adsabs/SciX_UAT_keywords huggingface dataset:
The Rapid Buildup of Massive Early-type Galaxies: Supersolar Metallicity, High Velocity Dispersion, and Young Age for an Early-type Galaxy at z = 3.35

How massive early-type galaxies (ETGs) assembled their mass, on which timescales the star formation quenched, and when their supersolar metallicity has been established are still open and debated issues. Thanks to very deep spectroscopic observations carried out at the Large Binocular Telescope, we simultaneously measured stellar age, metallicity, and velocity dispersion for C1-23152, an ETG at redshift z = 3.352, corresponding to an epoch when the universe was ∼1.8 Gyr old. The analysis of its spectrum shows that this galaxy, hosting an active galactic nucleus (AGN), formed and assembled ∼2 × 1011 M⊙, shaping its morphology within the ∼600 Myr preceding the observations, since z ∼ 4.6. The stellar population has a mean mass-weighted age of ${400}_{-70}^{+30}$ Myr, and it is formed between ∼600 and ∼150 Myr before the observed epoch, the latter being the time since quenching. Its high stellar velocity dispersion, σe = 409 ± 60 km s-1, confirms the high mass (Mdyn = 2.2 (±0.4) × 1011 M⊙) and the high mass density ( ${{\rm{\Sigma }}}_{e}^{{M}^{* }}$ = Σ1kpc = 3.2 (±0.7) × 1010 M⊙ kpc-2), suggesting a fast dissipative process at its origin. The analysis points toward a supersolar metallicity, [Z/H] = 0.25 ${}_{-0.10}^{+0.006}$ , in agreement with the above picture, suggesting a star formation efficiency much higher than the replenishment time. However, subsolar-metallicity values cannot be firmly ruled out by our analysis. Quenching must have been extremely efficient to reduce the star formation to SFR < 6.5 M⊙ yr-1 in less than 150 Myr. This could be explained by the presence of the AGN, even if a causal relation cannot be established from the data. C1-23152 has the same stellar and physical properties of the densest ETGs in the local universe of comparable mass, suggesting that they are C1-23152-like galaxies that evolved to z = 0 unperturbed.

Keywords: galaxy formation; galaxy evolution; high-redshift galaxies; elliptical galaxies; galaxy stellar content; galaxy properties
NEOWISE Variability of the New Gaia Herbig Ae/Be and Classical Be Stars-Variability Sample and Statistical Analysis

Light variability is an essential attribute of young stellar objects (YSOs) at the pre-main-sequence (PMS) stage, which can be treated as an indicator to trace star formation. We present a statistical study on the infrared NEOWISE variability of new and large-sized PMS stars as well as Herbig Ae/Be (HAeBe) and classical Be (CBe) stars identified from Gaia Data Release 2. A total of 3792 (including 714 HAeBe), 417, and 473 NEOWISE variable sources were detected from the catalog of 8470 PMS (including 1361 HAeBe), 693 CBe, and 1309 uncertain (possibly belonging to either HAeBe or CBe) stars, respectively. We found that 80% of the PMS variables are dominated by irregular infrared variability, whereas variables in the CBe and uncertain categories exhibit comparable contributions from secular (linear, curved, and periodic) and stochastic (burst, drop, and irregular) variables. This, in combination with infrared W1-W2 colors, W4 luminosities, and the spectral energy distribution slope at near- and mid-infrared wavelengths, suggests different evolutionary stages of the PMS (including HAeBe), uncertain, and CBe stars, from less to more evolved. A statistical analysis of variable source properties (e.g., period and fractional amplitude) further reveals a potential sequence possibly associated with disk evolution for different types of light curves (from linear, to curved, periodic, stochastic, and nonvariable stars). Possible mechanisms for the variable sources are suggested to be related to either extinction via circumstellar matter, or contribution of multiple systems surrounding the YSOs, as opposed to variable accretion (e.g., episodic accretion or accretion burst).

Keywords: young stellar objects; herbig ae/be stars; b(e) stars; pre-main sequence stars; protoplanetary disks; protostars
The Emergence of Structure in the Binary Black Hole Mass Distribution

We use the gravitational wave signals from binary black hole merger events observed by LIGO and Virgo to reconstruct the underlying mass and spin distributions of the population of merging black holes. We reconstruct the population using the mixture model framework VAMANA using observations in GWTC-2 occurring during the first two observing runs and the first half of the third run (O1, O2, and O3a). Our analysis identifies a structure in the chirp mass distribution of the observed population. Specifically, we identify peaks in the chirp mass distribution at 8, 14, 26, and 45 M⊙ and a complementary structure in the component mass distribution with an excess of black holes at masses of 9, 16, 45, and 57 M⊙. Intriguingly, for both the distributions, the location of subsequent peaks are separated by a factor of around two and there is a lack of mergers with chirp masses of 10-12 M⊙. The appearance of multiple peaks is a feature of a hierarchical merger scenario when, due to a gap in the black hole mass spectrum, a pile-up occurs at the first peak followed by mergers of lower mass black holes to hierarchically produce higher mass black holes. However, cross-generation merger peaks and observations with high spins are also predicted to occur in such a scenario that we are not currently observing. The results presented are limited in measurement accuracy due to small numbers of observations but if corroborated by future gravitational wave observations these features have far-reaching implications.

Keywords: gravitational wave sources; gravitational waves; gravitational wave astronomy
The Behavior of HgMn Stars in the Far UV -5: υ Her

The analysis of twelve high resolution SWP spectra of the HgMn star HD 144206 (υ Her) obtained through the large aperture recorded by the International Ultraviolet Explorer (IUE) reveals that the far ultraviolet flux of this star remained constant over the various observations with IUE, except for one spectrum. The increase of FUV flux in SWP 13513 and the simultaneous brightening of υ Her in the V band could reflect a flare similar to those reported in other late B-type stars. The analysis of two high resolution ELODIE spectra obtained four years apart does not show any variations of the lines, either in reduced intensity nor in radial velocity. The absence of far ultraviolet variability and the reproducibility of the brightness in the V band during most IUE observations do not support the presence of large chemical gradients over the surface of υ Her.

Keywords: chemically peculiar stars; chemical abundances
Chemical Analysis of the Ultrafaint Dwarf Galaxy Grus II. Signature of High-mass Stellar Nucleosynthesis

We present a detailed abundance analysis of the three brightest member stars at the top of the giant branch of the ultrafaint dwarf (UFD) galaxy Grus II. All stars exhibit a higher than expected [Mg/Ca] ratio compared to metal-poor stars in other UFD galaxies and in the Milky Way (MW) halo. Nucleosynthesis in high-mass ( $\geqslant $ 20 M⊙) core-collapse supernovae has been shown to create this signature. The abundances of this small sample (three) stars suggests the chemical enrichment of Grus II could have occurred through substantial high-mass stellar evolution, and is consistent with the framework of a top-heavy initial mass function. However, with only three stars it cannot be ruled out that the abundance pattern is the result of a stochastic chemical enrichment at early times in the galaxy. The most metal-rich of the three stars also possesses a small enhancement in rapid neutron-capture (r-process) elements. The abundance pattern of the r-process elements in this star matches the scaled r-process pattern of the solar system and r-process enhanced stars in other dwarf galaxies and in the MW halo, hinting at a common origin for these elements across a range of environments. All current proposed astrophysical sites of r-process element production are associated with high-mass stars, thus the possible top-heavy initial mass function of Grus II would increase the likelihood of any of these events occurring. The time delay between the α and r-process element enrichment of the galaxy favors a neutron star merger as the origin of the r-process elements in Grus II. * This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

Keywords: dwarf galaxies; chemical abundances; chemically peculiar stars; stellar abundances
Bridging the Gap between Protoplanetary and Debris Disks: Separate Evolution of Millimeter and Micrometer-sized Dust

The connection between the nature of a protoplanetary disk and that of a debris disk is not well understood. Dust evolution, planet formation, and disk dissipation likely play a role in the processes involved. We aim to reconcile both manifestations of dusty circumstellar disks through a study of optically thin Class III disks and how they correlate to younger and older disks. In this work, we collect literature and Atacama Large Millimeter/submillimeter Array archival millimeter fluxes for 85 disks (8%) of all Class III disks across nearby star-forming regions. We derive millimeter-dust masses Mdust and compare these with Class II and debris disk samples in the context of excess infrared luminosity, accretion rate, and age. The mean Mdust of Class III disks is 0.29 ± 0.19 M⊕. We propose a new evolutionary scenario wherein radial drift is very efficient for nonstructured disks during the Class II phase resulting in a rapid Mdust decrease. In addition, we find possible evidence for long infrared protoplanetary disk timescales, ~8 Myr, consistent with overall slow disk evolution. In structured disks, the presence of dust traps allows for the formation of planetesimal belts at large radii, such as those observed in debris disks. We propose therefore that the planetesimal belts in debris disks are the result of dust traps in structured disks, whereas protoplanetary disks without dust traps decrease in dust mass through radial drift and are therefore undetectable as debris disks after the gas dissipation. These results provide a hypothesis for a novel view of disk evolution.

Keywords: protoplanetary disks; kuiper belt; pre-main sequence stars; young stellar objects; submillimeter astronomy
Observational Evidence for Cosmological Coupling of Black Holes and its Implications for an Astrophysical Source of Dark Energy

Observations have found black holes spanning 10 orders of magnitude in mass across most of cosmic history. The Kerr black hole solution is, however, provisional as its behavior at infinity is incompatible with an expanding universe. Black hole models with realistic behavior at infinity predict that the gravitating mass of a black hole can increase with the expansion of the universe independently of accretion or mergers, in a manner that depends on the black hole's interior solution. We test this prediction by considering the growth of supermassive black holes in elliptical galaxies over 0 < z ≲ 2.5. We find evidence for cosmologically coupled mass growth among these black holes, with zero cosmological coupling excluded at 99.98% confidence. The redshift dependence of the mass growth implies that, at z ≲ 7, black holes contribute an effectively constant cosmological energy density to Friedmann's equations. The continuity equation then requires that black holes contribute cosmologically as vacuum energy. We further show that black hole production from the cosmic star formation history gives the value of ΩΛ measured by Planck while being consistent with constraints from massive compact halo objects. We thus propose that stellar remnant black holes are the astrophysical origin of dark energy, explaining the onset of accelerating expansion at z ~ 0.7.

Keywords: astrophysical black holes; black hole physics; supermassive black holes; dark energy; star formation; cosmological constant
UVIT Observations of the Small Magellanic Cloud: Point-source Catalog

Three fields in the outskirts of the Small Magellanic Cloud were observed by the UltraViolet Imaging Telescope (UVIT) on board AstroSat, between 2017 December 31 and 2018 January 1. The observations were carried out on a total of seven filters, three in the far-ultraviolet (FUV; 1300-1800 Å) band and four in the near-ultraviolet (NUV; 2000-3000 Å) band. We carried out photometry of these observations that have a spatial resolution better than 1.″5. We present here the first results of this work, which is a matched catalog of 11,241 sources detected in three FUV and four NUV wavelengths. We make the catalog available online, which would be of use to the astronomical community to address a wide variety of astrophysical problems. We provide an expression to estimate the total count rate in the full point-spread function of UVIT that also incorporates the effect of saturation.

Keywords: ultraviolet astronomy; ultraviolet telescopes; ultraviolet photometry; ultraviolet sources
Quasar UV Luminosity Function at 3.5 < z < 5.0 from SDSS Deep Imaging Data

We present a well-designed sample of more than 1000 type 1 quasars at 3.5 < z < 5 and derive UV quasar luminosity functions (QLFs) in this redshift range. These quasars were selected using the Sloan Digital Sky Survey (SDSS) imaging data in the Stripe 82 and overlap regions with repeat imaging observations that are about 1 mag fainter than the SDSS single-epoch data. The follow-up spectroscopic observations were conducted by the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS) as one of the BOSS ancillary programs. Reaching i ~ 21.5 mag, our sample bridges previous samples from brighter and deeper surveys. We use a 1/V a method to derive binned QLFs at 3.6 < z < 4.0, 4.0 < z < 4.5, and 4.5 < z < 4.9 and then use a double power-law model to parameterize the QLFs. We also combine our data with literature QLFs to better constrain the QLFs across a much wider luminosity baseline. The faint- and bright-end slopes of the QLFs in this redshift range are around -1.7 and -3.7, respectively, with uncertainties from 0.2 to 0.3 to >0.5. The evolution of the QLFs from z ~ 5 to 3.5 can be described by a pure density evolution model (∝10 kz ) with a parameter k similar to that at 5 < z < 7, suggesting a nearly uniform evolution of the quasar density at z = 3.5-7.

Keywords: quasars; redshift surveys; luminosity function
Millimeter Observations of the Type II SN 2023ixf: Constraints on the Proximate Circumstellar Medium

We present 1.3 mm (230 GHz) observations of the recent and nearby Type II supernova, SN 2023ixf, obtained with the Submillimeter Array (SMA) at 2.6-18.6 days after explosion. The observations were obtained as part the SMA Large Program, POETS (Pursuit of Extragalactic Transients with the SMA). We do not detect any emission at the location of SN 2023ixf, with the deepest limits of L ν (230 GHz) ≲ 8.6 × 1025 erg s-1 Hz-1 at 2.7 and 7.7 days, and L ν (230 GHz) ≲ 3.4 × 1025 erg s-1 Hz-1 at 18.6 days. These limits are about a factor of 2 times dimmer than the millimeter emission from SN 2011dh (IIb), about 1 order of magnitude dimmer compared to SN 1993J (IIb) and SN 2018ivc (IIL), and about 30 times dimmer than the most luminous nonrelativistic SNe in the millimeter band (Type IIb/Ib/Ic). Using these limits in the context of analytical models that include synchrotron self-absorption and free-free absorption, we place constraints on the proximate circumstellar medium around the progenitor star, to a scale of ~2 × 1015 cm, excluding the range $\dot{M}\sim \mathrm{few}\times {10}^{-6}-{10}^{-2}$ M ⊙ yr-1 (for a wind velocity, v w = 115 km s-1, and ejecta velocity, v ej ~ (1 - 2) × 104 km s-1). These results are consistent with an inference of the mass-loss rate based on optical spectroscopy (~2 × 10-2 M ⊙ yr-1 for v w = 115 km s-1), but are in tension with the inference from hard X-rays (~7 × 10-4 M ⊙ yr-1 for v w = 115 km s-1). This tension may be alleviated by a nonhomogeneous and confined CSM, consistent with results from high-resolution optical spectroscopy.

Keywords: supernovae; type ii supernovae; core-collapse supernovae; massive stars; stellar mass loss; circumstellar matter
Internal Rotation and Inclinations of Slowly Pulsating B Stars: Evidence of Interior Angular Momentum Transport

One of the largest uncertainties in stellar structure and evolution theory is the transport of angular momentum in the stellar interiors. Asteroseismology offers a powerful tool for measuring the internal rotation frequencies of pulsating stars, but the number of such measurements has remained few for ≳3 M ⊙ main-sequence stars. In this work, we compile a list of 52 slowly pulsating B stars for which the interior rotation has been measured asteroseismically. The measurements of the spin parameters, which describe the relative importance of rotation, for the gravito-inertial mode oscillations show that for 40 of the stars the oscillations fall within the subinertial regime. We find that the core rotation frequencies of the stars decrease as a function of age and show evidence of angular momentum transport occurring on the main sequence. Finally, we derive the inclination angles of the stars, showing that they are generally consistent with the expectations from surface cancellation effects for the given oscillation modes.

Keywords: stellar rotation; stellar cores; stellar interiors; stellar pulsations; stellar evolution
Multi-frequency General Relativistic Radiation-hydrodynamics with M1 Closure

We report on recent upgrades to our general relativistic radiation-magnetohydrodynamics code, Cosmos++, which expands the two-moment, M1, radiation treatment from gray to multi-frequency transport, including Doppler and gravitational frequency shifts. The solver accommodates either photon (Bose-Einstein) or neutrino (Fermi-Dirac) statistical distribution functions with absorption, emission, and elastic scattering processes. An implicit scheme is implemented to simultaneously solve the primitive inversion problem together with the radiation-matter coupling source terms, providing stability over a broad range of opacities and optical depths where the interaction terms can be stiff. We discuss our formulations and numerical methods, and validate our methods against a wide variety of test problems spanning optically thin to thick regimes in flat, weakly curved, and strongly curved spacetimes.

Keywords: computational methods; radiative magnetohydrodynamics; astrophysical fluid dynamics
A Comparative Study of Host Galaxy Properties between Fast Radio Bursts and Stellar Transients

Recent arcsecond localizations of fast radio bursts and identifications of their host galaxies confirmed their extragalactic origin. While FRB 121102 resides in the bright region of a dwarf star-forming galaxy, other FRBs reside in more massive galaxies and are related to older stellar populations. We compare the host galaxy properties of nine FRBs with those of several types of stellar transients: from young to old populations, long-duration gamma-ray bursts (LGRBs), superluminous supernovae (SLSNe), SNe Ibc, SNe II, SNe Ia, and short-duration gamma-ray bursts (SGRBs). We find that the stellar mass and star formation rate of the FRB host galaxies, taken as a whole sample, prefer a medium to old population, and are against a young population, similar to LGRBs and SLSNe by a null probability of 0.02. Individually, the host of FRB 121102 is consistent with that of young population objects; the environment of FRB 180924 is similar to that of SGRBs; and the environment of FRB 190523 is similar to those of SNe Ia. These results are consistent with the magnetar engine model for FRBs, if magnetars produced from extreme explosions (GRBs/SLSNe) and those from regular channels (e.g., those producing Galactic magnetars) can both produce FRBs.

Keywords: radio transient sources
The Birth of a Massive First-star Binary

We study the formation of massive Population III binary stars using a newly developed radiation hydrodynamics code with the adaptive mesh refinement and adaptive ray-tracing methods. We follow the evolution of a typical primordial star-forming cloud obtained from a cosmological hydrodynamics simulation. Several protostars form as a result of disk fragmentation and grow in mass by the gas accretion, which is finally quenched by the radiation feedback from the protostars. Our code enables us, for the first time, to consider the feedback by both the ionizing and dissociating radiation from the multiple protostars, which is essential for self-consistently determining their final masses. At the final step of the simulation, we observe a very wide (≳104 au) binary stellar system consisting of 60 and 70 M⊙ stars. One of the member stars also has two smaller mass (10 M⊙) companion stars orbiting at 200 and 800 au, making up a mini-triplet system. Our results suggest that massive binary or multiple systems are common among Population III stars.

Keywords: population iii stars; star formation; early universe
Strong Near-infrared Carbon Absorption in the Transitional Type Ia SN 2015bp

Unburned carbon is potentially a powerful probe of Type Ia supernova (SN) explosion mechanisms. We present comprehensive optical and near-infrared (NIR) data on the "transitional" Type Ia SN 2015bp. An early NIR spectrum ( $t=-9.9$ days with respect to B-band maximum) displays a striking C I 1.0693 μm line at 11.9 × 103 km s-1, distinct from the prominent Mg II 1.0927 μm feature, which weakens toward maximum light. SN 2015bp also displays a clear C II 6580 Å notch early ( $t=-10.9$ days) at 13.2 × 103 km s-1, consistent with our NIR carbon detection. At ${M}_{B}=-18.46$ , SN 2015bp is less luminous than a normal SN Ia and, along with iPTF 13ebh, is the second member of the transitional subclass to display prominent early-time NIR carbon absorption. We find it unlikely that the C I feature is misidentified He I 1.0830 μm because this feature grows weaker toward maximum light, while the helium line produced in some double-detonation models grows stronger at these times. Intrigued by these strong NIR carbon detections, but lacking NIR data for other SNe Ia, we investigated the incidence of optical carbon in the sample of nine transitional SNe Ia with early-time data (t ≲ -4 days). We find that four display C II 6580 Å, while two others show tentative detections, in line with the SN Ia population as a whole. We conclude that at least ~50% of transitional SNe Ia in our sample do not come from sub-Chandrasekhar-mass explosions due to the clear presence of carbon in their NIR and optical spectra. * This paper includes data gathered with the 6.5 m Magellan Telescope at Las Campanas Observatory, Chile.

Keywords: supernovae; observational astronomy; white dwarf stars; type ia supernovae
A New Member of the Milky Way's Family Tree: Characterizing the Pontus Merger of Our Galaxy

We study the Pontus structure-a recently discovered merger that brought in ~7 globular clusters in the course of the hierarchical buildup of the Milky Way's halo. Here, we analyze the stellar population of Pontus and examine (1) its phase-space distribution using the ESA/Gaia data set, (2) its metallicity and chemical abundances (i.e., [Fe/H], [α/Fe], [Mg/Fe], and [Al/Fe]) using the spectroscopic catalog of APOGEE DR17, and (3) the color-magnitude diagram that shows interesting features, including a possibly double horizontal branch and a small population of blue stragglers. In sum, the Pontus stars show some unique properties that suggest they likely originated from the merging of an independent satellite galaxy; however, future analysis will shed more light on the true nature of this structure. This chemodynamical analysis of Pontus stars is another step forward in our bigger quest to characterize all the merging events of our Milky Way.

Keywords: milky way stellar halo; chemical abundances; galaxy formation; surveys; galaxy kinematics