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titanium isotopes are potential tracers of processes of evaporation/condensation in the solar nebula and magmatic differentiation in planetary bodies. to gain new insights into the processes that control ti isotopic variations in planetary materials, 25 komatiites, 15 chondrites, 11 hed-clan meteorites, 5 angrites, 6 aubrites, a martian shergottite, and a kreep-rich impact melt breccia have been analyzed for their mass-dependent ti isotopic compositions, presented using the δ49ti notation (deviation in permil of the 49ti/47ti ratio relative to the ol-ti standard). no significant variation in δ49ti is found among ordinary, enstatite, and carbonaceous chondrites, and the average chondritic δ49ti value of +0.004 ± 0.010‰ is in excellent agreement with the published estimate for the bulk silicate earth, the moon, mars, and the hed and angrite parent-bodies. the average δ49ti value of komatiites of -0.001 ± 0.019‰ is also identical to that of the bulk silicate earth and chondrites. ol-ti has a ti isotopic composition that is indistinguishable from chondrites and is therefore a suitable material for reporting δ49ti values. previously published isotope data on another highly refractory element, ca, show measurable variations among chondrites. the decoupling between ca and ti isotope systematics most likely occurred during condensation in the solar nebula. aubrites exhibit significant variations in δ49ti, from -0.07 to +0.24‰. this is likely due to the uniquely reducing conditions under which the aubrite parent-body differentiated, allowing chalcophile ti3+ and lithophile ti4+ to co-exist. consequently, the observed negative correlation between δ49ti values and mgo concentrations among aubrites is interpreted to be the result of isotope fractionation driven by the different oxidation states of ti in this environment, such that isotopically heavy ti4+ was concentrated in the residual liquid during magmatic differentiation. finally, kreepy impact melt breccia sau 169 exhibits a heavy δ49ti value of +0.330 ± 0.034‰ which is interpreted to result from ti isotopic fractionation during ilmenite precipitation in the late stages of lunar magma ocean crystallization. a rayleigh distillation calculation predicts that a δ49ti value of +0.330‰ is achieved after removal of 94% of ti in ilmenite. | titanium stable isotopic variations in chondrites, achondrites and lunar rocks |
we present new atacama large millimeter array observations of the molecular gas and far-infrared continuum around the brightest cluster galaxy (bcg) in the cool-core cluster macs 1931.8-2635. our observations reveal (1.9 ± 0.3) × 1010 m ⊙ of molecular gas, on par with the largest known reservoirs of cold gas in a cluster core. we detect co(1-0), co(3-2), and co(4-3) emission from both diffuse and compact molecular gas components that extend from the bcg center out to ∼30 kpc to the northwest, tracing the uv knots and hα filaments observed by the hubble space telescope. due to the lack of morphological symmetry, we hypothesize that the ∼300 km s-1 velocity of the co in the tail is not due to concurrent uplift by active galactic nucleus (agn) jets; rather, we may be observing the aftermath of a recent agn outburst. the co spectral line energy distribution suggests that molecular gas excitation is influenced by processes related to both star formation and recent agn feedback. continuum emission in bands 6 and 7 arises from dust and is spatially coincident with young stars and nebular emission observed in the uv and optical. we constrain the temperature of several dust clumps to be ≲10 k, which is too cold to be directly interacting with the surrounding ∼4.8 kev intracluster medium (icm). the cold dust population extends beyond the observed co emission and must either be protected from interacting with the icm or be surrounded by local volumes of icm that are several kev colder than observed by chandra. | the dust and molecular gas in the brightest cluster galaxy in macs 1931.8-2635 |
in the core accretion paradigm of planet formation, gas giants only form a massive atmosphere after their progenitors exceeded a threshold mass: the critical core mass. most (exo)planets, being smaller and rock/ice-dominated, never crossed this line. nevertheless, they were massive enough to attract substantial amounts of gas from the disc, while their atmospheres remained in pressure-equilibrium with the disc. our goal is to characterize the hydrodynamical properties of the atmospheres of such embedded planets and the implications for their (long-term) evolution. in this paper - the first in series - we start to investigate the properties of an isothermal and inviscid flow past a small, embedded planet by conducting local, 2d hydrodynamical simulations. using the pluto code, we confirm that the flow is steady and bound. this steady outcome is most apparent for the log-polar grid (with the grid spacing proportional to the distance from the planet). for low-mass planets, cartesian grids are somewhat less efficient as they have difficulty to follow the circular, large speeds in the deep atmosphere. relating the amount of rotation to the gas fraction of the atmosphere, we find that more massive atmospheres rotate faster - a finding consistent with kelvin's circulation theorem. rotation therefore limits the amount of gas that planets can acquire from the nebula. dependent on the toomre-q parameter of the circumstellar disc, the planet's atmosphere will reach keplerian rotation before self-gravity starts to become important. | hydrodynamics of embedded planets' first atmospheres - i. a centrifugal growth barrier for 2d flows |
context. detailed modelling of the high-energy emission from gamma-ray binaries has been propounded as a path to pulsar wind physics.aims: fulfilling this ambition requires a coherent model of the flow and its emission in the region where the pulsar wind interacts with the stellar wind of its companion.methods: we have developed a code that follows the evolution and emission of electrons in the shocked pulsar wind based on inputs from a relativistic hydrodynamical simulation. the code is used to model the well-documented spectral energy distribution and orbital modulations from ls 5039.results: the pulsar wind is fully confined by a bow shock and a back shock. the particles are distributed into a narrow maxwellian, emitting mostly gev photons, and a power law radiating very efficiently over a broad energy range from x-rays to tev gamma rays. most of the emission arises from the apex of the bow shock. doppler boosting shapes the x-ray and very high energy (vhe) lightcurves, constraining the system inclination to i ≈ 35°. there is tension between the hard vhe spectrum and the level of x-ray to mev emission, which requires differing magnetic field intensities that are hard to achieve with constant magnetisation σ and lorentz factor γp of the pulsar wind. our best compromise implies σ ≈ 1 and γp ≈ 5 × 103, so respectively higher and lower than the typical values in pulsar wind nebulae.conclusions: the high value of σ derived here, where the wind is confined close to the pulsar, supports the classical picture that has pulsar winds highly magnetised at launch. however, such magnetisations will require that further investigations are based on relativistic mhd simulations. movies associated to figs. a.1-a.4 are available in electronic form at http://www.aanda.org | modelling the high-energy emission from gamma-ray binaries using numerical relativistic hydrodynamics |
aims: we present and analyse late-time observations of the type-ib supernova with possible pre-supernova progenitor detection, iptf13bvn, which were done ~300 days after the explosion. we discuss them in the context of constraints on the supernova's progenitor. previous studies have proposed two possible natures for the progenitor of the supernova, i.e. a massive wolf-rayet star or a lower-mass star in a close binary system.methods: our observations show that the supernova has entered the nebular phase, with the spectrum dominated by mg i]λλ4571, [o i]λλ6300, 6364, and [ca ii]λλ7291, 7324 emission lines. we measured the emission line fluxes to estimate the core oxygen mass and compared the [o i]/[ca ii] line ratio with other supernovae. results.the core oxygen mass of the supernova progenitor was estimated to be ≲0.7 m⊙, which implies initial progenitor mass that does not exceed ~15-17 m⊙.since the derived mass is too low for a single star to become a wolf-rayet star, this result lends more support to the binary nature of the progenitor star of iptf13bvn. the comparison of [o i]/[ca ii] line ratio with other supernovae also shows that iptf13bvn appears to be in close association with the lower mass progenitors of stripped-envelope and type-ii supernovae. based on observations obtained at the southern astrophysical research (soar) telescope, which is a joint project of the ministério da ciência, tecnologia, e inovação (mcti) da república federativa do brasil, the us national optical astronomy observatory (noao), the university of north carolina at chapel hill (unc), and michigan state university (msu); chilean telescope time allocation committee proposal cn2014a-91. | nebular phase observations of the type-ib supernova iptf13bvn favour a binary progenitor |
galactic supernova remnants (snrs) with angular dimensions greater than a few degrees are relatively rare, as are remnants located more than 10° off the galactic plane. here we report a uv and optical investigation of two previously suspected snrs more than 10° in both angular diameter and galactic latitude. one is a proposed remnant discovered in 2008 through 1420 mhz polarization maps near galactic coordinates l = 353°, b = -34°. galex far-uv (fuv) and hα emission mosaics show the object's radio emission coincident with an 11° × 14° shell of uv filaments that surrounds a diffuse hα emission ring. another proposed high-latitude snr is the 20° × 26° antlia nebula (g275.5+18.4) discovered in 2002 through low-resolution all-sky hα and rosat soft x-ray emissions. galex fuv and hα mosaics along with optical spectra indicate the presence of shocks throughout the antlia nebula with estimated shock velocities of 70 to over 100 km s-1. we also present evidence that it has collided with the ne rim of the gum nebula. we find both of these large nebulae are bona fide snrs with ages less than 105 yr despite their unusually large angular dimensions. we also present fuv and optical images along with optical spectra of a new high-latitude snr (g249.7+24.7) some 4.5° in diameter which has also been independently discovered in x-rays and radio (becker at al. 2021). we find this remnant's distance to be ≤400 pc based on the detection of red and blue na i absorption features in the spectra of two background stars. | far-uv and optical emissions from three very large supernova remnants located at unusually high galactic latitudes |
when a protoplanetary disc loses gas, it leaves behind planets and one or more planetesimal belts. the belts get dynamically excited, either by planets (`planet stirring') or by embedded big planetesimals (`self-stirring'). collisions between planetesimals become destructive and start to produce dust, creating an observable debris disc. following kenyon & bromley, it is often assumed that self-stirring starts to operate as soon as the first ∼ 1000 km sized embedded `plutos' have formed. however, state-of-the-art pebble concentration models robustly predict planetesimals between a few km and ∼ 200 km in size to form in protoplanetary discs rapidly, before then slowly growing into pluto-sized bodies. we show that the time-scale, on which these planetesimals excite the disc sufficiently for fragmentation, is shorter than the formation time-scale of plutos. using an analytic model based on the ida & makino theory, we find the excitation time-scale to be t_excite ≈ 100 x_m^{-1} m_\star ^{-3/2} a^3 myr, where xm is the total mass of a protoplanetary disc progenitor in the units of the minimum-mass solar nebula, a is its radius in the units of 100 au, and m⋆ is the stellar mass in solar masses. these results are applied to a set of 23 debris discs that have been well resolved with alma or sma. we find that the majority of these discs are consistent with being self-stirred. however, three large discs around young early-type stars do require planets as stirrers. these are 49 cet, hd 95086, and hr 8799, of which the latter two are already known to have planets. | self-stirring of debris discs by planetesimals formed by pebble concentration |
we characterize the stellar and gas volume density, potential, and gravitational field profiles in the central ∼0.5 pc of the orion nebula cluster (onc), the nearest embedded star cluster (or rather, protocluster) hosting massive star formation available for detailed observational scrutiny. we find that the stellar volume density is well characterized by a plummer profile ρstars(r) = 5755 m⊙ pc- 3 (1 + (r/a)2)- 5/2, where a = 0.36 pc. the gas density follows a cylindrical power law ρgas(r) = 25.9 m⊙ pc- 3 (r/pc)- 1.775. the stellar density profile dominates over the gas density profile inside r ∼ 1 pc. the gravitational field is gas-dominated at all radii, but the contribution to the total field by the stars is nearly equal to that of the gas at r ∼ a. this fact alone demonstrates that the protocluster cannot be considered a gas-free system or a virialized system dominated by its own gravity. the stellar protocluster core is dynamically young, with an age of ∼2-3 myr, a 1d velocity dispersion of σobs = 2.6 km s-1, and a crossing time of ∼0.55 myr. this time-scale is almost identical to the gas filament oscillation time-scale estimated recently by stutz & gould. this provides strong evidence that the protocluster structure is regulated by the gas filament. the protocluster structure may be set by tidal forces due to the oscillating filamentary gas potential. such forces could naturally suppress low density stellar structures on scales ≳ a. the analysis presented here leads to a new suggestion that clusters form by an analogue of the 'slingshot mechanism' previously proposed for stars. | slingshot mechanism for clusters: gas density regulates star density in the orion nebula cluster (m42) |
we present a very large telescope/multi unit spectroscopic explorer (muse) survey of lensed high-redshift galaxies behind the z = 0.77 cluster rcs 0224-0002. we study the detailed internal properties of a highly magnified (μ ∼ 29) z = 4.88 galaxy seen through the cluster. we detect widespread nebular c iv λλ1548,1551 å emission from this galaxy as well as a bright lyα halo with a spatially uniform wind and absorption profile across 12 kpc in the image plane. blueshifted high- and low-ionization interstellar absorption indicate the presence of a high-velocity outflow (δv ∼ 300 km s- 1) from the galaxy. unlike similar observations of galaxies at z ∼ 2 - 3, the lyα emission from the halo emerges close to the systemic velocity - an order of magnitude lower in velocity offset than predicted in 'shell'-like outflow models. to explain these observations, we favour a model of an outflow with a strong velocity gradient, which changes the effective column density seen by the lyα photons. we also search for high-redshift lyα emitters and identify 14 candidates between z = 4.8 - 6.6, including an overdensity at z = 4.88, of which only one has a detected counterpart in hubble space telescope/advanced camera for surveys+wide field camera 3 imaging. | a gravitationally boosted muse survey for emission-line galaxies at z ≳ 5 behind the massive cluster rcs 0224 |
we perform a spectroscopic survey of the foreground population in orion a with mmt/hectospec. we use these data, along with archival spectroscopic data and photometric data, to derive spectral types, extinction values, and masses for 691 stars. using the spitzer space telescope data, we characterize the disk properties of these sources. we identify 37 new transition disk (td) objects, 1 globally depleted disk candidate, and 7 probable young debris disks. we discover an object with a mass of less than 0.018-0.030 m ⊙, which harbors a flaring disk. using the hα emission line, we characterize the accretion activity of the sources with disks, and confirm that the fraction of accreting tds is lower than that of optically thick disks (46% ± 7% versus 73% ± 9%, respectively). using kinematic data from the sloan digital sky survey and apogee infrared spectroscopy of the young nebulous clusters program (in-sync), we confirm that the foreground population shows similar kinematics to their local molecular clouds and other young stars in the same regions. using the isochronal ages, we find that the foreground population has a median age of around 1-2 myr, which is similar to that of other young stars in orion a. therefore, our results argue against the presence of a large and old foreground cluster in front of orion a. | ngc 1980 is not a foreground population of orion: spectroscopic survey of young stars with low extinction in orion a |
rcw 38 is a deeply embedded young (∼1 myr), massive star cluster located at a distance of 1.7 kpc. twice as dense as the orion nebula cluster, orders of magnitude denser than other nearby star-forming regions and rich in massive stars, rcw 38 is an ideal place to look for potential differences in brown dwarf formation efficiency as a function of environment. we present deep, high-resolution adaptive optics data of the central ∼0.5 × 0.5 pc2 obtained with naco at the very large telescope. through comparison with evolutionary models, we determine masses and extinction for ∼480 candidate members, and derive the first initial mass function (imf) of the cluster extending into the substellar regime. representing the imf as a set of power laws in the form dn/dm ∝ m-α, we derive the slope α = 1.60 ± 0.13 for the mass range 0.5-20 m⊙,which is shallower than the salpeter slope, but in agreement with results in several other young massive clusters. at the low-mass side, we find α = 0.71 ± 0.11 for masses between 0.02 and 0.5 m⊙, or α = 0.81 ± 0.08 for masses between 0.02 and 1 m⊙. our result is in agreement with the values found in other young star-forming regions, revealing no evidence that a combination of high stellar densities and the presence of numerous massive stars affects the formation efficiency of brown dwarfs and very-low-mass stars. we estimate that the milky way galaxy contains between 25 and 100 billion brown dwarfs (with masses >0.03 m⊙). | the low-mass content of the massive young star cluster rcw 38 |
a significant fraction of ob-type, main-sequence massive stars are classified as runaway and move supersonically through the interstellar medium (ism). their strong stellar winds interact with their surroundings, where the typical strength of the local ism magnetic field is about 3.5-7 μg, which can result in the formation of bow shock nebulae. we investigate the effects of such magnetic fields, aligned with the motion of the flow, on the formation and emission properties of these circumstellar structures. our axisymmetric, magneto-hydrodynamical simulations with optically thin radiative cooling, heating and anisotropic thermal conduction show that the presence of the background ism magnetic field affects the projected optical emission of our bow shocks at hα and [o iii] λ 5007 which become fainter by about 1-2 orders of magnitude, respectively. radiative transfer calculations against dust opacity indicate that the magnetic field slightly diminishes their projected infrared emission and that our bow shocks emit brightly at 60 μm. this may explain why the bow shocks generated by ionizing runaway massive stars are often difficult to identify. finally, we discuss our results in the context of the bow shock of ζ ophiuchi and we support the interpretation of its imperfect morphology as an evidence of the presence of an ism magnetic field not aligned with the motion of its driving star. | bow shock nebulae of hot massive stars in a magnetized medium |
planets grow via the collisional accretion of small bodies in a protoplanetary disk. such small bodies feel strong gas drag, and their orbits are significantly affected by the gas flow and atmospheric structure around the planet. we investigate the gas flow in the protoplanetary disk perturbed by the gravity of the planet by 3d hydrodynamical simulation. we then calculate the orbital evolutions of particles in the gas structure obtained from the hydrodynamical simulation. based on the orbital calculations, we obtain the collision rate between the planet and centimeter-to-kilometer-sized particles. our results show that meter-sized or larger particles effectively collide with the planet owing to the atmospheric gas drag, which significantly enhances the collision rate. on the other hand, the gas flow plays an important role for smaller particles. finally, considering the effects of the atmosphere and gas flow, we derive the new analytic formula for the collision rate, which is in good agreement with our simulations. we estimate the growth timescale and accretion efficiency of drifting bodies for the formation of a gas giant solid core using the formula. we find that the accretion of sub-kilometer-sized bodies achieves a short growth timescale (~0.05 myr) and a high accretion efficiency (~1) for the core formation at 5 au in the minimum-mass solar nebula model. | the growth of protoplanets via the accretion of small bodies in disks perturbed by the planetary gravity |
we present arcminute-resolution intensity and polarization maps of the galactic center made with the atacama cosmology telescope. the maps cover a 32 deg2 field at 98, 150, and 224 ghz with ∣l∣ ≤ 4°, ∣b∣ ≤ 2°. we combine these data with planck observations at similar frequencies to create coadded maps with increased sensitivity at large angular scales. with the coadded maps, we are able to resolve many known features of the central molecular zone (cmz) in both total intensity and polarization. we map the orientation of the plane-of-sky component of the galactic magnetic field inferred from the polarization angle in the cmz, finding significant changes in morphology in the three frequency bands as the underlying dominant emission mechanism changes from synchrotron to dust emission. selected galactic center sources, including sgr a*, the brick molecular cloud (g0.253+0.016), the mouse pulsar wind nebula (g359.23-0.82), and the tornado supernova remnant candidate (g357.7-0.1), are examined in detail. these data illustrate the potential for leveraging ground-based cosmic microwave background polarization experiments for galactic science. | the atacama cosmology telescope: microwave intensity and polarization maps of the galactic center |
recently, gamma-ray halos of a few degree extension have been detected around two middle-aged pulsars, namely, geminga and psr b0656+14, by the high altitude water cherenkov observatory (hawc). the gamma-ray radiation arises from relativistic electrons that escape the pulsar wind nebula and diffuse in the surrounding medium. the diffusion coefficient is found to be significantly lower than the average value in the galactic disk. if so, given a typical transverse velocity of 300-500 km s-1 for a pulsar, its displacement could be important in shaping the morphology of its gamma-ray halos. motivated by this, we study the morphology of pulsar halos considering the proper motion of pulsar. we define three evolutionary phases of the pulsar halo to categorize its morphological features. the morphology of pulsar halos below 10 tev is double peaked or single peaked with an extended tail, which depends on the electron injection history. above 10 tev, the morphology of pulsar halos is nearly spherical, due to the short cooling timescale (<50 kyr) for tens of teraelectronvolt electrons. we also quantitatively evaluate the separation between the pulsar and the center of the gamma-ray halo, as well as the influence of different assumptions on the pulsar characteristics and the injected electrons. our results suggest that the separation between the center of the gamma-ray halo above 10 tev and the associated pulsar is usually too small to be observable by hawc or the large high altitude air shower observatory. hence, our results provide a useful approach to constrain the origin of extended sources at very high energies. | morphology of gamma-ray halos around middle-aged pulsars: influence of the pulsar proper motion |
astronomical observations and isotopic measurements of meteorites suggest that substructures are common in protoplanetary disks and may even have existed in the solar nebula. here, we conduct paleomagnetic measurements of chondrules in co carbonaceous chondrites to investigate the existence and nature of these disk sub-structures. we show that the paleomagnetism of chondrules in co carbonaceous chondrites indicates the presence of a 101 $\pm$ 48 $\mu$t field in the solar nebula in the outer solar system ($\sim$3 to 7 au from the sun). the high intensity of this field relative to that inferred from inner solar system ($\lesssim$3 au) meteorites indicates a factor of $\sim$5 to 150 mismatch in nebular accretion between the two reservoirs. this suggests substantial mass loss from the disk associated with a major disk substructure, possibly due to a magnetized disk wind. | paleomagnetic evidence for a disk substructure in the early solar system |
an episode of dynamical instability is thought to have sculpted the orbital structure of the outer solar system. when modeling this instability, a key constraint comes from jupiter's fifth eccentric mode (quantified by its amplitude m55), which is an important driver of the solar system's secular evolution. starting from commonly-assumed near-circular orbits, the present-day giant planets' architecture lies at the limit of numerically generated systems, and m55 is rarely excited to its true value. here we perform a dynamical analysis of a large batch of artificially triggered instabilities, and test a variety of configurations for the giant planets' primordial orbits. in addition to more standard setups, and motivated by the results of modern hydrodynamical simulations of the giant planets' evolution within the primordial gaseous disk, we consider the possibility that jupiter and saturn emerged from the nebular gas locked in 2:1 resonance with non-zero eccentricities. we show that, in such a scenario, the modern jupiter-saturn system represents a typical simulation outcome, and m55 is commonly matched. furthermore, we show that uranus and neptune's final orbits are determined by a combination of the mass in the primordial kuiper belt and that of an ejected ice giant. | born eccentric: constraints on jupiter and saturn's pre-instability orbits |
aims: we study iptf14hls, a luminous and extraordinary long-lived type ii supernova, which lately has attracted much attention and disparate interpretation.methods: we have presented new optical photometry that extends the light curves up to more than three years past discovery. we also obtained optical spectroscopy over this period, and furthermore present additional space-based observations using swift and hst.results: after an almost constant luminosity for hundreds of days, the later light curve of iptf14hls finally fades and then displays a dramatic drop after about 1000 d, but the supernova is still visible at the latest epochs presented. the spectra have finally turned nebular, and our very last optical spectrum likely displays signatures from the deep and dense interior of the explosion. a high-resolution hst image highlights the complex environment of the explosion in this low-luminosity galaxy.conclusions: we provide a large number of additional late-time observations of iptf14hls, which are (and will continue to be) used to assess the many different interpretations for this intriguing object. in particular, the very late (+1000 d) steep decline of the optical light curve is difficult to reconcile with the proposed central engine models. the lack of very strong x-ray emission, and the emergence of intermediate-width emission lines including [s ii] that we propose originate from dense, processed material in the core of the supernova ejecta, are also key observational tests for both existing and future models. | late-time observations of the extraordinary type ii supernova iptf14hls |
we present the stromlo stellar tracks, a set of stellar evolutionary tracks, computed by modifying the modules for experiments in stellar astrophysics (mesa) 1d stellar evolution package, to fit the galactic concordance abundances for hot (t > 8000 k) massive (≥10 m⊙) main-sequence (ms) stars. until now, all stellar evolution tracks have been computed at solar, scaled-solar, or α-element-enhanced abundances, and none of these models correctly represent the galactic concordance abundances at different metallicities. this paper is the first implementation of galactic concordance abundances to the stellar evolution models. the stromlo tracks cover massive stars (10 ≤ m/m⊙ ≤ 300) with varying rotations (v/vcrit = 0.0, 0.2, 0.4) and a finely sampled grid of metallicities (-2.0 ≤ [z/h] ≤ +0.5; δ[z/h] = 0.1) evolved from the pre-main sequence to the end of 12c burning. we find that the implementation of galactic concordance abundances is critical for the evolution of ms, massive hot stars in order to estimate accurate stellar outputs (l, teff, g), which, in turn, have a significant impact on determining the ionizing photon luminosity budgets. we additionally support prior findings of the importance that rotation plays on the evolution of massive stars and their ionizing budget. the evolutionary tracks for our galactic concordance abundance scaling provide a more empirically motivated approach than simple uniform abundance scaling with metallicity for the analysis of h ii regions and have considerable implications for determining nebular emission lines and metallicity. therefore, it is important to refine existing stellar evolutionary models for comprehensive high-redshift extragalactic studies. the stromlo tracks are available to the astronomical community. | stromlo stellar tracks: non-solar-scaled abundances for massive stars |
we present alma observations on and around the radio-quiet quasar um 287 at z = 2.28. together with a companion quasar, um 287 is believed to play a major role in powering the surrounding enormous lyα nebula (elan), dubbed the slug elan, that has an end-to-end size of 450 physical kpc. in addition to the quasars, we detect a new dusty star-forming galaxy (dsfg), dubbed the slug-dsfg, in 2 mm continuum with a single emission line consistent with co(4-3). the slug-dsfg sits at a projected distance of 100 kpc southeast from um 287, with a systemic velocity difference of -360 ± 30 km s-1 with respect to um 287, suggesting it is a possible contributor to the powering of the slug elan. with careful modeling of the sed and dynamical analyses, it is found that the slug-dsfg and um 287 appear low in both gas fraction and gas-to-dust ratio, suggesting environmental effects due to the host's massive halo. in addition, our keck long-slit spectra reveal significant lyα emissions from the slug-dsfg, as well as a lyα tail that starts at the location and velocity of the slug-dsfg and extends toward the south, with a projected length of about 100 kpc. supported by various analytical estimates we propose that the lyα tail is a result of the slug-dsfg experiencing ram pressure stripping. the gas mass stripped is estimated to be about 109 m ⊙, contributing to the dense warm/cool gas reservoir that is believed to help power the exceptional lyα luminosity. | a multiwavelength study of elan environments (amuse2). detection of a dusty star-forming galaxy within the enormous lyα nebula at z=2.3 sheds light on its origin |
we present hubble space telescope (hst) observations of the type iib supernova (sn) sn 2016gkg at 652, 1698, and 1795 days from explosion with the advanced camera for surveys (acs) and wide field camera 3 (wfc3). comparing to pre-explosion imaging from 2001 obtained with the wide field planetary camera 2, we demonstrate that sn 2016gkg is now fainter than its candidate counterpart in the latest wfc3 imaging, implying that the counterpart has disappeared and confirming that it was the sn progenitor star. we show the latest light curve and keck spectroscopy of sn 2016gkg, which imply that sn 2016gkg is declining more slowly than the expected rate for 56co decay during its nebular phase. we find that this emission is too luminous to be powered by other radioisotopes and infer that sn 2016gkg is entering a new phase in its evolution where it is powered primarily by interaction with circumstellar matter. finally, we reanalyze the progenitor star spectral energy distribution and late-time limits in the context of binary evolution models. including emission from a potential companion star, we find that all such predicted companion stars would be fainter than our limiting magnitudes. | updated photometry of the yellow supergiant progenitor and late-time observations of the type iib supernova sn 2016gkg |
we present results constraining the multiplicity of the very low mass stars and substellar objects in the orion nebula cluster (onc). our sample covers primary masses 0.012-0.1 m ⊙ using archival hubble space telescope data obtained with the advanced camera for surveys using multiple filters. studying the binary populations of clusters provides valuable constraints of how the birth environment affects binary formation and evolution. prior surveys have shown that the binary populations of high-mass, high-density star clusters like the onc may substantially differ from those in low-mass associations. very low mass stellar and substellar binaries at wide separations, >20 au, are statistically rare in the galactic field and have been identified in stellar associations like taurus-auriga and ophiuchus. they also may be susceptible to dynamical interactions, and their formation may be suppressed by feedback from ongoing star formation. we implement a double point-spread function (psf) fitting algorithm using empirical, position-dependent psf models to search for binary companions at projected separations >10 au (0.″025). with this technique, we identify seven very low mass binaries, five of which are new detections, resulting in a binary frequency of ${12}_{-3.2}^{+6} \% $ over mass ratios of 0.5-1.0 and projected separations of 20-200 au. we find an excess of very low mass binaries in the onc compared to the galactic field, with a probability of 10-6 that the populations are statistically consistent. the substellar population of the onc may require further dynamical processing of the lowest binding energy binaries to resemble the field population. | binary formation in the orion nebula cluster: exploring the substellar limit |
we present here the exploration of the physical properties of the sample of h ii regions and aggregations of the last h ii regions catalogue of the calar alto legacy integral field area (califa) survey. this sample comprises the optical spectroscopic properties of more than ~26 000 ionized regions corresponding to 924 galaxies from the integral field spectroscopy data, including the flux intensity and equivalent widths and the properties of their underlying stellar population. in the current study, we derive a set of physical quantities for all these regions based on those properties, including (i) the fraction of young stars; (ii) the ionization strength (using six different estimations); (iii) the oxygen abundance (using 25 different calibrators); (iv) the nitrogen and nitrogen-to-oxygen abundance; (v) the dust extinction; and (vi) the electron density. using this data set, we explore how the loci in the classical diagnostic diagrams are connected with those quantities, the radial distributions of these parameters, and the interrelations between themselves and with the properties of the underlying stellar populations. we conclude that many properties of the h ii regions are tightly related to the galactic stellar evolution at the location where those regions are observed. those properties are modulated only as a second-order effect by the properties of the ionizing stars and the ionized nebulae that do not depend on the astrophysical context in which they are formed. our results highlight the importance of h ii regions to explore the chemical evolution in galaxies, clarifying which of their properties can be used as proxies of that evolution. | h ii regions in califa survey: ii. the relation between their physical properties and galaxy evolution |
we present the results of two-dimensional radiation-hydrodynamic simulations of expanding supernova ejecta with a central energy source. as suggested in previous multidimensional hydrodynamic simulations, a sufficiently powerful central energy source can blow away the expanding supernova ejecta, leading to efficient mixing of stratified layers in the ejecta. we assume that the energy injection is realized in the form of nonthermal radiation from the wind nebula embedded at the center of the ejecta. we found that the multidimensional mixing in the ejecta assists the injected nonthermal radiation escaping from the ejecta. when the nonthermal radiation is absorbed by the ejecta, it is converted into bright thermal radiation or is consumed as the kinetic energy of the supernova ejecta. we found that central energy sources with injection timescale similar to the photon diffusion timescale realize an efficient conversion of the injected energy into thermal radiation. on the other hand, rapid energy injection ends up accelerating the ejecta rather than giving rise to bright thermal emission. this remarkable difference potentially explains the diversity of energetic supernovae including broad-lined ic and superluminous supernovae. | two-dimensional radiation-hydrodynamic simulations of supernova ejecta with a central power source |
recent wide-field integral-field spectroscopy has revealed the detailed properties of high-redshift lyα nebulae, most often targeted due to the presence of an active galactic nucleus (agn). here, we use vlt/muse to resolve the morphology and kinematics of a nebula initially identified due to strong lyα emission at z ~ 3.2 (labn06). our observations reveal a two-lobed lyα nebula, at least ~173 pkpc in diameter, with a light-weighted centroid near a mid-infrared source (within ≈17.2 pkpc) that appears to host an obscured agn. the lyα emission near the agn is also coincident in velocity with the kinematic center of the nebula, suggesting that the nebula is both morphologically and kinematically centered on the agn. compared to agn-selected lyα nebulae, the surface-brightness profile of this nebula follows a typical exponential profile at large radii (>25 pkpc), although at small radii, the profile shows an unusual dip at the location of the agn. the kinematics and asymmetry are similar to, and the c iv and he ii upper limits are consistent with, other agn-powered lyα nebulae. double-peaked and asymmetric line profiles suggest that lyα resonant scattering may be important in this nebula. these results support the picture of the agn being responsible for powering a lyα nebula that is oriented roughly in the plane of the sky. further observations will explore whether the central surface-brightness depression is indicative of either an unusual gas or dust distribution or variation in the ionizing output of the agn over time. | mapping the morphology and kinematics of a lyα-selected nebula at z = 3.15 with muse |
nebulabayes is a new bayesian code that implements a general method of comparing observed emission-line fluxes to photoionization model grids. the code enables us to extract robust, spatially resolved measurements of abundances in the extended narrow-line regions (enlrs) produced by active galactic nuclei (agn). we observe near-constant ionization parameters but steeply radially declining pressures, which together imply that radiation pressure regulates the enlr density structure on large scales. our sample includes four “pure seyfert” galaxies from the s7 survey that have extensive enlrs. ngc 2992 shows steep metallicity gradients from the nucleus into the ionization cones. an inverse metallicity gradient is observed in eso 138-g01, which we attribute to a recent gas inflow or minor merger. a uniformly high metallicity and hard ionizing continuum are inferred across the enlr of mrk 573. our analysis of ic 5063 is likely affected by contamination from shock excitation, which appears to soften the inferred ionizing spectrum. the peak of the ionizing continuum e peak is determined by the nuclear spectrum and the absorbing column between the nucleus and the ionized nebula. we cannot separate variation in this intrinsic e peak from the effects of shock or h ii region contamination, but e peak measurements nevertheless give insights into enlr excitation. we demonstrate the general applicability of nebulabayes by analyzing a nuclear spectrum from the non-active galaxy ngc 4691 using a h ii region grid. the nlr and h ii region model grids are provided with nebulabayes for use by the astronomical community. | interrogating seyferts with nebulabayes: spatially probing the narrow-line region radiation fields and chemical abundances |
we introduce vlt-muse observations of the central 2'× 2' (30 × 30 pc) of the tarantula nebula in the large magellanic cloud. the observations provide an unprecedented spectroscopic census of the massive stars and ionised gas in the vicinity of r136, the young, dense star cluster located in ngc 2070, at the heart of the richest star-forming region in the local group. spectrophotometry and radial-velocity estimates of the nebular gas (superimposed on the stellar spectra) are provided for 2255 point sources extracted from the muse datacubes, and we present estimates of stellar radial velocities for 270 early-type stars (finding an average systemic velocity of 271 ± 41 km s-1). we present an extinction map constructed from the nebular balmer lines, with electron densities and temperatures estimated from intensity ratios of the [s ii], [n ii], and [s iii] lines. the interstellar medium, as traced by hα and [n ii] λ6583, provides new insights in regions where stars are probably forming. the gas kinematics are complex, but with a clear bi-modal, blue- and red-shifted distribution compared to the systemic velocity of the gas centred on r136. interesting point-like sources are also seen in the eastern cavity, western shell, and around r136; these might be related to phenomena such as runaway stars, jets, formation of new stars, or the interaction of the gas with the population of wolf-rayet stars. closer inspection of the core reveals red-shifted material surrounding the strongest x-ray sources, although we are unable to investigate the kinematics in detail as the stars are spatially unresolved in the muse data. further papers in this series will discuss the detailed stellar content of ngc 2070 and its integrated stellar and nebular properties. based on observations made with eso telescopes at the paranal observatory under programme id 60.a-9351(a).table 3 is only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/614/a147 | mapping the core of the tarantula nebula with vlt-muse. i. spectral and nebular content around r136 |
using multi-epoch very large array observations, covering a time baseline of 29.1 years, we have measured the proper motions of 88 young stars with compact radio emission in the core of the orion nebula cluster (onc) and the neighboring bn/kl region. our work increases the number of young stars with measured proper motion at radio frequencies by a factor of 2.5 and enables us to perform a better statistical analysis of the kinematics of the region than was previously possible. most stars (79 out of 88) have proper motions consistent with a gaussian distribution centered on \overline{{μ }α \cos δ }=1.07+/- 0.09 mas yr-1, and \overline{{μ }δ }=-0.84+/- 0.16 mas yr-1, with velocity dispersions of {σ }α =1.08+/- 0.07 mas yr-1, {σ }δ =1.27+/- 0.15 mas yr-1. we looked for organized movements of these stars but found no clear indication of radial expansion/contraction or rotation. the remaining nine stars in our sample show peculiar proper motions that differ from the mean proper motions of the onc by more than 3σ. one of these stars, v 1326 ori, could have been expelled from the orion trapezium 7000 years ago. two could be related to the multi-stellar disintegration in the bn/kl region, in addition to the previously known sources bn, i and n. the others either have high uncertainties (so their anomalous proper motions are not firmly established) or could be foreground objects. | radio measurements of the stellar proper motions in the core of the orion nebula cluster |
we report on the study of interstellar extinction across the tarantula nebula (30 doradus), in the large magellanic cloud, using observations from the hubble tarantula treasury project in the 0.3-1.6 μm range. the considerable and patchy extinction inside the nebula causes about 3500 red clump stars to be scattered along the reddening vector in the colour-magnitude diagrams, thereby allowing an accurate determination of the reddening slope in all bands. the measured slope of the reddening vector is remarkably steeper in all bands than in the the galactic diffuse interstellar medium. at optical wavelengths, the larger ratio of total-to-selective extinction, namely rv = 4.5 ± 0.2, implies the presence of a grey component in the extinction law, due to a larger fraction of large grains. the extra large grains are most likely ices from supernova ejecta and will significantly alter the extinction properties of the region until they sublimate in 50-100 myr. we discuss the implications of this extinction law for the tarantula nebula and in general for regions of massive star formation in galaxies. our results suggest that fluxes of strongly star-forming regions are likely to be underestimated by a factor of about 2 in the optical. | hubble tarantula treasury project - iv. the extinction law |
we present multi unit spectroscopic explorer (muse) integral field spectroscopic observations of the host galaxy (pgc 043234) of one of the closest (z = 0.0206, d ≃ 90 mpc) and best-studied tidal disruption events (tdes), asassn-14li. the muse integral field data reveal asymmetric and filamentary structures that extend up to ≳10 kpc from the post-starburst host galaxy of asassn-14li. the structures are traced only through the strong nebular [o iii] λ5007, [n ii] λ6584, and hα emission lines. the total off-nuclear [o iii] λ5007 luminosity is 4.7 × 1039 erg s-1, and the ionized h mass is ∼ {10}4(500/{n}{{e}}) {m}⊙ . based on the baldwin-phillips-terlevich diagram, the nebular emission can be driven by either agn photoionization or shock excitation, with agn photoionization favored given the narrow intrinsic line widths. the emission line ratios and spatial distribution strongly resemble ionization nebulae around fading agns such as ic 2497 (hanny's voorwerp) and ionization “cones” around seyfert 2 nuclei. the morphology of the emission line filaments strongly suggest that pgc 043234 is a recent merger, which likely triggered a strong starburst and agn activity leading to the post-starburst spectral signatures and the extended nebular emission line features we see today. we briefly discuss the implications of these observations in the context of the strongly enhanced tde rates observed in post-starburst galaxies and their connection to enhanced theoretical tde rates produced by supermassive black hole binaries. | muse reveals a recent merger in the post-starburst host galaxy of the tde asassn-14li |
sn 2012ec is a type iip supernova (sn) with a progenitor detection and comprehensive photospheric phase observational coverage. here, we present very large telescope and public eso spectroscopic survey of transient objects observations of this sn in the nebular phase. we model the nebular [o i] λλ6300, 6364 lines and find their strength to suggest a progenitor main-sequence mass of 13-15 m⊙. sn 2012ec is unique among hydrogen-rich sne in showing a distinct line of stable nickel [ni ii] λ7378. this line is produced by 58ni, a nuclear burning ash whose abundance is a sensitive tracer of explosive burning conditions. using spectral synthesis modelling, we use the relative strengths of [ni ii] λ7378 and [fe ii] λ7155 (the progenitor of which is 56ni) to derive a ni/fe production ratio of 0.20 ± 0.07 (by mass), which is a factor 3.4 ± 1.2 times the solar value. high production of stable nickel is confirmed by a strong [ni ii] 1.939 μm line. this is the third reported case of a core-collapse sn producing a ni/fe ratio far above the solar value, which has implications for core-collapse explosion theory and galactic chemical evolution models. | supersolar ni/fe production in the type iip sn 2012ec |
in this paper we compute models for relativistic white dwarfs in the presence of strong magnetic fields. these models possibly contribute to superluminous snia. with an assumed axisymmetric and poloidal magnetic field, we study the possibility of the existence of super-chandrasekhar magnetized white dwarfs by solving numerically the einstein-maxwell equations, by means of a pseudospectral method. we obtain a self-consistent rotating and nonrotating magnetized white dwarf model. according to our results, a maximum mass for a static magnetized white dwarf is 2.13 m⊙ in the newtonian case, and 2.09 m⊙ when taking into account general relativistic effects. furthermore, we present results for rotating magnetized white dwarfs. the maximum magnetic field strength reached at the center of white dwarfs is of the order of 1015 g in the static case, whereas for magnetized white dwarfs, rotating with the keplerian angular velocity, it is of the order of 1014 g . | effects of strong magnetic fields and rotation on white dwarf structure |
aims: we aim to study the rotating and expanding gas in the red rectangle, which is a well known bipolar nebula surrounding a double stellar system whose primary is a post-asymptotic giant branch (post-agb) star. we analyze the properties of both components and the relation between them. rotating disks have been very elusive in post-agb nebulae, in which gas is almost always found to be in expansion.methods: we present new high-quality alma observations of this source in c17o j = 6-5 and h13cn j = 4-3 line emission and results from a new reduction of already published 13co j = 3-2 data. a detailed model fitting of all the molecular line data, also discussing previous maps and single-dish observations of lines of co, cii, and ci, was performed using a sophisticated code that includes an accurate nonlocal treatment of radiative transfer in 2d (assuming axial symmetry). these observations (of low- and high-opacity lines requiring various degrees of excitation) and the corresponding modeling allowed us to deepen the analysis of the nebular properties. we also stress the uncertainties, particularly in the determination of the boundaries of the co-rich gas and some properties of the outflow.results: we confirm the presence of a rotating equatorial disk and an outflow, which is mainly formed of gas leaving the disk. the mass of the disk is ~0.01 m⊙, and that of the co-rich outflow is around ten times smaller. high temperatures of ≳100 k are derived for most components. from comparison of the mass values, we roughly estimate the lifetime of the rotating disk, which is found to be of about 10 000 yr. taking data of a few other post-agb composite nebulae into account, we find that the lifetimes of disks around post-agb stars typically range between about 5000 and more than 20 000 yr. the angular momentum of the disk is found to be high, ~9 m⊙ au km s-1, which is comparable to that of the stellar system at present. our observations of h13cn show a particularly wide velocity dispersion and indicate that this molecule is only abundant in the inner keplerian disk, at ≲60 au from the stellar system. we suggest that hcn is formed in a dense photodissociation region (pdr) due to the uv excess known to be produced by the stellar system, following chemical mechanisms that are well established for interstellar medium pdrs and disks orbiting young stars. we further suggest that this uv excess could lead to an efficient formation and excitation of pahs and other c-bearing macromolecules, whose emission is very intense in the optical counterpart. | further alma observations and detailed modeling of the red rectangle |
it is widely believed that super-eddington accretion flow can produce powerful outflow, but where it originates from and how much mass and energy are carried away to which directions? to answer to these questions, we newly perform a large-box, two-dimensional radiation hydrodynamic simulation, paying special attention lest the results should depend on adopted initial and boundary conditions. we could achieve a quasi-steady state in an unprecedentedly large range, $r=2~r_{\rm s}$-$600~r_{\rm s}$ (with $r_{\rm s}$ being the schwarzschild radius) from the black hole. the accretion rate onto the central $10 ~m_{\odot}$ black hole is $\dot{m}_{\rm bh} \sim 180 ~l_{\rm edd}/c^{2}$, whereas the mass outflow rate is ${\dot m}_{\rm outflow} \sim 24 ~l_{\rm edd}/c^2$ (where $l_{\rm edd}$ and $c$ are the eddington luminosity and the speed of light, respectively). the ratio (${\dot m}_{\rm outflow}/{\dot m}_{\rm bh} \sim 0.14$) is much less than those reported previously. by careful inspection we find that most of outflowing gas which reach the outer boundary originates from the region at $r\lesssim140~r_{\rm s}$, while gas at $140~r_{\rm s}$-$230 ~r_{\rm s}$ forms failed outflow. therefore, significant outflow occurs inside the trapping radius $\sim 450 ~r_{\rm s}$. the mechanical energy flux (or mass flux) reaches its maximum in the direction of $\sim 15^\circ$ ($\sim 80^\circ$) from the rotation axis. the total mechanical luminosity is $l_{\rm mec}\sim 0.16~l_{\rm edd}$, while the isotropic x-ray luminosity varies from $l_{\rm x}^{\rm iso}\sim 2.9~l_{\rm edd}$, (for a face-on observer) to $\sim 2.1~l_{\rm edd}$ (for a nearly edge-on observer). the power ratio is $l_{\rm mec}/l_{\rm x}^{\rm iso}\sim 0.05$-$0.08$, in good agreement with the observations of ultra-luminous x-ray sources surrounded by optical nebulae. | outflow from super-eddington flow: where it originates from and how much impact it gives? |
we present the results from a muse survey of twelve z ≃ 3.15 quasars, which were selected to be much fainter (20 < isdss < 23) than in previous studies of giant ly α nebulae around the brightest quasars (16.6 < iab < 18.7). we detect h i> ly α nebulae around 100 per cent of our target quasars, with emission extending to scales of at least 60 physical kpc, and up to 190 pkpc. we explore correlations between properties of the nebulae and their host quasars, with the goal of connecting variations in the properties of the illuminating qso to the response in nebular emission. we show that the surface brightness profiles of the nebulae are similar to those of nebulae around bright quasars, but with a lower normalization. our targeted quasars are on average 3.7 mag (≃30 times) fainter in uv continuum than our bright reference sample, and yet the nebulae around them are only 4.3 times fainter in mean ly α surface brightness, measured between 20 and 50 pkpc. we find significant correlations between the surface brightness of the nebula and the luminosity of the quasar in both uv continuum and ly α. the latter can be interpreted as evidence for a substantial contribution from unresolved inner parts of the nebulae to the narrow components seen in the ly α lines of some of our faint quasars, possibly from the inner circumgalactic medium or from the host galaxy's interstellar medium. | revealing the impact of quasar luminosity on giant ly α nebulae |
we present spectroscopic and photometric observations of the type iip supernova, sn 2020jfo, in ultraviolet and optical wavelengths. sn 2020jfo occurred in the spiral galaxy m61 (ngc 4303), with eight observed supernovae in the past 100 yr. sn 2020jfo exhibited a short plateau lasting < 65 days, and achieved a maximum brightness in vband of mv= -17.4 ± 0.4 mag at about 8.0 ± 0.5 days since explosion. from the bolometric light curve, we have estimated the mass of 56ni synthesized in the explosion to be 0.033 ± 0.006 m ⊙. the observed spectral features are typical for a type iip supernova except for shallow hα absorption throughout the evolution and the presence of stable 58ni feature at 7378 å, in the nebular phase. using hydrodynamical modeling in the mesa + stella framework, an ejecta mass of ~5 m ⊙ is estimated. models also indicate sn 2020jfo could be the result of a red supergiant progenitor with m zams ~ 12 m ⊙. bolometric light-curve modeling revealed the presence of a secondary radiation source for initial ~20 days, which has been attributed to interaction with a circumstellar material of mass ~ 0.2 m ⊙, which most likely was ejected due to enhanced mass loss about 20 yr prior to the supernova explosion. | sn 2020jfo: a short-plateau type ii supernova from a low-mass progenitor |
the solar system was once rich in the short-lived radionuclide (slr) 26al but poor in 60fe. several models have been proposed to explain these anomalous abundances in slrs, but none has been set within a self-consistent framework of the evolution of the solar system and its birth environment. the anomalous abundance in 26al may have originated from the accreted material in the wind of a massive ≳20 m⊙ wolf-rayet star, but the star could also have been a member of the parental star-cluster instead of an interloper or an older generation that enriched the proto-solar nebula. the protoplanetary disk at that time was already truncated around the kuiper-cliff (at 45 au) by encounters with other cluster members before it was enriched by the wind of the nearby wolf-rayet star. the supernova explosion of a nearby star, possibly but not necessarily the exploding wolf-rayet star, heated the disk to ≳1500 k, melting small dust grains and causing the encapsulation and preservation of 26al in vitreous droplets. this supernova, and possibly several others, caused a further abrasion of the disk and led to its observed tilt of 5.6 ± 1.2° with respect to the equatorial plane of the sun. the abundance of 60fe originates from a supernova shell, but its preservation results from a subsequent supernova. at least two supernovae are needed (one to deliver 60fe and one to preserve it in the disk) to explain the observed characteristics of the solar system. the most probable birth cluster therefore has n = 2500 ± 300 stars and a radius of rvir = 0.75 ± 0.25 pc. we conclude that systems equivalent to our solar system form in the milky way galaxy at a rate of about 30 myr-1, in which case approximately 36 000 solar-system analogs roam the milky way. | the formation of solar-system analogs in young star clusters |
we investigate the effect of mixing of radioactive nickel (56ni) on the early-time color evolution of type ib and ic supernovae (sne ib/ic) using multigroup radiation hydrodynamics simulations. we consider both helium-rich and helium-poor progenitors. mixing of 56ni is parameterized using a gaussian distribution function. we find that the early-time color evolution with a weak 56ni mixing is characterized by three different phases: initial rapid reddening, blueward evolution due to the delayed effect of 56ni heating, and redward evolution thereafter until the transition to the nebular phase. with a strong 56ni mixing, the color evolution is characterized by a monotonic reddening. we compare our models with the early-time color evolution of several sne ib/ic (sn 1999ex, sn 2008d, sn 2009jf, iptf13bvn, sn 1994i, sn 2007gr, sn 2013ge, and 2017ein) and find signatures of relatively weak and strong 56ni mixing for sne ib and sne ic, respectively. this suggests that sne ib progenitors are distinct from sn ic progenitors in terms of helium content and that 56ni mixing is generally stronger in the carbon-oxygen core and weaker in the helium-rich envelope. we conclude that the early-time color evolution is a powerful probe of 56ni mixing in sne ib/ic. | type ib/ic supernovae: effect of nickel mixing on the early-time color evolution and implications for the progenitors |
we report the discovery of a multiply lensed lyman-α blob (lab) behind the galaxy cluster as1063 using the multi unit spectroscopic explorer (muse) on the very large telescope (vlt). the background source is at z = 3.117 and is intrinsically faint compared to almost all previously reported labs. we used our highly precise strong lensing model to reconstruct the source properties, and we find an intrinsic luminosity of llyα = 1.9 × 1042 erg s-1, extending to 33 kpc. we find that the lab is associated with a group of galaxies, and possibly a protocluster, in agreement with previous studies that find labs in overdensities. in addition to lyman-α (lyα) emission, we find c iv, he ii, and o iii] ultraviolet (uv) emission lines arising from the centre of the nebula. we used the compactness of these lines in combination with the line ratios to conclude that the lyα nebula is likely powered by embedded star formation. resonant scattering of the lyα photons then produces the extended shape of the emission. thanks to the combined power of muse and strong gravitational lensing, we are now able to probe the circumgalatic medium of sub-l∗ galaxies at z ≈ 3. | discovery of a faint, star-forming, multiply lensed, lyman-α blob |
we present the analysis and results of a spectroscopic follow-up program of a mass-selected sample of six galaxies at 3< z< 4 using data from keck-nirpsec and vlt-xshooter. we confirm the z> 3 redshifts for half of the sample through the detection of strong nebular emission lines, and improve the z phot accuracy for the remainder of the sample through the combination of photometry and spectra. the modeling of the emission-line-corrected spectral energy distributions (seds) adopting improved redshifts confirms the very large stellar masses of the sample ({m}* ∼ 1.5{--}4× {10}11{m}⊙ ) in the first 2 gyr of cosmic history, with a diverse range in stellar ages, star-formation rates, and dust content. from the analysis of emission-line luminosities and widths, and far-infrared (fir) fluxes, we confirm that ≳ 80 % of the sample are hosts to luminous hidden active galactic nuclei (agns), with bolometric luminosities of ∼1044-46 erg s-1. we find that the mips 24 μm photometry is largely contaminated by agn continuum, rendering the sfrs derived using only 24 μm photometry to be severely overestimated. by including the emission from the agn in the modeling of the uv-to-fir seds, we confirm that the presence of the agn does not considerably bias the stellar masses (< 0.3 dex at 1σ). we show evidence for a rapid increase of the agn fraction from ∼30% to ∼60%-100% over the 1 gyr between z∼ 2 and z∼ 3. although we cannot exclude some enhancement of the agn fraction for our sample due to selection effects, the small measured [o iii] contamination to the observed k-band fluxes suggests that our sample is not significantly biased toward massive galaxies hosting agns. | a spectroscopic follow-up program of very massive galaxies at 3 < z < 4: confirmation of spectroscopic redshifts, and a high fraction of powerful agns |
mergers of carbon-oxygen (co) white dwarfs (wds) are considered to be one of the potential progenitors of type ia supernovae (sne ia). recent hydrodynamical simulations showed that the less massive (secondary) wd violently accretes onto the more massive (primary) one, carbon detonation occurs, the detonation wave propagates through the primary, and the primary finally explodes as a sub-chandrasekhar mass sn ia. such an explosion mechanism is called the violent merger scenario. based on the smoothed particle hydrodynamics simulations of merging co wds, we derived a critical mass ratio (qcr) leading to the violent merger scenario that is more stringent than previous results. we conclude that this difference mainly comes from the differences in the initial condition of whether or not the wds are synchronously spinning. using our new results, we estimated the brightness distribution of sne ia in the violent merger scenario and compared it with previous studies. we found that our new qcr does not significantly affect the brightness distribution. we present the direct outcome immediately following co wd mergers for various primary masses and mass ratios. we also discussed the final fate of the central system of the bipolar planetary nebula henize 2-428, which was recently suggested to be a double co wd system whose total mass exceeds the chandrasekhar-limiting mass, merging within the hubble time. even considering the uncertainties in the proposed binary parameters, we concluded that the final fate of this system is almost certainly a sub-chandrasekhar mass sn ia in the violent merger scenario. | the critical mass ratio of double white dwarf binaries for violent merger-induced type ia supernova explosions |
the integral shaped filament (isf) is the nearest molecular cloud with rapid star formation, including massive stars, and it is therefore a star-formation laboratory. we use gaia parallaxes, to show that the distances to young class ii stars ('disks') projected along the spine of this filament are related to the gas radial velocity by $$ v = -{d\over\tau} + k;\qquad \tau = 4\,{\rm myr}, $$ where $k$ is a constant. this implies that the isf is a standing wave, which is consistent with the stutz & gould (2016) 'slingshot' prediction. the $\tau=4\,{\rm myr}$ timescale is consistent with the 'slingshot' picture that the orion nebula cluster (onc) is the third cluster to be violently split off from the orion a cloud (following ngc 1981 and ngc 1987) at few-myr intervals due to gravito-magnetic oscillations. we also present preliminary evidence that the truncation of the isf is now taking place $16^\prime$ south of the onc and is mediated by a torsional wave that is propagating south with a characteristic timescale $\tau_{\rm torsion} = 0.5\,{\rm myr}$, i.e. eight times shorter. the relation between these two wave phenomena is not presently understood. | gaia: orion's integral shaped filament is a standing wave |
the δ37cl from different generations of apatite in martian meteorite chassigny has a range of ≈10‰ and is almost as great as measurements made on all martian meteorites (≈14‰). this range represents the mixing of distinct cl isotope reservoirs during the formation of chassigny: (1) an isotopically light-cl mantle reservoir (δ37cl = -4 to -6‰) that exhibits limited variability and (2) an isotopically heavy cl crustal reservoir (δ37cl > 0) that exhibits significant variability. the mantle component documented in chassigny melt inclusions that host a solar noble gas composition are derived from pristine, martian mantle. the incompatible element depleted and enriched shergottite sources as defined by radiogenic isotope systematics and trace element concentration ratios have very similar cl isotopic signatures and suggest that both are derived from the martian mantle. the enrichment of isotopically heavy cl in the crust resulted from protracted loss of 35cl to space that started early in the history of mars. the cl isotopic signature of the martian mantle is different from the earth, moon, and many primitive meteorites (δ37cl = 0), suggesting that these differences represent distinct cl sources in the solar nebula. the low δ37cl source represents the primordial solar system composition from which mars accreted. the higher δ37cl values observed for the earth, moon, and many chondrites are not primordial, rather they represent the later incorporation of 37cl-enriched hcl-hydrates into accreting material. | distinct chlorine isotopic reservoirs on mars. implications for character, extent and relative timing of crustal interactions with mantle-derived magmas, evolution of the martian atmosphere, and the building blocks of an early mars |
there is both observational and theoretical evidence that the ejecta of core-collapse supernovae (sne) are structured. rather than being smooth and homogeneous, the material is made of over-dense and under-dense regions of distinct composition. here, we have explored the effect of clumping on the sn radiation during the photospheric phase using 1d non-local thermodynamic equilibrium radiative transfer and an ejecta model arising from a blue-supergiant explosion (yielding a type ii-peculiar sn). neglecting chemical segregation, we adopted a velocity-dependent volume-filling factor approach that assumes that the clumps are small but does not change the column density along any sightline. we find that clumping boosts the recombination rate in the photospheric layers, leading to a faster recession of the photosphere, an increase in bolometric luminosity, and a reddening of the sn colors through enhanced blanketing. the sn bolometric light curve peaks earlier and transitions faster to the nebular phase. on the rise to maximum, the strongest luminosity contrast between our clumped and smooth models is obtained at the epoch when the photosphere has receded to ejecta layers where the clumping factor is only 0.5 - this clumping factor may be larger in nature. clumping is seen to have a similar influence in a type ii-plateau sn model. as we neglected both porosity and chemical segregation, our models underestimate the true impact of clumping. these results warrant further study of the influence of clumping on the observables of other sn types during the photospheric phase. | impact of clumping on core-collapse supernova radiation |
context. planetary nebula distance scales often suffer from model-dependent solutions. model-independent trigonometric parallaxes have been rare. space-based trigonometric parallaxes are now available for a larger sample using the second data release of gaia.aims: we aim to derive a high-quality approach for selection criteria of trigonometric parallaxes for planetary nebulae and discuss possible caveats and restrictions in the use of this data release.methods: a few hundred sources from previous distance scale surveys were manually cross-identified with data from the second gaia data release (dr2) because coordinate-based matching does not work reliably. the data were compared with the results of previous distance scales and to the results of a recent similar study that used the first data release gaia dr1.results: while the few available previous ground-based trigonometric parallaxes as well as those obtained with the hubble space telescope perfectly match the new data sets, older statistical distance scales, reaching larger distances, do show small systematic differences. when we restrict the comparison to the central stars for which the photometric colors of gaia show a negligible contamination by the surrounding nebula, the difference is negligible for statistical distances based on radio flux, while those derived from hα surface brightness still show minor differences. the dr2 study significantly improves the previous recalibration of the statistical distance scales using dr1/tgas. table a.1 is 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/616/l2 | planetary nebula distances in gaia dr2 |
recent improvements in stellar models for intermediate-mass stars and massive stars (mss) are recalled, together with their expectations for the synthesis of radioactive nuclei of lifetimes τ ≲ 25 myr, in order to re-examine the origins of now extinct radioactivities that were alive in the solar nebula. the galactic inheritance broadly explains most of them, especially if r-process nuclei are produced by neutron star merging, according to recent models. instead, 26al, 41ca, 135cs, and possibly 60fe require nucleosynthetic events close to the solar formation. we outline the persisting difficulties to account for these nuclei by intermediate-mass stars (2 ≲ m/m ⊙ ≲ 7-8). models of their final stages now predict the ubiquitous formation of a 13c reservoir as a neutron capture source; hence, even in the presence of 26al production from deep mixing or hot bottom burning, the ratio 26al/107pd remains incompatible with measured data, with a large excess in 107pd. this is shown for two recent approaches to deep mixing. even a late contamination by an ms encounters problems. in fact, the inhomogeneous addition of supernova debris predicts nonmeasured excesses on stable isotopes. revisions invoking specific low-mass supernovae and/or the sequential contamination of the presolar molecular cloud might be affected by similar problems, although our conclusions here are weakened by our schematic approach to the addition of sn ejecta. the limited parameter space that remains to be explored for solving this puzzle is discussed. | on the origin of early solar system radioactivities: problems with the asymptotic giant branch and massive star scenarios |
we present a new catalog of spectrophotometric distances and line of sight systemic velocities to 103 h ii regions between 90^\circ ≤slant {\ell }≤slant 195^\circ (longitude quadrants ii and part of iii). two new velocities for each region are independently measured using 1 arcmin resolution 21 cm h i and 2.6 mm 12co line maps (from the canadian galactic plane survey and five college radio astronomy observatory outer galaxy surveys) that show where gaseous shells are observed around the periphery of the ionized gas. known and neighboring o- and b-type stars with published ubv photometry and mk classifications are overlaid onto 21 cm continuum maps, and those stars observed within the boundary of the h ii emission (and whose distance is not more than three times the standard deviation of the others) are used to calculate new mean stellar distances to each of the 103 nebulae. using this approach of excluding distance outliers from the mean distance to a group of many stars in each h ii region lessens the impact of anomalous reddening for certain individuals. the standard deviation of individual stellar distances in a cluster is typically 20% per stellar distance, and the error in the mean distance to the cluster is typically ±10%. final mean distances of nine common objects with very long baseline interferometry parallax distances show a 1:1 correspondence. further, comparison with previous catalogs of h ii regions in these quadrants shows a 50% reduction in scatter for the distance to perseus spiral arm objects in the same region, and a reduction by ∼1/\sqrt{2} in scatter around a common angular velocity relative to the sun {{ω }}-{{{ω }}}0(km s-1 kpc-1). the purpose of the catalog is to provide a foundation for more detailed large-scale galactic spiral structure and dynamics (rotation curve, density wave streaming) studies in the 2nd and 3rd quadrants, which from the sun’s location is the most favorably viewed section of the galaxy. | a cgps look at the spiral structure of the outer milky way. i. distances and velocities to star-forming regions |
context. dense molecular filaments are central to the star formation process, but the detailed manner in which they fragment into prestellar cores is not well understood yet.aims: here, we investigate the fragmentation properties and dynamical state of several star-forming filaments in the x-shaped nebula region of the california molecular cloud in an effort to shed some light on this issue.methods: we used multiwavelength far-infrared images from herschel as well as the getsources and getfilaments extraction methods to identify dense cores and filaments in the region and derive their basic properties. we also used a map of 13co(2-1) emission from the arizona 10m submillimeter telescope (smt) to constrain the dynamical state of the filaments.results: we identified ten filaments with aspect ratios of ar > 4 and column density contrasts of c > 0.5, as well as 57 dense cores, including two protostellar cores, 20 robust prestellar cores, 11 candidate prestellar cores, and 24 unbound starless cores. all ten filaments have roughly the same deconvolved full width at half maximum (fwhm), with a median value of 0.12 ± 0.03 pc, which is independent of their column densities ranging from <1021 cm-2 to >1022 cm-2. two star-forming filaments (# 8 and # 10) stand out since they harbor quasi-periodic chains of dense cores with a typical projected core spacing of ~0.15 pc. these two filaments have thermally supercritical line masses and are not static. filament 8 exhibits a prominent transverse velocity gradient, suggesting that it is accreting gas from the parent cloud gas reservoir at an estimated rate of ~40 ± 10 m⊙ myr-1 pc-1. filament 10 includes two embedded protostars with outflows and it is likely at a somewhat later evolutionary stage than filament 8. in both cases, the observed (projected) core spacing is similar to the filament width and significantly shorter than the canonical separation of ~4 times the filament width predicted by classical cylinder fragmentation theory. it is unlikely that projection effects can explain this discrepancy. we suggest that the continuous accretion of gas onto the two star-forming filaments, as well as the geometrical bending of the filaments, may account for the observed core spacing.conclusions: our findings suggest that the characteristic fragmentation lengthscale of molecular filaments is quite sensitive to external perturbations from the parent cloud, such as the gravitational accretion of ambient material. the reduced 12co datacube is 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/642/a76 | fragmentation of star-forming filaments in the x-shaped nebula of the california molecular cloud |
we report on the first detection of very high-energy gamma-ray emission from the crab nebula by a cherenkov telescope in dual-mirror schwarzschild-couder (sc) configuration. this result has been achieved by means of the 4 m astri-horn telescope, operated on mt. etna, italy, and developed in the context of the cherenkov telescope array observatory preparatory phase. the dual-mirror sc design is aplanatic and characterized by a small plate scale, which allows us to implement large cameras with a large field of view, with small-size pixel sensors and a high level of compactness. the curved focal plane of the astri camera is covered by silicon photo-multipliers, managed by an unconventional front-end electronic system that is based on a customized peak-sensing detector mode. the system includes internal and external calibration systems, hardware and software for control and acquisition, and the complete data archiving and processing chain. these observations of the crab nebula were carried out in december 2018 during the telescope verification phase for a total observation time (after data selection) of 24.4 h, equally divided between on- and off-axis source exposure. the camera system was still under commission and its functionality was not yet completely exploited. furthermore, due to recent eruptions of the etna volcano, the mirror reflection efficiency was reduced. nevertheless, the observations led to the detection of the source with a statistical significance of 5.4σ above an energy threshold of ∼3 tev. this result provides an important step toward the use of dual-mirror systems in cherenkov gamma-ray astronomy. a pathfinder mini-array based on nine astri-like telescopes with a large field-of-view is in the course of implementation. | first detection of the crab nebula at tev energies with a cherenkov telescope in a dual-mirror schwarzschild-couder configuration: the astri-horn telescope |
based on a combined analysis of sdss imaging and califa integral field spectroscopy data, we report on the detection of faint (24 <μr mag/□″< 26) star-forming spiral-arm-like features in the periphery of three nearby early-type galaxies (etgs). these features are of considerable interest because they document the still ongoing inside-out growth of some local etgs and may add valuable observational insight into the origin and evolution of spiral structure in triaxial stellar systems. a characteristic property of the nebular component in the studied etgs, classified i+, is a two-radial-zone structure, with the inner zone that displays faint (ew(hα) ≃ 1 å) low-ionization nuclear emission-line region (liner) properties, and the outer one (3 å <ew(hα)≲ 20 å) hii-region characteristics. this spatial segregation of nebular emission in two physically distinct concentric zones calls for an examination of aperture effects in studies of type i+ etgs with single-fiber spectroscopic data. based on observations collected at the centro astronómico hispano alemán (caha) at calar alto, operated jointly by the max-planck-institut für astronomie (mpia) and the instituto de astrofísica de andalucía (csic). | spiral-like star-forming patterns in califa early-type galaxies |
the crab pulsar has striking radio emission properties, with the two dominant pulse components-the main pulse and the interpulse-consisting entirely of giant pulses. the emission is scattered in both the crab nebula and the interstellar medium, causing multipath propagation and thus scintillation. we study the scintillation of the crab's giant pulses using phased westerbork synthesis radio telescope data at 1668 mhz. we find that giant pulse spectra correlate at only ~2%, much lower than the one-third correlation expected from a randomized signal imparted with the same impulse response function. in addition, we find that the main pulse and the interpulse appear to scintillate differently; the 2d cross-correlation of scintillation between the interpulse and main pulse has a lower amplitude and is wider in time and frequency delay than the 2d autocorrelation of the main pulses. these lines of evidence suggest that the giant pulse emission regions are extended, and that the main pulse and interpulse arise in physically distinct regions that are resolved by the scattering screen. assuming the scattering takes place in the nebular filaments, the emission regions are of order a light-cylinder radius, as projected on the sky. with further very long baseline interferometry and multifrequency data, it may be possible to measure the distance to the scattering screens, the size of giant pulse emission regions, and the physical separation between the pulse components. | resolving the emission regions of the crab pulsar's giant pulses |
the next generation of spectroscopic surveys will target emission-line galaxies (elgs) to produce constraints on cosmological parameters. we study the large-scale structure traced by elgs using a combination of a semi-analytical model of galaxy formation, a code that computes the nebular emission from h ii regions using the properties of the interstellar medium, and a large-volume, high-resolution n-body simulation. we consider fixed number density samples where galaxies are selected by their h α, [o iii] λ5007, or [o ii] λλ3727-3729 emission-line luminosities. we investigate the assembly bias signatures of these samples, and compare them to those of stellar mass- and star formation rate-selected samples. interestingly, we find that the [o iii]- and [o ii]-selected samples display scale-dependent bias on large scales and that their assembly bias signatures are also scale dependent. both these effects are more pronounced for lower number density samples. the [o iii] and [o ii] emitters that contribute most to the scale dependence tend to have a low gas-phase metallicity and are preferentially found in low-density regions. we also measure the baryon acoustic oscillation (bao) feature and the β parameter related to the growth rate of overdensities. we find that the scale of the bao peak is roughly the same for all selections and that β is scale dependent at large scales. our results suggest that elg samples include environmental effects that should be modelled in order to remove potential systematic errors that could affect the estimation of cosmological parameters. | the assembly bias of emission-line galaxies |
context. blazars are variable sources on various timescales over a broad energy range spanning from radio to very high energy (>100 gev, hereafter vhe). mrk 501 is one of the brightest blazars at tev energies and has been extensively studied since its first vhe detection in 1996. however, most of the γ-ray studies performed on mrk 501 during the past years relate to flaring activity, when the source detection and characterization with the available γ-ray instrumentation was easier toperform.aims: our goal is to characterize the source γ-ray emission in detail, together with the radio-to-x-ray emission, during the non-flaring (low) activity, which is less often studied than the occasional flaring (high) activity.methods: we organized a multiwavelength (mw) campaign on mrk 501 between march and may 2008. this multi-instrument effort included the most sensitive vhe γ-ray instruments in the northern hemisphere, namely the imaging atmospheric cherenkov telescopes magic and veritas, as well as swift, rxte, the f-gamma, gasp-webt, and other collaborations and instruments. this provided extensive energy and temporal coverage of mrk 501 throughout the entire campaign.results: mrk 501 was found to be in a low state of activity during the campaign, with a vhe flux in the range of 10%-20% of the crab nebula flux. nevertheless, significant flux variations were detected with various instruments, with a trend of increasing variability with energy and a tentative correlation between the x-ray and vhe fluxes. the broadband spectral energy distribution during the two different emission states of the campaign can be adequately described within the homogeneous one-zone synchrotron self-compton model, with the (slightly) higher state described by an increase in the electron number density.conclusions: the one-zone ssc model can adequately describe the broadband spectral energy distribution of the source during the two months covered by the mw campaign. this agrees with previous studies of the broadband emission of this source during flaring and non-flaring states. we report for the first time a tentative x-ray-to-vhe correlation during such a low vhe activity. although marginally significant, this positive correlation between x-ray and vhe, which has been reported many times during flaring activity, suggests that the mechanisms that dominate the x-ray/vhe emission during non-flaring-activity are not substantially different from those that are responsible for the emission during flaring activity. the data for figs. 2 and 5 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/573/a50 | multiwavelength observations of mrk 501 in 2008 |
we have commenced a detailed analysis of the known sample of galactic post-asymptotic giant branch (pagb) objects compiled in the toruń catalogue of szczerba et al., and present, for the first time, homogeneously derived distance determinations for the 209 likely and 87 possible catalogued pagb stars from that compilation. knowing distances are essential in determining meaningful physical characteristics for these sources and this has been difficult to determine for most objects previously. the distances were determined by modelling their spectral energy distributions (seds) with multiple blackbody curves, and integrating under the overall fit to determine the total distance-dependent flux. this approach was undertaken for consistency as precise spectral types, needed for more detailed fitting, were unknown in the majority of cases. the sed method works because the luminosity of these central stars is very nearly constant from the tip of the agb phase to the beginning of the white dwarf cooling track. this then enables us to use a standard-candle luminosity to estimate the sed distances. for galactic thin-disc pagb objects, we use three luminosity bins based on typical observational characteristics, ranging between 3500 and 12 000 l⊙. we further adopt a default luminosity of 4000 l⊙ for bulge objects and 1700 l⊙ for the thick-disc and halo objects. we have also applied the above technique to a further sample of 54 related nebulae not in the current edition of the toruń catalogue. in a follow-up paper, we will estimate distances to the subset of rv tauri variables using empirical period-luminosity relations, and to the r crb stars, allowing a population comparison of these objects with the other subclasses of pagb stars for the first time. | new light on galactic post-asymptotic giant branch stars - i. first distance catalogue |
the formation of wolf-rayet central stars of planetary nebulae ([wr] cspne) whose spectroscopic appearance mimics massive wr stars remains poorly understood. least understood is the nature and frequency of binary companions to [wr] cspne that may explain their h-deficiency. we have conducted a systematic radial velocity (rv) study of six [wr] cspne to search for post-common-envelope (post-ce) [wr] binaries. we used a cross-correlation method to construct the rv time series as successfully done for massive close binary wr stars. no significant rv variability was detected for the late-[wc] type nuclei of hen 2-113, hen 3-1333, pmr 2 and hen 2-99. significant, large-amplitude variability was found in the [wc4] nucleus of ngc 5315. in the [wo1] nucleus of ngc 5189, we discovered significant periodic variability that reveals a close binary with porb = 4.04 ± 0.1 d. we measured a semi-amplitude of 62.3 ± 1.3 km s-1 that gives a companion mass of m2 ≥ 0.5 m⊙ or m2 = 0.84 m⊙ (assuming i = 45°). the most plausible companion type is a massive white dwarf (wd) as found in fleming 1. the spectacular nebular morphology of ngc 5189 fits the pattern of recently discovered post-ce pne extremely well with its dominant low-ionization structures (e.g. as in ngc 6326) and collimated outflows (e.g. as in fleming 1). the long 4.04 d orbital period is either anomalous (e.g. ngc 2346) or it may indicate that there is a sizeable population of [wr] binaries with massive wd companions in relatively wide orbits, perhaps influenced by interactions with the strong [wr] wind. | a radial velocity survey for post-common-envelope wolf-rayet central stars of planetary nebulae: first results and discovery of the close binary nucleus of ngc 5189 |
using 1d, non-local thermodynamic equilibrium and time-dependent radiative transfer simulations, we study the ejecta properties required to match the early- and late-time photometric and spectroscopic properties of supernovae (sne) associated with long-duration γ-ray bursts (lgrbs). matching the short rise time, narrow light curve peak and extremely broad spectral lines of sn 1998bw requires a model with ≲3 m⊙ ejecta but a high explosion energy of a few 1052 erg and 0.5 m⊙ of 56ni. the relatively high luminosity, presence of narrow spectral lines of intermediate mass elements, and low ionisation at the nebular stage, however, are matched with a more standard c-rich wolf-rayet (wr) star explosion, an ejecta of ≳10 m⊙, an explosion energy ≳1051 erg, and only 0.1 m⊙ of 56ni. as the two models are mutually exclusive, the breaking of spherical symmetry is essential to match the early- and late-time photometric and spectroscopic properties of sn 1998bw. this conclusion confirms the notion that the ejecta of sn 1998bw is highly aspherical on large scales. more generally, with asphericity, the energetics and 56ni masses of lgrb/sne are reduced and their ejecta masses are increased, favouring a massive fast-rotating wolf-rayet star progenitor. contrary to persisting claims in favour of the proto-magnetar model for lgrb/sne, such progenitor/ejecta properties are compatible with collapsar formation. ejecta properties of lgrb/sne inferred from 1d radiative-transfer modelling are fundamentally flawed. | radiative-transfer models for explosions from rotating and non-rotating single wc stars. implications for sn 1998bw and lgrb/sne |
preplanetary nebulae and planetary nebulae are evolved, mass-losing stellar objects that show a wide variety of morphologies. many of these nebulae consist of outer structures that are nearly spherical (spiral/shell/arc/halo) and inner structures that are highly asymmetric (bipolar/multipolar) 1,2 . the coexistence of such geometrically distinct structures is enigmatic because it hints at the simultaneous presence of both wide and close binary interactions, a phenomenon that has been attributed to stellar binary systems with eccentric orbits 3 . here, we report high-resolution molecular line observations of the circumstellar spiral-shell pattern of afgl 3068, an asymptotic giant branch star transitioning to the preplanetary nebula phase. the observations clearly reveal that the dynamics of the mass loss is influenced by the presence of an eccentric-orbit binary. this quintessential object opens a window on the nature of deeply embedded binary stars through the circumstellar spiral-shell patterns that reside at distances of several thousand au from the stars. | the large-scale nebular pattern of a superwind binary in an eccentric orbit |
context. the morphology and the distribution of material observed in supernova remnants (snrs) reflect the interaction of the supernova (sn) blast wave with the ambient environment, the physical processes associated with the sn explosion, and the internal structure of the progenitor star. ic 443 is a mixed-morphology (mm) snr located in a quite complex environment: it interacts with a molecular cloud in the northwestern and southeastern areas and with an atomic cloud in the northeast.aims: in this work, we aim to investigate the origin of the complex morphology and multi-thermal x-ray emission observed in snr ic 443 through the study of the effect of the inhomogeneous ambient medium in shaping its observed structure and an exploration of the main parameters characterizing the remnant.methods: we developed a 3d hydrodynamic (hd) model for ic 443, which describes the interaction of the snr with the environment, parametrized in agreement with the results of the multi-wavelength data analysis. we performed an ample exploration of the parameter space describing the initial blast wave and the environment, including the mass of the ejecta, the energy and position of the explosion, as well as the density, structure, and geometry of the surrounding clouds. from the simulations, we synthesized the x-ray emission maps and spectra and compared them with actual x-ray data collected by xmm-newton.results: our model explains the origin of the complex x-ray morphology of snr ic 443 in a natural way, with the ability to reproduce, for the first time, most of the observed features, including the centrally-peaked x-ray morphology (characteristic of mm snrs) when considering the origin of the explosion at the position where the pulsar wind nebula cxou j061705.3+222127 was at the time of the explosion. in the model that best reproduces the observations, the mass of the ejecta and the energy of the explosion are ~7 m⊙ and ~1 × 1051 erg, respectively. from the exploration of the parameter space, we find that the density of the clouds is n > 300 cm−3 and that the age of snr ic 443 is ~8000 yr.conclusions: the observed inhomogeneous ambient medium is the main property responsible for the complex structure and the x-ray morphology of snr ic 443, resulting in a very asymmetric distribution of the ejecta due to the off-centered location of the explosion inside the cavity formed by the clouds. it can be argued that the centrally peaked morphology (typical of mm snrs) is a natural consequence of the interaction with the complex environment. a combination of high resolution x-ray observations and accurate 3d hd modeling is needed to confirm whether this scenario is applicable to other mm snrs. movies are available at https://www.aanda.org | modeling the mixed-morphology supernova remnant ic 443. origins of its complex morphology and x-ray emission |
m16, the eagle nebula, is an outstanding hii region where extensive high-mass star formation is taking place in the sagittarius arm, and hosts the remarkable "pillars" observed with hst. we made new co observations of the region in the 12co j=1--0 and j=2--1 transitions with nanten2. these observations revealed for the first time that a giant molecular cloud of $\sim 1.3 \times 10^5$ \msun \ is associated with m16, which is elongated vertically to the galactic plane over 35 pc at a distance of 1.8 kpc. we found a cavity of the molecular gas of $\sim 10$ pc diameter toward the heart of m16 at \lbeq (16.95\degree, 0.85\degree), where more than 10 o-type stars and $\sim 400$ stars are associated, in addition to a close-by molecular cavity toward a spitzer bubble n19 at \lbeq (17.06\degree, 1.0\degree). we found three velocity components which show spatially complementary distribution in the entire m16 giant molecular cloud (gmc) including ngc6611 and n19, suggesting collisional interaction between them. based on the above results we frame a hypothesis that collision between the red-shifted and blue-shifted components at a relative of $\sim 10$ \kms \ triggered formation of the o-type stars in the m16 gmc in the last 1-2 myr. the collision is two fold in the sense that one of the collisional interactions is major toward the m16 cluster and the other toward n19 with a rcw120 type, the former triggered most of the o star formation with almost full ionization of the parent gas, and the latter an o star formation in n19. | a new view of the giant molecular cloud m16 (eagle nebula) in 12co j=1-0 and 2-1 transitions with nanten2 |
we characterize local large-scale regular magnetic fields as well as small-scale magnetic features in the solar vicinity by using the rotation measures of 494 pulsars within 3 kpc from the sun. the local magnetic field in the galactic disc is found to follow local spiral arms and to have a field strength of 1.6 μg, with a reversal at 140 pc inside the solar circle in the direction of the galactic centre. a field reversal in the first quadrant towards the sagittarius arm is identified at about 1 kpc from the sun. in the local galactic halo, the toroidal fields have a field strength of more than 1.6 μg. local small-scale magnetic bubbles are investigated by using nearby pulsars in and behind these structures. the local bubble might have a line-of-sight magnetic field strength of 0.5-2 μg mainly towards l ∼ 90°; the upper shell of the gum nebula shows a possible amplification of the magnetic field with a factor of 2 probably by compression; the north polar spur does not contribute significant faraday rotation, and perhaps its magnetic field is nearly perpendicular to the line of sight. an anomalous region in the fourth quadrant is found to have a field of 1.4 μg over a scale of 1 kpc, which implies a sub-galactic structure with ordered fields opposite in direction to the large-scale disc field. we develop a model for the magnetic field in the galactic halo based on the rotation measures of pulsars and averaged rotation measures of background radio sources. | magnetic fields in the solar vicinity and in the galactic halo |
most of the exoplanets with known masses at earth-like distances to sun-like stars are heavier than jupiter, which raises the question of whether such planets are accompanied by detectable, possibly habitable moons. here we simulate the accretion disks around super-jovian planets and find that giant moons with masses similar to mars can form. our results suggest that the galilean moons formed during the final stages of accretion onto jupiter, when the circumjovian disk was sufficiently cool. in contrast to other studies, with our assumptions, we show that jupiter was still feeding from the circumsolar disk and that its principal moons cannot have formed after the complete photoevaporation of the circumsolar nebula. to counteract the steady loss of moons into the planet due to type i migration, we propose that the water ice line around jupiter and super-jovian exoplanets acted as a migration trap for moons. heat transitions, however, cross the disk during the gap opening within ≈104 years, which makes them inefficient as moon traps and indicates a fundamental difference between planet and moon formation. we find that icy moons larger than the smallest known exoplanet can form at about 15-30 jupiter radii around super-jovian planets. their size implies detectability by the kepler and plato space telescopes as well as by the european extremely large telescope. observations of such giant exomoons would be a novel gateway to understanding planet formation, as moons carry information about the accretion history of their planets. | water ice lines and the formation of giant moons around super-jovian planets |
we present a radiative transfer code to model the nebular phase spectra of supernovae (sne) in non-lte (nlte). we apply it to a systematic study of sne ia using parameterized 1d models and show how nebular spectral features depend on key physical parameters, such as the time since explosion, total ejecta mass, kinetic energy, radial density profile, and the masses of 56ni, intermediate-mass elements, and stable iron-group elements. we also quantify the impact of uncertainties in atomic data inputs. we find the following. (1) the main features of sn ia nebular spectra are relatively insensitive to most physical parameters. degeneracy among parameters precludes a unique determination of the ejecta properties from spectral fitting. in particular, features can be equally well fit with generic chandrasekhar mass ({m}ch}), sub-{m}ch}, and super-{m}ch} models. (2) a sizable (≳0.1 {m}⊙ ) central region of stable iron-group elements, often claimed as evidence for {m}ch} models, is not essential to fit the optical spectra and may produce an unusual flat-top [co iii] profile. (3) the strength of [s iii] emission near 9500 å can provide a useful diagnostic of explosion nucleosynthesis. (4) substantial amounts (≳0.1 {m}⊙ ) of unburned c/o mixed throughout the ejecta produce [o iii] emission not seen in observations. (5) shifts in the wavelength of line peaks can arise from line-blending effects. (6) the steepness of the ejecta density profile affects the line shapes, offering a constraint on explosion models. (7) uncertainties in atomic data limit the ability to infer physical parameters. | how do type ia supernova nebular spectra depend on explosion properties? insights from systematic non-lte modeling |
as part of the global view on star formation (glostar) survey we have used the karl g. jansky very large array (vla) in its b-configuration to observe the part of the galactic plane between longitudes of 28° and 36° and latitudes from −1° to +1° at the c-band (4-8 ghz). to reduce the contamination of extended sources that are not well recovered by our coverage of the (u, υ)-plane, we discarded short baselines that are sensitive to emission on angular scales >4″. the resulting radio continuum images have an angular resolution of 1.″0 and a sensitivity of ~60 µjy beam−1, making it the most sensitive radio survey covering a large area of the galactic plane with this angular resolution. an automatic source extraction algorithm was used in combination with visual inspection to identify a total of 3325 radio sources. a total of 1457 radio sources are ≥7σ and comprise our highly reliable catalog; 72 of these are grouped as 22 fragmented sources, for example, multiple components of an extended and resolved source to explore the nature of the cataloged radio sources, we searched for counterparts at millimeter and infrared wavelengths. our classification attempts resulted in 93 h ii region candidates, 104 radio stars, and 64 planetary nebulae, while it is suggested that most of the remaining radio sources are extragalactic sources. we investigated the spectral indices (α, sv ∝ vα) of radio sources classified as h ii region candidates and found that many have negative values. this may imply that these radio sources represent young stellar objects that are members of the star clusters around the high-mass stars that excite the h ii regions, but not these h ii regions themselves. by comparing the peak flux densities from the glostar and cornish surveys, we have identified 49 variable radio sources, most of them with an unknown nature. additionally, we provide a list of 1866 radio sources detected within 5 to 7σ levels. full tables 1 and a.1 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/670/a9 | a global view on star formation: the glostar galactic plane survey. vi. radio source catalog ii: 28° < ℓ < 36° and |b| < 1°, vla b-configuration |
it has been shown that some aspects of the terrestrial planets can be explained, particularly the earth/mars mass ratio, when they form from a truncated disk with an outer edge near 1.0 au. this has been previously modeled starting from an intermediate stage of growth utilizing pre-formed planetary embryos. we present simulations that were designed to test this idea by following the growth process from km-sized objects located between 0.7 and 1.0 au up to terrestrial planets. the simulations explore initial conditions where the solids in the disk are planetesimals with radii initially between 3 and 300 km, alternately including effects from a dissipating gaseous solar nebula and collisional fragmentation. we use a new lagrangian code known as lipad, which is a particle-based code that models the fragmentation, accretion, and dynamical evolution of a large number of planetesimals, and can model the entire growth process from km-sizes up to planets. a suite of large (∼ mars mass) planetary embryos is complete in only ∼1 myr, containing most of the system mass. a quiescent period then persists for 10-20 myr characterized by slow diffusion of the orbits and continued accretion of the remaining planetesimals. this is interrupted by an instability that leads to embryos crossing orbits and embryo-embryo impacts that eventually produce the final set of planets. while this evolution is different than that found in other works exploring an annulus, the final planetary systems are similar, with roughly the correct number of planets and good mars-analogs. | terrestrial planet formation from an annulus |
context. the orion complex is arguably the most studied star-forming region in the galaxy. while stars are still being born in the orion nebula, the oldest part was believed to be no more than 13 myr old.aims: in order to study the full hierarchy of star formation across the orion complex, we perform a clustering analysis of the ori ob1a region using new stellar surveys and derive robust ages for each identified stellar aggregate.methods: we use gaia dr2 parameters supplemented with radial velocities from the galah and apogee surveys to perform clustering of the ori ob1a association. five overdensities are resolved in a six-dimensional parameter space (positions, distance, proper motions, and radial velocity). most correspond to previously known structures (ascc 16, 25 orionis, ascc 20, ascc 21). we use gaia dr2, pan-starrs1 and 2mass photometry to fit isochrones to the colour-magnitude diagrams of the identified clusters. the ages of the clusters can thus be measured with ∼10% precision.results: while four of the clusters have ages between 11 and 13 myr, the ascc 20 cluster stands out at an age of 21 ± 3 myr. this is significantly greater than the age of any previously known component of the orion complex. to some degree, all clusters overlap in at least one of the six phase-space dimensions.conclusions: we argue that the formation history of the orion complex, and its relation to the gould belt, must be reconsidered. a significant challenge in reconstructing the history of the ori ob1a association is to understand the impact of the newly discovered 21 myr old population on the younger parts of the complex, including their formation. movie associated to fig. 3 is available at https://www.aanda.org tables b.1-b.5 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/631/a166 | discovery of a 21 myr old stellar population in the orion complex⋆ |
thulium is a heavy rare earth element (ree) whose geochemical behavior is intermediate between er and yb, and that is not expected to be decoupled from these elements during accretion of planetary bodies and geological processes. however, irregularities in ree volatilities at higher temperature could have decoupled the rees relative to one another during the early stages of condensation of the solar nebula. indeed, positive tm anomalies are found in some refractory inclusions from carbonaceous chondrites, and it is possible that large scale nebular reservoirs displaying positive or negative tm anomalies were formed during the early history of the solar system. we analyzed a series of meteorites and terrestrial rocks in order to evaluate the existence of tm anomalies in planetary materials. relative to cis (ivuna-type carbonaceous chondrites), carbonaceous chondrites display unresolved or positive tm anomalies, while most of the noncarbonaceous chondrites show slightly negative tm anomalies. quantification of these anomalies in terrestrial samples is complicated when samples display fractionated heavy ree patterns. taking this effect into account, we show that the earth, mars, vesta, the aubrite and ureilite parent bodies display small negative anomalies (tm/tm∗ ≈ 0.975), very similar to those found in ordinary and enstatite chondrites. we suggest that a slight negative tm anomaly relative to ci is a widespread feature of the materials from the inner solar system. this finding suggests that ci chondrites may not be appropriate for normalizing ree abundances of most planetary materials as they may be enriched in a high-temperature refractory component with non-solar composition. the presence of tm anomalies at a bulk planetary scale is, to this day, the strongest piece of evidence that refractory lithophile elements are not present in constant ci proportions in planetary bodies. | evidence from tm anomalies for non-ci refractory lithophile element proportions in terrestrial planets and achondrites |
context. stars in the solar neighbourhood have refractory element ratios slightly different from that of the sun. it is unclear how much the condensation of solids and thus the composition of planets forming around these stars is affected.aims: we aim to understand the impact of changing the ratios of the refractory elements mg, si, and fe within the range observed in solar-type stars within 150 pc of the sun on the composition of planets forming around them.methods: we use the ggchem code to simulate the condensation of solids in protoplanetary disks with a minimum mass solar nebula around main sequence g-type stars in the solar neighbourhood. we extract the stellar elemental composition from the hypatia database.results: we find that a lower mg/si ratio shifts the condensation sequence from forsterite (mg2sio4) and sio to enstatite (mgsio3) and quartz (sio2); a lower fe/s ratio leads to the formation of fes and fes2 and few or no fe-bearing silicates. ratios of refractory elements translate directly from the gas phase to the condensed phase for t < 1000 k. however, ratios with respect to volatile elements (e.g. oxygen and sulphur) in the condensates - the building blocks of planets - differ from the original stellar composition.conclusions: our study shows that the composition of planets crucially depends on the abundances of the stellar system under investigation. our results can have important implications for planet interiors, which depend strongly on the degree of oxidation and the sulphur abundance. | forming planets around stars with non-solar elemental composition |
using offset-corrected gaia edr3 parallax measurements and spectrophotometric methods, we have determined distances for 69 massive stars in the carina ob1 association and associated clusters: trumpler 16 (21 stars), trumpler 14 (20 stars), trumpler 15 (three stars), bochum 11 (five stars), and south pillars region (20 stars). past distance estimates to the carina nebula range from 2.2 to 3.6 kpc, with uncertainties arising from photometry and anomalous dust extinction. the edr3 parallax solutions show considerable improvement over dr2, with typical errors σϖ/ϖ ≈ 3%-5%. the o-type stars in the great carina nebula lie at essentially the same distance (2.35 ± 0.08 kpc), quoting mean and rms variance. the clusters have distances of 2.32 ± 0.12 kpc (tr 16), 2.37 ± 0.15 kpc (tr 14), 2.36 ± 0.09 kpc (tr 15), and 2.33 ± 0.12 kpc (bochum 11) in good agreement with the η car distance of around 2.3 kpc. o-star proper motions suggest internal (3d) velocity dispersions ~4 km s-1 for tr 14 and tr 16. reliable distances allow estimates of cluster sizes, stellar dynamics, luminosities, and fluxes of photoionizing radiation incident on photodissociation regions in the region. we estimate that tr 14 and tr 16 have half-mass radii rh = 1.5-1.8 pc, stellar crossing times tcr = rh/vm ≈ 0.7-0.8 myr, and two-body relaxation times trh ≈ 40-80 myr. the underlying velocity dispersion for tr 14, if a bound cluster, would be ${v}_{{\rm{m}}}\approx {2.1}_{-0.4}^{+0.7}$ km s-1 for $n={7600}_{-2600}^{+5800}$ stars. with the higher dispersions of the o stars, inward drift would occur slowly, on timescales of 3-6 myr. | gaia edr3 parallax distances to the great carina nebula and its star clusters (trumpler 14, 15, 16) |
the unidentified tev source mgro j1908+06, with emission extending from hundreds of gev to beyond 100 tev, is one of the most intriguing sources in the galactic plane. mgro j1908+06 spatially associates with an icecube hotspot of neutrino emission. although the hotspot is not significant yet, this suggests a possible hadronic origin of the observed gamma-ray radiation. here we describe a multiwavelength analysis on mgro j1908+06 to determine its nature. we identify, for the first time, an extended gev source as the counterpart of mgro j1908 + 06, discovering possibly associated molecular clouds (mcs). the gev spectrum shows two well-differentiated components: a soft spectral component below ∼10 gev, and a hard one (γ ∼ 1.6) above these energies. the lower-energy part is likely associated with the dense mcs surrounding the supernova remnant (snr) g40.5-0.5, whereas the higher-energy component, which connects smoothly with the spectrum observed in tev range, resembles the inverse compton emission observed in relic pulsar wind nebulae. this simple scenario seems to describe the data satisfactorily, but raises questions about the interpretation of the emission at hundreds of tev. in this scenario, no detectable neutrino flux would be expected. | investigating the nature of mgro j1908+06 with multiwavelength observations |
the central area (40″ × 40″) of the bipolar nebula s106 was mapped in the [o i] line at 63.2 μm (4.74 thz) with high angular (6″) and spectral (0.24 mhz) resolution, using the great heterodyne receiver on board sofia. the spatial and spectral emission distribution of [o i] is compared to emission in the co 16 →15, [c ii] 158 μm, and co 11 →10 lines, mm-molecular lines, and continuum. the [o i] emission is composed of several velocity components in the range from -30 to 25 km s-1. the high-velocity blue- and red-shifted emission (v = -30 to -9 km s-1 and 8 to 25 km s-1) can be explained as arising from accelerated photodissociated gas associated with a dark lane close to the massive binary system s106 ir, and from shocks caused by the stellar wind and/or a disk-envelope interaction. at velocities from -9 to -4 km s-1 and from 0.5 to 8 km s-1 line wings are observed in most of the lines that we attribute to cooling in photodissociation regions (pdrs) created by the ionizing radiation impinging on the cavity walls. the velocity range from -4 to 0.5 km s-1 is dominated by emission from the clumpy molecular cloud, and the [o i], [c ii], and high-j co lines are excited in pdrs on clump surfaces that are illuminated by the central stars. modelling the line emission in the different velocity ranges with the kosma-τ code constrains a radiation field χ of a few times 104 and densities n of a few times 104 cm-3. considering self-absorption of the [o i] line results in higher densities (up to 106 cm-3) only for the gas component seen at high blue- and red velocities. we thus confirm the scenario found in other studies that the emission of these lines can be explained by a two-phase pdr, but attribute the high-density gas to the high-velocity component only. the dark lane has a mass of 275 m⊙ and shows a velocity difference of 1.4 km s-1 along its projected length of 1 pc, determined from h13co+ 1 →0 mapping. its nature depends on the geometry and can be interpreted as a massive accretion flow (infall rate of 2.5 × 10-4 m⊙ yr-1), or the remains of it, linked to s106 ir/fir. the most likely explanation is that the binary system is at a stage of its evolution where gas accretion is counteracted by the stellar winds and radiation, leading to the very complex observed spatial and kinematic emission distribution of the various tracers. movie associated to fig. 16 is available at http://www.aanda.org | anatomy of the massive star-forming region s106. the [o i] 63 μm line observed with great/sofia as a versatile diagnostic tool for the evolution of massive stars |
we report the discovery of a young (only 30-40 myr) snake-like structure (dubbed a stellar snake) in the solar neighborhood from gaia dr2. the average distance of this structure is about 310 pc from us. both the length and width are over 200 pc, but the thickness is only about 80 pc. the snake has one tail and two dissolving cores, which can be clearly distinguished in the 6d phase space. the whole structure includes thousands of members with a total mass of larger than 2000 m⊙ in a uniform population. the population is so young that it cannot be well explained with the classical theory of tidal tails. we therefore suspect that the snake is hierarchically primordial, rather than the result of dynamically tidal stripping, even if the snake is probably expanding. the coherent 5d phase information and the ages suggest that the snake was probably born in the same environment as the filamentary structure of beccari et al. if so, the snake could extend the sky region of the vela ob2 association by a factor of ∼2 and supplement the census of its coeval structures. this finding is useful to understanding the history of the formation and evolution of the vela ob2 complex. the age of the snake well matches with that of the gould belt. in the sky region of our interest, we detect one new open cluster, which is named tian 1 in this work. | discovery of a young stellar snake with two dissolving cores in the solar neighborhood |
we conduct a three-dimensional hydrodynamical simulation to study the interaction of two opposite inclined jets inside the envelope of a giant star, and find that the jets induce many vortexes inside the envelope and that they efficiently remove mass from the envelope and form a very clumpy outflow. we assume that this very rare type of interaction occurs when a tight binary system enters the envelope of a giant star, and that the orbital plane of the tight binary system and that of the triple stellar system are inclined to each other. we further assume that one of the stars of the tight binary system accretes mass and launches two opposite jets and that the jets' axis is inclined to the angular momentum axis of the triple stellar system. the many vortexes that the jets induce along the orbit of the tight binary system inside the giant envelope might play an important role in the common envelope evolution (cee) by distributing energy in the envelope. the density fluctuations that accompany the vortexes lead to an outflow with many clumps that might facilitate the formation of dust. this outflow lacks any clear symmetry, and it might account for very rare types of `messy' planetary nebulae and `messy' nebulae around massive stars. on a broader scope, our study adds to the notion that jets can play important roles in the cee, and that they can form a rich variety of shapes of nebulae around evolved stars. | inclined jets inside a common envelope of a triple stellar system |
we present a sample of local analogs for high-redshift galaxies selected in the sloan digital sky survey (sdss). the physical conditions of the interstellar medium (ism) in these local analogs resemble those in high-redshift galaxies. these galaxies are selected based on their positions in the [o iii]/hβ versus [n ii]/hα nebular emission-line diagnostic diagram. we show that these local analogs share similar physical properties with high-redshift galaxies, including high specific star formation rates (ssfrs), flat uv continuums, and compact galaxy sizes. in particular, the ionization parameters and electron densities in these analogs are comparable to those in z ≃ 2-3 galaxies, but higher than those in normal sdss galaxies by ≃0.6 dex and ≃0.9 dex, respectively. the mass-metallicity relation (mzr) in these local analogs shows -0.2 dex offset from that in sdss star-forming galaxies at the low-mass end, which is consistent with the mzr of the z∼ 2{--}3 galaxies. we compare the local analogs in this study with those in other studies, including lyman break analogs (lba) and green pea (gp) galaxies. the analogs in this study share a similar star formation surface density with lbas, but the ionization parameters and electron density in our analogs are higher than those in lbas by factors of 1.5 and 3, respectively. the analogs in this study have comparable ionization parameters and electron densities to the gp galaxies, but our method can select galaxies in a wider redshift range. we find the high ssfr and sfr surface density can increase the electron density and ionization parameters, but still cannot fully explain the difference in ism condition between nearby galaxies and the local analogs/high-redshift galaxies. | local analogs for high-redshift galaxies: resembling the physical conditions of the interstellar medium in high-redshift galaxies |
we present synthetic observations for the first generations of galaxies in the universe and make predictions for future deep field observations for redshifts greater than 6. due to the strong impact of nebular emission lines and the relatively compact scale of h ii regions, high-resolution cosmological simulations and a robust suite of analysis tools are required to properly simulate spectra. we created a software pipeline consisting of fsps, hyperion, cloudy and our own tools to generate synthetic ir observations from a fully three-dimensional arrangement of gas, dust, and stars. our prescription allows us to include emission lines for a complete chemical network and tackle the effect of dust extinction and scattering in the various lines of sight. we provide spectra, 2d binned photon imagery for both hst and jwst ir filters, luminosity relationships, and emission-line strengths for a large sample of high-redshift galaxies in the renaissance simulations. our resulting synthetic spectra show high variability between galactic haloes with a strong dependence on stellar mass, metallicity, gas mass fraction, and formation history. haloes with the lowest stellar mass have the greatest variability in [o iii]/hβ, [o iii], and c iii], while haloes with higher masses are seen to show consistency in their spectra and [o iii] equivalent widths between 1 and 10 å. viewing angle accounted for threefold difference in flux due to the presence of ionized gas channels in a halo. furthermore, jwst colour plots show a discernible relationship between redshift, colour, and mean stellar age. | first light: exploring the spectra of high-redshift galaxies in the renaissance simulations |
we report a detailed analysis of all regions of current star formation in the walls of the supergiant h i shell (sgs) in the galaxy holmberg ii based on observations with a scanning fabry-perot interferometer at the russian 6-m telescope. we compare the structure and kinematics of ionized gas with that of atomic hydrogen and with the stellar population of the sgs. our deep hα images and archival images taken by the hubble space telescope demonstrate that current star formation episodes are larger and more complicated than previously thought: they represent unified star-forming complexes with sizes of several hundred pc rather than `chains' of separate bright nebulae in the walls of the sgs. the fact that we are dealing with unified complexes is evidenced by identified faint shell-like structures of ionized and neutral gas which connect several distinct bright h ii regions. formation of such complexes is due to the feedback of stars with very inhomogeneous ambient gas in the walls of the sgs. the arguments supporting an idea about the triggering of star formation in sgs by the h i supershells collision are presented. we also found a faint ionized supershell inside the h i sgs expanding with a velocity of no greater than 10-15 km s-1. five ob stars located inside the inner supershell are sufficient to account for its radiation, although a possibility of leakage of ionizing photons from bright h ii regions is not ruled out as well. | complexes of triggered star formation in supergiant shell of holmberg ii |
context. the winds of massive stars create large (>10 pc) bubbles around their progenitors. as these bubbles expand they encounter the interstellar coherent magnetic field which, depending on its strength, can influence the shape of the bubble.aims: we wish to investigate if, and how much, the interstellar magnetic field can contribute to the shape of an expanding circumstellar bubble around a massive star.methods: we use the mpi-amrvac code to make magneto-hydrodynamical simulations of bubbles, using a single star model, combined with several different field strengths: b = 5, 10, and 20 μg for the interstellar magnetic field. this covers the typical field strengths of the interstellar magnetic fields found in the galactic disk and bulge. furthermore, we present two simulations that include both a 5 μg interstellar magnetic field and a warm (10 000 k) interstellar medium (ism) and two different ism densities to demonstrate how the magnetic field can combine with other external factors to influence the morphology of the circumstellar bubbles.results: our results show that low magnetic fields, as found in the galactic disk, inhibit the growth of the circumstellar bubbles in the direction perpendicular to the field. as a result, the bubbles become ovoid, rather than spherical. strong interstellar fields, such as observed for the galactic bulge, can completely stop the expansion of the bubble in the direction perpendicular to the field, leading to the formation of a tube-like bubble. when combined with an ism that is both warm and high density the bubble is greatly reduced in size, causing a dramatic change in the evolution of temporary features inside the bubble such as wolf-rayet ring nebulae.conclusions: the magnetic field of the interstellar medium can affect the shape of circumstellar bubbles. this effect may have consequences for the shape and evolution of circumstellar nebulae and supernova remnants, which are formed within the main wind-blown bubble. appendices and movies associated to figs. a.1-a.12 are available in electronic form at http://www.aanda.org | shape and evolution of wind-blown bubbles of massive stars: on the effect of the interstellar magnetic field |
bright lyα blobs (labs)—extended nebulae with sizes of ∼100 kpc and lyα luminosities of ∼1044 erg s-1—often reside in overdensities of compact lyα emitters (laes) that may be galaxy protoclusters. the number density, variance, and internal kinematics of labs suggest that they themselves trace group-like halos. here, we test this hierarchical picture, presenting deep, wide-field lyα narrowband imaging of a 1° × 0.°5 region around a lab pair at z = 2.3 discovered previously by a blind survey. we find 183 lyα emitters, including the original lab pair and three new labs with lyα luminosities of (0.9{--}1.3)× {10}43 erg s-1 and isophotal areas of 16-24 arcsec2. using the laes as tracers and a new kernel density estimation method, we discover a large-scale overdensity (boötes j1430+3522) with a surface density contrast of {δ }{{σ }}=2.7, a volume density contrast of δ ∼10.4, and a projected diameter of ≈20 comoving mpc. comparing with cosmological simulations, we conclude that this lae overdensity will evolve into a present-day coma-like cluster with {log}(m/{m}⊙ ) ∼ 15.1 ± 0.2. in this and three other wide-field lae surveys re-analyzed here, the extents and peak amplitudes of the largest lae overdensities are similar, not increasing with survey size, and implying that they were indeed the largest structures then and today evolve into rich clusters. intriguingly, labs favor the outskirts of the densest lae concentrations, i.e., intermediate lae overdensities of {δ }{{σ }}=1{--}2. we speculate that these labs mark infalling protogroups being accreted by the more massive protocluster. | discovery of a protocluster associated with a lyα blob pair at z = 2.3 |
context. hess j1809−193 is an unassociated very-high-energy γ-ray source located on the galactic plane. while it has been connected to the nebula of the energetic pulsar psr j1809−1917, supernova remnants and molecular clouds present in the vicinity also constitute possible associations. recently, the detection of γ-ray emission up to energies of ∼100 tev with the hawc observatory has led to renewed interest in hess j1809−193.aims: we aim to understand the origin of the γ-ray emission of hess j1809−193.methods: we analysed 93.2 h of data taken on hess j1809−193 above 0.27 tev with the high energy stereoscopic system (h.e.s.s.), using a multi-component, three-dimensional likelihood analysis. in addition, we provide a new analysis of 12.5 yr of fermi-lat data above 1 gev within the region of hess j1809−193. the obtained results are interpreted in a time-dependent modelling framework.results: for the first time, we were able to resolve the emission detected with h.e.s.s. into two components: an extended component (modelled as an elongated gaussian with a 1-σ semi-major and semi-minor axis of ∼0.62° and ∼0.35°, respectively) that exhibits a spectral cutoff at ∼13 tev, and a compact component (modelled as a symmetric gaussian with a 1-σ radius of ∼0.1°) that is located close to psr j1809−1917 and shows no clear spectral cutoff. the fermi-lat analysis also revealed extended γ-ray emission, on scales similar to that of the extended h.e.s.s. component.conclusions: our modelling indicates that based on its spectrum and spatial extent, the extended h.e.s.s. component is likely caused by inverse compton emission from old electrons that form a halo around the pulsar wind nebula. the compact component could be connected to either the pulsar wind nebula or the supernova remnant and molecular clouds. due to its comparatively steep spectrum, modelling the fermi-lat emission together with the h.e.s.s. components is not straightforward. | hess j1809−193: a halo of escaped electrons around a pulsar wind nebula? |
the messenger interface monte carlo mappings v (m3) is a photoionization code adopting the fully self-consistent monte carlo radiative transfer (mcrt) technique, which presents a major advance over previous photoionization models with simple geometries. m3 is designed for modeling nebulae in arbitrary three-dimensional geometries. in this paper, we describe the mcrt technique and the microphysics implemented in m3, including photoionization, collisional ionization, free-free and free-bound recombination, and two-photon radiation. we put m3 through the lexington/meudon benchmarks to test the reliability of the new code. we apply m3 to three h ii region models with fiducial geometries, demonstrating that m3 is capable of dealing with nebulae with complex geometries. m3 is a promising tool for understanding emission-line behavior in the era of sdss-v/lvm and james webb space telescope, which will provide high-quality data of spatially resolved nearby h ii regions and highly turbulent local and high-redshift h ii regions. | messenger monte carlo mappings v (m3)-a self-consistent, three-dimensional photoionization code |
in this work, we have discussed a spatially homogeneous and anisotropic bianchi type-i space-time in the presence of barrow holographic dark energy (infrared cut-off is the hubble’s horizon) proposed by barrow recently [j. d. barrow, phys. lett. b 808, 135643 (2020).] and matter in the framework of f(q) gravity where the nonmetricity q is responsible for the gravitational interaction for the specific choice of f(q)=λq2 (where λ<0 is a constant). to find the exact solutions to the field equations, we consider the deceleration parameter q, which is a function of the hubble’s parameter h i.e. q=b−nh (where b and n are constants). we have studied the physical behavior of important cosmological parameters such as the eos parameter, bhde and matter density, skewness parameter, squared sound speed and ωb−ωb′ plane. also, we constrain the values of the model parameters b and n using 57 hubble’s parameter measurements. | bianchi type-i barrow holographic dark energy model in symmetric teleparallel gravity |
we report results from chandra observations analyzed for evidence of variability and proper motion in the x-ray jet of centaurus a. using data spanning 15 yr, collective proper motion of 11.3 ± 3.3 mas yr-1, or 0.68 ± 0.20c, is detected for the fainter x-ray knots and other substructure present within the jet. the three brightest knots (ax1a, ax1c, and bx2) are found to be stationary to an upper limit of 0.10c. brightness variations up to 27% are detected for several x-ray knots in the jet. for the fading knots, bx2 and ax1c, the changes in spectral slope expected to accompany synchrotron cooling are not found, ruling it out and placing upper limits of ≃80 μg for each of their magnetic field strengths. adiabatic expansion can account for the observed decreases in brightness. constraints on models for the origin of the knots are established. jet plasma overrunning an obstacle is favored as the generator of stationary knots, while moving knots are likely produced either by internal differences in jet speed or the late stages of jet interaction with nebular or cloud material. | variability and proper motion of x-ray knots in the jet of centaurus a |
lyman-α nebulae are typically found in massive environments at high redshift (z ≳ 2). the origin of their lyman-α (lyα) emission remains debated. recent polarimetric observations showed that at least some lyα sources are polarized. this is often interpreted as proof that the photons are centrally produced and contradicts the scenario in which the lyα emission is the cooling radiation emitted by gas that is heated during the accretion onto the halo. we suggest that this cooling radiation scenario is compatible with the polarimetric observations. to test this idea, we post-processed a radiative hydrodynamics simulation of a blob with the mclya monte carlo transfer code. we computed radial profiles for the surface brightness and the degree of polarization and compared them to existing observations. we found that computed and observed profiles both are consistent with a significant contribution of the extragalactic gas to the lyα emission. most of the photons are centrally emitted and are subsequently scattered inside the filament, which produces the observed high level of polarization. we argue that the contribution of the extragalactic gas to the lyα emission does not prevent polarization. on the contrary, we find that pure galactic emission causes the polarization profile to be too steep to be consistent with observations. | lyman-α blobs: polarization arising from cold accretion |
we report multiwavelength observations and characterization of the ultraluminous transient at 2021lwx (ztf20abrbeie; aka "barbie") identified in the alert stream of the zwicky transient facility (ztf) using a recommender engine for intelligent transient tracking filter on the antares alert broker. from a spectroscopically measured redshift of 0.995, we estimate a peak-observed pseudo-bolometric luminosity of log( ${l}_{\max }/[\mathrm{erg}\,{{\rm{s}}}^{-1}]$ ) = 45.7 from slowly fading ztf-g and ztf-r light curves spanning over 1000 observer-frame days. the host galaxy is not detected in archival pan-starrs observations (g > 23.3 mag), implying a lower limit to the outburst amplitude of more than 5 mag relative to the quiescent host galaxy. optical spectra exhibit strong emission lines with narrow cores from the h balmer series and ultraviolet semi-forbidden lines of si iii] λ1892, c iii] λ1909, and c ii] λ2325. typical nebular lines in active galactic nucleus (agn) spectra from ions such as [o ii] and [o iii] are not detected. these spectral features, along with the smooth light curve that is unlike most agn flaring activity and the luminosity that exceeds any observed or theorized supernova, lead us to conclude that at 2021lwx is most likely an extreme tidal disruption event (tde). modeling of ztf photometry with mosfit suggests that the tde was between a ≈14m ⊙ star and a supermassive black hole of mass m bh ~ 108 m ⊙. continued monitoring of the still-evolving light curve along with deep imaging of the field once at 2021lwx has faded can test this hypothesis and potentially detect the host galaxy. | scary barbie: an extremely energetic, long-duration tidal disruption event candidate without a detected host galaxy at z = 0.995 |
constraining the evolution of pb isotopes in the bulk silicate earth (bse) is hampered due to the lack of a direct determination of earth's u/pb and initial pb isotope composition. all estimates of these parameters are strongly model dependent and most pb evolution models start with a meteoritic source, i.e., the primordial pb composition determined in troilite from the canyon diablo iron meteorite. during the condensation of the elements in the solar nebula, accretion of the earth, and its subsequent chemical evolution, the u/pb was modified. different models make different assumptions about the timing and extent of this u-pb fractionation during earth's chemical evolution that cannot always be related to known global geological processes at the time of this modification. this study explores geochemical constraints that can be related to known geological processes to derive an internally consistent model for the evolution of the u-th-pb systematics of the silicate earth. lead is chalcophile, moderately volatile, and as a result strongly depleted in the bse compared to primitive meteorites. any process affecting the abundance and isotope composition of pb in earth throughout its early history has to be consistent with the abundance of elements with similar chemical and physical properties in the same reservoir. the abundances of refractory to moderately and highly volatile elements in the bse imply that the proto earth was highly depleted in volatile elements, and therefore evolved with a very high u/pb (238u/204pb = μ ≥ 100) prior to collision with the moon-forming giant impactor. this impactor had close to chondritic abundances of moderately to highly volatile elements and delivered most of earth's volatile elements, including the pb budget. addition of this volatile-rich component caused oxidation of earth's mantle and allowed effective transfer of pb into the core via sulfide melt segregation. sequestration of pb into the core therefore accounts for the high μbse, which has affected ca. 53% of earth's pb budget. in order to account for the present-day pb isotope composition of bse, the giant impact must have occurred at 69 ± 10 myr after the beginning of the solar system. using this point in time, a model-derived μ-value and the corresponding initial pb isotope composition of bse, a single stage pb isotope evolution curve can be deduced. the result is a model evolution curve for bse in 208pb-207pb-206pb-204pb-isotope space that is fully consistent with geochemical constraints on earth's accretionary sequence and differentiation history. this pb-evolution model may act as a reference frame to trace the silicate earth's differentiation into crust and mantle reservoirs, similar to the chur reference line used for other radio-isotope systems. it also highlights the long-standing th/u paradox of the ancient earth. | the pb isotope evolution of bulk silicate earth: constraints from its accretion and early differentiation history |
ck vulpeculae was observed in outburst in 1670-1672 (ref. 1), but no counterpart was seen until 1982, when a bipolar nebula was found at its location. historically, ck vul has been considered to be a nova (nova vul 1670), but its similarity to `red transients', which are more luminous than classical novae and thought to be the results of stellar collisions, has re-opened the question of ck vul's status. red transients cool to resemble late m-type stars, surrounded by circumstellar material rich in molecules and dust. no stellar source has been seen in ck vul, though a radio continuum source was identified at the expansion centre of the nebula. here we report that ck vul is surrounded by chemically rich molecular gas in the form of an outflow, as well as dust. the gas has peculiar isotopic ratios, revealing that ck vul's composition was strongly enhanced by the nuclear ashes of hydrogen burning. the chemical composition cannot be reconciled with a nova or indeed any other known explosion. in addition, the mass of the surrounding gas is too large for a nova, though the conversion from observations of co to a total mass is uncertain. we conclude that ck vul is best explained as the remnant of a merger of two stars. | nuclear ashes and outflow in the eruptive star nova vul 1670 |
we find the central stars (css) of the planetary nebulae (pne) hatr 7 and eso 330-9 to be close-binary systems. both have orbital periods of less than half a day and contain an irradiated cool companion to the hot cs. we provide light curves, spectra, radial velocity curves, orbital periods, and binary modeling results for both systems. the binary modeling leads to system parameters, or ranges of allowed parameters for each system. we find that for the cs of hatr 7 we need to use limb-darkening values for the cool companion that are different than the expected values for an isolated star. we also fit the cs spectrum to determine {log}g and temperature values independent of the binary modeling. for eso 330-9 we find that based on our binary modeling, the hot cs is most likely a post-red giant branch (rgb) star with a mass of around 0.4 {m}⊙ . we discuss our derived stellar and nebular parameters in the broader context of close-binary css and their surrounding planetary nebulae (pne). we also discuss the present status of known or suspected post-rgb stars in pne. | binary central stars of planetary nebulae discovered through photometric variability. v. the central stars of hatr 7 and eso 330-9 |
eta carinae (η car) is an extremely massive binary system in which rapid spectrum variations occur near periastron. most notably, near periastron the he ii λ4686 line increases rapidly in strength, drops to a minimum value, then increases briefly before fading away. to understand this behavior, we conducted an intense spectroscopic monitoring of the he ii λ4686 emission line across the 2014.6 periastron passage using ground- and space-based telescopes. comparison with previous data confirmed the overall repeatability of the line equivalent width (ew), radial velocities, and the timing of the minimum, though the strongest peak was systematically larger in 2014 than in 2009 by 26%. the ew variations, combined with other measurements, yield an orbital period of 2022.7 ± 0.3 days. the observed variability of the ew was reproduced by a model in which the line flux primarily arises at the apex of the wind-wind collision and scales inversely with the square of the stellar separation, if we account for the excess emission as the companion star plunges into the hot inner layers of the primary’s atmosphere, and including absorption from the disturbed primary wind between the source and the observer. this model constrains the orbital inclination to 135°-153°, and the longitude of periastron to 234°-252°. it also suggests that periastron passage occurred on {t}0=2456874.4\quad (+/- 1.3 days). our model also reproduced ew variations from a polar view of the primary star as determined from the observed he ii λ 4686 emission scattered off the homunculus nebula. based in part on observations made with the nasa/esa hubble space telescope, obtained at the space telescope science institute, which is operated by the association of universities for research in astronomy, inc., under nasa contract nas 5-26555. these observations are associated with program numbers 11506, 12013, 12508, 12750, and 13054. support for program numbers 12013, 12508, and 12750 was provided by nasa through a grant from the space telescope science institute, which is operated by the association of universities for research in astronomy, inc., under nasa contract nas 5-26555. | he ii λ4686 emission from the massive binary system in η car: constraints to the orbital elements and the nature of the periodic minima |
we present first results from multi unit spectroscopic explorer (muse) observations at the very large telescope in the muse ultra deep field (mudf), a ≈1.2 × 1.4 arcmin2 region for which we are collecting ≈200 hours of integral field spectroscopy. the ≈40-h observation completed to date reveals the presence of a group of three lyα nebulae associated with a bright quasar pair at z ≃ 3.23 with projected separation of {≈ } 500 kpc. two of the nebulae are physically associated with the quasars which are likely powering the lyα emission, and extend for {≳ } 100 kpc at a surface brightness level of ≈6 × 10-19 erg s^{-1} cm^{-2} arcsec^{-2}. a third smaller (≈35 kpc) nebula lies at a velocity offset of ≈1550 km s-1. despite their clustered nature, the two large nebulae have properties similar to those observed in isolated quasars and exhibit no sharp decline in flux at the current depth, suggesting an even more extended distribution of gas around the quasars. we interpret the shape and the alignment of the two brighter nebulae as suggestive of the presence of an extended structure connecting the two quasar host galaxies, as seen for massive galaxies forming within gas-rich filaments in cosmological simulations. | the muse ultra deep field (mudf) - i. discovery of a group of lyα nebulae associated with a bright z ≈ 3.23 quasar pair |
the crab nebula is one of the most efficient accelerators in the galaxy and the only galactic source showing direct evidence of pev particles. in spite of this, the physical process behind such effective acceleration is still a deep mystery. while particle acceleration, at least at the highest energies, is commonly thought to occur at the pulsar wind termination shock, the properties of the upstream flow are thought to be non-uniform along the shock surface, and important constraints on the mechanism at work come from exact knowledge of where along this surface particles are being accelerated. here we use axisymmetric relativistic magnetohydrodynamic simulations to obtain constraints on the acceleration site(s) of particles of different energies in the crab nebula. various scenarios are considered for the injection of particles responsible for synchrotron radiation in the different frequency bands, radio, optical and x-rays. the resulting emission properties are compared with available data on the multiwavelength time variability of the inner nebula. our main result is that the x-ray emitting particles are accelerated in the equatorial region of the pulsar wind. possible implications on the nature of the acceleration mechanism are discussed. | constraints on particle acceleration sites in the crab nebula from relativistic magnetohydrodynamic simulations |
emission signatures from galactic winds provide an opportunity to directly map the outflowing gas, but this is traditionally challenging because of the low surface brightness. using very deep observations (27 h) of the hubble deep field south with the multi unit spectroscopic explorer (muse) instrument, we identify signatures of an outflow in both emission and absorption from a spatially resolved galaxy at z = 1.29 with a stellar mass m⋆ = 8 × 109m⊙, star formation rate sfr = 77+40-25 m⊙ yr-1, and star formation rate surface brightness σsfr = 1.6m⊙ kpc-2 within the [oii] λλ3727,3729 half-light radius r1/2, [oii] = 2.76 ± 0.17 kpc. from a component of the strong resonant mg ii and fe ii absorptions at -350 km s-1, we infer a mass outflow rate that is comparable to the star formation rate. we detect non-resonant fe ii* emission, at λ2365, λ2396, λ2612, and λ2626, at 1.2-2.4-1.5-2.7 × 10-18 erg s-1 cm-2 respectively. the flux ratios are consistent with the expectations for optically thick gas. by combining the four non-resonant fe ii* emission lines, we spatially map the fe ii* emission from an individual galaxy for the first time. the fe ii* emission has an elliptical morphology that is roughly aligned with the galaxy minor kinematic axis, and its integrated half-light radius, r1/2, fe ii ∗ =4.1 ± 0.4 kpc, is 70% larger than the stellar continuum (r1/2,⋆ ≃2.34 ± 0.17) or the [oii] nebular line. moreover, the fe ii* emission shows a blue wing extending up to -400 km s-1, which is more pronounced along the galaxy minor kinematic axis and reveals a c-shaped pattern in a p-v diagram along that axis. these features are consistent with a bi-conical outflow. based on observations of the hubble deep field south made with eso telescopes at the la silla paranal observatory under program id 60.a-9100(c). advanced data products are available at http://muse-vlt.eu/ science | galactic winds with muse: a direct detection of fe ii* emission from a z = 1.29 galaxy |
the first water cherenkov detector of the lhaaso experiment (wcda-1) has been operating since april 2019. the data for the first year have been analyzed to test its performance by observing the crab nebula as a standard candle. the wcda-1 achieves a sensitivity of 65 mcu per year, with a statistical threshold of 5 $\sigma$ . to accomplish this, a 97.7% cosmic-ray background rejection rate around 1 tev and 99.8% around 6 tev with an approximate photon acceptance of 50% is achieved after applying an algorithm to separate gamma-induced showers. the angular resolution is measured using the crab nebula as a point source to be approximately 0.45° at 1 tev and better than 0.2° above 6 tev, with a pointing accuracy better than 0.05°. these values all match the design specifications. the energy resolution is found to be 33% for gamma rays around 6 tev. the spectral energy distribution of the crab nebula in the range from 500 gev to 15.8 tev is measured and found to be in agreement with the results from other tev gamma ray observatories. * supported by the following grants: the national key r&d program of china (2018yfa0404201, 2018yfa0404202, 2018yfa0404203), the national natural science foundation of china (12022502, 11905227, u1931112, 11635011, 11761141001, y811a35, 11675187, u1831208, u1931111) and in thailand by rta6280002 from thailand science research and innovation | performance of lhaaso-wcda and observation of the crab nebula as a standard candle |
the magellanic clouds are uniquely placed to study the stellar contribution to dust emission. individual stars can be resolved in these systems even in the mid-infrared, and they are close enough to allow detection of infrared excess caused by dust. we have searched the spitzer space telescope data archive for all infrared spectrograph (irs) staring-mode observations of the small magellanic cloud (smc) and found that 209 infrared array camera (irac) point sources within the footprint of the surveying the agents of galaxy evolution in the small magellanic cloud (sage-smc) spitzer legacy programme were targeted, within a total of 311 staring-mode observations. we classify these point sources using a decision tree method of object classification, based on infrared spectral features, continuum and spectral energy distribution shape, bolometric luminosity, cluster membership and variability information. we find 58 asymptotic giant branch (agb) stars, 51 young stellar objects, 4 post-agb objects, 22 red supergiants, 27 stars (of which 23 are dusty ob stars), 24 planetary nebulae (pne), 10 wolf-rayet stars, 3 h ii regions, 3 r coronae borealis stars, 1 blue supergiant and 6 other objects, including 2 foreground agb stars. we use these classifications to evaluate the success of photometric classification methods reported in the literature. | spitzer infrared spectrograph point source classification in the small magellanic cloud |
there is no conclusive explanation of why ∼80 per cent of planetary nebulae (pne) are non-spherical. in the binary hypothesis, a binary interaction is a preferred channel to form a non-spherical pn. a fundamental step to corroborate or disprove the binary hypothesis is to estimate the binary fraction of central stars of pne (cspne) and compare it with a prediction based on the binary fraction of the progenitor, main-sequence population. in this paper, the second in a series, we search for spatially unresolved i- and j-band flux excess in an extended sample of 34 cspn by a refined measurement technique with a better quantification of the uncertainties. the detection rate of i- (j-)band flux excess is 32 ± 16 per cent (50 ± 24 per cent). this result is very close to what was obtained in paper i with a smaller sample. we account conservatively for unobserved cool companions down to brown dwarf luminosities, increasing these fractions to 40 ± 20 per cent (62 ± 30 per cent). this step is very sensitive to the adopted brightness limit of our survey. accounting for visual companions increases the binary fraction to 46 ± 23 per cent (71 ± 34 per cent). these figures are lower than in paper i. the error bars are better quantified, but still unacceptably large. taken at face value, the current cspn binary fraction is in line with the main-sequence progenitor population binary fraction. however, including white dwarfs companions could increase this fraction by as much as 13 (21) per cent points. | the binary fraction of planetary nebula central stars - ii. a larger sample and improved technique for the infrared excess search |
a growing body of evidence indicates that binary neutron-star mergers are the primary origin of heavy elements produced exclusively through rapid neutron capture1-4 (the `r-process'). as neutron-star mergers occur infrequently, their deposition of radioactive isotopes into the pre-solar nebula could have been dominated by a few nearby events. although short-lived r-process isotopes—with half-lives shorter than 100 million years—are no longer present in the solar system, their abundances in the early solar system are known because their daughter products were preserved in high-temperature condensates found in meteorites5. here we report that abundances of short-lived r-process isotopes in the early solar system point to their origin in neutron-star mergers, and indicate substantial deposition by a single nearby merger event. by comparing numerical simulations with the early solar system abundance ratios of actinides produced exclusively through the r-process, we constrain the rate of occurrence of their galactic production sites to within about 1-100 per million years. this is consistent with observational estimates of neutron-star merger rates6-8, but rules out supernovae and stellar sources. we further find that there was probably a single nearby merger that produced much of the curium and a substantial fraction of the plutonium present in the early solar system. such an event may have occurred about 300 parsecs away from the pre-solar nebula, approximately 80 million years before the formation of the solar system. | a nearby neutron-star merger explains the actinide abundances in the early solar system |
we report optical integral-field spectroscopy in the field of one of the most luminous quasars in the z < 1 universe, pks 0454-22, with the multi-unit spectroscopic explorer. these data enable the discovery of three large ionized nebulae emitting in [o ii], h β, and [o iii] with projected areas of 1720, 1520, and 130 pkpc2, which we refer to as n1, n2, and n3, respectively. n1 spatially and kinematically surrounds the quasar host and five nearby galaxies. the morphology and kinematics of n1 are most consistent with stripped interstellar medium resulting from ongoing interactions. its ionization properties can be explained by quasar photoionization. n2 spatially and kinematically surrounds two galaxies that are at projected distances of d ≈ 90 pkpc and line-of-sight velocities of δv ≈+1410 km s-1 from the quasar. the morphology and kinematics of n2 are also consistent with stripped interstellar medium. however, its ionization state requires additional ionization sources beyond the quasar, likely from fast shocks as it moves through the hot halo associated with a galaxy overdensity around the quasar. n3 is not coincident with any galaxies with secure redshifts, and may arise from a cool gas structure in the intragroup medium or a dwarf galaxy. these large ionized nebulae demonstrate that interactions can produce cool gas structures on halo scales, while also possibly facilitating quasar fueling. the growing availability of wide-area integral field spectroscopic data will continue to reveal the morphologies, kinematics, and conditions of the gas flows, which may fuel galaxy and black hole growth. | discovery and origins of giant optical nebulae surrounding quasar pks 0454-22 |
the international gamma-ray astrophysics laboratory (integral) continues to successfully work in orbit after its launch in 2002. the mission provides the deepest ever survey of hard x-ray sources throughout the galaxy at energies above 20 kev. we report on a catalogue of new hard x-ray source candidates based on the latest sky maps comprising 14 yr of data acquired with the ibis telescope onboard integral in the galactic plane (|b| < 17.5°). the current catalogue includes in total 72 hard x-ray sources detected at s/n > 4.7σ and not known to previous integral surveys. among them, 31 objects have also been detected in the on-going all-sky survey by the bat telescope of the swift observatory. for 26 sources on the list, we suggest possible identifications: 21 active galactic nuclei, two cataclysmic variables, two isolated pulsars or pulsar wind nebulae and one supernova remnant; 46 sources from the catalogue remain unclassified. | new hard x-ray sources discovered in the ongoing integral galactic plane survey after 14 yr of observations |
we perform a comparative study between the only radio-detected type i superluminous supernova (slsn) ptf10hgi, and the most active repeating fast radio burst frb121102. this study has its root in the hypothesized frb-slsn connection that states that magnetars born in slsn can power frbs. the wide-band spectrum (0.6-15 ghz) of ptf10hgi presented here, provides strong evidence for the magnetar wind nebular origin of the radio emission. the same spectrum also enables us to make robust estimates of the radius and the magnetic field of the radio-emitting region and demonstrates that the nebula is powered by the rotational energy of the magnetar. this spectrum is then compared with that of frb121102 which we extend down to 400 mhz using archival data. the newly added measurements put very tight constraint on the emission models of the compact persistent source associated with frb121102. we find that while both sources can be powered by the rotational energy of the underlying magnetar, the average energy injection rate is much higher in frb121102. hence, we hypothesize that, if ptf10hgi is indeed emitting fast radio bursts, those will be much weaker energetically than those from frb121102. | radio emission from a decade old type i superluminous supernova, ptf10hgi: comparison with frb121102 |
magnetic fields of order 101-102 gauss that are present in the envelopes of red giant stars are ejected in common envelope scenarios. these fields could be responsible for the launching of magnetically driven winds in protoplanetary nebulae. using 2d simulations of magnetized winds interacting with an envelope drawn from a 3d simulation of the common envelope phase, we study the confinement, heating, and magnetic field development of post-common envelope winds. we find that the ejected magnetic field can be enhanced via compression by factors up to ∼104 in circumbinary disks during the self-regulated phases. we find values for the kinetic energy of the order of 1046 erg that explain the large values inferred in protoplanetary nebula outflows. we show that the interaction of the formed circumbinary disk with a spherical, stellar wind produces a "tapered" flow that is almost indistinguishable from an imposed tapered flow. this increases the uncertainty of the origin of protoplanetary nebula winds, which could be either stellar, circumstellar (stellar accretion disk), circumbinary (circumbinary accretion disk), or a combination of all three. within this framework, a scenario for self-collimation of weakly magnetized winds is discussed, which can explain the two objects where the collimation process is observationally resolved, hd 101584 and hen 3-1475. an explanation for the equatorial, molecular hydrogen emission in crl 2688 is also presented. | common envelope shaping of planetary nebulae. ii. magnetic solutions and self-collimated outflows |
we investigate the dust attenuation in both stellar populations and ionized gas in kiloparsec-scale regions in nearby galaxies using integral field spectroscopy data from manga mpl-9. we identify star-forming (h ii) and diffuse ionized gas (dig) regions from manga data cubes. from the stacked spectrum of each region, we measure the stellar attenuation, $e{\left(b-v\right)}_{\mathrm{star}}$ , using the technique developed by li et al., as well as the gas attenuation, $e{\left(b-v\right)}_{\mathrm{gas}}$ , from the balmer decrement. we then examine the correlation of $e{\left(b-v\right)}_{\mathrm{star}}$ , $e{\left(b-v\right)}_{\mathrm{gas}}$ , $e{\left(b-v\right)}_{\mathrm{gas}}-e{\left(b-v\right)}_{\mathrm{star}}$ , and $e{\left(b-v\right)}_{\mathrm{star}}/e{\left(b-v\right)}_{\mathrm{gas}}$ with 16 regional/global properties, and for regions with different hα surface brightnesses (σhα). we find a stronger correlation between $e{\left(b-v\right)}_{\mathrm{star}}$ and $e{\left(b-v\right)}_{\mathrm{gas}}$ in regions of higher σhα. the luminosity-weighted age (tl) is found to be the property that is the most strongly correlated with $e{\left(b-v\right)}_{\mathrm{star}}$ , and consequently, with $e{\left(b-v\right)}_{\mathrm{gas}}-e{\left(b-v\right)}_{\mathrm{star}}$ and $e{\left(b-v\right)}_{\mathrm{star}}/e{\left(b-v\right)}_{\mathrm{gas}}$ . at fixed σhα, ${\mathrm{log}}_{10}$ tl is linearly and negatively correlated with $e{\left(b-v\right)}_{\mathrm{star}}/e{\left(b-v\right)}_{\mathrm{gas}}$ at all ages. gas-phase metallicity and ionization level are important for the attenuation in the gas. our results indicate that the ionizing source for dig regions is likely distributed in the outskirts of galaxies, while for h ii regions, our results can be well explained by the two-component dust model of charlot & fall. | estimating dust attenuation from galactic spectra. ii. stellar and gas attenuation in star-forming and diffuse ionized gas regions in manga |
we reassess the historical lx/lbol relation for early-type stars from a comparison between t-rex, the chandra acis x-ray survey of the tarantula nebula in the large magellanic cloud (lmc), and contemporary spectroscopic analysis of massive stars obtained primarily from vlt/flames, vlt/muse, and hst/stis surveys. for 107 sources in common (some host to multiple stars), the majority of which are bolometrically luminous (40 per cent exceed 106l⊙), we find an average log lx/lbol = -6.90 ± 0.65. excluding extreme systems mk 34 (wn5h+wn5h), r140a (wc4+wn6+), and vfts 399 (o9 iiin+?), plus four wr sources with anomalously hard x-ray components (r130, r134, r135, mk 53) and 10 multiple sources within the spatially crowded core of r136a, log lx/lbol = -7.00 ± 0.49, in good agreement with galactic ob stars. no difference is found between single and binary systems, nor between o, of/wn, and wr stars, although there does appear to be a trend towards harder x-ray emission from o dwarfs, through o (super)giants, of/wn stars, and wr stars. the majority of known ob stars in the tarantula are not detected in the t-rex point source catalogue, so we have derived upper limits for all undetected ob stars for which log lbol/l⊙ ≥ 5.0. a survival analysis using detected and upper limit log lx/lbol values indicates no significant difference between luminous o stars in the lmc and the carina nebula. this analysis suggests that metallicity does not strongly influence lx/lbol. plasma temperatures for single, luminous o stars in the tarantula ($\overline{kt_{m}}=1.0$ kev) are higher than counterparts in carina ($\overline{kt_{m}}=0.5$ kev). | x-ray properties of early-type stars in the tarantula nebula from t-rex |
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