adsabs/SciX_UAT_keywords huggingface dataset:
The Impact of Star-formation-rate Surface Density on the Electron Density and Ionization Parameter of High-redshift Galaxies

We use the large spectroscopic data set of the MOSFIRE Deep Evolution Field survey to investigate some of the key factors responsible for the elevated ionization parameters (U) inferred for high-redshift galaxies, focusing in particular on the role of star-formation-rate surface density (ΣSFR). Using a sample of 317 galaxies with spectroscopic redshifts z spec ≃ 1.9-3.7, we construct composite rest-frame optical spectra in bins of ΣSFR and infer electron densities, n e, using the ratio of the [O II] λ λ3727, 3730 doublet. Our analysis suggests a significant (≃3σ) correlation between n e and ΣSFR. We further find significant correlations between U and ΣSFR for composite spectra of a subsample of 113 galaxies, and for a smaller sample of 25 individual galaxies with inferences of U. The increase in n e-and possibly also the volume filling factor of dense clumps in H II regions-with ΣSFR appear to be important factors in explaining the relationship between U and ΣSFR. Further, the increase in n e and SFR with redshift at a fixed stellar mass can account for most of the redshift evolution of U. These results suggest that the gas density, which sets n e and the overall level of star formation activity, may play a more important role than metallicity evolution in explaining the elevated ionization parameters of high-redshift galaxies. *Based on data obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W.M. Keck Foundation.

Keywords: galaxy evolution; high-redshift galaxies; galaxy abundances; emission line galaxies; ionization
Detection of Pb II in the Ultraviolet Spectra of Three Metal-poor Stars

We report the first detection of the Pb II line at 2203.534 Šin three metal-poor stars, using ultraviolet spectra obtained with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. We perform a standard abundance analysis assuming local thermodynamic equilibrium (LTE) to derive lead (Pb, Z = 82) abundances. The Pb II line yields a higher abundance than Pb I lines by +0.36 ± 0.34 dex and +0.49 ± 0.28 dex in the stars HD 94028 and HD 196944, where Pb I lines had been detected previously. The Pb II line is likely formed in LTE, and these offsets affirm previous calculations showing that Pb I lines commonly used as abundance indicators underestimate the Pb abundance in LTE. Pb is enhanced in the s-process-enriched stars HD 94028 ([Pb/Fe] = +0.95 ± 0.14) and HD 196944 ([Pb/Fe] = +2.28 ± 0.23), and we show that 208Pb is the dominant Pb isotope in these two stars. The $\mathrm{log}\varepsilon $ (Pb/Eu) ratio in the r-process-enhanced star HD 222925 is 0.76 ± 0.14, which matches the solar system r-process ratio and indicates that the solar system r-process residuals for Pb are, in aggregate, correct. The Th/Pb chronometer in HD 222925 yields an age of 8.2 ± 5.8 Gyr, and we highlight the potential of the Th/Pb chronometer as a relatively model-insensitive age indicator in r-process-enhanced stars. * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under NASA contract NAS 5-26555. These observations are associated with programs GO-14161, GO-14765, and GO-15657. This Letter includes data taken at The McDonald Observatory of The University of Texas at Austin.

Keywords: nucleosynthesis; r-process; s-process; stellar abundances; ultraviolet astronomy
Gaia Pulsars and Where to Find Them in EDR3

The Early Gaia Data Release 3 (EDR3) provides precise astrometry for nearly 1.5 billion sources across the entire sky. A few tens of these are associated with neutron stars in the Milky Way and Magellanic Clouds. Here, we report on a search for EDR3 counterparts to known rotation-powered pulsars using the method outlined in Antoniadis. A cross-correlation between EDR3 and the ATNF pulsar catalog identifies 41 close astrometric pairs (≲0"5 at the reference epoch of the pulsar position). Twenty six of these are related to previously known optical counterparts, while the rest are candidate pairs that require further follow-up. Highlights include the Crab Pulsar (PSR B0531+21), for which EDR3 yields a distance of ${2.08}_{-0.45}^{+0.78}$ kpc (or ${2.00}_{-0.38}^{+0.56}$ kpc taking into account the dispersion-measure prior; errors indicate 95% confidence limits) and PSR 1638-4608, a pulsar thus-far considered to be isolated that lies within 0"056 of a Gaia source.

Keywords: binary pulsars; millisecond pulsars; optical pulsars; radio pulsars; rotation powered pulsars; sky surveys
A Large-scale Kinematic Study of Molecular Gas in High-z Cluster Galaxies: Evidence for High Levels of Kinematic Asymmetry

We investigate the resolved kinematics of the molecular gas, as traced by the Atacama Large Millimeter/submillimeter Array in CO (2-1), of 25 cluster member galaxies across three different clusters at a redshift of z ~ 1.6. This is the first large-scale analysis of the molecular gas kinematics of cluster galaxies at this redshift. By separately estimating the rotation curve of the approaching and receding sides of each galaxy via kinematic modeling, we quantify the difference in total circular velocity to characterize the overall kinematic asymmetry of each galaxy. 3/14 of the galaxies in our sample that we are able to model have similar degrees of asymmetry as that observed in galaxies in the field at similar redshift based on observations of mainly ionized gas. However, this leaves 11/14 galaxies in our sample with significantly higher asymmetry, and some of these galaxies have degrees of asymmetry of up to ~50 times higher than field galaxies observed at similar redshift. Some of these extreme cases also have one-sided tail-like morphology seen in the molecular gas, supporting a scenario of tidal and/or ram pressure interaction. Such stark differences in the kinematic asymmetry in clusters versus the field suggest the evolutionary influence of dense environments, established as being a major driver of galaxy evolution at low redshift, is also active in the high-redshift universe.

Keywords: galaxy clusters; high-redshift galaxy clusters; galactic and extragalactic astronomy; radio astronomy; molecular gas; galaxy kinematics
Understanding the Variability of Helium Abundance in the Solar Corona Using Three-fluid Modeling and Ultraviolet Observations

The variability of helium abundance in the solar corona and the solar wind is an important signature of solar activity, solar cycle, and solar wind sources, as well as coronal heating processes. Motivated by recently reported remote-sensing UV imaging observations by Helium Resonance Scattering in the Corona and Heliosphere payload sounding rocket of helium abundance in the inner corona on 2009 September 14 near solar minimum, we present the results of the first three-dimensional three-fluid (electrons, protons, and alpha particles) model of tilted coronal streamer belt and slow solar wind that illustrates the various processes leading to helium abundance differentiation and variability. We find good qualitative agreement between the three-fluid model and the coronal helium abundance variability deduced from UV observations of streamers, providing insight on the effects of the physical processes, such as heating, gravitational settling, and interspecies Coulomb friction in the outflowing solar wind that produce the observed features. The study impacts our understanding of the origins of the slow solar wind.

Keywords: slow solar wind; solar coronal streamers; solar ultraviolet emission; magnetohydrodynamics
Mode Changing in PSR B0844-35 and PSR B1758-29 with Enhanced Emission at the Profile Centers

We have studied the single pulse emission from two pulsars, PSR B0844-35 and PSR B1758-29, over a wide frequency range of 300-750 MHz using the upgraded Giant Metrewave Radio Telescope. The two pulsars have relatively wide profiles with multiple components, which are a result of the line of sight traversing near the center of the emission beam. In both pulsars, the single pulse sequences show the presence of two distinct emission states, where the profiles become much brighter at the center, with prominent core components during one of the modes, while in the other mode the single pulses show odd-even subpulse drifting with a periodicity of around 2P, P being the rotation period of the pulsar. The centrally bright mode was seen for 10% of the observing duration in PSR B0844-35, which usually lasted for short durations of around 10 pulses, but had two longer sequences of around 100 pulses. On the contrary, the centrally bright mode was dominant in PSR B1758-29 and was seen for around 60% of the observing duration. PSR B1758-29 also showed period amplitude modulations of 60P-70P in both modes. The mode changing in these two pulsars facilitates investigation of the sparking process in the inner acceleration region, dominated by nondipolar magnetic fields. The change in the surface magnetic field configurations likely results in the emission mode change.

Keywords: radio pulsars; pulsars
SN 2022joj: A Peculiar Type Ia Supernova Possibly Driven by an Asymmetric Helium-shell Double Detonation

We present observations of SN 2022joj, a peculiar Type Ia supernova discovered by the Zwicky Transient Facility. SN 2022joj exhibits an unusually red g ZTF - r ZTF color at early times and a rapid blueward evolution afterward. Around maximum brightness, SN 2022joj shows a high luminosity ( ${M}_{{g}_{\mathrm{ZTF}},\max }\simeq -19.7$ mag), a blue broadband color (g ZTF - r ZTF ≃ -0.2 mag), and shallow Si II absorption lines, consistent with those of overluminous, SN 1991T-like events. The maximum-light spectrum also shows prominent absorption around 4200 Å, which resembles the Ti II features in subluminous, SN 1991bg-like events. Despite the blue optical-band colors, SN 2022joj exhibits extremely red ultraviolet minus optical colors at maximum luminosity (u - v ≃ 0.6 mag and uvw1 - v ≃ 2.5 mag), suggesting a suppression of flux at ~2500-4000 Å. Strong C II lines are also detected at peak. We show that these unusual spectroscopic properties are broadly consistent with the helium-shell double detonation of a sub-Chandrasekhar mass (M ≃ 1 M ⊙) carbon/oxygen white dwarf from a relatively massive helium shell (M s ≃ 0.04-0.1 M ⊙), if observed along a line of sight roughly opposite to where the shell initially detonates. None of the existing models could quantitatively explain all the peculiarities observed in SN 2022joj. The low flux ratio of [Ni II] λ7378 to [Fe II] λ7155 emission in the late-time nebular spectra indicates a low yield of stable Ni isotopes, favoring a sub-Chandrasekhar mass progenitor. The significant blueshift measured in the [Fe II] λ7155 line is also consistent with an asymmetric chemical distribution in the ejecta, as is predicted in double-detonation models.

Keywords: supernovae; type ia supernovae; white dwarf stars; observational astronomy; surveys
The Impact of Rotation Velocity on Measuring Magnetic Fields of K and M Stars

Magnetic fields are a critical component of interior and atmospheric models of low-mass stars. Additionally, stellar activity associated with magnetic fields may make exoplanets around K and M stars uninhabitable. Here we describe the measurement of the magnetic fields of K and M dwarfs from high-resolution spectra, and discuss the impact of projected rotational velocity (v sin i) on these measurements. We determine the magnetic fields by measuring the Zeeman effect on Na, Ti, and Ca spectral lines. Observed spectra in our analysis come from the Immersion GRating INfrared Spectrometer (IGRINS), while synthetic spectra were created using the MoogStokes software along with MARCS atmosphere models. We found that measuring Zeeman splitting in R ∼ 45,000 spectra is limited primarily by the projected rotational velocity of the star, but also by spectral resolution, line strength, and spectral signal-to-noise.

Keywords: stellar magnetic fields; low mass stars; brown dwarfs; infrared astronomy
Luminosity Functions of the Host Galaxies of Supernova

We present the luminosity functions and stellar mass functions of supernova (SN) host galaxies and test if they differ from the functions of normal field galaxies. We utilize homogeneous samples consisting of 273 SNe Ia (z ≤ 0.3) and 44 core-collapse (CC) SNe (z ≤ 0.1) from the Sloan Digital Sky Survey II Supernova Survey and the high-signal-to-noise-ratio photometry of galaxies from the Hyper Suprime-Cam Subaru Strategic Program. SN hosts are classified into star-forming and passive galaxy groups based on the spectral energy distribution fitting. We find that the SN host luminosity functions and stellar mass functions deviate from those of normal field galaxies. Star-forming galaxies dominate the low-mass end of the SN Ia host mass function, while passive galaxies dominate the high-mass end. CC SNe are predominantly hosted by star-forming galaxies. In addition, intermediate-mass hosts produce CC SNe with the highest efficiency, while the efficiency of producing SNe Ia monotonically increases as the hosts become more massive. Furthermore, we derive the pseudo mass normalized SN rates (pSNuM) based on the mass functions. We find that the star-forming component of pSNuM Ia is less sensitive to the changes in stellar mass, in comparison with the total rate. The behavior of pSNuM CC suggests that the CC rate is proportional to the star-forming rate.

Keywords: supernovae; luminosity function; type ia supernovae; core-collapse supernovae; stellar mass functions
Cosmology Large Angular Scale Surveyor (CLASS): 90 GHz Telescope Pointing, Beam Profile, Window Function, and Polarization Performance

The Cosmology Large Angular Scale Surveyor (CLASS) is a telescope array that observes the cosmic microwave background (CMB) over ∼75% of the sky from the Atacama Desert, Chile, at frequency bands centered near 40, 90, 150, and 220 GHz. CLASS measures the large angular scale CMB polarization to constrain the tensor-to-scalar ratio and the optical depth to last scattering. This paper presents the optical characterization of the 90 GHz telescope. Observations of the Moon establish the pointing while dedicated observations of Jupiter are used for beam calibration. The standard deviations of the pointing error in azimuth, elevation, and boresight angle are 1.'3, 2.'1, and 2.'0, respectively, over the first 3 yr of observations. This corresponds to a pointing uncertainty ∼7% of the beam's full width at half-maximum (FWHM). The effective azimuthally symmetrized instrument 1D beam estimated at 90 GHz has an FWHM of 0.°620 ± 0.°003 and a solid angle of 138.7 ± 0.6(stats.) ± 1.1(sys.) μsr integrated to a radius of 4°. The corresponding beam window function drops to at ℓ = 30, 100, 300, respectively. Far-sidelobes are studied using detector-centered intensity maps of the Moon and measured to be at a level of 10‑3 or below relative to the peak. The polarization angle of Tau A estimated from preliminary survey maps is 149°.6 ± 0°.2(stats.) in equatorial coordinates. The instrumental temperature-to-polarization (T → P) leakage fraction, inferred from per-detector demodulated Jupiter scan data, has a monopole component at the level of 1.7 × 10‑3, a dipole component with an amplitude of 4.3 × 10‑3, with no evidence of quadrupolar leakage.

Keywords: astronomical instrumentation; telescopes; polarimeters; cosmic microwave background radiation; observational cosmology
Mars' Formation Can Constrain the Primordial Orbits of the Gas Giants

Recent high-precision meteoritic data infers that Mars finished its accretion rapidly within 10 Myr of the beginning of the Solar System and had an accretion zone that did not entirely overlap with the Earth's. Here we present a detailed study of the accretion zone of planetary embryos from high-resolution simulations of planetesimals in a disk. We found that all simulations with Jupiter and Saturn on their current eccentric orbits (EJS) result in a similar accretion zone between fast-forming Mars and Earth-region embryos. Assuming more circular orbits for Jupiter and Saturn (CJS), on the other hand, has a significantly higher chance of forming Mars with an accretion zone not entirely dominated by Earth and Venus-region embryos; however, CJS in general forms Mars slower than in EJS. By further quantifying the degree of overlap between accretion zones of embryos in different regions with the average overlap coefficient (OVL), we found that the OVL of CJS shows a better match with the OVL from a chondritic isotopic mixing model of Earth and Mars, which indicates that the giant planets are likely to have resided on more circular orbits during gas disk dissipation than they do today, matching their suggested pre-instability orbits. More samples, including those from Mercury and Venus, could potentially confirm this hypothesis.

Keywords: mars; n-body simulations; cosmochronology; planet formation; cosmochemistry; meteorites
Photometric Confirmation and Characterization of the Ennomos Collisional Family in the Jupiter Trojans

Collisional families offer a unique window into the interior composition of asteroid populations. Previous dynamical studies of the Jupiter Trojans have uncovered a handful of potential collisional families, two of which have been subsequently confirmed through spectral characterization. In this paper, we present new multiband photometric observations of the proposed Ennomos family and derive precise g - i colors of 75 candidate family members. While the majority of the targets have visible colors that are indistinguishable from background objects, we identify 13 objects with closely grouped dynamical properties that have significantly bluer colors. We determine that the true Ennomos collisional family is tightly confined to $a{{\prime} }_{p}\gt 5.29\,\mathrm{au}$ and $0.45\lt \sin {i}_{p}\lt 0.47$ , and the majority of its confirmed members have near-solar spectral slopes, including some of the bluest objects hitherto discovered in the Trojan population. The property of distinctly neutral colors that is shared by both the Ennomos family and the previously characterized Eurybates family indicates that the spectral properties of freshly exposed surfaces in the Jupiter region are markedly different than the surfaces of uncollided Trojans. This implies that the processes of ice sublimation and space weathering at 5.2 au yield a distinct regolith chemistry from the primordial environment within which the Trojans were initially accreted. It also suggests that the Trojans were emplaced in their present-day location from elsewhere sometime after the initial population formed, which is a key prediction of recent dynamical instability models of solar system evolution.

Keywords: jupiter trojans; multi-color photometry; surface composition
On the Energetics of a Possible Relativistic Jet Associated with the Binary Neutron Star Merger Candidate S190425z

Advanced LIGO and Virgo (AdvLIGO/VIRGO) detectors reported the first binary neutron star merger candidate in the third observing run, S190425z, on 2019 April 25. A weak γ-ray excess was reported nearly coincidentally by the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) satellite, which accidentally covered the entire localization region of AdvLIGO/VIRGO. Electromagnetic follow-up in longer wavelengths has not lead to the detection of any associated counterparts. Here we combine the available information from gravitational wave measurements and upper limits of fluence from INTEGRAL to show that the observations are completely consistent with a relativistic Gaussian structured jet and a typical short duration gamma-ray burst (GRB) being produced in the merger. We obtain posterior bounds on the on-axis isotropic equivalent energy of the associated GRB under different prior distributions. This study demonstrates that even limited gravitational wave and electromagnetic information could be combined to produce valuable insights about outflows from mergers. Future follow-ups may help constrain the jet structure further, especially if there is an orphan afterglow detection associated with the candidate.

Keywords: gravitational wave sources
Possible Periodic Activity in the Short Bursts of SGR 1806-20: Connection to Fast Radio Bursts

Magnetars are highly magnetized neutron stars that are characterized by recurrent emission of short-duration bursts in soft gamma-rays/hard X-rays. Recently, FRB 200428 was found to be associated with an X-ray burst from a Galactic magnetar. Two fast radio bursts show mysterious periodic activity. However, it is unclear whether magnetar X-ray bursts are periodic phenomena. In this paper, we investigate the activity period of SGR 1806-20. More than 3000 short bursts observed by different telescopes are collected, including the observations of RXTE, HETE-2, ICE, and Konus. We consider the observation windows and divide the data into two subsamples to alleviate the effect of uneven sampling. The epoch-folding and Lomb-Scargle methods are used to derive the period of the short bursts. We find a possible period of about 398.20 ± 25.45 days, but other peaks exist in the periodograms. If the period is real, the connection between short bursts of magnetars and fast radio bursts should be investigated extensively.

Keywords: radio transient sources; magnetars; soft gamma-ray repeaters
Impact of Dark Photon Emission on Massive Star Evolution and Pre-supernova Neutrino Signal

We study the effects of additional cooling due to the emission of a dark matter candidate particle, the dark photon, on the final phases of the evolution of a 15 M⊙ star and resulting modifications of the pre-supernova neutrino signal. For a substantial portion of the dark photon parameter space the extra cooling speeds up Si burning, which results in a reduced number of neutrinos emitted during the last day before core collapse. This reduction can be described by a systematic acceleration of the relevant timescales and the results can be estimated semi-analytically in good agreement with the numerical simulations. Outside the semi-analytic regime we find more complicated effects. In a narrow parameter range, low-mass dark photons lead to an increase in the number of emitted neutrinos because of additional shell-burning episodes that delay core collapse. Furthermore, relatively strong couplings produce a thermonuclear runaway during O burning, which could result in a complete disruption of the star but requires more detailed simulations to determine the outcome. Our results show that pre-supernova neutrino signals are a potential probe of the dark photon parameter space.

Keywords: late stellar evolution; supernova neutrinos; dark matter; massive stars
Radiation GRMHD Simulations of the Hard State of Black Hole X-Ray Binaries and the Collapse of a Hot Accretion Flow

We present global radiation GRMHD simulations of strongly magnetized accretion onto a spinning, stellar mass black hole at sub-Eddington rates. Using a frequency-dependent Monte Carlo procedure for Compton scattering, we self-consistently evolve a two-temperature description of the ion-electron fluid and its radiation field. For an Eddington ratio L/LEdd ≳ 10-3, the emergent spectrum forms an apparent power-law shape from thermal Comptonization up to a cutoff at ≃100 keV, characteristic of that seen in the hard spectral states of black hole X-ray binary systems. At these luminosities, the radiative efficiency is high (≈24%) and results in a denser midplane region where magnetic fields are dynamically important. For L/LEdd ~ 10-2, our hot accretion flow appears to undergo thermal runaway and collapse. Our simulations demonstrate that hot accretion flows can be radiatively efficient and provide an estimate of their maximum luminosity.

Keywords: accretion; black hole physics; radiative transfer; magnetohydrodynamics; x-ray binary stars