Sazuna/UAT_keywords huggingface dataset:
Cosmological-scale Lyα Forest Absorption around Galaxies and AGNs Probed with the HETDEX and SDSS Spectroscopic Data. We present cosmological-scale three-dimensional neutral hydrogen (H I) tomographic maps at z = 2-3 over a total of 837 deg2 in two blank fields that are developed with Lyα forest absorptions of 14,736 background Sloan Digital Sky Survey (SDSS) quasars at z = 2.08-3.67. Using the tomographic maps, we investigate the large-scale (≳10 h -1 cMpc) average H I radial profiles and two-direction profiles of the line-of-sight (LOS) and transverse directions around galaxies and active galactic nuclei (AGNs) at z = 2-3 identified by the Hobby-Eberly Telescope Dark Energy eXperiment survey and SDSS, respectively. The peak of the H I radial profile around galaxies is lower than the one around AGNs, suggesting that the dark matter halos of galaxies are less massive on average than those of AGNs. The LOS profile of AGNs is narrower than the transverse profile, indicating the Kaiser effect. There exist weak absorption outskirts at ≳30 h -1 cMpc beyond H I structures of galaxies and AGNs found in the LOS profiles that can be explained by the H I gas at ≳30 h -1 cMpc falling toward the source position. Our findings indicate that the H I radial profile of AGNs has transitions from proximity zones (≲a few h -1 cMpc) to the H I structures (~1-30 h -1 cMpc) and the weak absorption outskirts (≳30 h -1 cMpc). Although there is no significant dependence of AGN types (type 1 vs. type 2) on the H I profiles, the peaks of the radial profiles anticorrelate with AGN luminosities, suggesting that AGNs' ionization effects are stronger than the gas mass differences.

Keywords: High-redshift galaxies, Galaxy evolution, Galaxies, Intergalactic medium
Distant Echoes of the Milky Way's Last Major Merger. The majority of the Milky Way's stellar halo consists of debris from our galaxy's last major merger, the Gaia-Sausage-Enceladus (GSE). In the past few years, stars from the GSE have been kinematically and chemically studied in the inner 30 kpc of our galaxy. However, simulations predict that accreted debris could lie at greater distances, forming substructures in the outer halo. Here we derive metallicities and distances using Gaia DR3 XP spectra for an all-sky sample of luminous red giant stars, and map the outer halo with kinematics and metallicities out to 100 kpc. We obtain follow-up spectra of stars in two strong overdensities-including the previously identified outer Virgo Overdensity-and find them to be relatively metal rich and on predominantly retrograde orbits, matching predictions from simulations of the GSE merger. We argue that these are apocentric shells of GSE debris, forming 60-90 kpc counterparts to the 15-20 kpc shells that are known to dominate the inner stellar halo. Extending our search across the sky with literature radial velocities, we find evidence for a coherent stream of retrograde stars encircling the Milky Way from 50 to 100 kpc, in the same plane as the Sagittarius Stream but moving in the opposite direction. These are the first discoveries of distant and structured imprints from the GSE merger, cementing the picture of an inclined and retrograde collision that built up our galaxy's stellar halo.

Keywords: Milky Way formation, Stellar streams, Milky Way stellar halo, Galaxy mergers, Milky Way Galaxy
The Most Obscured AGNs in the XMM-SERVS Fields. We perform X-ray spectral analyses to derive the characteristics (e.g., column density, X-ray luminosity) of ≈10,200 active galactic nuclei (AGNs) in the XMM-Spitzer Extragalactic Representative Volume Survey, which was designed to investigate the growth of supermassive black holes across a wide dynamic range of cosmic environments. Using physical torus models (e.g., Borus02) and a Bayesian approach, we uncover 22 representative Compton-thick (CT; N H &gt; 1.5 × 1024 cm-2) AGN candidates with good signal-to-noise ratios as well as a large sample of 136 heavily obscured AGNs. We also find an increasing CT fraction (f CT) from low (z &lt; 0.75) to high (z &gt; 0.75) redshift. Our CT candidates tend to show hard X-ray spectral shapes and dust extinction in their spectral energy distribution fits, which may shed light on the connection between AGN obscuration and host-galaxy evolution.

Keywords: AGN host galaxies, X-ray astronomy, X-ray active galactic nuclei, Active galactic nuclei, Extragalactic astronomy
Dynamical He Flashes in Double White Dwarf Binaries. The detonation of an overlying helium layer on a 0.8-1.1 M ⊙ carbon-oxygen (CO) white dwarf (WD) can detonate the CO WD and create a thermonuclear supernova (SN). Many authors have recently shown that when the mass of the He layer is low (≲0.03 M ⊙), the ashes from its detonation minimally impact the spectra and light curve from the CO detonation, allowing the explosion to appear remarkably similar to Type Ia SNe. These new insights motivate our investigation of dynamical He shell burning and our search for a binary scenario that stably accumulates thermally unstable He shells in the 0.01-0.08 M ⊙ range, thick enough to detonate, but also often thin enough for minimal impact on the observables. We first show that our improved nonadiabatic evolution of convective He shell burning in this range of shell mass leads to conditions ripe for a He detonation. We also find that a stable mass transfer scenario with a high-entropy He WD donor of mass 0.15-0.25 M ⊙ yields the He shell masses needed to achieve the double detonations. This scenario also predicts that the surviving He donor leaves with a spatial velocity consistent with the unusual runaway object, D6-2. We find that hot He WD donors originate in common-envelope events when a 1.3-2.0 M ⊙ star fills its Roche lobe at the base of the red giant branch at orbital periods of 1-10 days with the CO WD.

Keywords: Binary stars, Helium-rich stars, AM Canum Venaticorum stars, White dwarf stars, High-velocity stars, Type Ia supernovae
An Updated Dust-to-Star Geometry: Dust Attenuation Does Not Depend on Inclination in 1.3 ≤z ≤2.6 Star-forming Galaxies from MOSDEF. We investigate dust attenuation and its dependence on viewing angle for 308 star-forming galaxies at 1.3 ≤ z ≤ 2.6 from the MOSFIRE Deep Evolution Field survey. We divide galaxies with a detected Hα emission line and coverage of Hβ into eight groups by stellar mass, star formation rate (SFR), and inclination (i.e., axis ratio), and we then stack their spectra. From each stack, we measure the Balmer decrement and gas-phase metallicity, and then we compute the median A V and UV continuum spectral slope (β). First, we find that none of the dust properties (Balmer decrement, A V, or β) varies with the axis ratio. Second, both stellar and nebular attenuation increase with increasing galaxy mass, showing little residual dependence on SFR or metallicity. Third, nebular emission is more attenuated than stellar emission, and this difference grows even larger at higher galaxy masses and SFRs. Based on these results, we propose a three-component dust model in which attenuation predominantly occurs in star-forming regions and large, dusty star-forming clumps, with minimal attenuation in the diffuse ISM. In this model, nebular attenuation primarily originates in clumps, while stellar attenuation is dominated by star-forming regions. Clumps become larger and more common with increasing galaxy mass, creating the above mass trends. Finally, we argue that a fixed metal yield naturally leads to mass regulating dust attenuation. Infall of low-metallicity gas increases the SFR and lowers the metallicity, but leaves the dust column density mostly unchanged. We quantify this idea using the Kennicutt-Schmidt and fundamental metallicity relations, showing that galaxy mass is indeed the primary driver of dust attenuation.

Keywords: Star formation, High-redshift galaxies, Galaxy evolution, Galaxy properties
HD 222925: A New Opportunity to Explore the Astrophysical and Nuclear Conditions of r-process Sites. With the most trans-iron elements detected of any star outside the solar system, HD 222925 represents the most complete chemical inventory among metal-poor stars enhanced with elements made by the rapid neutron capture ("r") process. As such, HD 222925 may be a new "template" for the observational r-process, where before the (much higher-metallicity) solar r-process residuals were used. In this work, we test under which conditions a single site accounts for the entire elemental r-process abundance pattern of HD 222925. We found that several of our tests-with the single exception of the black hole-neutron star merger case-challenge the single-site assumption by producing an ejecta distribution that is highly constrained, in disagreement with simulation predictions. However, we found that ejecta distributions that are more in line with simulations can be obtained under the condition that the nuclear data near the second r-process peak are changed. Therefore, for HD 222925 to be a canonical r-process template likely as a product of a single astrophysical source, the nuclear data need to be reevaluated. The new elemental abundance pattern of HD 222925-including the abundances obtained from space-based, ultraviolet (UV) data-call for a deeper understanding of both astrophysical r-process sites and nuclear data. Similar UV observations of additional r-process-enhanced stars will be required to determine whether the elemental abundance pattern of HD 222925 is indeed a canonical template (or an outlier) for the r-process at low metallicity.

Keywords: Nucleosynthesis, R-process, Nuclear astrophysics, Population II stars, Nuclear physics
On the Origin of Radio-loudness in Active Galactic Nuclei Using Far-infrared Polarimetric Observations. The dichotomy between radio-loud (RL) and radio-quiet (RQ) active galactic nuclei (AGNs) is thought to be intrinsically related to radio jet production. This difference may be explained by the presence of a strong magnetic field (B-field) that enhances, or is the cause of, the accretion activity and the jet power. Here we report the first evidence of an intrinsic difference in the polarized dust emission cores of four RL and five RQ obscured AGNs using 89 μm polarization with SOFIA/HAWC+. We find that the thermal polarized emission increases with the nuclear radio-loudness, R 20 = L 5GHz/L 20μm. The dust emission cores of RL AGNs are measured to be polarized, ~5%-11%, while RQ AGNs are unpolarized, &lt;1%. For RQ AGNs, our results are consistent with the observed region being filled with an unmagnetized or highly turbulent disk and/or expanding outflow at scales of 5-130 pc from the AGNs. For RL AGNs, the measured 89 μm polarization arises primarily from magnetically aligned dust grains associated with a 5-130 pc scale dusty obscuring structure with a toroidal B-field orientation highly offset, 65° ± 22°, with respect to the jet axis. Our results indicate that the size and strength of the B-fields surrounding the AGNs are intrinsically related to the strength of the jet power-the stronger the jet power is, the larger and stronger the toroidal B-field is. The detection of a ≤130 pc scale ordered toroidal B-field suggests that (a) the infalling gas that fuels RL AGNs is magnetized, (b) there is a magnetohydrodynamic wind that collimates the jet, and/or (c) the jet is able to magnetize its surroundings.

Keywords: AGN host galaxies, Supermassive black holes, Magnetohydrodynamics, Far infrared astronomy, Astrophysical dust processes, Seyfert galaxies, Active galactic nuclei, Radio galaxies, Polarimetry, Extragalactic magnetic fields
Theoretical Water Binding Energy Distribution and Snowline in Protoplanetary Disks. Water is one of the most important and abundant molecules in star-forming regions. In protoplanetary disks, where planets and comets form, H2O is in a gas or solid form, depending on the dust temperature, i.e., the distance from the center and its binding energy (BE). Not surprisingly, several experimental and theoretical studies of the H2O BE have been published. We report new ab initio calculations carried out on a large model of interstellar ice, where we identified 144 different adsorption sites. The BE associated with those sites ranges between 14.2 kJ mol-1 (1705 K) and 61.6 kJ mol-1 (7390 K). The distribution of the computed BEs as a function of BE follows a Gaussian peaked at 35.4 kJ mol-1 (4230 K) with a standard deviation of 9.7 kJ mol-1 (1160 K). The computed pre-exponential factor (ν) ranges between 9 × 1012 and 6 × 1014 s-1. We evaluated the impact of the newly calculated BE and ν distributions on the snowline of a generic protoplanetary disk. We found that the region where water is frozen onto the ice is much smaller (a factor of 10 smaller radius) than that computed with the single BE (5600 K) and ν (2 × 1012 s-1) values commonly adopted by astrochemical models. Besides, ~10% of water remains frozen in relatively warm (~150 K) regions, where the single BE and ν model would predict a full release of the ice in the gas phase. This last aspect may have an impact on the quantity trapped in the planetesimals eventually forming rocky planets.

Keywords: Interstellar molecules, Astrochemistry
A 7 Day Multiwavelength Flare Campaign on AU Mic. I. High-time-resolution Light Curves and the Thermal Empirical Neupert Effect. We present light curves and flares from a 7 day, multiwavelength observational campaign of AU Mic, a young and active dM1e star with exoplanets and a debris disk. We report on 73 unique flares between the X-ray to optical data. We use high-time-resolution near-UV (NUV) photometry and soft X-ray (SXR) data from the X-ray Multi-Mirror Mission to study the empirical Neupert effect, which correlates the gradual and impulsive phase flaring emissions. We find that 65% (30 of 46) flares do not follow the Neupert effect, which is 3 times more excursions than seen in solar flares, and propose a four-part Neupert effect classification (Neupert, quasi-Neupert, non-Neupert types I and II) to explain the multiwavelength responses. While the SXR emission generally lags behind the NUV as expected from the chromospheric evaporation flare models, the Neupert effect is more prevalent in larger, more impulsive flares. Preliminary flaring rate analysis with X-ray and U-band data suggests that previously estimated energy ratios hold for a collection of flares observed over the same time period, but not necessarily for an individual, multiwavelength flare. These results imply that one model cannot explain all stellar flares and care should be taken when extrapolating between wavelength regimes. Future work will expand wavelength coverage using radio data to constrain the nonthermal empirical and theoretical Neupert effects to better refine models and bridge the gap between stellar and solar flare physics.

Keywords: Stellar x-ray flares, Red dwarf flare stars, Stellar activity, Stellar flares, Optical flares, Planet hosting stars
Supernova 2020wnt: An Atypical Superluminous Supernova with a Hidden Central Engine. We present observations of a peculiar hydrogen- and helium-poor stripped-envelope (SE) supernova (SN) 2020wnt, primarily in the optical and near-infrared (near-IR). Its peak absolute bolometric magnitude of -20.9 mag (L bol, peak = (6.8 ± 0.3) × 1043 erg s-1) and a rise time of 69 days are reminiscent of hydrogen-poor superluminous SNe (SLSNe I), luminous transients potentially powered by spinning-down magnetars. Before the main peak, there is a brief peak lasting &lt;10 days post explosion, likely caused by interaction with circumstellar medium (CSM) ejected ~years before the SN explosion. The optical spectra near peak lack a hot continuum and O II absorptions, which are signs of heating from a central engine; they quantitatively resemble those of radioactivity-powered hydrogen/helium-poor Type Ic SESNe. At ~1 yr after peak, nebular spectra reveal a blue pseudo-continuum and narrow O I recombination lines associated with magnetar heating. Radio observations rule out strong CSM interactions as the dominant energy source at +266 days post peak. Near-IR observations at +200-300 days reveal carbon monoxide and dust formation, which causes a dramatic optical light-curve dip. Pair-instability explosion models predict slow light curve and spectral features incompatible with observations. SN 2020wnt is best explained as a magnetar-powered core-collapse explosion of a 28 M ☉ pre-SN star. The explosion kinetic energy is significantly larger than the magnetar energy at peak, effectively concealing the magnetar-heated inner ejecta until well after peak. SN 2020wnt falls into a continuum between normal SNe Ic and SLSNe I, and demonstrates that optical spectra at peak alone cannot rule out the presence of a central engine.

Keywords: Massive stars, Core-collapse supernovae, Dust formation
Interstellar Bow Shocks around Fast Stars Passing through the Local Interstellar Medium. Bow shocks are produced in the local interstellar medium by the passage of fast stars from the Galactic thin-disk and thick-disk populations with velocities V * = 40-80 km s-1. Stellar transits of local H I clouds occur every 3500-7000 yr on average and last between 104 and 105 yr. There could be 10-20 active bow shocks around low-mass stars inside clouds within 15 pc of the Sun. At local cloud distances of 3-10 pc, their turbulent wakes have transverse radial extents R wake ≈ 100-300 au, angular sizes 10″-100″, and Lyα surface brightnesses of 2-8 R in gas with total hydrogen density n H ≈ 0.1 cm-3 and V * = 40-80 km s-1. These transit wakes may cover an area fraction f A ≈ (R wake/R cl) ≈ 10-3 of local H I clouds and be detectable in IR (dust), UV (Lyα, two-photon), or nonthermal radio emission. Turbulent heating in these wakes could produce the observed elevated rotational populations of H2 (J ≥ 2) and influence the endothermic formation of CH+ in diffuse interstellar gas at T &gt; 103 K.

Keywords: Interstellar clouds, Stellar bow shocks
Misaligned Jets from Sgr A* and the Origin of Fermi/eROSITA Bubbles. One of the leading explanations for the origin of Fermi Bubbles is past jet activity in the Galactic center supermassive black hole Sgr A*. The claimed jets are often assumed to be perpendicular to the Galactic plane. Motivated by the orientation of pc-scale nuclear stellar disk and gas streams, as well as a low inclination of the accretion disk around Sgr A* inferred by the Event Horizon Telescope, we perform hydrodynamical simulations of nuclear jets significantly tilted relative to the Galactic rotation axis. The observed axisymmetry and hemisymmetry (north-south symmetry) of Fermi/eROSITA bubbles (FEBs) due to quasi-steady jets in Sgr A* could be produced if the jet had a super-Eddington power (≳5 × 1044 erg s-1) for a short time (jet active period ≲6 kyr) for a reasonable jet opening angle (≲10°). Such powerful explosions are, however, incompatible with the observed O VIII/O VII line ratio toward the bubbles, even after considering electron-proton temperature nonequilibrium. We argue that the only remaining options for producing FEBs are (i) a low-luminosity (≈1040.5-41 erg s-1) magnetically dominated jet or accretion wind from the Sgr A*, or (ii) a supernovae or tidal disruption event driven wind of a similar luminosity from the Galactic center.

Keywords: Hydrodynamical simulations, Galactic center, Jets, Circumgalactic medium, Diffuse x-ray background, Milky Way Galaxy, Superbubbles
Drop in the Hard Pulsed Fraction and a Candidate Cyclotron Line in IGR J16320-4751 Seen by NuSTAR. We report on a timing and spectral analysis of a 50 ks NuSTAR observation of IGR J16320-4751 (= AX J1631.9-4752), a high-mass X-ray binary hosting a slowly rotating neutron star. In this observation from 2015, the spin period was 1308.8 ± 0.4 s giving a period derivative $\dot{P}\sim 2\times {10}^{-8}$ s s-1 when compared with the period measured in 2004. In addition, the pulsed fraction decreased as a function of energy, as opposed to the constant trend that was seen previously. This suggests a change in the accretion geometry of the system during the intervening 11 yr. The phase-averaged spectra were fit with the typical model for accreting pulsars: a power law with an exponential cutoff. This left positive residuals at 6.4 keV attributable to the known iron Kα line, as well as negative residuals around 14 keV from a candidate cyclotron line detected at a significance of 5σ. We found no significant differences in the spectral parameters across the spin period, other than the expected changes in flux and component normalizations. A flare lasting around 5 ks was captured during the first half of the observation, where the X-ray emission hardened and the local column density decreased. Finally, the binary orbital period was refined to 8.9912 ± 0.0078 days thanks to Swift/BAT monitoring data from 2005-2022.

Keywords: Neutron stars, X-ray binary stars, Massive stars, High mass x-ray binary stars, Pulsars, Compact objects
Cosmic Rays Self-arising Turbulence with Universal Spectrum -8/3. In the inertial subrange of scales, an exact compressible turbulence universal spectrum law -8/3 for the density fluctuations of cosmic rays (CRs) in the frame of the known two-fluid model of CR dynamics is obtained. It is shown that the origin of this scaling law may be due to the arising of shocks at the breaking of the nonlinear simple waves of CRs near the scale of their Larmor's radii, as it is well known for the solar wind with the same turbulent spectrum law -8/3. The consistency of the turbulence spectrum -8/3 of CRs with the observed nonthermal differential energy distribution of CRs with a similar index -8/3 due to the possibility of self-reacceleration of the CRs on the self-arising shocks is stated. The turbulent diffusion mechanism for the observed CRs energy spectrum breaks is considered.

Keywords: Interplanetary shocks, Interplanetary turbulence, Spectral energy distribution, Particle astrophysics, Ultra-high-energy cosmic radiation, Cosmic rays
Unveiling the Formation of the Massive DR21 Ridge. We present new 13CO (1-0), C18O (1-0), HCO+ (1-0), and H13CO+ (1-0) maps from the IRAM 30 m telescope and a spectrally resolved [C II] 158 μm map observed with the SOFIA telescope toward the massive DR21 cloud. This traces the kinematics from low- to high-density gas in the cloud, which allows us to constrain the formation scenario of the high-mass star-forming DR21 ridge. The molecular line data reveal that the subfilaments are systematically redshifted relative to the dense ridge. We demonstrate that [C II] unveils the surrounding CO-poor gas of the dense filaments in the DR21 cloud. We also show that this surrounding gas is organized in a flattened cloud with curved redshifted dynamics perpendicular to the ridge. The subfilaments thus form in this curved and flattened mass reservoir. A virial analysis of the different lines indicates that self-gravity should drive the evolution of the ridge and surrounding cloud. Combining all results, we propose that bending of the magnetic field, due to the interaction with a mostly atomic colliding cloud, explains the velocity field and resulting mass accretion on the ridge. This is remarkably similar to what was found for at least two nearby low-mass filaments. We tentatively propose that this scenario might be a widespread mechanism to initiate star formation in the Milky Way. However, in contrast to low-mass clouds, gravitational collapse plays a role on the parsec scale of the DR21 ridge because of the higher density. This allows more effective mass collection at the centers of collapse and should facilitate massive cluster formation.

Keywords: Star formation, Molecular clouds, Interstellar medium