adsabs/SciX_UAT_keywords huggingface dataset:
Conditional H I Mass Functions and the H I-to-halo Mass Relation in the Local Universe

We present a new H I mass estimator that relates ${\mathrm{log}}_{10}$ (M HI/M *) to a linear combination of four galaxy properties: stellar surface mass density, color index u - r, stellar mass, and concentration index, with the scatter of individual galaxies around the mean H I mass modeled with a Gaussian distribution function. We calibrate the estimator using the xGASS sample, including both H I detection and nondetection, and constrain the model parameters through Bayesian inferences. Tests with mock catalogs demonstrate that our estimator provides unbiased H I masses for optical samples like SDSS. We apply our estimator to the SDSS spectroscopic sample to estimate the H I mass function (HIMF) of local galaxies, as well as the conditional H I mass function in galaxy groups and the H I-halo mass relation. Our HIMF agrees with the ALFALFA measurements at M HI ≳ 5 × 109 M ⊙, but with higher amplitude and a steeper slope at lower masses. We show that this discrepancy is caused primarily by the cosmic variance, which is corrected for the SDSS sample but not for ALFALFA. The total CHIMFs for all halo masses can be described by a single Schechter function, while those of central galaxies show a double-Gaussian profile. The total H I mass in a group increases monotonically with halo mass, but for central galaxies, the H I mass shows weak dependence on halo mass when M h ≳ 1012 M ☉. The observed H I-halo mass relation is not reproduced by current hydrodynamic simulations and semianalytic models of galaxy formation.

Keywords: neutral hydrogen clouds; interstellar clouds; galaxy dark matter halos; cold dark matter; cold neutral medium
A Study of the Soft X-Ray Emission Lines in NGC 4151. II. The Internal Plasma Properties

We showcase a tool suite that enables the fitting of soft X-ray spectra in active galactic nuclei (AGNs), without the need for specialist software, allowing access to AGN physics for school students. While these standardized Python tools were useful for measuring velocities, they offered significantly fewer capabilities for radiative recombination continua, and R and G ratios, utilized to obtain the internal plasma properties within the outflowing wind seen in NGC 4151. Although further work is required for these tools to be used in outreach projects, we present findings of the plasma temperature and density in NGC 4151 spanning a 15 yr period.

Keywords: active galactic nuclei; supermassive black holes; high resolution spectroscopy
Measurement of the Charge Exchange Cross Section for N7+, O7+ Ions in Collision with Atomic H

The absolute total cross sections for the charge exchange between highly charged ions 15N7+, O7+, and atomic H have been measured with the ion-atom merged-beams apparatus at Oak Ridge National Laboratory. The collision energy range is from 1224 down to 2 eV u-1, which covers outflowing hot components of astrophysical charge exchange plasmas like stellar-wind and supernova remnants. Good agreement with the previous measurements and theory is found for the collision energies above 100 eV u-1, while below 100 eV u-1 limited agreement is achieved with the available calculations. These cross-section data are useful for modeling X-ray emission resulting from the charge exchange at the interface of hot plasma interacting with ambient neutral gas.

Keywords: atomic physics; atomic data benchmarking; charge exchange recombination
Searching for New Globular Clusters in M31 with Gaia EDR3

We have found 50 new globular cluster (GC) candidates around M31 with Gaia Early Data Release 3 (EDR3), with the help of Pan-STARRS1 DR1 magnitudes and Pan-Andromeda Archaeological Survey (PAndAS) images. Based on the latest Revised Bologna Catalog and simbad, we trained two random forest (RF) classifiers, the first one to distinguish extended sources from point sources and the second one to further select GCs from extended sources. From 1.85 million sources of 16 m < g < 19.5 m and within a large area of ~392 deg2 around M31, we selected 20,658 extended sources and 1934 initial GC candidates. After visual inspection of the PAndAS images, to eliminate the contamination from noncluster sources, particularly galaxies, we finally got 50 candidates. These candidates are divided into three types (a, b, and c), according to their projected distance D to the center of M31 and their probability of being a true GC, P GC, which is calculated by our second RF classifier. Among these candidates, 14 are found to be associated (in projection) with the large-scale structures within the halo of M31. We also provide several simple parameter criteria for selecting extended sources effectively from Gaia EDR3, which can reach a completeness of 92.1% with a contamination fraction lower than 10%.

Keywords: globular star clusters; star clusters; random forests; observational astronomy
A Robust Test of the Existence of Primordial Black Holes in Galactic Dark Matter Halos

If very low mass primordial black holes (PBH) within the asteroid/moon-mass range indeed reside in galactic dark matter halos, they must necessarily collide with galactic neutron stars (NSs). These collisions must, again necessarily, form light black holes (LBHs) with masses of typical NSs, M LBH ≈ 1-2 M ⊙. LBHs may be behind events already detected by ground-based gravitational-wave detectors (GW170817, GW190425, and others such as a mixed stellar black hole-NS-mass event GW191219_163120), and most recently by microlensing (OGLE-BLG-2011-0462). Although the status of these observations as containing LBHs is not confirmed, there is no question that gravitational-wave detectors and microlensing are in principle and in practice capable of detecting LBHs. We have calculated the creation rate of LBHs resulting from these light primordial black hole (PBH) collisions with NSs. On this basis, we claim that if improved gravitational-wave detectors and microlensing statistics of the LBH events would indicate that the number of LBHs is significantly lower that what follows from the calculated creation rate, then this would be an unambiguous proof that there is no significant light PBH contribution to the galactic dark matter halos. Otherwise, if observed and calculated numbers of LBHs roughly agree, then the hypothesis of primordial black hole existence gets strong observational support, and in addition their collisions with NSs may be considered a natural creation channel for the LBHs, solving the problem of their origin, as it is known that they cannot be a product of standard stellar evolution.

Keywords: dark matter; primordial black holes; neutron stars; black holes
Reading Between the Lines: Investigating the Ability of JWST to Identify Discerning Features in exoEarth and exoVenus Transmission Spectra

The success of the Transiting Exoplanet Survey Satellite mission has led to the discovery of an abundance of Venus Zone terrestrial planets that orbit relatively bright host stars. Atmospheric observations of these planets play a crucial role in understanding the evolutionary history of terrestrial planets, past habitable states, and the divergence of Venus and Earth climates. The transmission spectrum of a Venus-like exoplanet can be difficult to distinguish from that of an Earthlike exoplanet however, which could severely limit what can be learned from studying exoVenuses. In this work we further investigate differences in transmission between hypothetical exoEarths and exoVenuses, both with varying amounts of atmospheric carbon dioxide (CO2). The exoEarths and exoVenuses were modeled assuming they orbit TRAPPIST-1 on the runaway greenhouse boundary. We simulated James Webb Space Telescope Near-Infrared Spectrograph PRISM transit observations of both sets of planets between 0.6 and 5.2 μm, and quantified the detectability of major absorption features in their transmission spectra. The exoEarth spectra include several large methane (CH4) features that can be detected in as few as six transits. The CH4 feature at 3.4 μm is the optimal for feature for discerning an exoEarth from an exoVenus since it is easily detectable and does not overlap with CO2 features. The sulfur dioxide (SO2) feature at 4.0 μm is the best indicator of an exoVenus, but it is detectable in atmospheres with reduced CO2 abundance.

Keywords: venus; exoplanet atmospheres; exoplanets; exoplanet atmospheric composition; transmission spectroscopy; observational astronomy; planetary science
Spectroscopic Determination of Stellar Parameters and Oxygen Abundances for Hyades/Field G-K Dwarfs

It has been suggested that Fe abundances of K dwarfs derived from Fe I and Fe II lines show considerable discrepancies, and oxygen abundances determined from high-excitation O I 7771-5 triplet lines are appreciably overestimated (the problem becoming more serious toward lower Teff), which, however, has not yet been widely confirmed. With the aim of clarifying this issue, we spectroscopically determined the atmospheric parameters of 148 G-K dwarfs (Hyades cluster stars and field stars) by assuming the classical Fe I/Fe II ionization equilibrium as usual, and determined their oxygen abundances by applying the non-local thermal equilibrium spectrum fitting analysis to O I 7771-5 lines. It turned out that the resulting parameters did not show any significant inconsistency with those determined by other methods (for example, the mean differences in Teff and $\mathrm{log}g from the well-determined solutions of Hyades dwarfs are mostly ≲100 K and ≲0.1 dex). Likewise, the oxygen abundances of Hyades stars are around [O/H] ∼ +0.2 dex (consistent with the metallicity of this cluster) without exhibiting any systematic Teff-dependence. Accordingly, we conclude that parameters can be spectroscopically evaluated to a sufficient precision in the conventional manner (based on the Saha-Boltzmann equation for Fe I/Fe II) and oxygen abundances can be reliably determined from the O I 7771-5 triplet for K dwarfs as far as stars of Teff ≳ 4500 K are concerned. We suspect that previously reported strongly Teff-dependent discrepancies may have stemmed mainly from overestimation of weak-line strengths and/or improper Teff scale.

Keywords: stellar abundances; stellar atmospheres; fundamental parameters of stars; late-type stars; open star clusters
The Impact of Low-luminosity AGNs on Their Host Galaxies: A Radio and Optical Investigation of the Kiloparsec-scale Outflow in MaNGA 1-166919

One way an active galactic nucleus (AGN) influences the evolution of their host galaxy is by generating a large-scale (kiloparsec-scale) outflow. The content, energetics, and impact of such outflows depend on the properties of both the AGN and host galaxy, and understanding the relationship between them requires measuring the properties of all three. In this paper, we do so by analyzing recent radio and optical integral field unit spectroscopic observations of MaNGA 1-166919. Our results indicate that the biconical outflow in this galaxy is powered by a low-luminosity, low Eddington ratio AGN ejecting material that drives ~100-200 km s-1 shocks into the surrounding interstellar medium-producing the hot, ionized gas and relativistic particles associated with the observed outflow. The energetics of the relativistic and ionized gas material produced at this shock are comparable, and both the mass outflow and kinetic power of the ionized gas in this outflow are higher than other AGNs with similar bolometric luminosities. Lastly, while the host galaxy's total star formation rate is comparable to that of other star-forming galaxies with a similar stellar mass, there is evidence that the outflow both suppresses and enhances star formation in its immediate surroundings.

Keywords: agn host galaxies; active galactic nuclei; low-luminosity active galactic nuclei; liner galaxies; radio continuum emission
Two Sites of r-process Production Assessed on the Basis of the Age-tagged Abundances of Solar Twins

Solar twins, i.e., stars that are nearly identical to the Sun, including their metallicities, in the solar vicinity show ages widely distributed from 0 to 10 Gyr. This fact matches the orbital history of solar twins in the new paradigm of galactic dynamics, in which stars radially move on the disk when they encounter transient spiral arms. This finding suggests that older twins were born closer to the Galactic center and traveled a longer distance to reach their present location, according to the hypothesis that chemical enrichment occurs more quickly and that solar metallicity is attained on a shorter timescale with a decreasing Galactocentric distance (RGC). We show that abundance patterns covering a wide range of heavy elements for solar twins sharing similar ages are identical and that their variation among different age groups can be understood on the basis of the age-RGC connection within the framework of Galactic chemical evolution. This study identifies the Galactic bulge as the birthplace of the oldest solar twins. Based on this scheme, we find that the relation between [r-process/Fe] and RGC for the inner Galactic region is incompatible with the hypothesis of a sole site for r-process production, that is, neutron star mergers, whose delay time distribution could be approximated by the power-law form (∝ tn). Alternatively, this relation suggests the presence of two distinct sites for r-process production: short-lived massive stars, ending with specific core-collapse supernovae, and neutron star mergers that are heavily inclined to emerge with longer delay times, as represented by n = 0-0.5.

Keywords: galactic bulge; galaxy chemical evolution; galaxy dynamics; milky way disk; solar abundances
Chemically Peculiar A and F Stars with Enhanced s-process and Iron-peak Elements: Stellar Radiative Acceleration at Work

We present ≳15,000 metal-rich ([Fe/H] > -0.2 dex) A and F stars whose surface abundances deviate strongly from solar abundance ratios and cannot plausibly reflect their birth material composition. These stars are identified by their high [Ba/Fe] abundance ratios ([Ba/Fe] > 1.0 dex) in the LAMOST DR5 spectra analyzed by Xiang et al. They are almost exclusively main-sequence and subgiant stars with Teff ≳ 6300 K. Their distribution in the Kiel diagram (Teff- $\mathrm{log}g$ ) traces a sharp border at low temperatures along a roughly fixed-mass trajectory (around 1.4 M⊙) that corresponds to an upper limit in convective envelope mass fraction of around 10-4. Most of these stars exhibit distinctly enhanced abundances of iron-peak elements (Cr, Mn, Fe, Ni) but depleted abundances of Mg and Ca. Rotational velocity measurements from GALAH DR2 show that the majority of these stars rotate slower than typical stars in an equivalent temperature range. These characteristics suggest that they are related to the so-called Am/Fm stars. Their abundance patterns are qualitatively consistent with the predictions of stellar evolution models that incorporate radiative acceleration, suggesting they are a consequence of stellar internal evolution, particularly involving the competition between gravitational settling and radiative acceleration. These peculiar stars constitute 40% of the whole population of stars with mass above 1.5 M⊙, affirming that "peculiar" photospheric abundances due to stellar evolution effects are a ubiquitous phenomenon for these intermediate-mass stars. This large sample of Ba-enhanced, chemically peculiar A/F stars with individual element abundances provides the statistics to test more stringently the mechanisms that alter the surface abundances in stars with radiative envelopes.

Keywords: am stars; barium stars; chemically peculiar stars; stellar types; heavy metal stars; chemical abundances; stellar abundances; stellar diffusion; stellar processes; stellar evolution; radiative processes; s-process
Evidence for Gravitational Lensing of GRB 200716C

Observationally, there is a small fraction of gamma-ray bursts (GRBs) with prompt emission observed by Fermi/GBM that are composed of two pulses. Occasionally, the distance to a GRB may be lensed when a high mass astrophysical object resides in the path between the GRB source and observer. In this paper, we describe GRB 200716C, which has a two-pulse emission and duration of a few seconds. We present a Bayesian analysis identifying gravitational lensing in both temporal and spectral properties, and calculate the time delay (Δt ~ 1.92 s) and magnification (γ ~ 1.5) between those two pulses based on the temporal fits. One can roughly estimate the lens mass to be about 2.4 × 105M⊙ in the rest frame. We also calculate the false alarm probability for this detection to be about 0.07% with trial factors, and a present-day number density of about 808Mpc-3 with an energy density Ω ~ 1.4 × 10-3. If the first pulse of this GRB near the trigger time is indeed gravitationally echoed by a second pulse, GRB 200716C may be a short GRB candidate with extended emission.

Keywords: gamma-ray bursts; gravitational lensing
TREASUREHUNT: Transients and Variability Discovered with HST in the JWST North Ecliptic Pole Time-domain Field

The James Webb Space Telescope (JWST) North Ecliptic Pole (NEP) Time-domain Field (TDF) is a >14' diameter field optimized for multiwavelength time-domain science with JWST. It has been observed across the electromagnetic spectrum both from the ground and from space, including with the Hubble Space Telescope (HST). As part of HST observations over three cycles (the "TREASUREHUNT" program), deep images were obtained with the Wide Field Camera on the Advanced Camera for Surveys in F435W and F606W that cover almost the entire JWST NEP TDF. Many of the individual pointings of these programs partially overlap, allowing an initial assessment of the potential of this field for time-domain science with HST and JWST. The cumulative area of overlapping pointings is ∼88 arcmin2, with time intervals between individual epochs that range between 1 day and 4+ yr. To a depth of m AB ≃ 29.5 mag (F606W), we present the discovery of 12 transients and 190 variable candidates. For the variable candidates, we demonstrate that Gaussian statistics are applicable and estimate that ∼80 are false positives. The majority of the transients will be supernovae, although at least two are likely quasars. Most variable candidates are active galactic nuclei (AGNs), where we find 0.42% of the general z ≲ 6 field galaxy population to vary at the ∼3σ level. Based on a 5 yr time frame, this translates into a random supernova areal density of up to ∼0.07 transients arcmin‑2 (∼245 deg‑2) per epoch and a variable AGN areal density of ∼1.25 variables arcmin‑2 (∼4500 deg‑2) to these depths.

Keywords: time domain astronomy; transient sources; supernovae; agn host galaxies; hst photometry
Chromospheric Activity of M Stars Based on LAMOST Low- and Medium-resolution Spectral Surveys

We have used the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) low-resolution and medium-resolution spectroscopic surveys to explore the chromospheric statistical properties and variations of M stars. There are 738,477 LAMOST low-resolution spectra of 622,523 M stars. We have calculated equivalent widths of the Ca II H&K, Hα, Hβ, Hγ, Hδ, He I D3, and Ca II infrared triplet lines. Based on the Hα EWs, we found that 33,374 objects showed Hα emissions. We revised the relationship between the active fraction and spectral subtype, and confirmed that the active fractions increased from M0 to M3, and possibly declined from M4 to subsequent types. Among 86,005 objects with repeated spectra, 19,422 objects showed Hα variations. The variation fraction of stars with M4 and subsequent types with a fully convective envelope was higher than those of M0-M3 with a partially convective envelope. By combining the distances from Gaia, we have determined the positions of the M dwarfs in the catalog for M stars. The active fraction decreased rapidly in the height range of 0-400 pc above and below the Galactic plane, and maintained a steady trend in 400-1000 pc. We cross-matched the M catalog of the LAMOST low-resolution survey with LAMOST medium-resolution spectra. We obtained 272,181 spectra of 13,355 M objects and calculated the Hα EWs. Among them, 3813 stars show variations, which might be caused by chromospheric activity evolution with orbital phase or time. The Hα emission for 972 objects shows variations over short and long timescales, especially on short timescales of 20 minutes.

Keywords: stellar activity; stellar chromospheres; m stars
Constraints on the Cosmological Parameters with Three-Parameter Correlation of Gamma-Ray Bursts

As one of the most energetic and brightest events, gamma-ray bursts (GRBs) can be treated as a promising probe of the high-redshift universe. Similar to type Ia supernovae, GRBs with the same physical origin could be treated as standard candles. We select GRB samples with the same physical origin, which are divided into two groups. The first group consists of 31 GRBs with a plateau phase feature of a constant luminosity followed by a decay index of about -2 in the X-ray afterglow light curves, and the second group has 50 GRBs with a shallow decay phase in the optical light curves. For the selected GRB samples, we confirm that there is a tight correlation between the plateau luminosity L 0, the end time of plateau t b , and the isotropic energy release E γ,iso. We also find that the L 0-t b - E γ,iso correlation is insensitive to the cosmological parameters and that no valid limitations on the cosmological parameters can be obtained using this correlation. We explore a new three-parameter correlation L 0, t b , and the spectral peak energy in the rest-frame E p,i (L 0-t b -E p,i ), and find that this correlation can be used as a standard candle to constrain the cosmological parameters. By employing the optical sample only, we find the constraints of ${{\rm{\Omega }}}_{m}={0.697}_{-0.278}^{+0.402}(1\sigma )$ for a flat ΛCDM model. For the non-flat ΛCDM model, the best-fitting results are ${{\rm{\Omega }}}_{m}={0.713}_{-0.278}^{+0.346}$ , ${{\rm{\Omega }}}_{{\rm{\Lambda }}}={0.981}_{-0.580}^{+0.379}(1\sigma )$ . For the combination of the X-ray and optical samples, we find ${{\rm{\Omega }}}_{m}={0.313}_{-0.125}^{+0.179}(1\sigma )$ for a flat ΛCDM model, and ${{\rm{\Omega }}}_{m}={0.344}_{-0.112}^{+0.176}$ , ${{\rm{\Omega }}}_{{\rm{\Lambda }}}={0.770}_{-0.416}^{+0.366}(1\sigma )$ for a non-flat ΛCDM model.

Keywords: gamma-ray bursters; cosmological parameters; magnetars
Far-ultraviolet Absorption and Photoluminescence of Monolayer Graphene and Its Implications for Extended Red Emission

A monolayer graphene (GR) film on a lithium fluoride substrate was prepared to measure the optical properties of graphene in the far-UV region. The photoabsorption of the GR/LiF sample was universal in the spectral region of 105-350 nm, with an excitonic band near 130 nm and the absorbance of the GR/LiF sample at 10 K was ∼10% larger than that at 300 K. Upon far-UV excitation, the photoluminescence (PL) spectra of the GR/LiF sample showed a broad band at 630 nm at 300 K and two adjacent bands at 560 and 634 nm at 10 K. GR had a PL similar to the extended red emission (ERE) band, fulfilling the known observational model constraints of the light-driven process dominated by far-UV excitations, carbonaceous nature of ERE carriers, and broad emission in the red and near-IR regions. The result implies that graphene materials are promising candidates for carriers for the ERE.

Keywords: interstellar emissions; laboratory astrophysics; astrochemistry; radiative processes