclusters. while high-redshift radio galaxies usually pinpoint the location of these environments, we have recently discovered at z ∼ 2-3 three enormous (> 200 kpc) lyman-α nebulae (elane) that host multiple active galactic nuclei (agn) and that are surrounded by overdensities of lyman-α emitters (lae). these regions are prime candidates for massive protoclusters in the early stages of assembly. to characterize the star-forming activity within these rare structures - both on elan and protocluster scales - we have initiated an observational campaign with the james clerk maxwell telescope (jcmt) and the atacama pathfinder experiment (apex) telescopes. in this paper we report on sensitive scuba-2/jcmt 850 and 450 μm observations of a ∼128 arcmin2 field comprising the elan mammoth-1, together with the peak of the hosting boss1441 lae overdensity at z = 2.32. these observations unveil 4.0 ± 1.3 times higher source counts at 850 μm with respect to blank fields, likely confirming the presence of an overdensity also in obscured tracers. we find a strong detection at 850 μm associated with the continuum source embedded within the elan mammoth-1, which - together with the available data from the literature - allow us to constrain the spectral energy distribution of this source to be of an ultra-luminous infrared galaxy (ulirg) with a far-infrared luminosity of lfirsf = 2.4-2.1+7.4×1012 l⊙, and hosting an obscured agn. such a source is thus able to power a hard photoionization plus outflow scenario to explain the extended lyman-α, he iiλ1640, and c ivλ1549 emission, and their kinematics. in addition, the two brightest detections at 850 μm (f850 > 18 mjy) sit at the density peak of the laes' overdensity, likely pinpointing the core of the protocluster. future multiwavelength and spectroscopic datasets targeting the full extent of the boss1441 overdensity have the potential to firmly characterize a cosmic nursery of giant elliptical galaxies, and ultimately of a massive cluster. the reduced images 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/620/a202 | overdensity of submillimeter galaxies around the z ≃ 2.3 mammoth-1 nebula. the environment and powering of an enormous lyman-α nebula |
the ic iron meteorite group is characterized utilizing nucleosynthetic mass-independent isotopic compositions and 182w age constraints, coupled with siderophile element concentration measurements and modeling of crystal-liquid fractionation processes. the six ic irons analyzed, arispe, bendego, chihuahua city, nocoleche, nwa 2743, and winburg have indistinguishable mo and w genetic isotopic compositions and are consistent with derivation from the same parent body, which formed in the non-carbonaceous (nc) nebular reservoir. a pre-exposure μ182w value (parts-per-million deviations in isotopic ratios from terrestrial standards) for the six ic irons of -337 ± 5 corresponds to a metal-silicate segregation age of 1.0 ± 0.4 myr after calcium-aluminum-rich inclusion (cai) formation. this age is similar to those determined for other nc iron groups. siderophile element abundances of the ic irons are generally similar and characterized by minor depletions in the more volatile siderophile elements. highly siderophile element (hse) distributions among the ic group suggest that the initial parent body core was s-rich, with preferred model results indicating an initial melt composition with ∼ 18 wt% s, 2 wt% p and 0.03 wt% c. processes in addition to fractional crystallization, such as late-stage parent body modification, possibly as a result of impacts, and subsequent metal-melt mixing, are required within the first 100 myr of solar system history to explain the range of hse abundances. | genetics, age, and crystallization history of group ic iron meteorites |
the gravitational force controls the evolution of the universe on several scales. it is responsible for the formation of galaxies from the primordial matter distribution and the formation of planets from solar nebulae. because the gravitational force is singular and has infinite range, making predictions based on fully three-dimensional models may be challenging. one-dimensional (1d) newtonian gravity models were proposed as toy models for understanding the dynamics of gravitational systems. they can be integrated exactly and were used for computer simulations starting in the 1960s, providing the first demonstration of violent relaxation and the rapid development of long-lived quasi-stationary states (qss). the present review provides the bases of the physics of 1d gravitational systems. it is divided into two main parts, the first concerning the approach to equilibrium and the second applications to cosmology. each part is self-contained and can be read independently of the other. in the first part, we provide an introduction to the equilibrium thermodynamics of the one-dimensional gravitational sheet (ogs) system in the vlasov limit. both fixed and periodic boundary conditions are considered. the relaxation to equilibrium of the ogs is studied through numerical simulations which establish the role played by qss and violent relaxation. we also survey existing work on the lyapunov exponents of the ogs and on the chaotic dynamics of 1d systems with few particles, focusing on the 1d three-body problem. the second part summarizes work on dynamical structure formation in cosmology using 1d systems. by transforming to comoving coordinates, which follow the global expansion of the universe, the 1d approach provides a useful laboratory for studying structure formation in various cosmological scenarios, from einstein-de sitter and λcdm to more recent, alternative cosmological models. a key result is the appearance of scale-free behavior with fractal dimension, which can be reliably studied in 1d for large systems over many epochs. finally, an appendix gives some details on the numerical simulation methods used in these studies. | from chaos to cosmology: insights gained from 1d gravity |
context after decades of political and economic isolation, myanmar is now the focus of large international investments, particularly from china, which raises questions of how to balance national development with safeguarding the indo-burma biodiversity hotspot. objective to evaluate the impact of five major developments in myanmar on forest ecosystems, using clouded leopard as a focal and umbrella species for wider biodiversity conservation. methods based on an empirical habitat relationships model, we identified core areas and corridors in myanmar, and compared them across the development scenarios. we simulated population dynamics and genetic diversity in each scenario using an individual-based, spatially explicit cost-distance population genetics model. results the predicted current clouded leopard population may be larger than the current carrying capacity of the landscape, raising the possibility that the species' population has not yet equilibrated with recent habitat loss and degradation. all the developments combined resulted in 36% decrease in landscape connectivity and 29% decrease in simulated clouded leopard population size, including substantial reduction in genetic diversity. each development was predicted to have a negative effect; however, emerging economic zones had disproportionally large impacts (− 24% in connectivity and − 25% in population size), resulting in fragmentation of the largest core areas. similarly, the indian highway and silk road caused fragmentation of the largest core habitats, and the pipeline railroad significantly decreased connectivity in the main stronghold for clouded leopards. conclusions spatially-explicit assessments like the one presented here provide quantitative evaluation on development impacts and help optimize the trade-offs between development and conservation. the rapid and increasing development of myanmar and surrounding southeast asian nations pose an enormous threat to the biodiversity of the region. optimizing the trade-off between development goals and conservation is essential to minimize the effects of rapid land use change on biodiversity. | simulating the impact of belt and road initiative and other major developments in myanmar on an ambassador felid, the clouded leopard, neofelis nebulosa |
three-dimensional (3d) structure-based tin disulfide/vertically aligned carbon nanotube arrays (vacnts) composites have been successfully fabricated via a facile hydrothermal method for self-assembly with the help of nebulization-assisted infiltration. the sns2 particles are anchored on the surface of the vacnts and the number of these nanoparticles increases as the nebulization time increase. the novel 3d structure-based sns2/vacnts sample with the sns2 content of 67 wt% exhibits excellent electrochemical performance, including high capacity (738 ma h g-1 at 50 ma g-1 after 1st cycle), good cycle stability (551 ma h g-1 at 100 ma g-1after 100 cycles), and excellent rate capability (223 ma h g-1 at 2000 ma g-1) when used as an anode in lithium ion batteries. the high electrochemical performance can be attributed to the synergistic effect of sns2 and the unique microstructure of vacnts, which provide the rapid pathways for ionic and electronic transport ascribing to their well-directed 1d conductive electron paths and well defined regular pore structures. the vacnts serve as not only conductive additives to improve the conductivity of sns2 in the composites, but also as buffer matrix to restrain the volume change of sns2 and stabilize the electrode structure during the alloying/dealloying process. | three-dimensional structure-based tin disulfide/vertically aligned carbon nanotube arrays composites as high-performance anode materials for lithium ion batteries |
we have measured astrometry for members of the orion nebula cluster with images obtained in 2015 with the wide field camera 3 on board the hubble space telescope. by comparing those data to previous measurements with the near-infrared camera and multi-object spectrometer on hubble in 1998, we have discovered that a star in the kleinmann-low nebula, source x from lonsdale et al., is moving with an unusually high proper motion of 29 mas yr-1, which corresponds to 55 km s-1 at the distance of orion. previous radio observations have found that three other stars in the kleinmann-low nebula (the becklin-neugebauer object and sources i and n) have high proper motions (5-14 mas yr-1) and were near a single location ∼540 years ago, and thus may have been members of a multiple system that dynamically decayed. the proper motion of source x is consistent with ejection from that same location 540 years ago, which provides strong evidence that the dynamical decay did occur and that the runaway star bn originated in the kleinmann-low nebula rather than the nearby trapezium cluster. however, our constraint on the motion of source n is significantly smaller than the most recent radio measurement, which indicates that it did not participate in the event that ejected the other three stars. based on observations made with the nasa/esa hubble space telescope and the nasa infrared telescope facility. | new evidence for the dynamical decay of a multiple system in the orion kleinmann-low nebula |
the amount of atmospheric gas absorbed into a planetary interior during formation depends on the temperature, pressure, composition, and dynamics of its atmosphere, along with the planet mass, its composition, rate of accretion, and the average age of its surface. we develop a boundary layer model for terrestrial planet ingassing during accretion that quantifies the amounts of hydrogen and helium dissolved into a global magma ocean from a hot, gravitationally captured nebular atmosphere in the first few million years of solar system history. assuming that most of earth's accretion occurred within the lifetime of its nebular atmosphere, one or more ocean masses of ingassed hydrogen are predicted if the surface pressure is high and the magma surface is young. in addition, earth would have acquired hundreds of petagrams of helium-3 from the same nebular atmosphere. our model predicts negligible hydrogen ingassing from a gravitationally captured nebular atmosphere on mars, but shows that vast amounts of hydrogen ingassing - tens of ocean masses - are possible during the accretion of super-earth-sized terrestrial planets. | hydrogen and helium ingassing during terrestrial planet accretion |
we present the results of two-dimensional hydrodynamic simulations of self-gravitating circumbinary discs around binaries whose parameters match those of the circumbinary planet-hosting systems kepler-16, kepler-34 and kepler-35. previous work has shown that non-self-gravitating discs in these systems form an eccentric precessing inner cavity due to tidal truncation by the binary, and planets which form at large radii migrate until stalling at this cavity. whilst this scenario appears to provide a natural explanation for the observed orbital locations of the circumbinary planets, previous simulations have failed to match the observed planet orbital parameters. the aim of this work is to examine the role of self-gravity in modifying circumbinary disc structure as a function of disc mass, prior to considering the evolution of embedded circumbinary planets. in agreement with previous work, we find that for disc masses between one and five times the minimum mass solar nebula (mmsn), disc self-gravity affects modest changes in the structure and evolution of circumbinary discs. increasing the disc mass to 10 or 20 mmsn leads to two dramatic changes in disc structure. first, the scale of the inner cavity shrinks substantially, bringing its outer edge closer to the binary. secondly, in addition to the eccentric inner cavity, additional precessing eccentric ring-like features develop in the outer regions of the discs. if planet formation starts early in the disc lifetime, these changes will have a significant impact on the formation and evolution of planets and precursor material. | the role of disc self-gravity in circumbinary planet systems - i. disc structure and evolution |
aims: we aim to identify bipolar galactic h ii regions and to understand their parental cloud structures, morphologies, evolution, and impact on the formation of new generations of stars.methods: we use the spitzer-glimpse, spitzer-mipsgal, and herschel-hi-gal surveys to identify bipolar h ii regions and to examine their morphologies. we search for their exciting star(s) using nir data from the 2mass, ukidss, and vista surveys. massive molecular clumps are detected near these bipolar nebulae, and we estimate their temperatures, column densities, masses, and densities. we locate class 0/i young stellar objects (ysos) in their vicinities using the spitzer and herschel-pacs emission.results: numerical simulations suggest bipolar h ii regions form and evolve in a two-dimensional flat- or sheet-like molecular cloud. we identified 16 bipolar nebulae in a zone of the galactic plane between ℓ ± 60° and |b| < 1°. this small number, when compared with the 1377 bubble h ii regions in the same area, suggests that most h ii regions form and evolve in a three-dimensional medium. we present the catalogue of the 16 bipolar nebulae and a detailed investigation for six of these. our results suggest that these regions formed in dense and flat structures that contain filaments. we find that bipolar h ii regions have massive clumps in their surroundings. the most compact and massive clumps are always located at the waist of the bipolar nebula, adjacent to the ionised gas. these massive clumps are dense, with a mean density in the range of 105 cm-3 to several 106 cm-3 in their centres. luminous class 0/i sources of several thousand solar luminosities, many of which have associated maser emission, are embedded inside these clumps. we suggest that most, if not all, massive 0/i yso formation has probably been triggered by the expansion of the central bipolar nebula, but the processes involved are still unknown. modelling of such nebula is needed to understand the star formation processes at play. | bipolar h ii regions. ii. morphologies and star formation in their vicinities |
the nebular-epoch spectrum of the rapidly declining, `transitional' type ia supernova (sn) 2007on showed double emission peaks, which have been interpreted as indicating that the sn was the result of the direct collision of two white dwarfs. the spectrum can be reproduced using two distinct emission components, one redshifted and one blueshifted. these components are similar in mass but have slightly different degrees of ionization. they recede from one another at a line-of-sight speed larger than the sum of the combined expansion velocities of their emitting cores, thereby acting as two independent nebulae. while this configuration appears to be consistent with the scenario of two white dwarfs colliding, it may also indicate an off-centre delayed detonation explosion of a near-chandrasekhar-mass white dwarf. in either case, broad emission line widths and a rapidly evolving light curve can be expected for the bolometric luminosity of the sn. this is the case for both sne 2007on and 2011iv, also a transitional sn ia that exploded in the same elliptical galaxy, ngc 1404. although sn 2011iv does not show double-peaked emission line profiles, the width of its emission lines is such that a two-component model yields somewhat better results than a single-component model. most of the mass ejected is in one component, however, which suggests that sn 2011iv was the result of the off-centre ignition of a chandrasekhar-mass white dwarf. | the nebular spectra of the transitional type ia supernovae 2007on and 2011iv: broad, multiple components indicate aspherical explosion cores |
the hard x-ray imager (hxi) is one of the instruments onboard the astro-h mission [1-4] to be launched in early 2016. the hxi is the focal plane detector of the hard x-ray reflecting telescope that covers an energy range from 5 to 80 kev. it will execute observations of astronomical objects with a sensitivity for point sources as faint as 1/100,000 of the crab nebula at > 10 kev. the hxi camera - the imaging part of the hxi - is realized by a hybrid semiconductor detector system that consists of silicon (si) and cadmium telluride (cdte) semiconductor detectors. here, we present the final design of the hxi camera and report on the development of the flight model. the camera is composed of four layers of double-sided silicon strip detectors (dssds) and one layer of cdte double-sided strip detector (cdte-dsd), each with an imaging area of 32 mm×32 mm. the strip pitch of the si and cdte sensors is 250 μm, and the signals from all 1280 strips are processed by 40 application specified integrated circuits (asics) developed for the hxi. the five layers of sensors are vertically stacked with a 4 mm spacing to increase the detection efficiency. the thickness of the sensors is 0.5 mm for the si, and 0.75 mm for the cdte. in this configuration, soft x-ray photons will be absorbed in the si part, while hard x-ray photons will go through the si part and will be detected in the cdte part. the design of the sensor trays, peripheral circuits, power connections, and readout schemes are also described. the flight models of the hxi camera have been manufactured, tested and installed in the hxi instrument and then on the satellite. | the si/cdte semiconductor camera of the astro-h hard x-ray imager (hxi) |
the role of major mergers in galaxy evolution is investigated through a detailed characterization of the stellar populations, ionized gas properties and star formation rates (sfr) in the early-stage merger luminous infrared galaxies (lirgs) ic 1623 w and ngc 6090, by analysing optical integral field spectroscopy and high-resolution hubble space telescope imaging. the spectra were processed with the starlight full spectral fitting code, and the emission lines measured in the residual spectra. the results are compared with non-interacting control spiral galaxies from the calar alto legacy integral field area survey. merger-induced star formation is extended and recent, as revealed by the young ages (50-80 myr) and high contributions to light of young stellar populations (50-90 per cent), in agreement with merger simulations in the literature. these early-stage mergers have positive central gradients of the stellar metallicity, with an average ∼0.6 z⊙. compared to non-interacting spirals, they have lower central nebular metallicity, and flatter profiles, in agreement with the gas inflow scenario. we find that they are dominated by star formation, although shock excitation cannot be discarded in some regions, where high velocity dispersion is found (170-200 km s-1). the average sfr in these early-stage mergers (∼23-32 m⊙ yr-1) is enhanced with respect to main-sequence sbc galaxies by factors of 6-9, slightly above the predictions from classical merger simulations, but still possible in about 15 per cent of major galaxy mergers, where u/lirgs belong. | star formation histories in mergers: the spatially resolved properties of the early-stage merger luminous infrared galaxies ic 1623 and ngc 6090 |
we construct a suite of discrete chemo-dynamical models of the giant elliptical galaxy ngc 5846. these models are a powerful tool to constrain both the mass distribution and internal dynamics of multiple tracer populations. we use jeans models to simultaneously fit stellar kinematics within the effective radius re, planetary nebula (pn) radial velocities out to 3 re, and globular cluster (gc) radial velocities and colours out to 6 re. the best-fitting model is a cored dark matter halo which contributes ∼10 per cent of the total mass within 1 re, and 67 per cent ± 10 per cent within 6 re, although a cusped dark matter halo is also acceptable. the red gcs exhibit mild rotation with vmax/σ0 ∼ 0.3 in the region r > re, aligned with but counter-rotating to the stars in the inner parts, while the blue gcs and pne kinematics are consistent with no rotation. the red gcs are tangentially anisotropic, the blue gcs are mildly radially anisotropic, and the pne vary from radially to tangentially anisotropic from the inner to the outer region. this is confirmed by general made-to-measure models. the tangential anisotropy of the red gcs in the inner regions could stem from the preferential destruction of red gcs on more radial orbits, while their outer tangential anisotropy - similar to the pne in this region - has no good explanation. the mild radial anisotropy of the blue gcs is consistent with an accretion scenario. | a discrete chemo-dynamical model of the giant elliptical galaxy ngc 5846: dark matter fraction, internal rotation, and velocity anisotropy out to six effective radii |
we have investigated the quadruple sulfur isotopic composition of inorganic sulfur-bearing phases from 13 carbonaceous chondrites of cm type. our samples include 4 falls and 9 antarctic finds. we extracted sulfur from sulfides, sulfates, and elemental sulfur (s0) from all samples. on average, we recover a bulk sulfur (s) content of 2.11 ± 0.39 wt.% s (1σ). the recovered sulfate, s0 and sulfide contents represent 25 ± 12%, 10 ± 7% and 65 ± 15% of the bulk s, respectively (all 1σ). there is no evidence for differences in the bulk s content between falls and finds, and there is no correlation between the s speciation and the extent of aqueous alteration. we report ranges of δ33s and δ36s values in cms that are significantly larger than previously observed. the largest variations are exhibited by s0, with δ33s values ranging between -0.104 ± 0.012‰ and +0.256 ± 0.018‰ (2σ). the δ36s/33s ratios of s0 are on average -3.1 ± 1.0 (2σ). two cms show distinct δ36s/33s ratios, of +1.3 ± 0.1 and +0.9 ± 0.1. we suggest that these mass independent s isotopic compositions record h2s photodissociation in the nebula. the varying δ36s/δ33s ratios are interpreted to reflect photodissociation that occurred at different uv wavelengths. the preservation of these isotopic features requires that the s-bearing phases were heterogeneously accreted to the cm parent body. non-zero δ33s values are also preserved in sulfide and sulfate, and are positively correlated with s0 values. this indicates a genetic relationship between the s-bearing phases: we argue that sulfates were produced by the direct oxidation of s0 (not sulfide) in the parent body. we describe two types of models that, although imperfect, can explain the major features of the cm s isotope compositions, and can be tested in future studies. sulfide and s0 could both be condensates from the nebula, as the residue and product, respectively, of incomplete h2s photodissociation by uv light (wavelength <150 nm). this idea requires that fes formation and the s0 condensation co-occur. as an alternative, ice accretion to the cm parent body could allow the delivery of s-mif in cms. in that case, sulfides would have been the only s-bearing condensate in cm precursors, and s0 would have been derived from the oxidation of h2s trapped in ices, after its photodissociation at low temperature (<500 k) in the nebula. in our models, the observations of h2s uv photodissociation is required to occur at the disk surface, and allowed in nebular environments with canonical c/o ratios. vertical motions in the disk would redistribute phases that condensed at high altitude to the midplane, where they accreted in the phases that make up the chondritic matrix. | mass independent sulfur isotope signatures in cms: implications for sulfur chemistry in the early solar system |
we propose that cosmic ray pevatrons are pulsar wind nebulae (pwne) inside supernova remnants (snrs). the pwn initially expands into the freely expanding stellar ejecta. then, the pwn catches up with the shocked region of the snr, where particles can be slightly accelerated by the back and forth motion between the pwn and the snr, and some particles diffuse into the pwn. afterwards the pwn is compressed by the snr, where the particles in the pwn are accelerated by the adiabatic compression. using a monte carlo simulation, we show that particles accelerated by the snr to 0.1 pev can be reaccelerated to 1 pev until the end of the pwn compression. | pulsar wind nebulae inside supernova remnants as cosmic-ray pevatrons |
we present non-lte (non-local-thermodynamic-equilibrium) time-dependent radiative transfer simulations for ejecta produced by the detonation of a helium shell at the surface of a low-mass carbon/oxygen white dwarf (wd). this mechanism is one possible origin for supernovae (sne) with faint and fast-decaying light curves, such as .ia sne and ca-rich transients. our initial ejecta conditions at 1 d are given by the 0.18 b explosion model cop45hep2 of waldman et al. the 0.2 m⊙ ejecta initially contains 0.11 m⊙ of he, 0.03 m⊙ of ca, and 0.03 m⊙ of ti. we obtain an ∼ 5 d rise to a bolometric maximum of 3.59 × 1041 erg s-1, primarily powered by 48v decay. multi-band light curves show distinct morphologies, with a rise to maximum magnitude (-14.3 to -16.7 mag) that varies between 3 to 9 d from the u to the k bands. near-ir light curves show no secondary maximum. because of the presence of both he i and si ii lines at early times we obtain a hybrid type ia/ib classification. during the photospheric phase line blanketing is caused primarily by ti ii. at nebular times, the spectra show strong ca ii lines in the optical (but no [o i] 6300-6364 å emission), and ti ii in the near-ir. overall, these results match qualitatively the very disparate properties of .ia sne and ca-rich transients. although the strong ti ii blanketing and red colours that we predict are rarely observed, they are seen, for example, in ogle-2013- sn-079. furthermore, we obtain a faster light-curve evolution than, for example, ptf10iuv, indicating an ejecta mass >0.2 m⊙. an alternate scenario may be the merger of two wds, one or both composed of he. | one-dimensional non-lte time-dependent radiative transfer of an he-detonation model and the connection to faint and fast-decaying supernovae |
using star-forming galaxies sample in the nearby universe (0.02 < z < 0.10) selected from the sloan digital sky survey (dr7) and galaxy evolution explorer all-sky survey (gr5), we present a new empirical calibration for predicting dust extinction of galaxies from the hα-to-fuv flux ratio. we find that the hα dust extinction (ahα) derived with hα/hβ ratio (balmer decrement) increases with increasing hα/uv ratio as expected, but there remains a considerable scatter around the relation, which is largely dependent on stellar mass and/or hα equivalent width (ewhα). at fixed hα/uv ratio, galaxies with higher stellar mass (or galaxies with lower ewhα) tend to be more highly obscured by dust. we quantify this trend and establish an empirical calibration for predicting ahα with a combination of hα/uv ratio, stellar mass, and ewhα, with which we can successfully reduce the systematic uncertainties accompanying the simple hα/uv approach by ∼15-30 per cent. the new recipes proposed in this study will provide a convenient tool for predicting dust extinction level of galaxies particularly when balmer decrement is not available. by comparing ahα (derived with balmer decrement) and auv (derived with ir/uv luminosity ratio) for a subsample of galaxies for which akari far-infrared photometry is available, we demonstrate that more massive galaxies tend to have higher extra extinction towards the nebular regions compared to the stellar continuum light. considering recent studies reporting smaller extra extinction towards nebular regions for high-redshift galaxies, we argue that the dust geometry within high-redshift galaxies resembles low-mass galaxies in the nearby universe. | predicting dust extinction properties of star-forming galaxies from hα/uv ratio |
we present optical and near-infrared observations of sn~2022crv, a stripped envelope supernova in ngc~3054, discovered within 12 hrs of explosion by the distance less than 40 mpc survey. we suggest sn~2022crv is a transitional object on the continuum between sne ib and sne iib. a high-velocity hydrogen feature ($\sim$$-$20,000 -- $-$16,000 $\rm km\,s^{-1}$) was conspicuous in sn~2022crv at early phases, and then quickly disappeared around maximum light. by comparing with hydrodynamic modeling, we find that a hydrogen envelope of $\sim 10^{-3}$ \msun{} can reproduce the behaviour of the hydrogen feature observed in sn~2022crv. the early light curve of sn~2022crv did not show envelope cooling emission, implying that sn~2022crv had a compact progenitor with extremely low amount of hydrogen. the analysis of the nebular spectra shows that sn~2022crv is consistent with the explosion of a he star with a final mass of $\sim$4.5 -- 5.6 \msun{} that has evolved from a $\sim$16 -- 22 \msun{} zero-age main sequence star in a binary system with about 1.0 -- 1.7 \msun{} of oxygen finally synthesized in the core. the high metallicity at the supernova site indicates that the progenitor experienced a strong stellar wind mass loss. in order to retain a small amount of residual hydrogen at such a high metallicity, the initial orbital separation of the binary system is likely larger than $\sim$1000~$\rm r_{\odot}$. the near-infrared spectra of sn~2022crv show a unique absorption feature on the blue side of he i line at $\sim$1.005~$\mu$m. this is the first time that such a feature has been observed in a type ib/iib, and could be due to \ion{sr}{2}. further detailed modelling on sn~2022crv can shed light on the progenitor and the origin of the mysterious absorption feature in the near infrared. | sn 2022crv: iib, or not iib: that is the question |
hess j1809-193 is an extended tev γ-ray source and the origin of its γ-ray emission remains ambiguous. the pulsar wind nebula (pwn) of psr j1j1809-193 lying inside the extended γ-ray emission is a possible candidate. powered by the central pulsar, ultrarelativistic electrons in the pwn can produce radio to x-ray emission through synchrotron and γ-ray emission by inverse compton (ic) scattering. to check whether this pwn is the counterpart of hess j1809-193, we analyzed the chandra x-ray radial intensity profile and spectral index profile of this pwn. we then adopted a one-zone isotropic diffusion model to fit the kev and tev data. we found diffuse nonthermal x-ray emission extending beyond the pwn, which is likely an x-ray halo radiated by escaping electron/positron pairs from the pwn. a relatively strong magnetic field of ~20 μg is required to explain the spatial evolution of the x-ray spectrum (i.e., the significant softening of the spectrum with increasing distance from the pulsar), which, however, would suppress the ic radiation of pairs. our result implies that a hadronic component may be needed to explain hess j1809-193. | revisiting the chandra observation on the region of psr j1809-193: indication of the existence of an x-ray halo and implication for the origin of hess j1809-193 |
we present design considerations for the transiting exosatellites, moons, and planets in orion (tempo) survey with the nancy grace roman space telescope. this proposed 30 days survey is designed to detect a population of transiting extrasolar satellites, moons, and planets in the orion nebula cluster (onc). the young (1-3 myr), densely populated onc harbors about a thousand bright brown dwarfs (bds) and free-floating planetary-mass objects (ffps). tempo offers sufficient photometric precision to monitor ffps with m >1 m j for transiting satellites. the survey is also capable of detecting ffps down to sub-saturn masses via direct imaging, although follow-up confirmation will be challenging. tempo yield estimates include 14 (3-22) exomoons/satellites transiting ffps and 54 (8-100) satellites transiting bds. of this population, approximately 50% of companions would be "super-titans" (titan to earth mass). yield estimates also include approximately 150 exoplanets transiting young orion stars, of which >50% will orbit mid-to-late m dwarfs. tempo would provide the first census demographics of small exosatellites orbiting ffps and bds, while simultaneously offering insights into exoplanet evolution at the earliest stages. this detected exosatellite population is likely to be markedly different from the current census of exoplanets with similar masses (e.g., earth-mass exosatellites that still possess h/he envelopes). although our yield estimates are highly uncertain, as there are no known exoplanets or exomoons analogous to these satellites, the tempo survey would test the prevailing theories of exosatellite formation and evolution, which limit the certainty surrounding detection yields. | the tempo survey. i. predicting yields of transiting exosatellites, moons, and planets from a 30 days survey of orion with the roman space telescope |
x-ray polarization from the imaging x-ray polarimetry explorer (ixpe) provides an important new probe of the geometry of the pulsar emission zone and of particle acceleration in the surrounding pulsar wind nebula. however, with ixpe's modest ~20″-30″ spatial resolution, separation of the pulsar signal from the nebula is a challenge. conventional analysis defines an "off" phase window as pure nebular emission and subtracts its polarization to isolate the phase-varying pulsar (on-off fitting). we present a more sensitive scheme that uses external measurements of the nebula structure and the pulsar's light curve to isolate their contributions to the phase- and spatially-varying polarization via least-squares regression (simultaneous fitting). tests with simulation data show ~30% improvement in pulse phase polarization uncertainties, decreased background systematics, and substantially improved nebular polarization maps. applying simultaneous fitting to early ixpe crab data extracts additional phase bins with significant polarization. these bins show interesting departures from the well-known optical polarization sweeps, although additional exposure will be needed for precise model confrontation. | improved measurements of the ixpe crab polarization |
the presence of carbon-chain molecules in the interstellar medium (ism) has been known since the early 1970s and $>100$ such species have been identified to date, making up $>40\%$ of the total of detected ism molecules. they are prevalent not only in star-forming regions in our galaxy but also in other galaxies. these molecules provide important information on physical conditions, gas dynamics, and evolutionary stages of star-forming regions. more complex species of polycyclic aromatic hydrocarbons (pahs) and fullerenes (c$_{60}$ and c$_{70}$) have been detected in circumstellar envelopes around carbon-rich asymptotic giant branch (agb) stars and planetary nebulae, while pahs are also known to be a widespread component of the ism in most galaxies. recently, two line survey projects toward the starless core taurus molecular cloud-1 with large single-dish telescopes have detected many new carbon-chain species, including molecules containing benzene rings. these new findings raise fresh questions about carbon-bearing species in the universe. this article reviews various aspects of carbon-chain molecules, including observational studies, chemical simulations, quantum calculations, and laboratory experiments, and discusses open questions and how future facilities may answer them. | carbon-chain chemistry in the interstellar medium |
we use rapidly cooled achondrites to test the assumption of 26 al homogeneity in the solar nebula, by checking if there is a single value of tss, the absolute "pb-pb" age of the solar system's t = 0 , that makes concordant their ages from the al-mg and pb-pb systems. we find that values tss = 4568 . 42 ± 0 . 24 myr do make these ages concordant, and therefore the hypothesis of homogeneous 26 al is not falsified. this age, defined to be when the solar nebula had (26 al/27 al) = 5 . 23 × 10-5 , is significantly older than the ≈4567.3 myr inferred from direct measurements of pb-pb ages in cais. discrepancies between the al-mg and pb-pb chronometers in chondrules and cais have previously been interpreted as arising from heterogeneities in 26 al , under the presumption that the al-mg and pb-pb systems in cais closed simultaneously. we examine this assumption and show that resetting is to be expected in cais. in particular, we quantitatively demonstrate that it is plausible that pb-pb ages of cais were reset at late times, without resetting the earlier al-mg ages, if they were transiently heated in the same manner as chondrules. we critically examine pb-pb isochrons, refining data and suggesting best practices for their calculation and reporting. we advocate reporting chronometry as times of formation after t = 0 rather than absolute ages, as only the former is useful for astrophysical models of the solar nebula. we advocate averaging of multiple samples, rather than anchoring to individual meteorites, to improve precision. | statistical chronometry of meteorites. i. a test of 26al homogeneity and the pb-pb age of the solar system's t = 0 |
we describe a revised procedure for the numerical simulation of planetary nebulae luminosity functions (pnlfs), improving on previous work. the procedure is now based on new h-burning post-asymptotic giant branch (agb) evolutionary tracks. for a given stellar mass, the new central stars are more luminous and evolve faster. we have slightly changed the distribution of the [o iii] 5007 intensities relative to those of {{h}}β and the generation of absorbing factors, while still basing their numerical modeling on empirical information extracted from studies of galactic planetary nebulae (pns) and their central stars. we argue that the assumption of pns being completely optically thick to h-ionizing photons leads to conflicts with observations and show that to account for optically thin pns is necessary. we then use the new simulations to estimate a maximum final mass, clarifying its meaning, and discuss the effect of internal dust extinction as a possible way of explaining the persistent discrepancy between pnlfs and surface brightness fluctuation distances. by adjusting the range of minimum to maximum final mass, it is also possible to explain the observed variety of pnlf shapes at intermediate magnitudes. the new pn formation rates are calculated to be slightly lower than suggested by previous simulations based on older post-agb evolutionary tracks. | revised simulations of the planetary nebulae luminosity function |
most massive stars exchange mass with a companion, leading to evolution which is altered drastically from that expected of stars in isolation. such systems result from unusual binary evolution pathways and can place stringent constraints on the physics of these interactions. we use the r4 binary system's b[e] supergiant, which has been postulated to be the product of a stellar merger, to guide our understanding of such outcomes by comparing observations of r4 to the results of simulating a merger with the 3d hydrodynamics code flash. our approach tailors the simulation initial conditions to observed properties of r4 and implements realistic stellar profiles from the 1d stellar evolution code mesa onto the 3d grid, resolving the merger inspiral to within 0.02 r⊙. we map the merger remnant into mesa to track its evolution on the h-r diagram over a period of 104 yr. this generates a model for a b[e] supergiant with stellar properties, age, and nebula structure in qualitative agreement with those of the r4 system. our calculations provide evidence to support the idea that r4's b[e] supergiant was originally a member of a triple system in which the inner binary merged after its most massive member evolved off the main sequence, producing a new object of similar mass but significantly more luminosity than the a supergiant companion. the code framework presented in this paper, which was constructed to model tidal encounters, can be used to generate accurate models of a wide variety of merger stellar remnants. | the art of modeling stellar mergers and the case of the b[e] supergiant r4 in the small magellanic cloud |
this paper presents data and analysis of sn 2010kd, a low-redshift (z = 0.101) h-deficient superluminous supernova (slsn), based on ultraviolet/optical photometry and optical spectroscopy spanning between -28 and +194 days relative to b-band maximum light. the b-band light-curve comparison of sn 2010kd with a subset of well-studied slsne i at comparable redshifts indicates that it is a slow-decaying ptf12dam-like slsn. analytical light-curve modeling using the minim code suggests that the bolometric light curve of sn 2010kd favors circumstellar matter interaction for the powering mechanism. synapps modeling of the early-phase spectra does not identify broad h or he lines, whereas the photospheric-phase spectra are dominated by o i, o ii, c ii, c iv, and si ii, in particular the presence of both low- and high-velocity components of o ii and si ii lines. the nebular-phase spectra of sn 2010kd are dominated by o i and ca ii emission lines similar to those seen in other slsne i. the line velocities in sn 2010kd exhibit flatter evolution curves similar to sn 2015bn but with comparatively higher values. sn 2010kd shows a higher single-zone local thermodynamic equilibrium temperature in comparison to ptf12dam and sn 2015bn, and it has an upper o i ejected mass limit of ∼10 m⊙. the host of sn 2010kd is a dwarf galaxy with a high star formation rate (∼0.18 ± 0.04 m⊙ yr-1) and extreme emission lines. | sn 2010kd: photometric and spectroscopic analysis of a slow-decaying superluminous supernova |
we present a model for magnetic energy dissipation in a pulsar wind nebula. a better understanding of this process is required to assess the likelihood that certain astrophysical transients may be powered by the spin-down of a “millisecond magnetar.” examples include superluminous supernovae, gamma-ray bursts, and anticipated electromagnetic counterparts to gravitational wave detections of binary neutron star coalescence. our model leverages recent progress in the theory of turbulent magnetic relaxation to specify a dissipative closure of the stationary magnetohydrodynamic (mhd) wind equations, yielding predictions of the magnetic energy dissipation rate throughout the nebula. synchrotron losses are self-consistently treated. to demonstrate the model’s efficacy, we show that it can reproduce many features of the crab nebula, including its expansion speed, radiative efficiency, peak photon energy, and mean magnetic field strength. unlike ideal mhd models of the crab (which lead to the so-called σ-problem), our model accounts for the transition from ultra to weakly magnetized plasma flow and for the associated heating of relativistic electrons. we discuss how the predicted heating rates may be utilized to improve upon models of particle transport and acceleration in pulsar wind nebulae. we also discuss implications for the crab nebula’s γ-ray flares, and point out potential modifications to models of astrophysical transients invoking the spin-down of a millisecond magnetar. | turbulent magnetic relaxation in pulsar wind nebulae |
we present a comparative study of the near-infrared (nir) h2 line emission from five regions near hot young stars: sharpless 140, ngc 2023, ic 63, the horsehead nebula, and the orion bar. this emission originates in photodissociation or photon-dominated regions (pdrs), interfaces between photoionized and molecular gas near hot (o) stars or reflection nebulae illuminated by somewhat cooler (b) stars. in these environments, the dominant excitation mechanism for nir emission lines originating from excited rotational-vibrational (rovibrational) levels of the ground electronic state is radiative or uv excitation (fluorescence), wherein absorption of far-uv photons pumps h2 molecules into excited electronic states from which they decay into the upper levels of the nir lines. our sources span a range of uv radiation fields (g0 = 102-105) and gas densities (nh = 104-106 cm-3), enabling examination of how these properties affect the emergent spectrum. we obtained high-resolution (r ≈ 45,000) spectra spanning 1.45-2.45 μm on the 2.7 m harlan j. smith telescope at mcdonald observatory with the immersion grating infrared spectrometer (igrins), detecting up to over 170 transitions per source from excited vibrational states (v = 1-14). the populations of individual rovibrational levels derived from these data clearly confirm uv excitation. among the five pdrs in our survey, the orion bar shows the greatest deviation of the populations and spectrum from pure uv excitation, while sharpless 140 shows the least deviation. however, we find that all five pdrs exhibit at least some modification of the level populations relative to their values under pure uv excitation, a result we attribute to collisional effects. | a near-infrared survey of uv-excited molecular hydrogen in photodissociation regions |
the galactic b[e] supergiant mwc 137 is surrounded by a large-scale optical nebula. to shed light on the physical conditions and kinematics of the nebula, we analyze the optical forbidden emission lines [n ii] λλ 6548,6583 and [s ii] λλ 6716,6731 in long-slit spectra taken with alfosc at the nordic optical telescope. the radial velocities display a complex behavior but, in general, the northern nebular features are predominantly approaching while the southern ones are mostly receding. the electron density shows strong variations across the nebula with values spreading from about zero to ~800 cm-3. higher densities are found closer to mwc 137 and in regions of intense emission, whereas in regions with high radial velocities the density decreases significantly. we also observe the entire nebula in the two [s ii] lines with the scanning fabry-perot interferometer attached to the 6 m telescope of the special astrophysical observatory. these data reveal a new bow-shaped feature at p.a. = 225°-245° and a distance 80″ from mwc 137. a new hα image has been taken with the danish 1.54 m telescope on la silla. no expansion or changes in the nebular morphology appear within 18.1 yr. we derive a mass of ${37}_{-5}^{+9}\,{m}_{\odot }$ and an age of 4.7 ± 0.8 myr for mwc 137. furthermore, we detect a period of 1.93 d in the time series photometry collected with the tess satellite, which could suggest stellar pulsations. other, low-frequency variability is seen as well. whether these signals are caused by internal gravity waves in the early-type star or by variability in the wind and circumstellar matter currently cannot be distinguished. * based on observations collected with (1) the nordic optical telescope, operated by the nordic optical telescope scientific association at the observatorio del roque de los muchachos, la palma, spain, of the instituto de astrofisica de canarias, (2) the danish 1.54 m telescope at la silla, chile, and (3) the 6 m telescope of the special astrophysical observatory (sao), russia. | resolving the circumstellar environment of the galactic b[e] supergiant star mwc 137.ii. nebular kinematics and stellar variability |
the common envelope phase was first proposed more than 40 years ago to explain the origins of evolved, close binaries like cataclysmic variables. it is now believed that the phase plays a critical role in the formation of a wide variety of other phenomena ranging from type ia supernovae through to binary black holes, while common envelope mergers are likely responsible for a range of enigmatic transients and supernova imposters. yet, despite its clear importance, the common envelope phase is still rather poorly understood. here, we outline some of the basic principles involved, the remaining questions as well as some of the recent observational hints from common envelope phenomena - namely planetary nebulae and luminous red novae - which may lead to answering these open questions. | observational constraints on the common envelope phase |
wolf-rayet stars are amongst the rarest but also most intriguing massive stars. their extreme stellar winds induce famous multiwavelength circumstellar gas nebulae of various morphologies, spanning from circles and rings to bipolar shapes. this study is devoted to the investigation of the formation of young, asymmetric wolf-rayet gas nebulae and we present a 2.5-dimensional magneto-hydrodynamical toy model for the simulation of wolf-rayet gas nebulae generated by wind-wind interaction. our method accounts for stellar wind asymmetries, rotation, magnetization, evolution, and mixing of materials. it is found that the morphology of the wolf-rayet nebulae of blue supergiant ancestors is tightly related to the wind geometry and to the stellar phase transition time interval, generating either a broadened peanut-like or a collimated jet-like gas nebula. radiative transfer calculations of our wolf-rayet nebulae for dust infrared emission at $24\, \mu \rm m$ show that the projected diffuse emission can appear as oblate, bipolar, ellipsoidal, or ring structures. important projection effects are at work in shaping observed wolf-rayet nebulae. this might call a revision of the various classifications of wolf-rayet shells, which are mostly based on their observed shape. particularly, our models question the possibility of producing pre-wolf-rayet wind asymmetries, responsible for bipolar nebulae like ngc 6888, within the single red supergiant evolution channel scenario. we propose that bipolar wolf-rayet nebulae can only be formed within the red supergiant scenario by multiple/merged massive stellar systems, or by single high-mass stars undergoing additional, e.g. blue supergiant, evolutionary stages prior to the wolf-rayet phase. | on the bipolarity of wolf-rayet nebulae |
wolf-rayet ([wr]) and weak-emission-line (wels) central stars of planetary nebulae (pns) have hydrogen-deficient atmospheres, whose origins are not well understood. in the present study, we have conducted plasma diagnostics and abundance analyses of 18 galactic pns surrounding [wr] and wels nuclei, using collisionally excited lines (cels) and optical recombination lines (orls) measured with the wide field spectrograph on the australian national university 2.3 m telescope at the siding spring observatory complemented with optical archival data. our plasma diagnostics imply that the electron densities and temperatures derived from cels are correlated with the intrinsic nebular hβ surface brightness and excitation class, respectively. self-consistent plasma diagnostics of heavy-element orls of n2+ and o2+ suggest that a small fraction of cool (≲7000 k), dense (~104-105 cm-3) materials may be present in some objects, though with large uncertainties. our abundance analyses indicate that the abundance discrepancy factors (adfs ≡ orls/cels) of o2+ are correlated with the dichotomies between forbidden-line and he i temperatures. our results likely point to the presence of a tiny fraction of cool, oxygen-rich dense clumps within diffuse warm ionized nebulae. moreover, our elemental abundances derived from cels are mostly consistent with asymptotic giant branch models in the range of initial masses from 1.5 to 5 m ⊙. further studies are necessary to understand better the origins of abundance discrepancies in pns around [wr] and wels stars. | physical and chemical properties of wolf-rayet planetary nebulae |
we present results on the nature of extreme ejective feedback episodes and the physical conditions of a population of massive (m * ~ 1011 m ⊙), compact starburst galaxies at z = 0.4-0.7. we use data from keck/nirspec, sdss, gemini/gmos, mmt, and magellan/mage to measure rest-frame optical and near-ir spectra of 14 starburst galaxies with extremely high star formation rate surface densities (mean σsfr ~ 2000 m ⊙ yr-1 kpc-2) and powerful galactic outflows (maximum speeds v 98 ~ 1000-3000 km s-1). our unique data set includes an ensemble of both emission ([o ii] λλ3726,3729, hβ, [o iii] λλ4959,5007, hα, [n ii] λλ6549,6585, and [s ii] λλ6716,6731) and absorption (mg ii λλ2796,2803, and fe ii λ2586) lines that allow us to investigate the kinematics of the cool gas phase (t ~ 104 k) in the outflows. employing a suite of line ratio diagnostic diagrams, we find that the central starbursts are characterized by high electron densities (median ne~ 530 cm-3), and high metallicity (solar or supersolar). we show that the outflows are most likely driven by stellar feedback emerging from the extreme central starburst, rather than by an agn. we also present multiple intriguing observational signatures suggesting that these galaxies may have substantial lyman continuum (lyc) photon leakage, including weak [s ii] nebular emission lines. our results imply that these galaxies may be captured in a short-lived phase of extreme star formation and feedback where much of their gas is violently blown out by powerful outflows that open up channels for lyc photons to escape. | physical properties of massive compact starburst galaxies with extreme outflows |
context. the nucleus of the planetary nebula hen 2-428 is a short orbital-period (4.2 h), double-lined spectroscopic binary, whose status as a potential supernova type ia progenitor has raised some controversy in the literature.aims: with the aim of resolving this debate, we carried out an in-depth reanalysis of the system.methods: our approach combines a refined wavelength calibration, thorough line-identifications, improved radial-velocity measurements, non-lte spectral modeling, as well as multi-band light-curve fitting. our results are then discussed in view of state-of-the-art stellar evolutionary models.results: besides systematic zero-point shifts in the wavelength calibration of the osiris spectra which were also used in the previous analysis of the system, we found that the spectra are contaminated with diffuse interstellar bands. our voigt-profile radial velocity fitting method, which considers the additional absorption of these diffuse interstellar bands, reveals significantly lower masses (m1 = 0.66 ± 0.11 m⊙ and m2 = 0.42 ± 0.07 m⊙) than previously reported and a mass ratio that is clearly below unity. our spectral and light curve analyses lead to consistent results, however, we find higher effective temperatures and smaller radii than previously reported. moreover, we find that the red-excess that was reported before to prove to be a mere artifact of an outdated reddening law that was applied.conclusions: our work shows that blends of he ii λ 5412 å with diffuse interstellar bands have led to an overestimation of the previously reported dynamical masses of hen 2-428. the merging event of hen 2-428 will not be recognised as a supernova type ia, but most likely leads to the formation of a h-deficient star. we suggest that the system was formed via a first stable mass transfer episode, followed by common envelope evolution, and it is now composed of a post-early asymptotic giant branch star and a reheated he-core white dwarf. | an in-depth reanalysis of the alleged type ia supernova progenitor henize 2-428 |
ultraluminous infrared galaxies (ulirgs) represent a critical stage in the merger-driven evolution of galaxies when active galactic nucleus (agn) activity is common and agn feedback is expected. we present high-sensitivity and large field-of-view integral field spectroscopy of the ulirg mrk 273 using new data from the keck cosmic web imager (kwci). the kcwi data capture the complex nuclear region and the two extended nebulae in the northeast (ne) and southwest (sw) to ~20 kpc scales. kinematics in the nuclear region show a fast, extended, bipolar outflow in the direction of the previously reported nuclear superbubbles spanning ~5 kpc, two to three times greater than the previously reported size. the larger-scale extended nebulae on ~20 kpc show fairly uniform kinematics with fwhm ~ 300 km s-1 in the sw nebula and fwhm ~ 120 km s-1 in the ne nebula. we detect for the first time high-ionization [ne v] 3426, [o iii] 4363, and he ii 4684 emission lines in the extended ne nebula. emission line ratios in the nuclear region correlate with the kinematic structures, with the bipolar outflow and the less collimated "outflow regions" showing distinct line ratio trends. line ratio diagnostics of high-ionization emission lines reveal a nontrivial contribution from shock plus precursor ionization in the ne nebula and the nuclear region mixed with agn photoionization. these data are highly constraining for models of cool ionized gas existing 20 kpc from a galactic nucleus. | kcwi observations of the extended nebulae in mrk 273 |
the relation between the progenitor mass and the kinetic energy of the explosion is a key toward revealing the explosion mechanism of stripped-envelope core-collapse supernovae (sesne). here, we present a method to derive this relation using the nebular spectra of sesne, based on the correlation between [o i]/[ca ii], which is an indicator of progenitor mass, and the width of [o i], which measures the expansion velocity of the oxygen-rich material. to explain the correlation, the kinetic energy (e k) is required to be positively correlated with the progenitor mass as represented by the co core mass (m co). we demonstrate that sne iib/ib and sne ic/ic-bl follow the same m co-e k scaling relation, which suggests that helium-rich and helium-deficient sne share the same explosion mechanism. the m co-e k relation derived in this work is compared with the ones derived from early phase observations. the results are largely in good agreement. combined with early phase observations, the method presented in this work provides a chance to scan through the ejecta from the outermost region to the dense inner core, which is important to reveal the global properties of the ejecta and constrain the explosion mechanism of core-collapse sne. | inferring the progenitor mass-kinetic energy relation of stripped-envelope core-collapse supernovae from nebular spectroscopy |
lyα emission nebulae are ubiquitous around high-redshift galaxies and are tracers of the gaseous environment on scales out to ≳100 pkpc (proper kiloparsec). high-redshift radio galaxies (hzrgs, type-2 radio-loud quasars) host large-scale nebulae observed in the ionised gas differ from those seen in other types of high-redshift quasars. in this work, we exploit muse observations of lyα nebulae around eight hzrgs (2.92 < z < 4.51). all of the hzrgs have large-scale lyα emission nebulae with seven of them extended over 100 pkpc at the observed surface brightness limit (∼2 − 20 × 10−19 erg s−1 cm−2 arcsec−2). because the emission line profiles are significantly affected by neutral hydrogen absorbers across the entire nebulae extent, we performed an absorption correction to infer maps of the intrinsic lyα surface brightness, central velocity, and velocity width, all at the last scattering surface of the observed lyα photons. we find the following: (i) that the intrinsic surface brightness radial profiles of our sample can be described by an inner exponential profile and a power law in the low luminosity extended part; (ii) our hzrgs have a higher surface brightness and more asymmetric nebulae than both radio-loud and radio-quiet type-1 quasars; (iii) intrinsic nebula kinematics of four hzrgs show evidence of jet-driven outflows but we find no general trends for the whole sample; (iv) a relation between the maximum spatial extent of the lyα nebula and the projected distance between the active galactic nuclei (agn) and the centroids of the lyα nebula; and (v) an alignment between radio jet position angles and the lyα nebula morphology. all of these findings support a scenario in which the orientation of the agn has an impact on the observed nebular morphologies and resonant scattering may affect the shape of the surface brightness profiles, nebular kinematics, and relations between the observed lyα morphologies. furthermore, we find evidence showing that the outskirts of the ionised gas nebulae may be `contaminated' by lyα photons from nearby emission halos and that the radio jet affects the morphology and kinematics of the nebulae. overall, this work provides results that allow us to compare lyα nebulae around various classes of quasars at and beyond cosmic noon (z ∼ 3). | 3d tomography of the giant lyα nebulae of z ≈ 3-5 radio-loud agn |
aims: we present a non-parametric morphology analysis of the stellar continuum and nebular emission lines for a sample of local galaxies. we explore the dependence of the various morphological parameters on wavelength and morphological type. our goal is to quantify the difference in morphology between the stellar and nebular components.methods: we derived the non-parametric morphological indicators of 364 galaxies from the calar alto legacy integral field area (califa) survey. to calculate those indicators, we applied the statmorph package on the high-quality integral field spectroscopic data cubes, as well as to the most prominent nebular emission-line maps, namely [o iii]λ5007, hα, and [n ii]λ6583.results: we show that the physical size of galaxies, m20 index, and concentration have a strong gradient from blue to red optical wavelengths. we find that the light distribution of the nebular emission is less concentrated than the stellar continuum. a comparison between the non-parametric indicators and the galaxy physical properties revealed a very strong correlation of the concentration with the specific star formation rate and morphological type. furthermore, we explore how the galaxy inclination affects our results. we find that edge-on galaxies show a more rapid change in physical size and concentration with increasing wavelength due to the increase in the optical free path.conclusions: we conclude that the apparent morphology of galaxies originates from the pure stellar distribution, but the morphology of the interstellar medium presents differences with respect to the morphology of the stellar component. our analysis also highlights the importance of dust attenuation and galaxy inclination in the measurement of non-parametric morphological indicators, especially in the wavelength range 4000−5000 å. data are only available at the cds via anonymous ftp to cdsarc.cds.unistra.fr (ftp://130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/j/a+a/673/a63 | non-parametric galaxy morphology from stellar and nebular emission with the califa sample |
context. mass and angular momentum are key parameters of galaxies. their coevolution establishes an empirical relation between the specific stellar angular momentum j* and the stellar mass m* that depends on morphology.aims: for this work, we measured j* in a sample of 32 early-type galaxies (etgs) from the epn.s survey, using the full two-dimensional kinematic information. we present local λ profiles and projected j* profiles in apertures. we derived the distribution of these galaxies on the total j* - m* plane and determined the ratio between the stellar j* and the specific angular momentum of the host dark matter halo.methods: we used integral-field-spectroscopic data in the central regions (one to two effective radii, re) and planetary nebula (pn) kinematics in the outskirts (out to a mean 6re). in the j* determination, we accounted for misaligned rotation and for the differences between light-weighted j* and mass-weighted j*, estimating also the effects of gradients in the mass-to-light ratio driven by variations in the initial mass function. we used simulated etgs from the illustristng simulation tng100 to correct for the limited radial coverage of the pn data and to account for projection effects on j*.results: the radially extended, two-dimensional kinematic data show that the stellar halos of etgs do not contain large stellar mass fractions of high j*. the j* profiles of fast-rotator etgs are largely converged within the range of the data. for slow rotators, j* is still rising and is estimated to increase beyond 6re by up to 40%, using simulated galaxies from tng100. more than 60% of their stellar halo angular momentum is in misaligned rotation. we find that the epn.s etg sample displays the well-known correlation between j*, m*, and morphology: elliptical galaxies have systematically lower j* than similar mass s0 galaxies. however, fast and slow rotators lie on the same relation within errors with the slow rotators falling at the high m* end. a power-law fit to the mass-weighted j* - m* relation gives a slope of 0.55 ± 0.17 for the s0s and 0.76 ± 0.23 for the ellipticals, with normalization about four and nine times lower than spirals, respectively. the estimated retained fraction of angular momentum at 1010 ≤ m* ≤ 1010.5 m⊙ is ∼25% for s0s and > 10% for ellipticals, and decreases by ∼1.5 orders of magnitude at m* ∼ 1012 m⊙.conclusions: our results show that etgs have substantially lower j* than spiral galaxies with similar m*. their j* must be lost during their evolution, and/or retained in the hot gas component and the satellite galaxies that have not yet merged with the central galaxy. | the extended planetary nebula spectrograph (epn.s) early-type galaxy survey: the specific angular momentum of etgs |
nearly all intragroup (igl) and intracluster light (icl) comes from stars that are not bound to any single galaxy but were formed in galaxies and later unbound from them. in this review we focus on the physical properties - phase space distribution, metallicity and age - of the icl and igl component of the clusters/groups in the local universe, within 100 mpc distance. kinematic information on these very low surface brightness structures mostly comes from discrete tracers such as planetary nebulae and globular clusters, showing highly unrelaxed velocity distributions. cosmological hydrodynamical simulations provide key predictions for the dynamical state of igl and icl and find that most ic stars are dissolved from galaxies that subsequently merge with the central galaxy. the increase of the measured velocity dispersion with radius in the outer halos of bright galaxies is a key feature to identify igl and icl components. in the local groups and clusters, igl and icl are more centrally concentrated than the galaxies, their typical fractions are few to ten percent, i.e. significantly lower than the average values in more evolved clusters, and mostly consist of old (10 gyr) and metal-poor stars ([m/fe]<-1.0) stars. the new imaging facility, like lsst and euclid, and the ``big eyes'' on the sky - elt and jwst with their advanced instrumentation -promise to greatly increase information on the satellite progenitors of the icl, their ages, metal content, masses, and evolution and, thereby, our understanding of this enigmatic component. | kinematics of the diffuse intragroup/intracluster light in groups and clusters of galaxies in the local universe (within 100 mpc distance) |
unbiased sky background modeling is crucial for the analysis of deep wide-field images, but it remains a major challenge in low surface brightness astronomy. traditional image processing algorithms are often designed to produce artificially flat backgrounds, erasing astrophysically meaningful structures. in this paper, we present three ideas that can be combined to produce wide-field astronomical data that preserve accurate representations of the background sky: (1) use of all-sky infrared/submillimeter data to remove the large-scale time-varying components while leaving the scattered light from galactic cirrus intact, with the assumptions of (a) the underlying background has little power on small scales, and (b) the galactic cirrus in the field is optically thin on large scales; (2) censoring of frames contaminated by anomalously prominent wings in the wide-angle point-spread function; and (3) incorporation of spatial covariance in image stacking that controls the local background consistency. we demonstrate these methods using example data sets obtained with the dragonfly telephoto array, but these general techniques are prospective to be applied to improve sky models in data obtained from other wide-field imaging surveys, including those from the upcoming vera rubin telescope. | a recipe for unbiased background modeling in deep wide-field astronomical images |
nebular emission lines are powerful diagnostics for the physical processes at play in galaxy formation and evolution. moreover, emission-line galaxies (elgs) are one of the main targets of current and forthcoming spectroscopic cosmological surveys. we investigate the contributions to the line luminosity functions (lfs) of different galaxy populations in the local universe, providing a benchmark for future surveys of earlier cosmic epochs. the large statistics of the observations from the sdss dr7 main galaxy sample and the mpa-jhu spectral catalogue enabled us to precisely measure the h$\alpha$, h$\beta$, [oii], [oiii], and, for the first time, the [nii], and [sii] emission-line lfs over ~2.4 gyrs in the low-z universe, 0.02<z<0.22. we present a generalized 1/vmax lf estimator capable of simultaneously correcting for spectroscopic, r-band magnitude, and emission-line incompleteness. we studied the contribution to the lf of different types of elgs classified using two methods: (i) the value of the specific star formation rate (ssfr), and (ii) the line ratios on the baldwin-phillips-terlevich (bpt) and the whan (i.e., h$\alpha$ equivalent width versus the [nii]/h$\alpha$ line ratio) diagrams. the elgs in our sample are mostly star forming, with 84 per cent having ssfr>10$^{-11}$/yr. when classifying elgs using the bpt+whan diagrams, we find that 63.3 per cent are star forming, only 0.03 are passively evolving, and 1.3 have nuclear activity (seyfert). the rest are low-ionization narrow emission-line regions (liners) and composite elgs. we found that a saunders function is the most appropriate to describe all of the emission-line lfs, both observed and dust-extinction-corrected. they are dominated by star-forming regions, except for the bright end of the [oiii] and [nii] lfs (i.e. l[nii]>10$^{42}$ erg/s, l[oiii]>10$^{43}$ erg/s), where the contribution of seyfert galaxies is not negligible. | characterizing the elg luminosity functions in the nearby universe |
we present atacama large millimeter/sub-millimeter array neutral carbon, [${\rm c\, \small {\rm i}}$](1-0), line observations that probe molecular hydrogen gas (h2) within seven radio galaxies at z = 2.9-4.5 surrounded by extended (≳100 kpc) ly α nebulae. we extract [${\rm c\, \small {\rm i}}$](1-0) emission from the radio-active galactic nuclei (agns) host galaxies whose positions are set by near-infrared detections and radio detections of the cores. additionally, we place constraints on the galaxies' systemic redshifts via ${\rm he\, \small {\rm ii}}$ λ1640 lines seen with the multi-unit spectroscopic explorer. we detect faint [${\rm c\, \small {\rm i}}$] emission in four out of seven sources. in two of these galaxies, we discover narrow-line emission of full width at half-maximum ≲100 km s-1 that may trace emission from bright kpc-scale gas clouds within the interstellar medium (ism). in the other two [${\rm c\, \small {\rm i}}$]-detected galaxies, line dispersions range from ~100-600 km s-1 and may be tracing the rotational component of the cold gas. overall, the [${\rm c\, \small {\rm i}}$] line luminosities correspond to h2 masses of $m_{\rm h_2,[{\rm c\, \small {\rm i}}]} \simeq (0.5{\!-\!}3) \times 10^{10}$ m⊙ for the detections and $m_{\rm h_2,[{\rm c\, \small {\rm i}}]}\lt 0.65\times 10^{10}$ m⊙ for the [${\rm c\, \small {\rm i}}$] non-detections in three out of seven galaxies within the sample. the molecular gas masses in our sample are relatively low in comparison to previously reported measures for similar galaxies that are $m_{\rm h_2,[{\rm c\, \small {\rm i}}]} \simeq (3{\!-\!}4) \times 10^{10}$ m⊙. our results imply that the observed faintness in carbon emission is representative of a decline in molecular gas supply from previous star formation epochs and/or a displacement of molecular gas from the ism due to jet-powered outflows. | faint [c i](1-0) emission in z 3.5 radio galaxies |
late-time spectra of type ia supernovae (sne ia) are important in clarifying the physics of their explosions, as they provide key clues to the inner structure of the exploding white dwarfs. we examined late-time optical spectra of 36 sne ia, including five from our own project (sne 2019np, 2019ein, 2021hpr, 2021wuf, and 2022hrs), with phase coverage of ~200 to ~400 d after maximum light. at this late phase, the outer ejecta have become transparent and the features of inner iron-group elements emerge in the spectra. based on multicomponent gaussian fits and reasonable choices for the pseudo-continuum around ni and fe emission features, we get reliable estimates of the ni to fe ratio, which is sensitive to the explosion models of sne ia. our results show that the majority (about 67 per cent) of our sne ia are more consistent with the sub-chandrasekhar-mass (i.e. double-detonation) model, although they could be affected by evolutionary or ionization effects. moreover, we find that the si ii λ6355 velocity measured around the time of maximum light tends to increase with the ni to fe ratio for the subsample with either redshifted or blueshifted nebular velocities, suggesting that progenitor metallicity might play an important role in accounting for the observed velocity diversity of sne ia. | implications for the explosion mechanism of type ia supernovae from their late-time spectra |
b[e] stars are massive b type emission line stars in different evolutionary stages ranging from pre-main sequence to post-main sequence. due to their mass loss and ejection events these objects deposit huge amounts of mass and energy into their environment and enrich it with chemically processed material, contributing significantly to the chemical and dynamical evolution of their host galaxies. however, the large-scale environments of these enigmatic objects have not attracted much attention. the first and so far only catalog reporting the detection of extended shells around a sample of b[e] stars was an hα imaging survey carried out in the year 2001, and was limited to bright targets in the northern hemisphere. we have recently started a follow-up of those targets to detect possible evolution of their nebulae in the plane of the sky over a baseline of two decades. furthermore, we extend our survey to southern targets and fainter northern ones to complement and complete our knowledge on large-scale ejecta surrounding b[e] stars. besides imaging in hα and selected nebular lines, we utilize long-slit and 3d spectral observations across the nebulae to derive their physical properties. we discovered pronounced nebula structures around 15 more objects, resulting in a total of 27 b[e] stars with a large-scale nebula. here we present our (preliminary) results for three selected objects: the two massive supergiants mwc137 and mwc 314, and the unclassified b[e] star mwc 819. | follow-up of extended shells around b[e] stars |
jwst near infrared camera (nircam) observations at 1.5-4.5 μm have provided broadband and narrowband imaging of the evolving remnant of sn 1987a with unparalleled sensitivity and spatial resolution. comparing with previous marginally spatially resolved spitzer infrared array camera (irac) observations from 2004 to 2019 confirms that the emission arises from the circumstellar equatorial ring (er), and the current brightness at 3.6 and 4.5 μm was accurately predicted by extrapolation of the declining brightness tracked by irac. despite the regular light curve, the nircam observations clearly reveal that much of this emission is from a newly developing outer portion of the er. spots in the outer er tend to lie at position angles in between the well-known er hotspots. we show that the bulk of the emission in the field can be represented by five standard spectral energy distributions, each with a distinct origin and spatial distribution. this spectral decomposition provides a powerful technique for distinguishing overlapping emission from the circumstellar medium and the supernova ejecta, excited by the forward and reverse shocks, respectively. | jwst nircam observations of sn 1987a: spitzer comparison and spectral decomposition |
we present the first spectroscopic measurement of multiple rest-frame optical emission lines at z > 4. during the mosfire deep evolution field survey, we observed the galaxy goodsn-17940 with the keck i/mosfire spectrograph. the k-band spectrum of goodsn-17940 includes significant detections of the [o ii]λλ3726,3729, [ne iii]λ3869, and hγ emission lines and a tentative detection of hδ, indicating z spec = 4.4121. goodsn-17940 is an actively star-forming z > 4 galaxy based on its k-band spectrum and broadband spectral energy distribution. a significant excess relative to the surrounding continuum is present in the spitzer/irac channel 1 photometry of goodsn-17940, due primarily to strong hα emission with a rest-frame equivalent width of ew(hα) = 1200 å. based on the assumption of 0.5 z ⊙ models and the calzetti attenuation curve, goodsn-17940 is characterized by {m}* ={5.0}-0.2+4.3× {10}9 {m}⊙ . the balmer decrement inferred from hα/hγ is used to dust correct the hα emission, yielding {{sfr(h}}α )={320}-140+190 {m}⊙{{{yr}}}-1. these m * and star formation rate (sfr) values place goodsn-17940 an order of magnitude in sfr above the z ∼ 4 star-forming “main sequence.” finally, we use the observed ratio of [ne iii]/[o ii] to estimate the nebular oxygen abundance in goodsn-17940, finding o/h ∼ 0.2 (o/h)⊙. combining our new [ne iii]/[o ii] measurement with those from stacked spectra at z ∼ 0, 2, and 3, we show that goodsn-17940 represents an extension to z > 4 of the evolution toward higher [ne iii]/[o ii] (i.e., lower o/h) at fixed stellar mass. it will be possible to perform the measurements presented here out to z ∼ 10 using the james webb space telescope. based on data obtained at the w.m. keck observatory, which is operated as a scientific partnership among the california institute of technology, the university of california, and the national aeronautics and space administration, and was made possible by the generous financial support of the w.m. keck foundation. | the mosdef survey: first measurement of nebular oxygen abundance at z > 4 |
we present the spectral and spatial evolution of h2o masers associated with the water fountain source iras 18043-2116, found in observations with the nobeyama 45 m telescope and the australia telescope compact array. we have found new highest-velocity components of the h2o masers (at the redshifted side v lsr ≃ 376 km s-1 and at the blueshifted side v lsr ≃ -165 km s-1), and the resulting velocity spread of ≃540 km s-1 breaks the speed record of fast jets/outflows in this type of sources. the locations of those components have offsets from the axis joining the two major maser clusters, indicating a large opening angle of the outflow (~60°). the evolution of the maser cluster separation of ~2.9 mas yr-1 and the compact (~0.″2) co emission source mapped with the atacama large millimeter-submillimeter array suggest a very short (~30 yr) timescale of the outflow. we also confirmed an increase in the flux density of the 22 ghz continuum source. the properties of the jet and the continuum sources and their possible evolution in the transition to the planetary nebula phase are further discussed. *released on 2021 march 1. | evolution of the outflow in the water fountain source iras 18043-2116 |
the origin of volatiles on earth is still a matter of debate. noble gases are an efficient geochemical tool to constrain earth formation processes due to their inertness. several studies have focused on the neon isotopic composition of the lower mantle because the 20ne/22ne ratio is thought to reflect that of earth's primordial components. two models to explain the origin of light noble gases on earth have been proposed: either solar wind implantation onto the earth's solid precursors or dissolution into the mantle of a primordial atmosphere captured from solar nebula gas. in order to test these two models, we analyzed the noble gas compositions (helium, neon and argon) of two submarine oceanic island basalt glasses from fernandina volcano (galápagos archipelago), which have among the most primitive/unradiogenic terrestrial helium and neon isotopic compositions. several sample pieces are studied both by step-crushing and by laser ablation analyses of single vesicles. results of step-crushing are consistent with those of laser ablation analyses, but the latter results provide new insights into the origin of atmospheric contamination. the single-vesicle laser-ablation measurements overlap with the step crushing results, but have systematically higher 40ar/36ar, and 3he/36ar, suggesting less atmospheric contamination using this method. the single vesicle data therefore suggest that atmospheric contamination is introduced by exposure to the modern atmosphere, after sample collection. 3he/4he values are about 23 times the atmospheric ratio (r/ra) for the two fernandina (galápagos) samples, in agreement with previous studies. we obtain 20ne/22ne and 40ar/36ar isotopic ratios as high as 12.91 and 9400, respectively, for the mantle source of the galápagos hotspot. the new data show that step-crushing and laser ablation analyses are complementary methods that should be used together to derive the noble gas ratios in uncontaminated samples. the results of neon compositions are consistent with previous hotspot studies and support the model of solar wind implantation associated with sputtering to explain helium and neon origins on earth. | neon isotopic composition of the mantle constrained by single vesicle analyses |
iron is the most abundant multivalent element in planetary reservoirs, meaning its isotope composition (expressed as δ57fe) may record signatures of processes that occurred during the formation and subsequent differentiation of the terrestrial planets. chondritic meteorites, putative constituents of the planets and remnants of undifferentiated inner solar system bodies, have δ57fe ≈ 0 ‰; an isotopic signature shared with the martian shergottite-nakhlite-chassignite (snc) suite of meteorites. the silicate earth and moon, as represented by basaltic rocks, are distinctly heavier, δ57fe ≈ + 0.1 ‰. however, some authors have recently argued, on the basis of iron isotope measurements of abyssal peridotites, that the composition of the earth's mantle is δ57fe = + 0.04 ± 0.04 ‰, indistinguishable from the mean martian value. to provide a more robust estimate for mars, we present new high-precision iron isotope data on 17 snc meteorites and 5 mineral separates. we find that the iron isotope compositions of martian meteorites reflect igneous processes, with nakhlites and evolved shergottites displaying heavier δ57fe (+ 0.05 ± 0.03 ‰), whereas mgo-rich rocks are lighter (δ57fe ≈ - 0.01 ± 0.02 ‰). these systematics are controlled by the fractionation of olivine and pyroxene, attested to by the lighter isotope composition of pyroxene compared to whole rock nakhlites. extrapolation of the δ57fe snc liquid line of descent to a putative martian mantle yields a δ57fe value lighter than its terrestrial counterpart, but indistinguishable from chondrites. iron isotopes in planetary basalts of the inner solar system correlate positively with fe/mn and silicon isotopes. while mars and iv-vesta are undepleted in iron and accordingly have chondritic δ57fe, the earth experienced volatile depletion at low (1300 k) temperatures, likely at an early stage in the solar nebula, whereas additional post-nebular fe loss is possible for the moon and angrites. | on the iron isotope composition of mars and volatile depletion in the terrestrial planets |
as shown by broadband observations, pulsar wind nebulae (pwne) are characterized by a broken power-law spectrum of synchrotron emission. based on modern magnetohydrodynamic (mhd) turbulence theories, we investigate the reacceleration of electrons in the pwn through the adiabatic stochastic acceleration (asa), which arises from fundamental dynamics of mhd turbulence. the asa acts to flatten the injected energy spectrum of electrons at low energies, while synchrotron cooling results in a steep spectrum of electrons at high energies. their dominance in different energy ranges leads to a flat radio spectrum (fν ) and a steep x-ray spectrum. our analytical spectral shapes generally agree well with the observed synchrotron spectra of radio- and x-ray-bright pwne. the spectral break corresponding to the balance between the asa and synchrotron losses provides a constraint on the acceleration timescale of the asa and the magnetic field strength in the pwn. | on the broadband synchrotron spectra of pulsar wind nebulae |
arcuate infrared nebulae are ubiquitous throughout the galactic plane and are candidates for partial shells, bubbles, or bowshocks produced by massive runaway stars. we tabulate infrared photometry for 709 such objects using images from the spitzer space telescope, the wide-field infrared explorer, and the herschel space observatory (hso). of the 709 objects identified at 24 or 22 μm, 422 are detected at the hso 70 μm bandpass. of these, only 39 are detected at hso 160 μm. the 70 μm peak surface brightnesses are 0.5-2.5 jy arcmin-2. color temperatures calculated from the 24 to 70 μm ratios range from 80 to 400 k. color temperatures from 70 to 160 μm ratios are systematically lower, 40-200 k. both of these temperature are, on average, 75% higher than the nominal temperatures derived by assuming that dust is in steady-state radiative equilibrium. this may be evidence of stellar wind bowshocks sweeping up and heating—possibly fragmenting but not destroying—interstellar dust. infrared luminosity correlates with standoff distance, r0, as predicted by published hydrodynamical models. infrared spectral energy distributions are consistent with interstellar dust exposed to either single radiant energy density, u= 103-105 (in more than half of the objects) or a range of radiant energy densities umin = 25 to umax = 103-105 times the mean interstellar value for the remainder. hence, the central ob stars dominate the energetics, making these enticing laboratories for testing dust models in constrained radiation environments. the spectral energy densities are consistent with polycyclic aromatic hydrocarbon fractions qpah ≲ 1% in most objects. | infrared photometric properties of 709 candidate stellar bowshock nebulae |
current detectors for very-high-energy γ-ray astrophysics are either pointing instruments with a small field of view (cherenkov telescopes), or large field-of-view instruments with relatively large energy thresholds (extensive air shower detectors). in this article, we propose a new hybrid extensive air shower detector sensitive in an energy region starting from about 100 gev. the detector combines a small water-cherenkov detector, able to provide a calorimetric measurement of shower particles at ground, with resistive plate chambers which contribute significantly to the accurate shower geometry reconstruction. a full simulation of this detector concept shows that it is able to reach better sensitivity than any previous gamma-ray wide field-of-view experiment in the sub-tev energy region. it is expected to detect with a 5σ significance a source fainter than the crab nebula in one year at 100 gev and, above 1 tev a source as faint as 10% of it. as such, this instrument is suited to detect transient phenomena making it a very powerful tool to trigger observations of variable sources and to detect transients coupled to gravitational waves and gamma-ray bursts. | design and expected performance of a novel hybrid detector for very-high-energy gamma-ray astrophysics |
how and when earth's volatile content was established is controversial with several mechanisms postulated, including planetesimal evaporation, core formation and the late delivery of undifferentiated chondrite-like materials. the isotopes of volatile elements such as sulfur can be fractionated during planetary accretion and differentiation and thus are potential tracers of these processes. using first-principles calculations, we examine sulfur isotope fractionation during core formation and planetesimal evaporation. we find no measurable sulfur isotope fractionation between silicate and metallic melts at core-forming conditions, indicating that the observed light sulfur isotope composition of the bulk silicate earth relative to chondrites cannot be explained by metal-silicate fractionation. our thermodynamic calculations show that sulfur evaporates mostly as h2s during planetesimal evaporation when nebular h2 is present. the observed bulk earth sulfur isotope signature and abundance can be reproduced by evaporative loss of about 90% sulfur mainly as h2s from molten planetesimals before nebular h2 is dissipated. the heavy sulfur isotope composition of the moon relative to the earth is consistent with evaporative sulfur loss under 94-98% saturation condition during the moon-forming giant impact. in summary, volatile evaporation from molten planetesimals before earth's formation probably played a key role in establishing earth's volatile element content. | sulfur isotopic signature of earth established by planetesimal volatile evaporation |
we present adaptive optics assisted near-ir integral field spectroscopic observations of a luminous quasar at z = 2.4, previously observed as the first known example at high redshift of large-scale quasar-driven outflow quenching star formation in its host galaxy. the nuclear spectrum shows broad and blueshifted hβ in absorption, which is tracing outflowing gas with high densities (>108-109 cm-3) and velocities in excess of 10 000 km s-1. the properties of the outflowing clouds (covering factor, density, column density and inferred location) indicate that they likely originate from the broad line region. the energetics of such nuclear regions is consistent with that observed in the large-scale outflow, supporting models in which quasar-driven outflows originate from the nuclear region and are energy conserving. we note that the asymmetric profile of both the hβ and hα emission lines is likely due to absorption by the dense outflowing gas along the line of sight. this outflow-induced asymmetry has implications on the estimation of the black hole mass using virial estimators, and warns about such effects for several other quasars characterized by similar line asymmetries. more generally, our findings may suggest a broader revision of the decomposition and interpretation of quasar spectral features, in order to take into account the presence of potential broad blueshifted balmer absorption lines. our high spatial resolution data also reveal redshifted nebular emission lines, which could be potentially tracing an inflowing stream. | an ultra-dense fast outflow in a quasar at z = 2.4 |
we decompose the observed 7.7 μm polycyclic aromatic hydrocarbon (pah) emission complexes in a large sample of over 7000 mid-infrared spectra of the interstellar medium using spectral cubes observed with the spitzer/irs-sl instrument. in order to fit the 7.7 μm pah emission complex we invoke four gaussian components, which are found to be very stable in terms of their peak positions and widths across all of our spectra, and subsequently define a decomposition with fixed parameters, which gives an acceptable fit for all the spectra. we see a strong environmental dependence on the interrelationships between our band fluxes—in the h ii regions all four components are intercorrelated, while in the reflection nebulae (rns) the inner and outer pairs of bands correlate in the same manner as previously seen for ngc 2023. we show that this effect arises because the maps of rns are dominated by emission from strongly irradiated photodissociation regions, while the much larger maps of h ii regions are dominated by emission from regions much more distant from the exciting stars, leading to subtly different spectral behavior. further investigation of this dichotomy reveals that the ratio of two of these components (centered at 7.6 and 7.8 μm) is linearly related to the uv-field intensity (log g 0). we find that this relationship does not hold for sources consisting of circumstellar material, which are known to have variable 7.7 μm spectral profiles. | polycyclic aromatic hydrocarbon emission in spitzer/irs maps. ii. a direct link between band profiles and the radiation field strength |
calcium-rich supernovae (sne) represent a significant challenge for our understanding of the fates of stellar systems. they are less luminous than other sn types and they evolve more rapidly to reveal nebular spectra dominated by strong calcium lines with weak or absent signatures of other intermediate- and iron-group elements, which are seen in other sne. strikingly, their explosion sites also mark them out as distinct from other sn types. their galactocentric offset distribution is strongly skewed to very large offsets (∼1/3 are offset >20 kpc), meaning they do not trace the stellar light of their hosts. many of the suggestions to explain this extreme offset distribution have invoked the necessity for unusual formation sites such as globular clusters or dwarf satellite galaxies, which are therefore difficult to detect. building on previous work attempting to detect host systems of nearby ca-rich sne, we here present hubble space telescope imaging of five members of the class - three exhibiting large offsets and two coincident with the disc of their hosts. we find no underlying sources at the explosion sites of any of our sample. combining with previous work, the lack of a host system now appears to be a ubiquitous feature amongst ca-rich sne. in this case the offset distribution is most readily explained as a signature of high-velocity progenitor systems that have travelled significant distances before exploding. | hubble space telescope observations of the host galaxies and environments of calcium-rich supernovae |
the high altitude water cherenkov (hawc) collaboration recently published their 2hwc catalog, listing 39 very high energy (vhe; >100 gev) gamma-ray sources based on 507 days of observation. among these, 19 sources are not associated with previously known teraelectronvolt (tev) gamma-ray sources. we have studied 14 of these sources without known counterparts with veritas and fermi-lat. veritas detected weak gamma-ray emission in the 1 tev-30 tev band in the region of da 495, a pulsar wind nebula coinciding with 2hwc j1953+294, confirming the discovery of the source by hawc. we did not find any counterpart for the selected 14 new hawc sources from our analysis of fermi-lat data for energies higher than 10 gev. during the search, we detected gigaelectronvolt (gev) gamma-ray emission coincident with a known tev pulsar wind nebula, snr g54.1+0.3 (ver j1930+188), and a 2hwc source, 2hwc j1930+188. the fluxes for isolated, steady sources in the 2hwc catalog are generally in good agreement with those measured by imaging atmospheric cherenkov telescopes. however, the veritas fluxes for snr g54.1+0.3, da 495, and tev j2032+4130 are lower than those measured by hawc, and several new hawc sources are not detected by veritas. this is likely due to a change in spectral shape, source extension, or the influence of diffuse emission in the source region. | veritas and fermi-lat observations of tev gamma-ray sources discovered by hawc in the 2hwc catalog |
we have investigated the tukh122 prestellar core in the orion a cloud using alma 3 mm dust continuum, n2h+ (j = 1-0), and ch3oh ({j}k={2}k-{1}k) molecular-line observations. previous studies showed that tukh122 is likely on the verge of star formation because the turbulence is almost dissipated and chemically evolved among other starless cores in the orion a cloud. by combining alma 12 m and aca data, we recover extended emission with a resolution of ∼5″ corresponding to 0.01 pc and identify six condensations with a mass range of 0.1-0.4 m ⊙ and a radius of ≲0.01 pc. these condensations are gravitationally bound following a virial analysis and are embedded in the filament, including the elongated core with a mass of ∼29 m ⊙ and a radial density profile of r -1.6 derived by herschel. the separation of these condensations is ∼0.035 pc, consistent with the thermal jeans length at a density of 4.4 × 105 cm-3. this density is similar to the central part of the core. we also find a tendency for the n2h+ molecule to deplete at the dust peak condensation. this condensation may be beginning to collapse because the line width becomes broader. therefore, the fragmentation still occurs in the prestellar core by thermal jeans instability, and multiple stars are formed within the tukh122 prestellar core. the ch3oh emission shows a large shell-like distribution and surrounds these condensations, suggesting that the ch3oh molecule formed on dust grains is released into the gas phase by nonthermal desorption such as photoevaporation caused by cosmic-ray-induced uv radiation. | gravitationally unstable condensations revealed by alma in the tukh122 prestellar core in the orion a cloud |
isotopic anomalies in chondrules hold important clues about the dynamics of mixing and transport processes in the solar accretion disk. the meaning of these anomalies is debated and they have been interpreted to indicate either disk-wide transport of chondrules or local heterogeneities of chondrule precursors. however, all previous studies relied on isotopic data for a single element (either cr, ti, or o), which does not allow distinguishing between source and precursor signatures as the cause of the chondrules' isotope anomalies. to overcome this problem, we obtained the first combined o, ti, and cr isotope data for individual chondrules from enstatite, ordinary, and carbonaceous chondrites. we find that chondrules from non-carbonaceous (nc) chondrites have relatively homogeneous δ17o, ɛ50ti, and ɛ54cr, which are similar to the compositions of their host chondrites. by contrast, chondrules from carbonaceous chondrites (cc) have more variable compositions, some of which differ from the host chondrite compositions. although the compositions of the analyzed cc and nc chondrules may overlap for either ɛ50ti, ɛ54cr, or δ17o, in multi-isotope space, none of the cc chondrules plot in the compositional field of nc chondrites, and no nc chondrule plots within the field of cc chondrites. as such, our data reveal a fundamental isotopic difference between nc and cc chondrules, which is inconsistent with a disk-wide transport of chondrules across and between the nc and cc reservoirs. instead, the isotopic variations among cc chondrules reflect local precursor heterogeneities, which most likely result from mixing between nc-like dust and a chemically diverse dust component that was isotopically similar to cais and aoas. the same mixing processes, but on a larger, disk-wide scale, were likely responsible for establishing the distinct isotopic compositions of the nc and cc reservoirs, which represent in inner and outer disk, respectively. | early evolution of the solar accretion disk inferred from cr-ti-o isotopes in individual chondrules |
h.e.s.s. has recently completed the first systematic survey of the galactic plane in the tev energy domain. we analyze the flux, latitude, and longitude distributions of γ-ray sources observed by h.e.s.s. in order to infer the properties of the galactic tev source population. we show that the total milky way luminosity in the 1-100 tev energy range is ${l}_{\mathrm{mw}}={1.7}_{-0.4}^{+0.5}\times {10}^{37}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$ . evaluating the cumulative flux expected at earth by the considered population, we show that h.e.s.s. unresolved sources provide a relevant contribution to the diffuse galactic emission. finally, in the hypothesis that the majority of bright sources detected by h.e.s.s. are powered by pulsar activity, like, e.g., pulsar wind nebulae or tev halos, we estimate the main properties of the pulsar population. | the tev gamma-ray luminosity of the milky way and the contribution of h.e.s.s. unresolved sources to very high energy diffuse emission |
in high-energy astronomy, spectro-imaging instruments such as x-ray detectors allow investigation of the spatial and spectral properties of extended sources including galaxy clusters, galaxies, diffuse interstellar medium, supernova remnants, and pulsar wind nebulae. in these sources, each physical component possesses a different spatial and spectral signature, but the components are entangled. extracting the intrinsic spatial and spectral information of the individual components from this data is a challenging task. current analysis methods do not fully exploit the 2d-1d (x, y, e) nature of the data, as spatial information is considered separately from spectral information. here we investigate the application of a blind source separation (bss) algorithm that jointly exploits the spectral and spatial signatures of each component in order to disentangle them. we explore the capabilities of a new bss method (the general morphological component analysis; gmca), initially developed to extract an image of the cosmic microwave background from planck data, in an x-ray context. the performance of the gmca on x-ray data is tested using monte-carlo simulations of supernova remnant toy models designed to represent typical science cases. we find that the gmca is able to separate highly entangled components in x-ray data even in high-contrast scenarios, and can extract the spectrum and map of each physical component with high accuracy. a modification of the algorithm is proposed in order to improve the spectral fidelity in the case of strongly overlapping spatial components, and we investigate a resampling method to derive realistic uncertainties associated to the results of the algorithm. applying the modified algorithm to the deep chandra observations of cassiopeia a, we are able to produce detailed maps of the synchrotron emission at low energies (0.6-2.2 kev), and of the red- and blueshifted distributions of a number of elements including si and fe k. | novel method for component separation of extended sources in x-ray astronomy |
with both nebular- and stellar-derived abundances of ≲1/10 z_{⊙ } and low foreground extinction, sextans a is a prime candidate to replace the small magellanic cloud as reservoir of metal-poor massive stars and reference to study the metal-poor universe. we report the discovery of two early o-type stars in sextans a, the earliest o-type stars with metallicity <1/7 z_{⊙ } known to date, and two additional o9 stars. colour-excess estimates towards individual targets, enabled by spectral typing, manifest that internal reddening is neither uniform nor negligible. the four targets define a new region of star formation far from the optically brightest centre of the galaxy and from its conspicuous h ii shells, but not devoid of neutral hydrogen. in fact, we detect a spatial correlation between ob stars and h i in sextans a and other dirr's that leads us to propose that the neutral phase may be fundamental to star formation in low-density environments. according to the existing evidence at least two of the targets formed in isolation, thus suggestive of an stochastic sampling of the initial mass function that would enable low-mass galaxies like sextans a to form very massive stars. the discovery of these four stars provide spatially resolved, spectroscopic confirmation of recent findings, suggesting that dwarf galaxies can sustain star formation despite the low density of the gas phase. | ongoing star formation at the outskirts of sextans a: spectroscopic detection of early o-type stars |
luminous type-2 quasars in which the glow from the central black hole is obscured by dust are ideal targets for studying their host galaxies and the quasars' effect on galaxy evolution. such feedback appears ubiquitous in luminous obscured quasars where high-velocity-ionized nebulae have been found. we present rest-frame yellow-band (∼5000 å) observations using the hubble space telescope (hst) for a sample of 20 luminous quasar host galaxies at 0.2 < z < 0.6 selected from the sloan digital sky survey. for the first time, we combine host galaxy observations with geometric measurements of quasar illumination using blue-band hst observations and [o iii] integral field unit observations probing the quasar winds. the hst images reveal bright merger signatures in about half the galaxies; a significantly higher fraction than in comparison inactive ellipticals. we show that the host galaxies are primarily bulge-dominated, with masses close to m*, but belong to <30 per cent of elliptical galaxies that are highly star forming at z ∼ 0.5. ionized gas signatures are uncorrelated with faint stellar discs (if present), confirming that the ionized gas is not concentrated in a disc. scattering cones and [o iii] ionized gas velocity field are aligned with the forward scattering cones being co-spatial with the blue-shifted side of the velocity field, suggesting the high-velocity gas is indeed photo-ionized by the quasar. based on the host galaxies' high star formation rates and bright merger signatures, we suggest that this low-redshift outbreak of luminous quasar activity is triggered by recent minor mergers. combining these novel observations, we present new quasar unification tests, which are in agreement with expectations of the orientation-based unification model for quasars. | towards a comprehensive picture of powerful quasars, their host galaxies and quasar winds at z ∼ 0.5 |
context. the galaxy m 49 (ngc 4472) is the brightest early-type galaxy in the virgo cluster. it is located in subcluster b and has an unusually blue, metal-poor outer halo. planetary nebulae (pne) are excellent tracers of diffuse galaxy and intragroup light (igl).aims: we aim to present a photometric survey of pne in the galaxy's extended halo to characterise its pn population, as well as the surrounding igl of the subcluster b.methods: pne were identified based on their bright [oiii]5007 å emission and absence of a broad-band continuum through automated detection techniques.results: we identify 738 pne out to a radius of 155 kpc from m 49's centre from which we define a complete sample of 624 pne within a limiting magnitude of m5007,lim = 28.8. comparing the pn number density to the broad-band stellar surface brightness profile, we find a variation of the pn-specific frequency (α-parameter) with radius. the outer halo beyond 60kpc has a 3.2 times higher α-parameter compared to the main galaxy halo (α2.5,innerm 49 = (3.20 ± 0.43) × 10-9 pn l-1⊙,bol), which is likely due to contribution from the surrounding blue igl. we use the planetary nebulae luminosity function (pnlf) as an indicator of distance and stellar population. its slope, which correlates empirically with galaxy type, varies within the inner halo. in the eastern quadrant of m 49, the pnlf slope is shallower, indicating an additional localised, bright pn population following an accretion event, likely that of the dwarf irregular galaxy vcc1249. we also determined a distance modulus of μpnlf = 31.29+ 0.07-0.08 for m 49, corresponding to a physical distance of 18.1 ± 0.6 mpc, which agrees with a recent surface-brightness fluctuations distance.conclusions: the pn populations in the outer halo of m 49 are consistent with the presence of a main sérsic galaxy halo with a slight (b - v) colour gradient of 10-4 mag arcsec-1 surrounded by igl with a very blue colour of (b - v) = 0.25 and a constant surface brightness μv = 28.0 mag arcsec-2. based on data collected at subaru telescope, which is operated by the national astronomical observatory of japan under programme s14a-006. | the halo of m 49 and its environment as traced by planetary nebulae populations |
we present the hr-pypopstar model, which provides a complete set (in ages) of high-resolution (hr) spectral energy distributions of single stellar populations. the model uses the most recent high-wavelength-resolution theoretical atmosphere libraries for main-sequence, post-agb/planetary nebulae and wolf-rayet stars. the spectral energy distributions are given for more than a hundred ages ranging from 0.1 myr to 13.8 gyr, at four different values of the metallicity (z = 0.004, 0.008, 0.019, and 0.05), considering four different imfs. the wavelength range goes from 91 to $24\, 000$ å in linear steps δλ = 0.1 å, giving a theoretical resolving power $r_{{\rm th},5000} \sim 50\, 000$ at 5000 å. this is the main novelty of these spectra, unique for their age and wavelength ranges. the models include the ionizing stellar populations that are relevant at both young (massive hot stars) and old (planetary nebulae) ages. we have tested the results with some examples of hr spectra recently observed with megara at gtc. we highlight the importance of wavelength resolution in reproducing and interpreting the observational data from the last and forthcoming generations of astronomical instruments operating at 8-10 m class telescopes, with higher spectral resolution than their predecessors. | hr-pypopstar: high-wavelength-resolution stellar populations evolutionary synthesis model |
we present an analysis of the effect of feedback from o- and b-type stars with data from the integral field spectrograph multi unit spectroscopic explorer (muse) mounted on the very large telescope of pillar-like structures in the carina nebular complex, one of the most massive star-forming regions in the galaxy. for the observed pillars, we compute gas electron densities and temperatures maps, produce integrated line and velocity maps of the ionized gas, study the ionization fronts at the pillar tips, analyse the properties of the single regions, and detect two ionized jets originating from two distinct pillar tips. for each pillar tip, we determine the incident ionizing photon flux q0, pil originating from the nearby massive o- and b-type stars and compute the mass-loss rate dot{m} of the pillar tips due to photoevaporation caused by the incident ionizing radiation. we combine the results of the carina data set with archival muse data of a pillar in ngc 3603 and with previously published muse data of the pillars of creation in m16, and with a total of 10 analysed pillars, find tight correlations between the ionizing photon flux and the electron density, the electron density and the distance from the ionizing sources, and the ionizing photon flux and the mass-loss rate. the combined muse data sets of pillars in regions with different physical conditions and stellar content therefore yield an empirical quantification of the feedback effects of ionizing radiation. in agreement with models, we find that dot{m}∝ q_0,pil^{1/2}. | connecting the dots: a correlation between ionizing radiation and cloud mass-loss rate traced by optical integral field spectroscopy |
aims: we present muffit, a new generic code optimized to retrieve the main stellar population parameters of galaxies in photometric multi-filter surveys, and check its reliability and feasibility with real galaxy data from the alhambra survey.methods: making use of an error-weighted χ2-test, we compare the multi-filter fluxes of galaxies with the synthetic photometry of mixtures of two single stellar populations at different redshifts and extinctions, to provide the most likely range of stellar population parameters (mainly ages and metallicities), extinctions, redshifts, and stellar masses. to improve the diagnostic reliability, muffit identifies and removes from the analysis those bands that are significantly affected by emission lines. the final parameters and their uncertainties are derived by a monte carlo method, using the individual photometric uncertainties in each band. finally, we discuss the accuracies, degeneracies, and reliability of muffit using both simulated and real galaxies from alhambra, comparing with results from the literature.results: muffit is a precise and reliable code to derive stellar population parameters of galaxies in alhambra. using the results from photometric-redshift codes as input, muffit improves the photometric-redshift accuracy by ~10-20%. muffit also detects nebular emissions in galaxies, providing physical information about their strengths. the stellar masses derived from muffit show excellent agreement with the cosmos and sdss values. in addition, the retrieved age-metallicity locus for a sample of z ≤ 0.22 early-type galaxies in alhambra at different stellar mass bins are in very good agreement with the ones from sdss spectroscopic diagnostics. moreover, a one-to-one comparison between the redshifts, ages, metallicities, and stellar masses derived spectroscopically for sdss and by muffit for alhambra reveals good qualitative agreements in all the parameters, hence reinforcing the strengths of multi-filter galaxy data and optimized analysis techniques, like muffit, to conduct reliable stellar population studies. | stellar populations of galaxies in the alhambra survey up to z ~ 1. i. muffit: a multi-filter fitting code for stellar population diagnostics |
context. vista variables in the vía láctea is an eso public survey dedicated to scanning the bulge and an adjacent portion of the galactic disk in the fourth quadrant using the vista telescope and its near-infrared camera vircam. one of the leading goals of the vvv survey is to contribute to knowledge of the star cluster population of the milky way.aims: to improve the census of galactic star clusters, we performed a systematic and careful scan of the jhks images of the galactic plane section of the vvv survey.methods: our detection procedure is based on a combination of stellar density maps and visual inspection of promising features in the j-, h-, and ks-band images. the material examined are vvv jhks color-composite images corresponding to data release 1 of vvv.results: we report the discovery of 493 new infrared star cluster candidates. the analysis of the spatial distribution show that the clusters are very concentrated in the galactic plane, presenting some local maxima around the position of large star-forming complexes, such as g305, rcw 95, and rcw 106. the vast majority of the new star cluster candidates are quite compact and generally surrounded by bright and/or dark nebulosities. iras point sources are associated with 59% of the sample, while 88% are associated with msx point sources. glimpse 8 μm images of the cluster candidates show a variety of morphologies, with 292 clusters dominated by knotty sources, while 361 clusters show some kind of nebulosity in this wavelength regime. spatial cross-correlation with young stellar objects, masers, and extended green-object catalogs suggest that a large sample of the new cluster candidates are extremely young. in particular, 104 star clusters associated with methanol masers are excellent candidates for ongoing massive star formation. also, there is a special set of sixteen cluster candidates that present clear signposts of star-forming activity having associated simultaneosly dark nebulae, young stellar objects, extended green objects, and masers. full tables 1-3 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/581/a120 | hundreds of new cluster candidates in the vista variables in the vía láctea survey dr1 |
the orion a molecular cloud is one of the most well-studied nearby star-forming regions, and includes regions of both highly clustered and more dispersed star formation across its full extent. here, we analyze dense, star-forming cores identified in the 850 and 450 μm scuba-2 maps from the jcmt gould belt legacy survey. we identify dense cores in a uniform manner across the orion a cloud and analyze their clustering properties. using two independent lines of analysis, we find evidence that clusters of dense cores tend to be mass segregated, suggesting that stellar clusters may have some amount of primordial mass segregation already imprinted in them at an early stage. we also demonstrate that the dense core clusters have a tendency to be elongated, perhaps indicating a formation mechanism linked to the filamentary structure within molecular clouds. | the jcmt gould belt survey: dense core clusters in orion a |
we study the hypothesis of high-metallicity clumps being responsible for the abundance discrepancy found in planetary nebulae between the values obtained from recombination and collisionally excited lines. we generate grids of photoionization models combining cold metal-rich clumps emitting the heavy element recombination lines, embedded in a normal metallicity region responsible for the forbidden lines. the two running parameters of the grid are the metallicity of the clumps and its volume fraction relative to the whole nebula. we determine the density and temperatures (from the balmer jump and the [o iii] 5007/4363 å line ratio) and the ionic abundances from the collisional and recombination lines, as an observer would do. the metallicity of the near-to-solar region is recovered, while the metallicity of the clumps is systematically underestimated by up to two orders of magnitude. this is mainly because most of the hβ emission is coming from the 'normal' region, and only the small contribution emitted by the metal-rich clumps should be used. we find that a given adf(o++) can be reproduced by a small amount of rich clumps, or a bigger amount of less rich clumps. finally, comparing with the observations of ngc 6153, we find two models that reproduce its adf(o++) and the observed electron temperatures. we determine the fraction of oxygen embedded in the metal-rich region (with a fraction of volume less than 1 per cent) to be roughly between 25 per cent and 60 per cent of the total amount of oxygen in the nebula (a few 10-3m⊙). | bi-abundance photoionization models of planetary nebulae: determining the amount of oxygen in the metal-rich component |
sn 2017eaw, the tenth supernova observed in ngc 6946, was a normal type ii-p supernova with an estimated 11-13 m⊙ red supergiant progenitor. here we present nebular-phase spectra of sn 2017eaw at +545 and +900 days post-max, extending approximately 50-400 days past the epochs of previously published spectra. while the +545 day spectrum is similar to spectra taken between days +400 and +493, the +900 day spectrum shows dramatic changes both in spectral features and emission-line profiles. the hα emission is flat-topped and boxlike with sharp blue and red profile velocities of ≃-8000 and +7500 km s-1. these late-time spectral changes indicate strong circumstellar interaction with a mass-loss shell, expelled ∼1700 yr before explosion. sn 2017eaw's +900 day spectrum is similar to those seen for sn 2004et and sn 2013ej observed 2-3 yr after explosion. we discuss the importance of late-time monitoring of bright sne ii-p and the nature of presupernova mass-loss events for sn ii-p evolution. | late-time circumstellar interaction of sn 2017eaw in ngc 6946 |
one of the key methods for determining the unknown nature of type ia supernovae (sne ia) is the search for traces of interaction between the sn ejecta and the circumstellar structures at the resulting supernova remnants (snrs ia). so far, the observables that we receive from well-studied snrs ia cannot be explained self-consistently by any model presented in the literature. in this study, we suggest that the circumstellar medium (csm) being observed to surround several snrs ia was mainly shaped by planetary nebulae (pne) that originated from one or both progenitor stars. performing two-dimensional hydrodynamic simulations, we show that the ambient medium shaped by pne can account for several properties of the csm that have been found to surround sne ia and their remnants. finally, we model kepler's snr considering that the sn explosion occurred inside a bipolar pn. our simulations show good agreement with the observed morphological and kinematic properties of kepler's snr. in particular, our model reproduces the current expansion parameter of kepler's snr, the partial interaction of the remnant with a dense csm at its northern region and finally the existence of two opposite protrusions ('ears') at the equatorial plane of the snr. | the interaction of type ia supernovae with planetary nebulae: the case of kepler's supernova remnant |
we calculate the decay width of the photon splitting into three photons in a model of quantum electrodynamics with broken lorentz invariance. we show that this process can lead to a cut-off in the very-high-energy part of a photon spectra of astrophysical sources. we obtain the 95% cl bound on the lorentz violating mass scale for photons from the analysis of the very-high-energy part of the crab nebula spectrum, obtained by hegra. this bound improves previous constraints by more than an order of magnitude. | photon splitting constraint on lorentz invariance violation from crab nebula spectrum |
we present the discovery and interpretation of ionized nebulae around two ultraluminous x-ray sources in m 51; both sources share the rare property of showing x-ray eclipses by their companion stars and are therefore prime targets for follow-up studies. using archival hubble space telescope images, we found an elongated, 100-pc-long emission-line structure associated with one x-ray source (cxom51 j132940.0+471237; ulx-1 for simplicity), and a more circular, ionized nebula at the location of the second source (cxom51 j132939.5+471244; ulx-2 for simplicity). we observed both nebulae with the large binocular telescope's multi-object double spectrograph. from our analysis of the optical spectra, we argue that the gas in the ulx-1 bubble is shock-ionized, consistent with the effect of a jet with a kinetic power of ≈2 × 1039 erg s-1. additional x-ray photoionization may also be present, to explain the strength of high-ionization lines such as he ii λ4686 and [ne v] λ3426. on the other hand, the emission lines from the ulx-2 bubble are typical for photoionization by normal o stars suggesting that the nebula is actually an h ii region not physically related to the ulx but is simply a chance alignment. from archival very large array data, we also detect spatially extended, steep-spectrum radio emission at the location of the ulx-1 bubble (consistent with its jet origin), but no radio counterpart for ulx-2 (consistent with the lack of shock-ionized gas around that source). | multiband counterparts of two eclipsing ultraluminous x-ray sources in m 51 |
our cycle 0 alma observations confirmed that the boomerang nebula is the coldest known object in the universe, with a massive high-speed outflow that has cooled significantly below the cosmic background temperature. our new co 1-0 data reveal heretofore unseen distant regions of this ultra-cold outflow, out to ≳120,000 au. we find that in the ultra-cold outflow, the mass-loss rate (\dot{m}) increases with radius, similar to its expansion velocity (v)—taking v\propto r, we find \dot{m}\propto {r}0.9{--2.2}. the mass in the ultra-cold outflow is ≳ 3.3 m ⊙, and the boomerang’s main-sequence progenitor mass is ≳ 4 m ⊙. our high angular resolution (∼ 0\buildrel{\prime\prime}\over{.} 3) co j = 3-2 map shows the inner bipolar nebula’s precise, highly collimated shape, and a dense central waist of size (fwhm) ∼1740 au × 275 au. the molecular gas and the dust as seen in scattered light via optical hubble space telescope imaging show a detailed correspondence. the waist shows a compact core in thermal dust emission at 0.87-3.3 mm, which harbors (4{--}7)× {10}-4 m ⊙ of very large (∼millimeter-to-centimeter sized), cold (∼ 20{--}30 k) grains. the central waist (assuming its outer regions to be expanding) and fast bipolar outflow have expansion ages of ≲ 1925 {years} and ≤slant 1050 {years}: the “jet-lag” (i.e., torus age minus the fast-outflow age) in the boomerang supports models in which the primary star interacts directly with a binary companion. we argue that this interaction resulted in a common-envelope configuration, while the boomerang’s primary was an rgb or early-agb star, with the companion finally merging into the primary’s core, and ejecting the primary’s envelope that now forms the ultra-cold outflow. | the coldest place in the universe: probing the ultra-cold outflow and dusty disk in the boomerang nebula |
context. the structure of the wind from the cool giants in symbiotic binaries carries important information for understanding the wind mass transfer to their white dwarf companions, its fuelling, and thus the path towards different phases of symbiotic-star evolution.aims: in this paper, we indicate a non-spherical distribution of the neutral wind zone around the red giant (rg) in the symbiotic binary star, eg and. we concentrate in particular on the wind focusing towards the orbital plane and its asymmetry alongside the orbital motion of the rg.methods: we achieved this aim by analysing the periodic orbital variations of fluxes and radial velocities of individual components of the hα and [o iii] λ5007 lines observed on our high-cadence medium (r ∼ 11 000) and high-resolution (r ∼ 38 000) spectra.results: the asymmetric shaping of the neutral wind zone at the near-orbital-plane region is indicated by: (i) the asymmetric course of the hα core emission fluxes along the orbit; (ii) the presence of their secondary maximum around the orbital phase φ = 0.1, which is possibly caused by the refraction effect; and (iii) the properties of the hα broad wing emission originating by raman scattering on h0 atoms. the wind is substantially compressed from polar directions to the orbital plane as constrained by the location of the [o iii] λ5007 line emission zones in the vicinity of the rg at/around its poles. the corresponding mass-loss rate from the polar regions of ≲10-8 m⊙ yr-1 is a factor of ≳10 lower than the average rate of ≈10-7 m⊙ yr-1 derived from nebular emission of the ionised wind from the rg. furthermore, it is two orders of magnitude lower than that measured in the near-orbital-plane region from rayleigh scattering.conclusions: the startling properties of the nebular [o iii] λ5007 line in eg and provides an independent indication of the wind focusing towards the orbital plane - the key to understanding the efficient wind mass transfer in symbiotic binary stars. full tables 1 and 2 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/cat/j/a+a/646/a116 | wind mass transfer in s-type symbiotic binaries. iii. confirmation of a wind focusing in eg andromedae from the nebular [o iii] λ5007 line |
the int galactic plane survey (igaps) is the merger of the optical photometric surveys iphas and uvex based on data from the isaac newton telescope (int) obtained between 2003 and 2018. it captures the entire northern galactic plane within the galactic coordinate range |b|< 5° and 30° < ℓ < 215°. from the beginning, the incorporation of narrow-band hα imaging has been a unique and distinctive feature of this effort. alongside a focused discussion of the nature and application of the hα data, we present the igaps world-accessible database of images for all five survey filters, i, r, g, urgo, and narrow-band hα, observed on a pixel scale of 0.33 arcsec and at an effective (median) angular resolution of 1.1−1.3 arcsec. the background, noise, and sensitivity characteristics of the narrow-band hα filter images are outlined. typical noise levels in this band correspond to a surface brightness at full ∼1 arcsec resolution of around 2 × 10−16 erg cm−2 s−1 arcsec−2. illustrative applications of the hα data to planetary nebulae and herbig-haro objects are outlined and, as part of a discussion of the mosaicking technique, we present a very large background-subtracted narrow-band mosaic of the supernova remnant simeis 147. finally, we lay out a method that exploits the database via an automated selection of bright ionised diffuse interstellar emission targets for the coming generation of wide-field massive-multiplex spectrographs. two examples of the diffuse hα map output from this selection process are presented and compared with previously published data. | high-resolution hα imaging of the northern galactic plane and the igaps image database |
in this work, we propose two convolutional neural network classifiers for detecting contaminants in astronomical images. once trained, our classifiers are able to identify various contaminants, such as cosmic rays, hot and bad pixels, persistence effects, satellite or plane trails, residual fringe patterns, nebulous features, saturated pixels, diffraction spikes, and tracking errors in images. they encompass a broad range of ambient conditions, such as seeing, image sampling, detector type, optics, and stellar density. the first classifier, maximask, performs semantic segmentation and generates bad pixel maps for each contaminant, based on the probability that each pixel belongs to a given contaminant class. the second classifier, maxitrack, classifies entire images and mosaics, by computing the probability for the focal plane to be affected by tracking errors. we gathered training and testing data from real data originating from various modern charged-coupled devices and near-infrared cameras, that are augmented with image simulations. we quantified the performance of both classifiers and show that maximask achieves state-of-the-art performance for the identification of cosmic ray hits. thanks to a built-in bayesian update mechanism, both classifiers can be tuned to meet specific science goals in various observational contexts. | maximask and maxitrack: two new tools for identifying contaminants in astronomical images using convolutional neural networks |
we present new karl g. jansky very large array (vla, 1.5 ghz) radio data for the giant elliptical galaxy ic 4296, supported by archival radio, x-ray (chandra, and xmm-newton) and optical (soar, and hst) observations. the galaxy hosts powerful radio jets piercing through the inner hot x-ray emitting atmosphere, depositing most of the energy into the ambient intracluster medium (icm). whereas the radio surface brightness of the a configuration image is consistent with a fanaroff-riley class i system, the d configuration image shows two bright, relative to the central region, large ({∼ } 160 {kpc} diameter), well-defined lobes, previously reported by killeen et al., at a projected distance r≳ 230 {kpc}. the xmm-newton image reveals an x-ray cavity associated with one of the radio lobes. the total enthalpy of the radio lobes is {∼ }7× 10^{59} {erg} and the mechanical power output of the jets is {∼ } 10^{44} {erg s}^{-1}. the jets are mildly curved and possibly rebrightened by the relative motion of the galaxy and the icm. the lobes display sharp edges, suggesting the presence of bow shocks, which would indicate that they are expanding supersonically. the central entropy and cooling time of the x-ray gas are unusually low and the nucleus hosts a warm hα + [n ii] nebula and a cold molecular co disc. because most of the energy of the jets is deposited far from the nucleus, the atmosphere of the galaxy continues to cool, apparently feeding the central supermassive black hole and powering the jet activity. | powerful agn jets and unbalanced cooling in the hot atmosphere of ic 4296 |
context. hydrogenated amorphous carbons (a-c:h) are a major component of the carbonaceous solids present in the interstellar medium. the production and existence of these grains is connected in particular with the balance between their photolysis, radiolysis, and hydrogenation. during grain processing, h2 and other small organic molecules, radicals, and fragments are released into the gas phase.aims: we perform photolytic experiments on laboratory produced interstellar a-c:h analogues to monitor and quantify the release of species and compare to relevant observations in the interstellar medium.methods: hydrogenated amorphous carbon analogues at low temperature are exposed to ultraviolet (uv) photons, under ultra-high vacuum conditions. the species produced are monitored using mass spectrometry and post irradiation temperature-programmed desorption. additional experiments are performed using deuterated analogues and the species produced are unambiguously separated from background contributions. we implement the laboratory measured yields for the released species in a time dependent model to investigate the effect of the uv photon irradiation of hydrogenated amorphous carbons in a photon dominated region, and estimate the associated time scale.results: the uv photolysis of hydrogenated amorphous carbons leads to the production of h2 molecules and small hydrocarbons. the model shows that the photolytic evolution of a-c:hs in photon dominated regions, such as the horsehead nebula, can raise the abundance of carbonaceous molecules by several orders of magnitude at intermediate visual extinctions, i.e., after the c+ maximum and before the dense cloud conditions prevail where models generally show a minimum abundance for such carbonaceous species. the injection time peak ranges from a thousand to ten thousand years in the models, considering only the destruction of such grains and no re-hydrogenation. this time scale is consistent with the estimated advection front of a photon dominated region, which replenishes it with freshly exposed material. appendices are available in electronic form at http://www.aanda.org | vacuum ultraviolet of hydrogenated amorphous carbons. ii. small hydrocarbons production in photon dominated regions |
water fountains are evolved stars showing early stages of collimated mass-loss during transition from the asymptotic giant branch, providing valuable insight into the formation of asymmetric planetary nebulae. we report the results of multi-epoch vlbi observations, which determine the spatial and three-dimensional kinematic structure of h2o masers associated with the water fountain iras 18113-2503. the masers trace three pairs of high-velocity (∼150-300 km s-1) bipolar bow shocks on a scale of 0{^''.}18 (∼2000 au). the expansion velocities of the bow shocks exhibit an exponential decrease as a function of distance from the central star, which can be explained by an episodic, jet-driven outflow decelerating due to drag forces in a circumstellar envelope. using our model, we estimate an initial ejection velocity ∼840 km s-1, a period for the ejections ∼10 yr, with the youngest being ∼12 yr old, and an average envelope density within the h2o maser region n_{h_2}{≈ }106 cm-3. we hypothesize that iras 18113-2503 hosts a binary central star with a separation of ∼10 au, revealing novel clues about the launching mechanisms of high-velocity collimated outflows in water fountains. | rapidly evolving episodic outflow in iras 18113-2503: clues to the ejection mechanism of the fastest water fountain |
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