Sazuna/UAT_keywords huggingface dataset:
The QuaStar Survey: Detecting Hidden Low-velocity Gas in the Milky Way's Circumgalactic Medium. From our position embedded within the Milky Way's interstellar medium, we have limited ability to detect gas at low relative velocities in the extended Galactic halo because those spectral lines are blended with much stronger signals from dense foreground gas. As a result, the content of the Milky Way's circumgalactic medium (CGM) is poorly constrained at ∣vLSR∣ ≲150 km s-1. To overcome this complication, the QuaStar survey applies a spectral differencing technique using paired quasar-star sight lines to measure the obscured content of the Milky Way's CGM for the first time. We present measurements of the C IV doublet (λλ1548, 1550), a rest-frame UV metal line transition, detected in Hubble Space Telescope/Cosmic Origins Spectrograph spectra of 30 halo-star/quasar pairs evenly distributed across the sky at Galactic latitudes ∣b∣ &gt; 30°. The 30 halo stars have well-constrained distances (d ≈ 5-14 kpc) and are paired with quasars separated by &lt;2°8. We argue that the difference in absorption between the quasar and stellar sight lines originates primarily in the Milky Way's extended CGM beyond ∼10 kpc. For the Milky Way's extended, low-velocity CGM (∣v∣ &lt;150 km s-1), we place an upper limit on the mean C IV column density of ${\rm{\Delta }}\mathrm{log}{N}_{\mathrm{LVCGM}}$ &lt; 13.39 and find a covering fraction of ${f}_{{\rm{C}}{\rm\small{IV}},\mathrm{LVCGM}}(\mathrm{log}N\gt 13.65)\,=$ 20% [6/30], a value significantly lower than the covering fraction for star-forming galaxies at low redshift. Our results suggest either that the bulk of Milky Way's C IV -traced CGM lies at low Galactic latitudes or that the Milky Way's CGM is lacking in warm, ionized material compared to low-redshift (z &lt; 0.1) star-forming galaxy halos.

Keywords: Ultraviolet astronomy, Warm ionized medium, Galaxy kinematics, Halo stars, Circumgalactic medium, Milky Way evolution, Magellanic Clouds, Milky Way Galaxy
CGM<SUP>2</SUP> I: The Extent of the Circumgalactic Medium Traced by Neutral Hydrogen. We present initial results from the Cosmic Origins Spectrograph (COS) and Gemini Mapping the Circumgalactic Medium (CGMCGM ≡ CGM2) survey. The CGM2 survey consists of 1689 galaxies, all with high-quality Gemini-GMOS spectra, within 1 Mpc of 22 z ≲ 1 quasars, all with a signal-to-noise ratio of ∼10 Hubble Space Telescope/COS G130M+G160M spectra. For 572 of these galaxies with stellar masses 107 M☉ &lt; M⋆ &lt; 1011 M☉ and z ≲ 0.5, we show that the H I covering fraction above a threshold of NHI &gt; 1014cm-2 is ≳0.5 within 1.5 virial radii (Rvir ∼ R200m). We examine the H I kinematics and find that the majority of absorption lies within ±250 km s-1 of the galaxy systemic velocity. We examine H I covering fractions over a range of impact parameters to infer a characteristic size of the CGM, ${R}_{\mathrm{CGM}}^{14}$ , as a function of galaxy mass. ${R}_{\mathrm{CGM}}^{14}$ is the impact parameter at which the probability of observing an absorber with NHI &gt;1014 cm-2 is &gt;50%. In this framework, the radial extent of the CGM of M⋆ &gt; 109.9 M☉ galaxies is ${R}_{\mathrm{CGM}}^{14}={346}_{-53}^{+57}$ kpc or ${R}_{\mathrm{CGM}}^{14}\simeq 1.2{R}_{\mathrm{vir}}$ . Intermediate-mass galaxies with 109.2 &lt; M⋆/M☉ &lt; 109.9 have an extent of ${R}_{\mathrm{CGM}}^{14}={353}_{-50}^{+64}$ kpc or ${R}_{\mathrm{CGM}}^{14}\simeq 2.4{R}_{\mathrm{vir}}$ . Low-mass galaxies, M⋆ &lt; 109.2 M☉, show a smaller physical scale of ${R}_{\mathrm{CGM}}^{14}={177}_{-65}^{+70}$ kpc and extend to ${R}_{\mathrm{CGM}}^{14}\simeq 1.6{R}_{\mathrm{vir}}$ . Our analysis suggests that using Rvir as a proxy for the characteristic radius of the CGM likely underestimates its extent.

Keywords: Astronomy databases, Quasar absorption line spectroscopy, Galaxy structure, Circumgalactic medium, Astronomy data analysis, Intergalactic medium, Extragalactic astronomy
Time Delay of Mg II Emission Response for the Luminous Quasar HE 0435-4312: toward Application of the High-accretor Radius-Luminosity Relation in Cosmology. Using six years of spectroscopic monitoring of the luminous quasar HE 0435-4312 (z = 1.2231) with the Southern African Large Telescope, in combination with photometric data (CATALINA, OGLE, SALTICAM, and BMT), we determined a rest-frame time delay of ${296}_{-14}^{+13}$ days between the Mg II broad-line emission and the ionizing continuum using seven different time-delay inference methods. Time-delay artifact peaks and aliases were mitigated using the bootstrap method and prior weighting probability function, as well as by analyzing unevenly sampled mock light curves. The Mg II emission is considerably variable with a fractional variability of ∼5.4%, which is comparable to the continuum variability (∼4.8%). Because of its high luminosity (L3000 = 1046.4 erg s-1), the source is beneficial for a further reduction of the scatter along the Mg II-based radius-luminosity relation and its extended versions, especially when the highly accreting subsample that has an rms scatter of ∼0.2 dex is considered. This opens up the possibility of using the high-accretor Mg II-based radius-luminosity relation for constraining cosmological parameters. With the current sample of 27 reverberation-mapped sources, the best-fit cosmological parameters (Ωm, ΩΛ) = (0.19; 0.62) are consistent with the standard cosmological model within the 1σ confidence level.

Keywords: Accretion, Quasars, Reverberation mapping, Galaxy accretion disks, Emission line galaxies, Galaxy photometry, Active galactic nuclei, Galaxy spectroscopy
Compact Starburst Galaxies with Fast Outflows: Central Escape Velocities and Stellar Mass Surface Densities from Multiband Hubble Space Telescope Imaging. We present multiband Hubble Space Telescope imaging that spans rest-frame near-ultraviolet through near-infrared wavelengths ( ${\lambda }_{\mathrm{rest}}=0.3$ -1.1 μm) for 12 compact starburst galaxies at z = 0.4-0.8. These massive galaxies ( ${{ \mathcal M }}_{* }\sim {10}^{11}\,{{ \mathcal M }}_{\odot }$ ) are driving very fast outflows ( ${v}_{\max }=1000$ -3000 km s-1), and their light profiles are dominated by an extremely compact starburst component (half-light radius ∼ 100 pc). Our goal is to constrain the physical mechanisms responsible for launching these fast outflows by measuring the physical conditions within the central kiloparsec. Based on our stellar population analysis, the central component typically contributes ≈25% of the total stellar mass, and the central escape velocities ${v}_{\mathrm{esc},\mathrm{central}}\approx 900$ km s-1 are a factor of two smaller than the observed outflow velocities. This Requires physical mechanisms that can accelerate gas to speeds significantly beyond the central escape velocities, and it makes clear that these fast outflows are capable of traveling into the circumgalactic medium, and potentially beyond. We find central stellar densities ${{\rm{\Sigma }}}_{{\rm{e}},\mathrm{central}}\approx 3\times {10}^{11}$ ${M}_{\odot }$ kpc-2 comparable to theoretical estimates of the Eddington limit, and we estimate ${{\rm{\Sigma }}}_{1}$ surface densities within the central kiloparsec comparable to those of compact massive galaxies at $0.5\lt z\lt 3.0$ . Relative to "red nuggets" and "blue nuggets" at $z\sim 2$ , we find significantly smaller re values at a given stellar mass, which we attribute to the dominance of a young stellar component in our sample and the better physical resolution for rest-frame optical observations at $z\sim 0.6$ versus $z\sim 2$ . We compare to theoretical scenarios involving major mergers and violent disk instability, and we speculate that our galaxies are progenitors of power-law ellipticals in the local universe with prominent stellar cusps.

Keywords: Starburst galaxies, Galaxy formation, Stellar feedback, Compact galaxies, Galaxy mergers, Extragalactic astronomy, Galaxies
Blow-away in the Extreme Low-mass Starburst Galaxy Pox 186. Pox 186 is an exceptionally small dwarf starburst galaxy hosting a stellar mass of ∼105 M☉. Undetected in H I (M &lt; 106 M☉) from deep 21 cm observations and with an [O III]/[O II] (5007/3727) ratio of 18.3 ± 0.11, Pox 186 is a promising candidate Lyman continuum emitter. It may be a possible analog of low-mass reionization-era galaxies. We present a spatially resolved kinematic study of Pox 186 and identify two distinct ionized gas components: a broad one with σ &gt; 400 km s-1 and a narrow one with σ &lt; 30 km s-1. We find strikingly different morphologies between the two components and direct evidence of outflows as seen in the high-velocity gas. Possible physical mechanisms driving the creation of high-velocity gas seen in [O III] are discussed, from outflow geometry to turbulent mixing between a hot (106 K) star-cluster wind and cooler (104 K) gas clouds. We find a modest mass-outflow rate of 0.022 M☉ yr-1 with a small mass-loading factor of 0.5, consistent with other low-mass galaxies. Finally, we compare the mass-loading factor of Pox 186 with extrapolations from numerical simulations and discuss possible reasons for the apparent discrepancy between them.

Keywords: Dwarf irregular galaxies, Galactic winds, Galaxy kinematics, Galaxy evolution
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: Massive stars, Supernova neutrinos, Dark matter, Late stellar evolution
Detectability of "Merger-nova" Emission from a Long-lived Magnetar in Short Gamma-Ray Bursts. One possible progenitor of short gamma-ray bursts (GRBs) is thought to be from a double neutron star (NS) merger, and the remnant of such a merger may be a supramassive NS, which is supported by rigid rotation and through its survival of hundreds of seconds before collapsing into a black hole (BH). If this is the case, an optical/infrared transient (namely merger-nova) is generated from the ejected materials and it is powered by radioactive decay from r-process, spin-down energy from a supramassive NS, as well as the magnetic wind from a newborn BH. In this paper, we systematically search for the signature of a supramassive NS central engine by analyzing the X-ray emission of short GRBs with internal plateau observed by Swift, and we find that five candidates of short GRBs have such a feature with redshift measurement. Then, we calculate the possible merger-nova emission from those candidates given the typical model parameters by considering the above three energy sources, and compare its brightness with the sensitivity of some optical telescopes. We find that the merger-nova emission of GRB 060801 in K-, r-, and U-bands with variations of Mej (10-4-10-2M⊙), κ (0.1-10 cm2 g-1), and β (0.1-0.3) is very difficult to detect using the Vera C. Rubin, Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), the Zwicky Transient Facility, and the Roman Space Telescope (Roman), except for the case of large ejecta mass Mej = 10-2M⊙. However, we are very hopeful to detect the merger-nova emission of GRBs 090515, 100625A, and 101219A using more sensitive instruments, such as Vera C. Rubin, Pan-STARRS, and Roman. Moreover, the merger-nova emission of GRB 160821B is bright enough to detect in our calculations, and it is also consistent with current real observations of merger-nova emission.

Keywords: Gamma-ray bursts
A Harsh Test of Far-field Scrambling with the Habitable-zone Planet Finder and the Hobby-Eberly Telescope. The Habitable-zone Planet Finder (HPF) is a fiber-fed precise radial velocity (RV) spectrograph at the 10 m Hobby-Eberly Telescope (HET). Due to its fixed-altitude design, the HET pupil changes appreciably across a track, leading to significant changes of the fiber far-field illumination. HPF's fiber scrambler is designed to suppress the impact of these illumination changes on the RVs—but the residual impact on the RV measurements has yet to be probed on-sky. We use GJ 411, a bright early type (M2) M dwarf to probe the effects of far-field input trends due to these pupil variations on HPF RVs. These large changes (∼2x) in the pupil area and centroid present a harsh test of HPF's far-field scrambling. Our results show that the RVs are effectively decoupled from these extreme far-field input changes due to pupil centroid offsets, attesting to the effectiveness of the scrambler design. This experiment allows us to test the impact of these changes with large pupil variation on-sky, something we would not easily be able to do at a conventional optical telescope. While the pupil and illumination changes expected at these other telescopes are small, scaling from our results enables us to estimate and bound these effects, and show that they are controllable even for the new and next generation of RV instruments in their quest to beat down instrumental noise sources toward the goal of a few $\,\mathrm{cm}\,{{\rm{s}}}^{-1}$ .

Keywords: Radial velocity, Exoplanet detection methods, Astronomical instrumentation, Astronomical methods
The Age of Westerlund 1 Revisited. The cluster Westerlund 1 (Wd1) is host to a large variety of post-main-sequence (MS) massive stars. The simultaneous presence of these stars can only be explained by stellar models if the cluster has a finely tuned age of 4-5 Myr, with several published studies independently claiming ages within this range. At this age, stellar models predict that the cool supergiants (CSGs) should have luminosities of $\mathrm{log}(L/{L}_{\odot })\approx 5.5$ , close to the empirical luminosity limit. Here, we test that prediction using archival data and new photometry from Stratospheric Observatory for Infrared Astronomy to estimate bolometric luminosities for the CSGs. We find that these stars are on average 0.4 dex too faint to be 5 Myr old, regardless of which stellar evolutionary model is used, and instead are indicative of a much older age of ${10.4}_{-1.2}^{+1.3}$ Myr. We argue that neither systematic uncertainties in the extinction law nor stellar variability can explain this discrepancy. In reviewing various independent age estimates of Wd1 in the literature, we first show that those based on stellar diversity are unreliable. Second, we reanalyze Wd1's pre-MS stars employing the Damineli extinction law, finding an age of ${7.2}_{-2.3}^{+1.1}$ Myr; older than that of previous studies, but which is vulnerable to systematic errors that could push the age close to 10 Myr. However, there remains significant tension between the CSG age and that inferred from the eclipsing binary W13. We conclude that stellar evolutionary models cannot explain Wd1 under the single-age paradigm. Instead, we propose that the stars in the Wd1 region formed over a period of several megayears.

Keywords: Red supergiant stars, Late stellar evolution, Massive stars, Young star clusters, Supergiant stars, Late-type supergiant stars, Stellar evolution
SRG/ART-XC and NuSTAR Observations of the X-Ray pulsar GRO J1008-57 in the Lowest Luminosity State. We report results of the first broadband observation of the transient X-ray pulsar GRO J1008-57 performed in the quiescent state. Observations were conducted quasi-simultaneously with NuSTAR and the Mikhail Pavlinsky ART-XC telescope on board SRG right before the beginning of a Type I outburst. GRO J1008-57 was detected in the state with the lowest observed luminosity around several ×1034 erg s-1 and consequently accreting from the cold disk. Timing analysis allowed us to detect pulsations during this state for the first time. The observed pulsed fraction of about 20% is, however, almost three times lower than in brighter states when the accretion proceeds through the standard disk. We traced the evolution of the broadband spectrum of the source on a scale of three orders of magnitude in luminosity and found that at the lowest luminosities the spectrum transforms into the double-hump structure similarly to other X-ray pulsars accreting at low luminosities (X Persei, GX 304-1, and A 0535+262) reinforcing the conclusion that this spectral shape is typical for these objects.

Keywords: Neutron stars, High mass x-ray binary stars, Pulsars
On Single-point Inversions of Magnetic Dipole Lines in the Corona. Prompted by a recent paper by Dima and Schad, we reconsider the problem of inferring magnetic properties of the corona using polarimetric observations of magnetic dipole (M1) lines. Dima and Schad point to a potential source of degeneracy in a formalism developed by Plowman, which under some circumstances can lead to the solution being under-determined. Here we clarify the nature of the problem. Its resolution lies in solving for the scattering geometry using the elongation of the observed region of the corona. We discuss some conceptual problems that arise when casting the problem for inversion in the observer's reference frame, and satisfactorily resolve difficulties identified by Plowman, Dima, and Schad.

Keywords: Spectropolarimetry, Solar E corona, Solar physics, Solar corona, Radiative processes
A Population of Heavily Reddened, Optically Missed Novae from Palomar Gattini-IR: Constraints on the Galactic Nova Rate. The nova rate in the Milky Way remains largely uncertain, despite its vital importance in constraining models of Galactic chemical evolution as well as understanding progenitor channels for Type Ia supernovae. The rate has been previously estimated to be in the range of ≈10-300 yr-1, either based on extrapolations from a handful of very bright optical novae or the nova rates in nearby galaxies; both methods are subject to debatable assumptions. The total discovery rate of optical novae remains much smaller (≈5-10 yr-1) than these estimates, even with the advent of all-sky optical time-domain surveys. Here, we present a systematic sample of 12 spectroscopically confirmed Galactic novae detected in the first 17 months of Palomar Gattini-IR (PGIR), a wide-field near-infrared time-domain survey. Operating in the J band (≈1.2 μm), which is significantly less affected by dust extinction compared to optical bands, the extinction distribution of the PGIR sample is highly skewed to a large extinction values (&gt;50% of events obscured by AV ≳ 5 mag). Using recent estimates for the distribution of Galactic mass and dust, we show that the extinction distribution of the PGIR sample is commensurate with dust models. The PGIR extinction distribution is inconsistent with that reported in previous optical searches (null-hypothesis probability &lt;0.01%), suggesting that a large population of highly obscured novae have been systematically missed in previous optical searches. We perform the first quantitative simulation of a 3π time-domain survey to estimate the Galactic nova rate using PGIR, and derive a rate of $\approx {43.7}_{-8.7}^{+19.5}$ yr-1. Our results suggest that all-sky near-infrared time-domain surveys are well poised to uncover the Galactic nova population.

Keywords: White dwarf stars, Interstellar dust extinction, Novae, Cataclysmic variable stars, Classical novae
Probing the Disk-Corona Systems and Broad-line Regions of Changing-look Quasars with X-Ray and Optical Observations. "Changing-look" quasars are a new class of highly variable active galactic nuclei that have changed their spectral type over surprisingly short timescales of just a few years. The origin of this phenomenon is debated, but is likely to reflect some change in the accretion flow. To investigate the disk-corona systems in these objects, we measure optical/UV-X-ray spectral indices ( ${\alpha }_{\mathrm{OX}}$ ) and Eddington ratios ( ${\lambda }_{\mathrm{Edd}}$ ) of 10 previously discovered changing-look quasars at two or more epochs. By comparing these data with simulated results based on the behavior of X-ray binaries, we find possible similarities in spectral indices below the 1% Eddington ratio. We further investigate the Eddington ratios of changing-look quasars before and after their spectral type changes, and find that changing-look quasars cross the 1% Eddington ratio boundary when their broad emission lines disappear/emerge. This is consistent with the disk-wind model as the origin of broad emission lines.

Keywords: Active galactic nuclei, Quasars
Late-time Radio and Millimeter Observations of Superluminous Supernovae and Long Gamma-Ray Bursts: Implications for Central Engines, Fast Radio Bursts, and Obscured Star Formation. We present the largest and deepest late-time radio and millimeter survey to date of superluminous supernovae (SLSNe) and long-duration gamma-ray bursts (LGRBs) to search for associated nonthermal synchrotron emission. Using the Karl G. Jansky Very Large Array (VLA) and the Atacama Large Millimeter/submillimeter Array (ALMA), we observed 43 sources at 6 and 100 GHz on a timescale of ∼ 1-19 yr post-explosion. We do not detect radio/millimeter emission from any of the sources, with the exception of a 6 GHz detection of PTF10hgi, as well as the detection of 6 GHz emission near the location of the SLSN PTF12dam, which we associate with its host galaxy. We use our data to place constraints on central engine emission due to magnetar wind nebulae and off-axis relativistic jets. We also explore nonrelativistic emission from the SN ejecta, and place constraints on obscured star formation in the host galaxies. In addition, we conduct a search for fast radio bursts (FRBs) from some of the sources using VLA phased-array observations; no FRBs are detected to a limit of 16 mJy (7σ; 10 ms duration) in about 40 minutes on source per event. A comparison to theoretical models suggests that continued radio monitoring may lead to detections of persistent radio emission on timescales of ≳ a decade.

Keywords: Core-collapse supernovae, Extragalactic radio sources, Relativistic jets, Radio astrometry, Supernova remnants, Stellar physics, Star formation, Magnetars, Radio transient sources