adsabs/SciX_UAT_keywords huggingface dataset:
Target Selection and Validation of DESI Luminous Red Galaxies

The Dark Energy Spectroscopic Instrument (DESI) is carrying out a five-year survey that aims to measure the redshifts of tens of millions of galaxies and quasars, including 8 million luminous red galaxies (LRGs) in the redshift range 0.4 < z ≲ 1.0. Here we present the selection of the DESI LRG sample and assess its spectroscopic performance using data from Survey Validation (SV) and the first two months of the Main Survey. The DESI LRG sample, selected using g, r, z, and W1 photometry from the DESI Legacy Imaging Surveys, is highly robust against imaging systematics. The sample has a target density of 605 deg-2 and a comoving number density of 5 × 10-4 h 3 Mpc-3 in 0.4 < z < 0.8; this is a significantly higher density than previous LRG surveys (such as SDSS, BOSS, and eBOSS) while also extending to z ~ 1. After applying a bright star veto mask developed for the sample, 98.9% of the observed LRG targets yield confident redshifts (with a catastrophic failure rate of 0.2% in the confident redshifts), and only 0.5% of the LRG targets are stellar contamination. The LRG redshift efficiency varies with source brightness and effective exposure time, and we present a simple model that accurately characterizes this dependence. In the appendices, we describe the extended LRG samples observed during SV.

Keywords: cosmology; redshift surveys
A Population-Informed Mass Estimate for Pulsar J0740+6620

Galactic double neutron star systems have a tight mass distribution around ∼1.35M⊙, but the mass distribution of all known pulsars is broader (Tauris et al. 2017). Here we reconstruct the Alsing et al. (2018), Antoniadis et al. (2016) bimodal mass distribution of pulsars observed in binary systems, incorporating data from observations of J0740+6620 which were not available at the time of those works. Because J0740+6620 is an outlier in the mass distribution with non-negligible uncertainty in its mass measurement, its mass receives a large correction from the population, becoming ${m}_{{\rm{J}}0740+6620}={2.03}_{-0.08}^{+0.10}\,{M}_{\odot }$ (median and 68% CI). Stochastic samples from our population model, including population-informed pulsar mass estimates, are available at https://github.com/farr/AlsingNSMassReplication and archived at Farr & Chatziioannou (2020).

Keywords: neutron stars
A Measurement of the Assembly of Milky Way Analogs at Redshifts 0.5 < z < 2 with Resolved Stellar Mass and Star Formation Rate Profiles

The resolved mass assembly of Milky Way–mass galaxies has been previously studied in simulations, the local Universe, and at higher redshifts using infrared (IR) light profiles. To better characterize the mass assembly of Milky Way analogs (MWAs), as well as their changes in star formation rate (SFR) and color gradients, we construct resolved stellar mass and SFR maps of MWA progenitors selected with abundance matching techniques up to z ∼2 using deep, multiwavelength imaging data from the Hubble Frontier Fields. Our results using stellar mass profiles agree well with previous studies that utilize IR light profiles, showing that the inner 2 kpc of the galaxies and the regions beyond 2 kpc exhibit similar rates of stellar mass growth. This indicates the progenitors of MWAs from z ∼ 2 to the present do not preferentially grow their bulges or their disks. The evolution of the SFR profiles indicates a greater decrease in SFR density in the inner regions versus the outer regions. Sérsic parameters indicate modest growth in the central regions at lower redshifts, perhaps indicating slight bulge growth. However, the Sérsic index does not rise above n ∼ 2 until z < 0.5, meaning these galaxies are still disk-dominated systems. We find that the half-mass radii of the MWA progenitors increase between 1.5 < z < 2, but remain constant at later epochs (z < 1.5). This implies mild bulge growth since z ∼ 2 in MWA progenitors, in line with previous MWA mass assembly studies.

Keywords: galaxy evolution; milky way evolution; high-redshift galaxies; galaxies
Young Stars near Cometary Globule CG 30 in the Tumultuous Gum Nebula

We have conducted a high-dispersion (R ∼ 34,000) optical spectroscopic study of 10 young stars near the cometary globule CG 30 in the Gum Nebula, a diffuse H II region home to at least 32 cometary globules. All 10 spectroscopically observed stars at the nebula's northern edge are of low mass (spectral types M4.5-K5), have broad Hα emission, and show spectral veiling. Eight of the 10 are classical T Tauri stars. We spectroscopically measure the photospheric properties of CG 30 IRS 4 inside CG 30. Though embedded, CG 30 IRS 4 is T Tauri-like, with relatively slow projected rotation and moderate veiling. Undepleted Li absorptions, strong Hα emissions, and positions well above the main sequence on an H-R diagram suggest that the 10 stars are ≲1 Myr old. Using our measurements, previous spectroscopy, and previous photometry of 11 other young stars in the area, we determine stellar, kinematic, and accretion properties of a total of 21 young stars. Shared radial velocities, proper motions, distances, and ages suggest that 14 of the young stars (including CG 30 IRS 4) are kinematically related to CG 30. From Gaia DR2 distances to six of these stars, we derive a distance of 358.1 ± 2.2 pc to the cometary globule complex CG 30/31/38. The CG 30 association has an accretor fraction of 29% ± 14%, low for quiescent clusters of similar age but consistent with other irradiated clusters. The Gum Nebula's moderate radiation environment ( ${G}_{0}={6.6}_{-2.7}^{+3.2}$ at CG 30) may be strong enough to shorten disk lifetimes.

Keywords: young star clusters; cometary globules; stellar accretion disks; protoplanetary disks; pre-main sequence; pre-main sequence stars; fundamental parameters of stars; low mass stars; stellar accretion; stellar properties; accretion; star forming regions
Turbulence-supported Massive Star Envelopes

The outer envelopes of massive (M ≳ 10 M ⊙) stars exhibit large increases in opacities from forests of lines and ionization transitions (particularly from iron and helium) that trigger near-surface convection zones. One-dimensional (1D) models predict density inversions and supersonic motions that must be resolved with computationally intensive three-dimensional (3D) radiation hydrodynamic (RHD) modeling. Only in the last decade have computational tools advanced to the point where ab initio 3D models of these turbulent envelopes can be calculated, enabling us to present five 3D RHD ATHENA++ models (four previously published and one new 13 M ⊙ model). When convective motions are subsonic, we find excellent agreement between 3D and 1D velocity magnitudes, stellar structure, and photospheric quantities. However, when convective velocities approach the sound speed, hydrostatic balance fails as the turbulent pressure can account for 80% of the force balance. As predicted by Henyey, we show that this additional pressure support leads to a modified temperature gradient, which reduces the superadiabaticity where convection is occurring. In addition, all five models display significant overshooting from the convection in the Fe convection zone. As a result, the turbulent velocities at the surface are indicative of those in the Fe zone. There are no confined convection zones as seen in 1D models. In particular, helium convection zones seen in 1D models are significantly modified. Stochastic low-frequency brightness variability is also present in the 13 M ⊙ model with comparable amplitude and characteristic frequency to observed stars.

Keywords: stellar physics; stellar convective zones; stellar surfaces; stellar structures
A New Limit on Intergalactic Magnetic Fields on Subkiloparsec Scales from Fast Radio Bursts

We use the measured scattering timescales of fast radio bursts (FRBs) from the CHIME catalog to derive an upper limit on the magnetic field on subkiloparsec scales in the intergalactic medium (IGM). A nonmagnetized, photoionized IGM is insufficient to explain the turbulent scattering at all redshifts, with a warm-hot component being marginally consistent with the data at z ~ 1. Accounting for the lower envelope of the temporal smearing distribution with a nonzero magnetic field leads to upper limits B < 10-30 nG on scales of 0.07-0.20 kpc in the IGM at z ~ 1-2. Our work introduces a novel technique to constrain small-scale magnetic fields in the IGM, in a regime unexplored by the rotation and dispersion measures of FRBs.

Keywords: radio transient sources; intergalactic medium; magnetic fields
SOFIA/HAWC+ View of an Extremely Luminous Infrared Galaxy: WISE 1013+6112

We present far-infrared (FIR) properties of an extremely luminous infrared galaxy (ELIRG) at zspec = 3.703, WISE J101326.25+611220.1 (WISE 1013+6112). This ELIRG is selected as an IR-bright dust-obscured galaxy based on the photometry from the Sloan Digital Sky Survey and the Wide-field Infrared Survey Explorer (WISE). In order to derive its accurate IR luminosity, we perform follow-up observations at 89 and 154 μm using the High-resolution Airborne Wideband Camera-plus (HAWC+) on board the 2.7 m Stratospheric Observatory For Infrared Astronomy (SOFIA) telescope. We conduct spectral energy distribution (SED) fitting with CIGALE using 15 photometric data (0.4-1300 μm). We successfully pin down FIR SED of WISE 1013+6112 and its IR luminosity is estimated to be LIR = (1.62 ± 0.08) × 1014L⊙, making it one of the most luminous IR galaxies in the universe. We determine the dust temperature of WISE 1013+6112 is Tdust = 89 ± 3 K, which is significantly higher than that of other populations such as submillimeter galaxies and FIR-selected galaxies at similar IR luminosities. The resultant dust mass is Mdust = (2.2 ± 0.1) × 108 M⊙. This indicates that WISE 1013+6112 has a significant active galactic nucleus and star-forming activity behind a large amount of dust.

Keywords: active galaxies; infrared galaxies; quasars; supermassive black holes
An Implementation of Stochastic Forces for the N-body Code REBOUND

We describe the implementation of a new module which can be used to simulate physical systems in which the motion of particles is affected by stochastic forces. Such forces are expected to be present in turbulent circumstellar disks or remnant planetesimal disks. Our implementation offers a convenient way to generate correlated noise with a user-specified amplitude and auto-correlation time for each particle. The module has minimal memory requirements and is freely available within the REBOUNDx additional effects library.

Keywords: n-body simulations; open source software; planetary migration
Modeling Kilonova Light Curves: Dependence on Nuclear Inputs

The mergers of binary neutron stars, as well as black hole-neutron star systems, are expected to produce an electromagnetic counterpart that can be analyzed to infer the element synthesis that occurred in these events. We investigate one source of uncertainties pertinent to lanthanide-rich outflows: the nuclear inputs to rapid neutron capture nucleosynthesis calculations. We begin by examining 32 different combinations of nuclear inputs: eight mass models, two types of spontaneous fission rates, and two types of fission daughter product distributions. We find that such nuclear physics uncertainties typically generate at least one order of magnitude uncertainty in key quantities such as the nuclear heating (one and a half orders of magnitude at 1 day post-merger), the bolometric luminosity (one order of magnitude at 5 days post-merger), and the inferred mass of material from the bolometric luminosity (factor of 8 when considering the 8-10 day region). Since particular nuclear processes are critical for determining the electromagnetic signal, we provide tables of key nuclei undergoing β-decay, α-decay, and spontaneous fission important for heating at different times, identifying decays that are common among the many nuclear input combinations.

Keywords: explosive nucleosynthesis; r-process; neutron stars; nuclear astrophysics; light curves; nucleosynthesis
LYRA. III. The Smallest Reionization Survivors

The dividing line between galaxies that are quenched by reionization ("relics") and galaxies that survive reionization (i.e., continue forming stars) is commonly discussed in terms of a halo mass threshold. We probe this threshold in a physically more complete and accurate way than has been possible to date, using five extremely high resolution (M target = 4 M ⊙) cosmological zoom-in simulations of dwarf galaxies within the halo mass range (1-4) × 109 M ⊙. The employed LYRA simulation model features resolved interstellar medium physics and individual, resolved supernova explosions. Interestingly, two out of five of the simulated dwarf galaxies lie close to the threshold mass but are neither full reionization relics nor full reionization survivors. These galaxies initially quench at the time of reionization but merely remain quiescent for ~500 Myr. At z ~ 5 they recommence star formation in a synchronous way and remain star-forming until the present day. The parallel timing indicates consistent sound-crossing and cooling times between the halos. While the star formation histories we find are diverse, we show that they are directly related to the ability of a given halo to retain and cool gas. Whereas the latter is most strongly dependent on the mass (or virial temperature) of the host halo at the time of reionization, it also depends on its growth history, the UV background (and its decrease at late times), and the amount of metals retained within the halo.

Keywords: galaxy formation; interstellar medium; reionization; dwarf galaxies; computational methods; galaxy quenching; population iii stars
Ne/O and Fe/O Characteristics of Large Solar Energetic Particle Events during Solar Cycles 23 and 24

We have examined the Ne/O and Fe/O characteristics of large solar energetic particle (SEP) events at the ion energy range of 3-40 MeV nucleon-1 during solar cycles 23 and 24. In each cycle, the solar activity displays an ~3 yr rising phase and a longer declining phase. While Fe-poor events only appeared in the declining phase of cycle 23, the properties of Fe-rich events were similar in the rising phases of both cycles. Also, very few Fe-rich events were seen in the declining phase of cycle 24. In addition, the Ne/O data in the corona, solar wind, and SEP events consistently reveal that the characteristics of SEP events are mainly governed by the solar wind turbulence status that exhibits a significant difference between slow and fast streams. During the rising phase of the solar cycles, slow streams are dominated by the two-dimensional turbulence component, which significantly reduces the injection energy of the quasi-perpendicular (Q-Perp) shock acceleration. Also, slow streams have an increased Ne/O ratio and hence enhanced temperature of coronal suprathermals, favoring the occurrence of Fe-rich events. In contrast, in the declining phase of the solar cycles, the fast streams are dominated by the slab turbulence component, which could significantly increase the injection energy of the Q-Perp shock acceleration. Consequently, in fast streams, most Fe-rich events originate from jet suprathermals. The coronal suprathermals may produce the Fe-poor events having abnormally low Ne/O ratios provided the speed of the associated coronal mass ejection is large enough.

Keywords: interplanetary turbulence; solar wind; solar particle emission; solar energetic particles; solar magnetic fields
Catching Tidal Dwarf Galaxies at a Later Evolutionary Stage with ALFALFA

We present deep optical imaging and photometry of four objects classified as "Almost-Dark" galaxies in the Arecibo Legacy Fast Arecibo L-band Feed Array (ALFALFA) survey because of their gas-rich nature and extremely faint or missing optical emission in existing catalogs. They have H I masses of 107-109 M ⊙ and distances of ~9-100 Mpc. Observations with the WIYN 3.5 m telescope and One Degree Imager reveal faint stellar components with central surface brightnesses of ~24-25 $\mathrm{mag}\,{\mathrm{arcsec}}^{-2}$ in the g band. We also present the results of H I synthesis observations with the Westerbork Synthesis Radio Telescope. These Almost-Dark galaxies have been identified as possible tidal dwarf galaxies (TDGs) based on their proximity to one or more massive galaxies. We demonstrate that AGC 229398 and AGC 333576 likely have the low dark matter content and large effective radii representative of TDGs. They are located much farther from their progenitors than previously studied TDGs, suggesting they are older and more evolved. AGC 219369 is likely dark matter dominated, while AGC 123216 has a dark matter content that is unusually high for a TDG, but low for a normal dwarf galaxy. We consider possible mechanisms for the formation of the TDG candidates such as a traditional major merger scenario and gas ejection from a high-velocity flyby. Blind H I surveys like ALFALFA enable the detection of gas-rich, optically faint TDGs that can be overlooked in other surveys, thereby providing a more complete census of the low-mass galaxy population and an opportunity to study TDGs at a more advanced stage of their life cycle.

Keywords: dwarf irregular galaxies; galaxy evolution; galaxy interactions; galaxy photometry
Optical Monitoring and Intraday Variabilities of BL Lacertae

BL Lacertae is a key monitoring target of the 1.26 m National Astronomical Observatory-Guangzhou University Infrared/Optical telescope. Within the monitored duration from 2020 September 4 to 2022 September 28, we report 13,948 observations at the g, r, and i bands (g band: 4498, r band: 4866, i band: 4584). (1) In the monitored duration, this source is located in a very bright and variable state. The maximum variabilities are Δm g = 2.013 ± 0.073 mag at g band, Δm r = 1.900 ± 0.049 mag at r band, and Δm i = 2.279 ± 0.089 mag at i band. (2) Among the gri intraday lightcurves, there are 104 portions of data sets displaying intraday variabilities (IDVs), with the IDV timescales (ΔT) being in the range of 15.84-375.84 minutes and the biggest variable value Δm = 0.430 ± 0.041 mag. (3) The distributions of ΔT show frequency-dependent behavior, and with the frequency increasing, ΔT tend to be shorter. The variable rates ( $V=\tfrac{{\rm{\Delta }}m}{{\rm{\Delta }}T}$ ) from the g band are more intense than the values (V r ) from the r band, but are more stable than the values (V i ) from the i band. (4) On three days (2020 September 7, 2020 September 19, and 2022 September 7), we find the intraday periodic oscillations, whose periods are around 150 minutes, 232 minutes, and 150 minutes, respectively, and which might come from the source "flickering." (5) Based on the distributions between flux densities (F gri ) and spectral indices (α), they show the bluer-when-brighter behaviors and some uneven locations, which should come from the ministructures of the jet, the shock-induced particle acceleration, or magnetic reconnection in the jet.

Keywords: galaxies; blazars; ccd photometry
Stellar Characterization of Keck HIRES Spectra with The Cannon

To accurately interpret the observed properties of exoplanets, it is necessary to first obtain a detailed understanding of host star properties. However, physical models that analyze stellar properties on a per-star basis can become computationally intractable for sufficiently large samples. Furthermore, these models are limited by the wavelength coverage of available spectra. We combine previously derived spectral properties from the Spectroscopic Properties of Cool Stars (SPOCS) catalog with generative modeling using The Cannon to produce a model capable of deriving stellar parameters ( $\mathrm{log}g$ , Teff, and $v\sin i$ ) and 15 elemental abundances (C, N, O, Na, Mg, Al, Si, Ca, Ti, V, Cr, Mn, Fe, Ni, and Y) for stellar spectra observed with Keck Observatory's High Resolution Echelle Spectrometer (HIRES). We demonstrate the high accuracy and precision of our model, which takes just ∼3 s to classify each star, through cross-validation with pre-labeled spectra from the SPOCS sample. Our trained model, which takes continuum-normalized template spectra as its inputs, is publicly available at https://github.com/malenarice/keckspec. Finally, we interpolate our spectra and employ the same modeling scheme to recover labels for 477 stars using archival stellar spectra obtained prior to Keck's 2004 detector upgrade, demonstrating that our interpolated model can successfully predict stellar labels for different spectrographs that have (1) sufficiently similar systematics and (2) a wavelength range that substantially overlaps with that of the post-2004 HIRES spectra.

Keywords: high resolution spectroscopy; spectroscopy; stellar abundances; metallicity; chemical abundances; stellar properties; stellar physics; exoplanets; catalogs; radial velocity; astrostatistics techniques; stellar spectral lines
WIYN Open Cluster Study LXXX: HDI CCD UBVRI Photometry of the Old Open Cluster NGC 7142 and Comparison to M67

We present UBVRI photometry of 8702 stars in a 0°5 × 0°5 field in the direction of NGC 7142, taken with the Half Degree Imager at the WIYN 0.9 m telescope, to improve knowledge of this cluster's basic parameters. Our photometry spans the ranges 10.6-20.4 mag in U, 10.6-22.0 mag in B, 10.0-21.8 mag in V, 9.2-20.7 mag in R, and 8.5-19.9 mag in I. Using color-color diagrams that employ all four color combinations that include U, versus B - V, we derive a reddening-metallicity relation for the cluster, with preferred values E(B - V) = 0.338 ± 0.031 mag for the left-edge fiducial of the main sequence and [Fe/H] = 0.0 ± 0.1 dex, where the Hyades cluster has been used as an unreddened reference cluster, the extinction relations of Cardelli have been employed, and the metallicity dependence of the Yonsei-Yale (Y2) isochrones has been assumed. Comparison of our data to the Y2 isochrones in multiple color-magnitude diagrams (CMDs) yields distance-metallicity and age-metallicity relations, with preferred values of $m-M=12.65\pm 0.23$ mag and age = ${4.0}_{+1.3}^{-0.7}$ Gyr. Re-evaluation of the parameters of M67 using Stetson's UBVI photometry yields [Fe/H] = -0.02 ± 0.05 dex, E(B - V) = 0.04 ± 0.01 mag, m - M = 9.75 ± 0.03 mag, and age = 3.85 ± 0.17 Gyr; we thus find the metallicity and age of the two clusters to be indistinguishable. A semi-independent analysis adopting the parameters of M67 and shifting the fiducials of the two clusters in six CMDs until they match strongly corroborates the values listed above. The differences between our inferred parallaxes and the Gaia DR2 values are 87 ± 60 μas for NGC 7142 and 48 ± 15 μas for M67, consistent with previous studies. * The WIYN Observatory is a joint facility of the University of Wisconsin-Madison, Indiana University, the National Optical Astronomy Observatory and the University of Missouri.

Keywords: open star clusters; johnson photometry; metallicity; interstellar reddening; stellar ages; stellar distance
SNART: Synchrotron Self Absorption Model For Non-relativistic Transients

We present SNART (DeMarchi & Finstad 2023), software for radio synchrotron self-absorption analysis, a generalized version of the model introduced in Chevalier, Chevalier & Fransson. SNART ingests flux density and frequency observations, fits them jointly, and outputs system physical parameters: magnetic field B, shock radius R, post shock energy U, electron number density n e , circumstellar density ρ CSM, and mass loss degenerate with wind velocity $\dot{M}/{v}_{\mathrm{wind}}$ . SNART is written in Python and is publicly available via GitHub. The repository hosts an in-depth derivation of the model and a detailed description of parameter definitions in the literature. SNART is a generalized treatment of synchrotron self absorption that leaves the choice of values for p (the power-law index of the electron distribution), q (shock front acceleration), θ (electron pitch angle, commonly π/2), and f (the "filling factor," often 0.5) explicit.

Keywords: interstellar synchrotron emission; supernovae; tidal disruption; radio transient sources; transient sources; high energy astrophysics; time domain astronomy; astronomy software