adsabs/SciX_UAT_keywords huggingface dataset:
Implications of Evaporative Cooling by H2 for 1I/'Oumuamua

The first interstellar object observed in our solar system, 1I/'Oumuamua, exhibited several peculiar properties, including extreme elongation and nongravitational acceleration. Bergner & Seligman (hereafter BS23) proposed that evaporation of trapped H2 created by cosmic rays can explain the nongravitational acceleration. However, their modeling of the thermal structure of 1I/'Oumuamua ignored the crucial cooling effect of evaporating H2. By taking into account the cooling by H2 evaporation, we show that the surface temperature of H2-water ice is a factor of 9 lower than the case without evaporative cooling. As a result, the thermal speed of outgassing H2 is decreased by a factor of 3. Our one-dimensional thermal modeling that takes into account evaporative cooling for two chosen values of thermal conductivity of κ = 0.01 and 0.1 WK-1 m-1 shows that the water ice volume available for H2 sublimation at T > 30 K would be reduced by a factor of 9 and 5 compared to the results of BS23, not enabling enough hydrogen to propel 1I/'Oumuamua.

Keywords: ocean planets; ice physics; astronomical object identification; interstellar objects
At Least One in Six Galaxies Is Always Dead

Via numerical experiments, we show that the ∼10%-20% passive fraction seen at z ≳ 3 is consistent with galaxy star formation histories being maximally correlated stochastic processes. If so, this fraction should reflect a time-independent baseline that holds at any epoch or mass regime where mean star formation rates are rising. Data at $\mathrm{log}{M}_{* }\leqslant 10$ and z ≲ 0.5 bear this out, as should future James Webb Space Telescope observations.

Keywords: galaxy evolution; galaxy quenching; star formation
Magnetic Helicity Flux Oscillations in the Atmospheres of Flaring and Nonflaring Active Regions

Analyzing the evolution of magnetic helicity flux at different atmospheric heights is key for identifying its role in the dynamics of active regions (ARs). The three-dimensional (3D) magnetic field of both flaring and nonflaring ARs is constructed using potential field extrapolations, enabling the derivation of emergence, shearing, and total magnetic helicity components at a range of atmospheric heights. An analysis of temporal oscillations of the derived components shows that the largest significant period of the three helicity fluxes are common (within ±2 hr) from the photosphere up to at least 1 Mm for flaring ARs-being consistent with the presence of a coupled oscillatory behavior that is absent in the nonflaring ARs. We suggest that large, energetic solar eruptions may have been produced in ARs when the vertical and horizontal helicity flux components became a coupled oscillatory system in the low solar atmosphere.

Keywords: solar active region magnetic fields; solar flares; solar atmospheric motions
An R V Map of the Milky Way Revealed by LAMOST

The total-to-selective extinction ratio, R V, is a key parameter for tracing the properties of interstellar dust, as it directly determines the variation of the extinction curve with wavelength. By utilizing accurate color excess measurements from the optical to the mid-infrared range, we have derived R V values for approximately three million stars from LAMOST data release 7 using a forward-modeling technique. This extensive data set enables us to construct a comprehensive 2D R V map of the Milky Way within the LAMOST footprint at a spatial resolution of ~27.'5. Based on reliable sight lines of E(B - V) > 0.1, we find that R V exhibits a Gaussian distribution centered around 3.25 with a standard deviation of 0.25. The spatial variability of R V in the Galactic disk exhibits a wide range, spanning from small scales within individual molecular clouds to large scales up to kiloparsecs. A striking correlation is observed between the distribution of R V and molecular clouds. Notably, we observe lower R V values within the regions of nearby molecular clouds compared to their surrounding areas. Furthermore, we have investigated the relationships between R V and various parameters, including dust temperature, dust emissivity spectral index, column densities and ratios of atomic and molecular hydrogen, as well as the gas-to-dust ratio. We find that these relationships vary with the level of extinction. These analyses provide new insights into the properties and evolution of dust grains in diverse interstellar environments and also hold significant importance for achieving accurate extinction corrections.

Keywords: interstellar dust; interstellar dust extinction
Early Results from GLASS-JWST. X. Rest-frame UV-optical Properties of Galaxies at 7 < z < 9

We present the first James Webb Space Telescope/NIRCam-led determination of 7 < z < 9 galaxy properties based on broadband imaging from 0.8 to 5 μm as part of the GLASS-JWST Early Release Science program. This is the deepest data set acquired at these wavelengths to date, with an angular resolution ≲0.″14. We robustly identify 13 galaxies with signal-to-noise ratio ≳ 8 in F444W from 8 arcmin2 of data at m AB ≤ 28 from a combination of dropout and photometric redshift selection. From simulated data modeling, we estimate the dropout sample purity to be ≳90%. We find that the number density of these F444W-selected sources is broadly consistent with expectations from the UV luminosity function determined from Hubble Space Telescope data. We characterize galaxy physical properties using a Bayesian spectral energy distribution fitting method, finding a median stellar mass of 108.5 M ⊙ and age 140 Myr, indicating they started ionizing their surroundings at redshift z > 9.5. Their star formation main sequence is consistent with predictions from simulations. Lastly, we introduce an analytical framework to constrain main-sequence evolution at z > 7 based on galaxy ages and basic assumptions, through which we find results consistent with expectations from cosmological simulations. While this work only gives a glimpse of the properties of typical galaxies that are thought to drive the reionization of the universe, it clearly shows the potential of JWST to unveil unprecedented details of galaxy formation in the first billion years.

Keywords: galaxy evolution; high-redshift galaxies
Stellar Outbursts and Chondrite Composition

The temperatures of observed protoplanetary disks are not sufficiently high to produce the accretion rate needed to form stars, nor are they sufficient to explain the volatile depletion patterns in CM, CO, and CV chondrites and terrestrial planets. We revisit the role that stellar outbursts, caused by high-accretion episodes, play in resolving these two issues. These outbursts provide the necessary mass to form the star during the disk lifetime and provide enough heat to vaporize planet-forming materials. We show that these outbursts can reproduce the observed chondrite abundances at distances near 1 au. These outbursts would also affect the growth of calcium-aluminum-rich inclusions and the isotopic compositions of carbonaceous and noncarbonaceous chondrites.

Keywords: protoplanetary disks; dust composition; planetary system formation
The Most Rapidly Declining Type I Supernova 2019bkc/ATLAS19dqr

We report observations of the hydrogen-deficient supernova (SN) 2019bkc/ATLAS19dqr. With B- and r-band decline between peak and 10 days post peak of ${\rm{\Delta }}{m}_{10}(B)=5.24\pm 0.07$ mag and ${\rm{\Delta }}{m}_{10}(r)=3.85\pm 0.10$ mag, respectively, SN 2019bkc is the most rapidly declining SN I discovered so far. While its closest matches are the rapidly declining SN 2005ek and SN 2010X, the light curves and spectra of SN 2019bkc show some unprecedented characteristics. SN 2019bkc appears "hostless," with no identifiable host galaxy near its location, although it may be associated with the galaxy cluster MKW1 at z = 0.02. We evaluate a number of existing models of fast-evolving SNe, and we find that none of them can satisfactorily explain all aspects of SN 2019bkc observations.

Keywords: supernovae
Conserving Local Magnetic Helicity in Numerical Simulations

Magnetic helicity is robustly conserved in systems with very large magnetic Reynolds numbers, including most systems of astrophysical interest, and unlike kinetic and magnetic energy, it is not dissipated at small scales. This plays a major role in suppressing the kinematic large-scale dynamo and may also be responsible for driving the large-scale dynamo through the magnetic helicity flux. Numerical simulations of astrophysical systems typically lack sufficient resolution to enforce global magnetic helicity over several dynamical times. In these simulations, magnetic helicity is lost either through numerical errors or through the action of an unrealistically large resistivity. Errors in the internal distribution of magnetic helicity are equally important and typically larger. Here, we propose an algorithm for enforcing strict local conservation of magnetic helicity in the Coulomb gauge in numerical simulations, so that their evolution more closely approximates that of real systems.

Keywords: astrophysical fluid dynamics; magnetic fields; magnetohydrodynamics
A Standard Siren Measurement of the Hubble Constant Using Gravitational-wave Events from the First Three LIGO/Virgo Observing Runs and the DESI Legacy Survey

We present a new constraint on the Hubble constant H 0 using a sample of well-localized gravitational-wave (GW) events detected during the first three LIGO/Virgo observing runs as dark standard sirens. In the case of dark standard sirens, a unique host galaxy is not identified, and the redshift information comes from the distribution of potential host galaxies. From the third LIGO/Virgo observing run detections, we add the asymmetric-mass binary black hole GW190412 and the high-confidence GW candidates S191204r, S200129m, and S200311bg to the sample of dark standard sirens analyzed in Palmese et al. Our sample contains the top 20% (based on localization) GW events and candidates to date with significant coverage by the Dark Energy Spectroscopic Instrument Legacy Survey. We combine the H 0 posterior for eight dark siren events, finding ${H}_{0}={79.8}_{-12.8}^{+19.1}\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$ (68% highest density interval) for a prior in H 0 uniform between [20, 140] km s-1 Mpc-1. This result shows that a combination of eight well-localized dark sirens combined with an appropriate galaxy catalog is able to provide an H 0 constraint that is competitive (~20% versus 18% precision) with a single bright standard siren analysis (i.e., assuming the electromagnetic counterpart) using GW170817. When combining the posterior with that from GW170817, we obtain ${H}_{0}={72.77}_{-7.55}^{+11.0}\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$ . This result is broadly consistent with recent H 0 estimates from both the cosmic microwave background and supernovae.

Keywords: cosmology; cosmological parameters; hubble constant; gravitational waves; redshift surveys
Vertical Structure of Galactic Disk Kinematics from LAMOST K Giants

We examine the vertical structure of Galactic disk kinematics over a Galactocentric radial distance range of R = 5-15 kpc and up to 3 kpc away from the Galactic plane, using the K-type giants surveyed by LAMOST. Based on robust measurements of three-dimensional velocity moments, a wobbly disk is detected in a phenomenological sense. An outflow dominates the radial motion of the inner disk, while in the outer disk there exist alternate outward and inward flows. The vertical bulk velocities is a combination of breathing and bending modes. A contraction-like breathing mode with amplitudes increasing with the distance to the plane and an upward bending mode dominate the vertical motion outside R0, and there are reversed breathing and bending modes at R < R0, with amplitudes much smaller than those outside R0. The mean azimuthal velocity decreases with the increasing distance to the plane, with gradients shallower for larger R. Stars in the south disk are rotating faster than stars in the north. The velocity ellipsoid orientation differs between different R: in the range of $5\lt R\lt 9\,\mathrm{kpc}$ , the gradient of the tilt angle with respect to $\arctan (Z/R)$ decreases from ~0.83 for the inner disk to ~0.52 for the outer disk; within $9\lt R\lt 15\,\mathrm{kpc}$ , the tilt of velocity ellipsoid deviates from vertical antisymmetry. A clear flaring signature is found for both north and south disks based on the observed vertical structures of velocity ellipsoid.

Keywords: galaxy kinematics; stellar kinematics; milky way disk
The Most Distant H I Galaxies Discovered by the 500 m Dish FAST

Neutral hydrogen (H I) is the primary component of the cool interstellar medium (ISM) and is the reservoir of fuel for star formation. Owing to the sensitivity of existing radio telescopes, our understanding of the evolution of the ISM in galaxies remains limited, as it is based on only a few hundred galaxies detected in H I beyond the local Universe. With the high sensitivity of the Five-hundred-meter Aperture Spherical radio Telescope (FAST), we carried out a blind H I search, the FAST Ultra-Deep Survey, which extends to redshifts up to 0.42 and a sensitivity of 50 μJy beam‑1. Here, we report the first discovery of six galaxies in H I at z > 0.38. For these galaxies, the FAST angular resolution of ∼4' corresponds to a mean linear size of $\sim 1.3\,{h}_{70}^{-1}\,$ Mpc. These galaxies are among the most distant H I emission detections known, with one having the most massive H I content ( ${10}^{10.93\pm 0.04}\,{h}_{70}^{-2}\,{M}_{\odot }$ ). Using recent data from the DESI survey and new observations with the Hale, Big Telescope Alt-azimuth, and Keck telescopes, optical counterparts are detected for all galaxies within the 3σ positional uncertainty ( $0.5\,{h}_{70}^{-1}\,$ Mpc) and 200 km s‑1 in recession velocity. Assuming that the dominant source of H I is the identified optical counterpart, we find evidence of evolution in the H I content of galaxies over the last 4.2 Gyr. Our new high-redshift H I galaxy sample provides the opportunity to better investigate the evolution of cool gas in galaxies. A larger sample size in the future will allow us to refine our knowledge of the formation and evolution of galaxies.

Keywords: h i line emission; high-redshift galaxies; galaxy evolution
The Hydrostatic Mass of A478: Discrepant Results from Chandra, NuSTAR, and XMM-Newton

Galaxy clusters are the most recently formed and most massive, gravitationally bound structures in the Universe. The number of galaxy clusters formed is highly dependent on cosmological parameters, such as the dark matter density, σ 8, and Ω m . The number density is a function of the cluster mass, which can be estimated from the density and temperature profiles of the intracluster medium under the assumption of hydrostatic equilibrium. The temperature of the plasma, hence its mass, is calculated from the X-ray spectra. However, effective-area calibration uncertainties in the soft band result in significantly different temperature measurements from various space-based X-ray telescopes. NuSTAR is potentially less susceptible to these issues than Chandra and XMM-Newton, having larger effective area, particularly at higher energies, enabling high-precision temperature measurements. In this work, we present analyses of Chandra, NuSTAR, and XMM-Newton data of A478 to investigate the nature of this calibration discrepancy. We find that NuSTAR temperatures are on average ~11% lower than those of Chandra, and XMM-Newton temperatures are on average ~5% lower than those of NuSTAR. This results in a NuSTAR mass at r 2500,Chandra of ${M}_{2500,\mathrm{NuSTAR}}\,=\,{3.39}_{-0.07}^{+0.07}\times {10}^{14}$ M ⊙, which is ~10% lower than that of M 2500,Chandra and ~4% higher than M 2500,XMM-Newton.

Keywords: galaxy clusters; x-ray astronomy
The Prompt Emission of GRB 130518A and the Study of Its Outflow through Hybrid Jet Models

The nature of the prompt emission mechanism in gamma-ray bursts (GRBs) remains uncertain to date. This question is also tied to the composition of the jet: thermal, Poynting flux dominated or hybrid with both types of components. In this work, we aim to study these questions in the context of GRB 130518A. By analysing its prompt emission data from the Fermi Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT), we find that the time-integrated spectrum has a nonthermal component along with a subdominant blackbody component. We use these results to study the properties of the jet in various scenarios through the frameworks developed by Hascoët et al. and Gao & Zhang. Both frameworks exclude the pure fireball model for this GRB. In all other cases, the initial magnetic fraction is greater than the thermal fraction. For small launching radii of the jet, the favored nonthermal emission process is internal shocks. Magnetic reconnection seems likely only for very large initial radii.

Keywords: gamma-ray bursts; gamma-ray astronomy; astronomy data analysis; high energy astrophysics; astronomy data modeling
WawHelioGlow: A Model of the Heliospheric Backscatter Glow. II. The Helioglow Buildup and the Potential Significance of the Anisotropy in the Solar EUV Output

The helioglow is the fluorescence of interstellar atoms inside the heliosphere, where they are excited by the solar EUV. Because the mean free path between collisions for interstellar gas is comparable to the size of the heliosphere, the distribution function of this gas inside the heliosphere strongly varies in space and with time and is non-Maxwellian. Coupling between realistically modeled solar factors and the distribution function of interstellar neutral gas is accounted for in a helioglow model that we have developed. WawHelioGlow is presented in the accompanying Paper I. Here, we present the evolution of the gas density, solar illumination, helioglow source function, and other relevant parameters building up the helioglow signal for selected lines of sight observed at 1 au. We compare these elements for various phases of the solar cycle, and we present the sensitivity of the results to the heliolatitudinal anisotropy of the solar EUV output. We assume a realistic latitudinal anisotropy of the solar wind flux using results from the analysis of interplanetary scintillations. We compare the simulated helioglow with selected maps observed by the SOHO/SWAN instrument. We demonstrate that WawHelioGlow is able to reproduce fundamental features of the sky distribution of the helioglow. For some phases of the solar cycle, the model with solar EUV output anisotropy better reproduces the observations, while for other phases, no EUV anisotropy is needed. In all simulated cases, the solar wind anisotropy following insight from interplanetary scintillation measurements is present.

Keywords: heliosphere; astrosphere interstellar medium interactions; solar extreme ultraviolet emission; solar wind; solar system; interplanetary gas; interstellar medium; interstellar atomic gas
Intergalactic Medium Dispersion Measures of Fast Radio Bursts Estimated from IllustrisTNG Simulation and Their Cosmological Applications

Fast radio bursts (FRBs) are millisecond-duration radio transients and can be used as a cosmological probe. However, the dispersion measure (DM) contributed by the intergalactic medium (IGM) is hard to distinguish from other components. In this paper, we use the IllustrisTNG simulation to realistically estimate DMIGM up to z ∼ 9. We find ${\mathrm{DM}}_{\mathrm{IGM}}={892}_{-270}^{+721}$ pc cm-3 at z = 1. The probability distribution of DMIGM can be well fitted by a quasi-Gaussian function with a long tail. The tail is caused by structures along the line of sight in the IGM. Subtracting DM contributions from the Milky Way and host galaxy for localized FRBs, the DMIGM value is close to that given by the derived DMIGM-z relation. We also show the ability to constrain the cosmic reionization history with DMIGM of high-redshift FRBs in the IllustrisTNG universe. The derived DMIGM-z relation at high redshifts can be well fitted by a tanh reionization model with the reionization redshift z = 5.95, which is compatible with the reionization model used by the IllustrisTNG simulation. DMIGM of high-redshift FRBs also provides an independent way to measure the optical depth of the cosmic microwave background. Our result can be used to derive the pseudo-redshifts of nonlocalized FRBs for DMIGM < 4000 pc cm-3.

Keywords: radio transient sources; intergalactic medium; reionization; radio bursts
Heliospheric Structure as Revealed by the 3-88 keV H ENA Spectra

Energetic neutral atoms (ENAs) are an important tool for investigating the structure of the heliosphere. Recently, it was observed that fluxes of ENAs (with energy ≤55 keV) coming from the upwind and downwind regions of the heliosphere are similar in strength. This led the authors of these observations to hypothesize that the heliosphere is bubble-like rather than comet-like, meaning that it has no extended tail. We investigate the directional distribution of the ENA flux for a wide energy range (3-88 keV) including observations from IBEX (Interstellar Boundary Explorer), INCA (Ion and Neutral Camera, on board Cassini), and HSTOF (High-energy Suprathermal Time Of Flight sensor, on board the Solar and Heliospheric Observatory). An essential element is the model of pickup ion (PUI) acceleration at the termination shock proposed by Zank. We use state-of-the-art models of the global heliosphere, interstellar neutral gas density, and PUI distributions. The results, based on the “comet-like” model of the heliosphere, are close in flux magnitude to ENA observations by IBEX, HSTOF, and partly those by INCA (except for the 5.2-13.5 keV energy channel). We find that the ENA flux from the tail dominates at high energy (in agreement with HSTOF, but not INCA). At low energy, our comet-like model produces ENA fluxes of similar strength from the upwind and downwind directions—which, therefore, removes this as a compelling argument for a bubble-like heliosphere.

Keywords: solar physics; solar wind; heliopause; interplanetary physics; pickup ions; solar wind termination; heliosphere; interplanetary particle acceleration
Migration and Evolution of giant ExoPlanets (MEEP). I. Nine Newly Confirmed Hot Jupiters from the TESS Mission

Hot Jupiters were many of the first exoplanets discovered in the 1990s, but in the decades since their discovery the mysteries surrounding their origins have remained. Here we present nine new hot Jupiters (TOI-1855 b, TOI-2107 b, TOI-2368 b, TOI-3321 b, TOI-3894 b, TOI-3919 b, TOI-4153 b, TOI-5232 b, and TOI-5301 b) discovered by NASA's TESS mission and confirmed using ground-based imaging and spectroscopy. These discoveries are the first in a series of papers named the Migration and Evolution of giant ExoPlanets survey and are part of an ongoing effort to build a complete sample of hot Jupiters orbiting FGK stars, with a limiting Gaia G-band magnitude of 12.5. This effort aims to use homogeneous detection and analysis techniques to generate a set of precisely measured stellar and planetary properties that is ripe for statistical analysis. The nine planets presented in this work occupy a range of masses (0.55M J < MP < 3.88M J) and sizes (0.967R J < RP < 1.438R J) and orbit stars that have an effective temperature in the range of 5360 K < T eff < 6860 K with Gaia G-band magnitudes ranging from 11.1 to 12.7. Two of the planets in our sample have detectable orbital eccentricity: TOI-3919 b ( ) and TOI-5301 b ( ). These eccentric planets join a growing sample of eccentric hot Jupiters that are consistent with high-eccentricity tidal migration, one of the three most prominent theories explaining hot Jupiter formation and evolution.

Keywords: exoplanet astronomy; exoplanet migration; exoplanet detection methods; exoplanets; transits; radial velocity; direct imaging