adsabs/SciX_UAT_keywords huggingface dataset:
Lyα Line Properties at z = 3.78 and Their Environmental Dependence: A Case Study around a Massive Protocluster

Lyα-emitting galaxies (LAEs) are easily detectable in the high-redshift universe and are potentially efficient tracers of large-scale structure at early epochs, as long as their observed properties do not depend strongly on environment. We investigate the luminosity and equivalent width functions of LAEs in the overdense field of a protocluster at redshift z ≃ 3.78. Using a large sample of LAEs (many spectroscopically confirmed), we find that the Lyα luminosity distribution is well represented by a Schechter function with $\mathrm{log}({L}^{* }/\mathrm{erg}\ {{\rm{s}}}^{-1})={43.26}_{-0.22}^{+0.20}$ and $\mathrm{log}({\phi }^{* }/{\mathrm{Mpc}}^{-3})=-{3.40}_{-0.04}^{+0.03}$ with α = -1.5. Fitting the equivalent width distribution as an exponential, we find a scale factor of $\omega ={79}_{-15}^{+15}$ Å. We also measured the Lyα luminosity and equivalent width functions using the subset of LAEs lying within the densest cores of the protocluster, finding similar values for L* and ω. Hence, despite having a mean overdensity more than 2× that of the general field, the shapes of the Lyα luminosity function and equivalent width distributions in the protocluster region are comparable to those measured in the field LAE population by other studies at similar redshift. While the observed Lyα luminosities and equivalent widths show correlations with the UV continuum luminosity in this LAE sample, we find that these are likely due to selection biases and are consistent with no intrinsic correlations within the sample. This protocluster sample supports the strong evolutionary trend observed in the Lyα escape fraction and suggests that LAEs at lower redshift can be on average significantly more dusty that their counterparts at higher redshift.

Keywords: high-redshift galaxies; protoclusters; luminosity function; narrow band photometry; high-redshift galaxy clusters
A Systematic Study of the Dust of Galactic Supernova Remnants. I. The Distance and the Extinction

By combining the photometric, spectroscopic, and astrometric information of the stars in the sightline of supernova remnants (SNRs), the distances to and the extinctions of 32 Galactic SNRs are investigated. The stellar atmospheric parameters are from the Sloan Digital Sky Survey-DR14/Apache Point Observatory Galaxy Evolution Experiment and Large sky Area Multi-Object fiber Spectroscopic Telescope-DR5/LEGUE spectroscopic surveys. The multiband photometry, from optical to infrared, are collected from the Gaia, APASS, Pan-STARRS1, Two Micron All Sky Survey, and Wide-field Infrared Survey Explorer surveys. With the calibrated Gaia distances of individual stars, the distances to 15 of 32 SNRs are well determined from their produced extinction and association with molecular clouds. The upper limits of distance are derived for three SNRs. The color excess ratios E({g}P1-λ)/E({g}P1-{r}P1) of 32 SNRs are calculated, and their variation with wavebands is fitted by a simple dust model. The inferred dust grain size distribution bifurcates: while the graphite grains have comparable size to the average interstellar medium dust, the silicate grains are generally larger. Along the way, the average extinction law from optical to near-infrared of the Milky Way is derived from the 1.3-million-star sample and found to agree with the CCM89 law with RV=3.15.

Keywords: extinction; supernova remnants; interstellar dust
The Galaxy-Halo Connection of DESI Luminous Red Galaxies with Subhalo Abundance Matching

We use subhalo abundance and age distribution matching to create magnitude-limited mock galaxy catalogs at z ~ 0.43, 0.52, and 0.63 with z-band and 3.4 μm W1-band absolute magnitudes and r - z and r - W1 colors. From these magnitude-limited mocks, we select mock luminous red galaxy (LRG) samples according to the (r - z)-based (optical) and (r - W1)-based (infrared) selection criteria for the LRG sample of the Dark Energy Spectroscopic Instrument (DESI) survey. Our models reproduce the number densities, luminosity functions, color distributions, and projected clustering of the DESI Legacy Surveys that are the basis for DESI LRG target selection. We predict the halo occupation statistics of both optical and IR DESI LRGs at fixed cosmology and assess the differences between the two LRG samples. We find that IR-based SHAM modeling represents the differences between the optical and IR LRG populations better than using the z band and that age distribution matching overpredicts the clustering of LRGs, implying that galaxy color is uncorrelated with halo age in the LRG regime. Both the optical and IR DESI LRG target selections exclude some of the most luminous galaxies that would appear to be LRGs based on their position on the red sequence in optical color-magnitude space. Both selections also yield populations with a nontrivial LRG-halo connection that does not reach unity for the most massive halos. We find that the IR selection achieves greater completeness (≳90%) than the optical selection across all redshift bins studied.

Keywords: large-scale structure of the universe; galaxies
Gravitational-wave Captures by Intermediate-mass Black Holes in Galactic Nuclei

Intermediate-mass black holes (IMBHs) have not been detected beyond any reasonable doubt, despite their potential role as massive seeds for quasars and sources of tidal disruption events, ultraluminous X-ray sources, dwarf galaxy feedback, and hypervelocity stars. Gravitational wave (GW) observations can help to find and confirm the existence of IMBHs. Current and upcoming detectors, such as LIGO, Virgo, KAGRA, LISA, ET, and DECIGO promise to identify the full range from stellar-mass to supermassive black holes. In this paper, we address the question of whether IMBHs can produce GWs in galactic nuclei. We consider the possibility that stellar black holes (SBHs) form bound systems and later coalesce with an IMBH through gravitational captures in the dense nucleus. We show that this mechanism is efficient for IMBH masses in the range $\sim 3\times {10}^{3}\,{M}_{\odot }$ - $2\times {10}^{4}\,{M}_{\odot }$ . We find that the typical distributions of peak frequencies and merger timescales depend mainly on the IMBH mass. In particular, the typical peak frequency is about 0.2 Hz, 0.1 Hz, 0.09 Hz, and 0.05 Hz for ${M}_{\mathrm{IMBH}}=5\times {10}^{3}\,{M}_{\odot }$ , $8\times {10}^{3}\,{M}_{\odot }$ , $1\times {10}^{4}\,{M}_{\odot }$ , and $2\times {10}^{4}\,{M}_{\odot }$ , respectively. Our results show that, at design sensitivity, both DECIGO and ET should be able to detect these IMBH-SBH mergers. Furthermore, most of the mergers will appear eccentric (e ≳ 0.1), providing an indication of their dynamical origin.

Keywords: gravitational wave detectors; gravitational waves; galaxy kinematics; galactic center; intermediate-mass black holes; astrophysical black holes; black hole physics; galaxy dynamics; gravitational wave sources; stellar dynamics; galaxy nuclei; gravitational wave astronomy
The SDSS-HET Survey of Kepler Eclipsing Binaries. A Sample of Four Benchmark Binaries

The purpose of this work is to extend a sample of accurately modeled, benchmark-grade eclipsing binaries (EBs) with accurately determined masses and radii. We select four "well-behaved" Kepler binaries, KIC 2306740, KIC 4076952, KIC 5193386 and KIC 5288543, each with at least eight double-lined spectra from the Apache Point Observatory Galactic Evolution Experiment instrument that is part of the Sloan Digital Sky Surveys III and IV, and from the Hobby-Eberly High Resolution Spectrograph. We obtain masses and radii with uncertainties of 2.5% or less for all four systems. Three of these systems have orbital periods longer than 9 days, and thus populate an undersampled region of the parameter space for extremely well-characterized detached EBs. We compare the derived masses and radii against MESA MIST isochrones to determine the ages of the systems. All systems were found to be coeval, showing that the results are consistent across MESA MIST and PHOEBE.

Keywords: binary stars; close binary stars; detached binary stars; eclipsing binary stars; spectroscopic binary stars; fundamental parameters of stars
Chemical Abundances in Sgr A East: Evidence for a Type Iax Supernova Remnant

Recent observations have shown a remarkable diversity of observational behaviors and explosion mechanisms in thermonuclear supernovae (SNe). An emerging class of peculiar thermonuclear SNe, called Type Iax, show photometric and spectroscopic behaviors distinct from normal Type Ia. Their origin remains highly controversial, but pure turbulent deflagration of white dwarfs (WDs) has been regarded as the leading formation theory. The large population of Type Iax indicates the existence of unidentified Galactic Type Iax supernova remnants (SNRs). We report evidence that SNR Sgr A East in the Galactic center resulted from a pure turbulent deflagration of a Chandrasekhar-mass carbon-oxygen WD, an explosion mechanism used for Type Iax SNe. Our X-ray spectroscopic study of Sgr A East using 3 Ms of Chandra data shows a low ratio of intermediate-mass elements to Fe and large Mn/Fe and Ni/Fe ratios. This abundance pattern does not accord with the core-collapse or normal Type Ia models. Sgr A East is thus the first Galactic SNR for which a likely Type Iax origin has been proposed and is the nearest target for studying this peculiar class. We compared Sgr A East with the Fe-rich SNRs 3C 397 and W49B, which also have high Mn and Cr abundances and were claimed to result from deflagration-to-detonation explosions of Chandrasekhar-mass WDs (although with disputes). Our study shows that they have distinct abundance patterns. The X-ray spectroscopic studies of thermonuclear SNRs provide observational evidence for the theories that there are diverse explosion channels and various metal outputs for Chandrasekhar-mass WDs.

Keywords: supernova remnants; type ia supernovae; explosive nucleosynthesis; white dwarf stars; galactic center
Modeling the Transmission and Emission Spectra of K2-18b: Determining the Surfaces of Exoplanets with Hydrogen Dominated Atmospheres

Exoplanets between the sizes of Earth and Neptune are abundant in the universe yet absent in our solar system. We do not know if these "sub-Neptune" planets have a surface or how deep their surfaces may be. Recent studies have shown atmospheric chemistry may reflect the surface depth of these planets. In this work, we aim to determine if future observations-at wavelengths and resolutions applicable to JWST-can determine the surface pressure of sub-Neptunes. We present model transmission and emission spectra of the canonical sub-Neptune K2-18b assuming four different surface pressures. The transmission spectra indicate the shallow surface (1 bar) is the most distinguishable from the deeper surfaces, with differences at 2, 4-5, and 10 μm. The emission spectra also show the shallow surface as most distinguishable, noticeably around 3-4 μm.

Keywords: exoplanet surfaces; mini neptunes; exoplanet atmospheres; extrasolar gaseous planets; exoplanets
Simulated JWST Data Sets for Multispectral and Hyperspectral Image Fusion

The James Webb Space Telescope (JWST) will provide multispectral and hyperspectral infrared images of a large number of astrophysical scenes. Multispectral images will have the highest angular resolution, while hyperspectral images (e.g., with integral field unit spectrometers) will provide the best spectral resolution. This paper aims at providing a comprehensive framework to generate an astrophysical scene and to simulate realistic hyperspectral and multispectral data acquired by two JWST instruments, namely, NIRCam Imager and NIRSpec IFU. We want to show that this simulation framework can be resorted to assess the benefits of fusing these images to recover an image of high spatial and spectral resolutions. To do so, we make a synthetic scene associated with a canonical infrared source, the Orion Bar. We develop forward models including corresponding noises for the two JWST instruments based on their physical features. JWST observations are then simulated by applying the forward models to the aforementioned synthetic scene. We test a dedicated fusion algorithm we developed on these simulated observations. We show that the fusion process reconstructs the high spatio-spectral resolution scene with a good accuracy on most areas, and we identify some limitations of the method to be tackled in future works. The synthetic scene and observations presented in the paper can be used, for instance, to evaluate instrument models, pipelines, or more sophisticated algorithms dedicated to JWST data analysis. Besides, fusion methods such as the one presented in this paper are shown to be promising tools to fully exploit the unprecedented capabilities of the JWST.

Keywords: infrared astronomy; photodissociation regions; astronomy data analysis; direct imaging; astronomy data modeling; spectroscopy
Cosmology with Galaxy Cluster Weak Lensing: Statistical Limits and Experimental Design

We forecast constraints on the amplitude of matter clustering σ8(z) achievable with the combination of cluster weak lensing and number counts, in current and next-generation weak lensing surveys. We advocate for an approach, analogous to galaxy-galaxy lensing, in which the observables in each redshift bin are the mean number counts and the mean weak lensing profile of clusters above a mass proxy threshold. The primary astrophysical nuisance parameter is the logarithmic scatter ${\sigma }_{\mathrm{ln}M}$ between the mass proxy and true mass near the threshold. For surveys similar to the Dark Energy Survey (DES), the Roman Space Telescope High Latitude Survey (HLS), and the Rubin Observatory Legacy Survey of Space and Time (LSST), we forecast aggregate precision on σ8 of 0.26%, 0.24%, and 0.10%, respectively, if the mass-observable scatter is known externally to ${\rm{\Delta }}{\sigma }_{\mathrm{ln}M}\leqslant 0.01$ . These constraints would be degraded by about 20% for ${\rm{\Delta }}{\sigma }_{\mathrm{ln}M}=0.05$ in the case of DES or HLS and for ${\rm{\Delta }}{\sigma }_{\mathrm{ln}M}=0.016$ for LSST. A 1 month observing program with Roman Space Telescope targeting ∼2500 massive clusters could achieve a ∼ 0.5% constraint on σ8(z = 0.7) on its own, or a ∼ 0.33% constraint in combination with the HLS. Realizing the constraining power of clusters Requires accurate knowledge of the mass-observable relation and stringent control of systematics. We provide analytic approximations to our numerical results that allow for easy scaling to other survey assumptions or other methods of cluster mass estimation.

Keywords: galaxy clusters; cosmology; weak gravitational lensing; cosmological parameters; sigma8
Do High-spin High-mass X-Ray Binaries Contribute to the Population of Merging Binary Black Holes?

Gravitational-wave observations of binary black hole (BBH) systems point to black hole spin magnitudes being relatively low. These measurements appear in tension with high spin measurements for high-mass X-ray binaries (HMXBs). We use grids of MESA simulations combined with the rapid population-synthesis code COSMIC to examine the origin of these two binary populations. It has been suggested that Case-A mass transfer while both stars are on the main sequence can form high-spin BHs in HMXBs. Assuming this formation channel, we show that depending on the critical mass ratios for the stability of mass transfer, 48%-100% of these Case-A HMXBs merge during the common-envelope phase and up to 42% result in binaries too wide to merge within a Hubble time. Both MESA and COSMIC show that high-spin HMXBs formed through Case-A mass transfer can only form merging BBHs within a small parameter space where mass transfer can lead to enough orbital shrinkage to merge within a Hubble time. We find that only up to 11% of these Case-A HMXBs result in BBH mergers, and at most 20% of BBH mergers came from Case-A HMXBs. Therefore, it is not surprising that these two spin distributions are observed to be different.

Keywords: gravitational waves; stellar mass black holes; stellar evolution; high mass x-ray binary stars; roche lobe overflow
Gaia22dkvLb: A Microlensing Planet Potentially Accessible to Radial-velocity Characterization

We report discovering an exoplanet from following up a microlensing event alerted by Gaia. The event Gaia22dkv is toward a disk source rather than the traditional bulge microlensing fields. Our primary analysis yields a Jovian planet with at a projected orbital separation au, and the host is a ∼1.1 M ⊙ turnoff star at ∼1.3 kpc. At , the host is far brighter than any previously discovered microlensing planet host, opening up the opportunity to test the microlensing model with radial velocity (RV) observations. RV data can be used to measure the planet's orbital period and eccentricity, and they also enable searching for inner planets of the microlensing cold Jupiter, as expected from the "inner–outer correlation" inferred from Kepler and RV discoveries. Furthermore, we show that Gaia astrometric microlensing will not only allow precise measurements of its angular Einstein radius θ E but also directly measure the microlens parallax vector and unambiguously break a geometric light-curve degeneracy, leading to the definitive characterization of the lens system.

Keywords: gravitational microlensing exoplanet detection
The Study of Quasar Clustering at Low Redshifts

We use a nearest neighbor algorithm combined with the machine learning clustering function Density-Based Spatial Clustering of Applications with Noise to analyze a subset of quasars from the Sloan Digital Sky Survey. Our analysis shows evidence of clustering up to z ~ 2, with evidence of an increase in clustering at lower redshifts (z < 0.5). Our findings may suggest that, over time, the gravitational interaction between quasars has led to more clustering at low redshifts.

Keywords: quasars; clustering
Blasts from the Past: Supernova Shock Breakouts among X-Ray Transients in the XMM-Newton Archive

The first electromagnetic signal from a supernova (SN) is released when the shock crosses the progenitor surface. This shock breakout (SBO) emission provides constraints on progenitor and explosion properties. Observationally, SBOs appear as minute- to hour-long extragalactic X-ray transients. They are challenging to detect and only one SBO has been observed to date. Here, we search the XMM-Newton archive and find 12 new SN SBO candidates. We identify host galaxies to nine of these at estimated redshifts of 0.1-1. The SBO candidates have energies of ∼1046 erg, timescales of 30-3000 s, and temperatures of 0.1-1 keV. They are all consistent with being SN SBOs, but some may be misidentified Galactic foreground sources or other extragalactic objects. SBOs from blue supergiants agree well with most of the candidates. However, a few could be SBOs from Wolf-Rayet stars surrounded by dense circumstellar media, whereas two are more naturally explained as SBOs from red supergiants. The observations tentatively support non-spherical SBOs and are in agreement with asymmetries predicted by recent three-dimensional SN explosion simulations. eROSITA may detect ∼2 SBOs per year, which could be detected in live analyses and promptly followed up.

Keywords: core-collapse supernovae; x-ray transient sources; massive stars; shocks
(Nearly) Model-independent Constraints on the Neutral Hydrogen Fraction in the Intergalactic Medium at z 5-7 Using Dark Pixel Fractions in Lyα and Lyβ Forests

Cosmic reionization was the last major phase transition of hydrogen from neutral to highly ionized in the intergalactic medium (IGM). Current observations show that the IGM is significantly neutral at z > 7 and largely ionized by z ~ 5.5. However, most methods to measure the IGM neutral fraction are highly model dependent and are limited to when the volume-averaged neutral fraction of the IGM is either relatively low ( ${\overline{x}}_{{\rm{H}}\,{\rm\small{I}}}\lesssim {10}^{-3}$ ) or close to unity ( ${\overline{x}}_{{\rm{H}}\,{\rm\small{I}}}\sim 1$ ). In particular, the neutral fraction evolution of the IGM at the critical redshift range of z = 6-7 is poorly constrained. We present new constraints on ${\overline{x}}_{{\rm{H}}\,{\rm\small{I}}}$ at z ~ 5.1-6.8 by analyzing deep optical spectra of 53 quasars at 5.73 < z < 7.09. We derive model-independent upper limits on the neutral hydrogen fraction based on the fraction of "dark" pixels identified in the Lyα and Lyβ forests, without any assumptions on the IGM model or the intrinsic shape of the quasar continuum. They are the first model-independent constraints on the IGM neutral hydrogen fraction at z ~ 6.2-6.8 using quasar absorption measurements. Our results give upper limits of ${\overline{x}}_{{\rm{H}}\,{\rm\small{I}}}(z=6.3)\lt 0.79\pm 0.04$ (1σ), ${\overline{x}}_{{\rm{H}}\,{\rm\small{I}}}(z=6.5)\lt 0.87\pm 0.03$ (1σ), and ${\overline{x}}_{{\rm{H}}\,{\rm\small{I}}}(z=6.7)\lt {0.94}_{-0.09}^{+0.06}$ (1σ). The dark pixel fractions at z > 6.1 are consistent with the redshift evolution of the neutral fraction of the IGM derived from Planck 2018.

Keywords: reionization; intergalactic medium; cosmology
Gas Accretion Can Drive Turbulence in Galaxies

The driving of turbulence in galaxies is deeply connected with the physics of feedback, star formation, outflows, accretion, and radial transport in disks. The velocity dispersion of gas in galaxies therefore offers a promising observational window into these processes. However, the relative importance of each of these mechanisms remains controversial. In this work we revisit the possibility that turbulence on galactic scales is driven by the direct impact of accreting gaseous material on the disk. We measure this effect in a disk-like star-forming galaxy in IllustrisTNG, using the high-resolution cosmological magnetohydrodynamical simulation TNG50. We employ Lagrangian tracer particles with a high time cadence of only a few million years to identify accretion and other events. The energies of particles are measured by stacking the events in bins of time around the event. The average effect of each event is measured by fitting explicit models for the kinetic and turbulent energies as a function of time. These measurements are corroborated by cross-correlating the turbulent energy with other time series and searching for signals of causality, i.e., asymmetries across zero time lag. We find that accretion contributes to the large-scale turbulent kinetic energy even if it does not dominate in this ~5 × 109 M ⊙ stellar mass galaxy. Extrapolating this finding to a range of galaxy masses, we find that there are regimes where energy from direct accretion may dominate the turbulent energy budget, particularly in disk outskirts, galaxies less massive than the Milky Way, and at redshift ~2.

Keywords: galaxy physics; galaxy processes; galaxy dynamics; galaxy formation; high-redshift galaxies; disk galaxies; star formation