Sazuna/UAT_keywords huggingface dataset:
The Discovery of a Low-energy Excess in Cosmic-Ray Iron: Evidence of the Past Supernova Activity in the Local Bubble. Since its launch, the Alpha Magnetic Spectrometer—02 (AMS-02) has delivered outstanding quality measurements of the spectra of cosmic-ray (CR) species ( $\bar{p}$ , e±, and nuclei, 1H-8O, 10Ne, 12Mg, 14Si) which resulted in a number of breakthroughs. One of the latest long-awaited surprises is the spectrum of 26Fe just published by AMS-02. Because of the large fragmentation cross section and large ionization energy losses, most of CR iron at low energies is local and may harbor some features associated with relatively recent supernova (SN) activity in the solar neighborhood. Our analysis of the new AMS-02 results, together with Voyager 1 and ACE-CRIS data, reveals an unexpected bump in the iron spectrum and in the Fe/He, Fe/O, and Fe/Si ratios at 1-2 GV, while a similar feature in the spectra of He, O, and Si and in their ratios is absent, hinting at a local source of low-energy CRs. The found excess extends the recent discoveries of radioactive 60Fe deposits in terrestrial and lunar samples and in CRs. We provide an updated local interstellar spectrum (LIS) of iron in the energy range from 1 MeV nucleon-1 to ∼10 TeV nucleon-1. Our calculations employ the GALPROP-HELMOD framework, which has proved to be a reliable tool in deriving the LIS of CR $\bar{p}$ , e-, and nuclei Z ≤ 28.

Keywords: Interplanetary medium, Heliosphere, Cosmic ray detectors, Galactic cosmic rays, Interstellar medium, Cosmic ray sources
Revisiting the Color-Color Selection: Submillimeter and AGN Properties of NUV-r-J Selected Quiescent Galaxies. We examine the robustness of the color-color selection of quiescent galaxies (QGs) against contamination of dusty star-forming galaxies using the latest submillimeter data. We selected 18,304 QG candidates out to z ∼ 3 using the commonly adopted NUV-r-J selection based on the high-quality multiwavelength COSMOS2015 catalog. Using extremely deep 450 and 850 μm catalogs from the latest JCMT SCUBA-2 Large Programs, S2COSMOS and STUDIES, as well as the Atacama Large Millimeter/submillimeter Array submillimeter, VLA 3 GHz, and Spitzer MIPS 24 μm catalogs, we identified luminous, dusty, star-forming galaxies among the QG candidates. We also conducted stacking analyses in the SCUBA-2 450 and 850 μm images to look for less-luminous dusty galaxies among the QG candidates. By cross matching to the 24 μm and 3 GHz data, we were able to identify a subgroup of "IR-radio-bright" QGs that possess strong 450 and 850 μm stacking signals. The potential contamination of these luminous and less-luminous dusty galaxies accounts for approximately 10% of the color-selected QG candidates. In addition, there exists a spatial correlation between the luminous star-forming galaxies and the QGs at a ≲60 kpc scale. Finally, we found a high QG fraction among radio active galactic nuclei (AGNs) at z &lt; 1.5. Our data show a strong correlation between QGs and radio AGNs, which may suggest a connection between the quenching process and the radio-mode AGN feedback.

Keywords: Observational astronomy, AGN host galaxies, Galaxy formation, Quenched galaxies, Galaxy quenching, Astrostatistics, Active galactic nuclei, Galaxy evolution, Extragalactic astronomy, Submillimeter astronomy, High-redshift galaxies, Early-type galaxies
Fuzzy Dark Matter and the 21 cm Power Spectrum. We model the 21 cm power spectrum across the Cosmic Dawn and the Epoch of Reionization (EoR) in fuzzy dark matter (FDM) cosmologies. The suppression of low-mass halos in FDM models leads to a delay in the onset redshift of these epochs relative to cold dark matter (CDM) scenarios. This strongly impacts the 21 cm power spectrum and its redshift evolution. The 21 cm power spectrum at a given stage—i.e., compared at fixed average brightness temperature but varying redshift—of the EoR/Cosmic Dawn process is also modified: in general, the amplitude of 21 cm fluctuations is boosted by the enhanced bias factor of galaxy-hosting halos in FDM. We forecast the prospects for discriminating between CDM and FDM with upcoming power spectrum measurements from HERA, accounting for degeneracies between astrophysical parameters and dark matter properties. If FDM constitutes the entirety of the dark matter and the FDM particle mass is 10-21 eV, HERA can determine the mass to within 20% at 2σ confidence.

Keywords: Cosmology, Galaxy dark matter halos, Large-scale structure of the universe, Reionization, Dark matter, Astronomical simulations
The Merger Dynamics of the Galaxy Cluster A1775: New Insights from Chandra and XMM-Newton for a Cluster Simultaneously Hosting a Wide-angle Tail and a Narrow-angle Tail Radio Source. We present a new study of the merger dynamics of A1775 by analyzing the high-quality Chandra and XMM-Newton archival data. We confirm/identify an arc-shaped edge (i.e., the head) at ∼48 kpc west of the X-ray peak, a split cold gas tail that extends eastward to ∼163 kpc, and a plume of spiral-like X-ray excess (within about 81-324 kpc northeast of the cluster core) that connects to the end of the tail. The head, across which the projected gas temperature rises outward from ${3.39}_{-0.18}^{+0.28}$ to ${5.30}_{-0.43}^{+0.54}$ keV, is found to be a cold front with a Mach number of ${ \mathcal M }\sim 0.79$ . Along the surfaces of the cold front and tail, typical Kelvin-Helmholtz instability features (noses and wings, etc.) are found and are used to constrain the upper limit of the magnetic field (∼11.2 μG) and the viscosity suppression factor (∼0.01). Combining optical and radio evidence, we propose a two-body merger (instead of systematic motion in a large-scale gas environment) scenario and have carried out idealized hydrodynamic simulations to verify it. We find that the observed X-ray emission and temperature distributions can be best reproduced with a merger mass ratio of 5 after the first pericentric passage. The NAT radio galaxy is thus more likely to be a single galaxy falling into the cluster center at a relative velocity of 2800 km s-1, a speed constrained by its radio morphology. The infalling subcluster is expected to have a relatively low gas content, because only a gas-poor subcluster can cause central-only disturbances as observed in such an off-axis merger.

Keywords: Galaxy clusters, Hydrodynamical simulations, Intracluster medium, Radio galaxies
Ice-coated Pebble Drift as a Possible Explanation for Peculiar Cometary CO/H<SUB>2</SUB>O Ratios. To date, at least three comets—2I/Borisov, C/2016 R2 (PanSTARRS), and C/2009 P1 (Garradd)—have been observed to have unusually high CO concentrations compared to water. We attempt to explain these observations by modeling the effect of drifting solid (ice and dust) material on the ice compositions in protoplanetary disks. We find that, independent of the exact disk model parameters, we always obtain a region of enhanced ice-phase CO/H2O that spreads out in radius over time. The inner edge of this feature coincides with the CO snowline. Almost every model achieves at least CO/H2O of unity, and one model reaches a CO/H2O ratio &gt;10. After running our simulations for 1 Myr, an average of 40% of the disk ice mass contains more CO than H2O ice. In light of this, a population of CO-ice-enhanced planetesimals are likely to generally form in the outer regions of disks, and we speculate that the aforementioned CO-rich comets may be more common, both in our own solar system and in extrasolar systems, than previously expected.

Keywords: Stellar accretion disks, Hydrodynamical simulations, Comet volatiles , Protoplanetary disks
Isotope Systematics of Presolar Silicate Grains: New Insights from Magnesium and Silicon. We report on Mg and Si isotope data of 86 presolar silicate grains identified through NanoSIMS oxygen ion imaging in thin sections of carbonaceous and ordinary chondrites. The O, Mg, and Si isotope data of 106 presolar silicates (including grains studied previously by our group) suggest division of O isotope Group 1 grains into four subpopulations: (i) "normal," (ii) 25Mg-rich, (iii) 26Mg-rich, and (iv) 25Mg-poor. Normal Group 1 grains (∼60% of Group 1 grains) formed in the winds of low-mass asymptotic giant branch (AGB) stars, with Mg and Si defining linear arrays with slopes of ∼0.9 and 1.37, respectively, in three-isotope representations, most likely representing Galactic chemical evolution (GCE). The 25Mg-rich grains (∼25%) show enrichments in 25Mg of up to a factor 2.4 relative to solar composition and most likely formed in supernova (SN) ejecta or the winds of intermediate-mass AGB stars. The 26Mg-rich and 25Mg-poor Group 1 grains lie below the Mg GCE line and their isotopic compositions favor origins from supergiants or SNe. The O isotope Group 2 grains show a wide range of Mg-isotopic compositions, similar to Group 1 grains, with likely origins from massive AGB stars, super-AGB stars, supergiants, and SNe. The Mg- and Si-isotopic compositions of Group 4 grains are compatible with previously proposed SN origins. Our results suggest that &gt;30% of presolar silicates formed in the winds of supergiants and in SN ejecta, and that low-mass AGB stars appear to have contributed only some 50% to presolar silicates, less than previously thought.

Keywords: Meteorites, Circumstellar matter, Interstellar dust, Stellar nucleosynthesis
Targeting Bright Metal-poor Stars in the Disk and Halo Systems of the Galaxy. We present the results of spectroscopic follow-up for 1897 low-metallicity star candidates, selected from the Best &amp; Brightest (B&amp;B) Survey, carried out with the GMOS-N/S (Gemini North/South telescopes) and Goodman (SOAR Telescope) spectrographs. From these low-resolution (R ∼ 2000) spectra, we estimate stellar atmospheric parameters, as well as carbon and magnesium abundance ratios. We confirm that 56% of our program stars are metal-poor ([Fe/H] &lt; - 1.0), 30% are very metal-poor (VMP; [Fe/H] &lt; - 2.0), and 2% are extremely metal-poor (EMP; [Fe/H] &lt; - 3.0). There are 191 carbon-enhanced metal-poor (CEMP) stars, resulting in CEMP fractions of 19% and 43% for the VMP and EMP regimes, respectively. A total of 94 confirmed CEMP stars belong to Group I (A(C) ≳ 7.25) and 97 to Group II (A(C) ≲ 7.25) in the Yoon-Beers A(C)-[Fe/H] diagram. Moreover, we combine these data with Gaia EDR3 astrometric information to delineate new target-selection criteria, which have been applied to the Goodman/SOAR candidates, to more than double the efficiency for identification of bona fide VMP and EMP stars in comparison to random draws from the B&amp;B catalog. We demonstrate that this target-selection approach can achieve success rates of 96%, 76%, 28%, and 4% for [Fe/H] ≤ - 1.5, ≤ - 2.0, ≤ - 2.5 and ≤ - 3.0, respectively. Finally, we investigate the presence of dynamically interesting stars in our sample. We find that several VMP/EMP ([Fe/H] ≤ - 2.5) stars can be associated with either the disk system or halo substructures like Gaia-Sausage/Enceladus and Sequoia.

Keywords: Milky Way formation, Milky Way dynamics, Chemical abundances, Milky Way disk, Milky Way stellar halo, Spectroscopy, Milky Way evolution, Population II stars, CEMP stars, Stellar atmospheres
Disentangled Representation Learning for Astronomical Chemical Tagging. Modern astronomical surveys are observing spectral data for millions of stars. These spectra contain chemical information that can be used to trace the Galaxy's formation and chemical enrichment history. However, extracting the information from spectra and making precise and accurate chemical abundance measurements is challenging. Here we present a data-driven method for isolating the chemical factors of variation in stellar spectra from those of other parameters (i.e., Teff, log g, [Fe/H]). This enables us to build a spectral projection for each star with these parameters removed. We do this with no ab initio knowledge of elemental abundances themselves and hence bypass the uncertainties and systematics associated with modeling that rely on synthetic stellar spectra. To remove known nonchemical factors of variation, we develop and implement a neural network architecture that learns a disentangled spectral representation. We simulate our recovery of chemically identical stars using the disentangled spectra in a synthetic APOGEE-like data set. We show that this recovery declines as a function of the signal-to-noise ratio but that our neural network architecture outperforms simpler modeling choices. Our work demonstrates the feasibility of data-driven abundance-free chemical tagging.

Keywords: Stellar astronomy, Stellar spectral lines, Neural networks
The Nature of Soft Excess in ESO 362-G18 Revealed by XMM-Newton and NuSTAR Spectroscopy. We present a detailed spectral analysis of the joint XMM-Newton and NuSTAR observations of the active galactic nuclei (AGNs) in the Seyfert 1.5 Galaxy ESO 362-G18. The broadband (0.3-79 keV) spectrum shows the presence of a power-law continuum with a soft excess below 2 keV, iron Kα emission (∼6.4 keV), and a Compton hump (peaking at ∼20 keV). We find that the soft excess can be modeled by two different possible scenarios: a warm (kTe ∼ 0.2 keV) and optically thick (τ ∼ 34) Comptonizing corona, or with a relativistically blurred reflection off a high-density ( $\mathrm{log}[{n}_{{\rm{e}}}/{\mathrm{cm}}^{-3}]\gt 18.3$ ) inner disk. These two models cannot be easily distinguished solely from their fit statistics. However, the low temperature (kTe ∼ 20 keV) and the thick optical depth (τ ∼ 5) of the hot corona required by the warm corona scenario are uncommon for AGNs. We also fit a "hybrid" model, which includes both disk reflection and a warm corona. Unsurprisingly, as this is the most complex of the models considered, this provides the best fit, and more reasonable coronal parameters. In this case, the majority of the soft excess flux arises in the warm corona component. However, based on recent simulations of warm coronae, it is not clear whether such a structure can really exist at the low accretion rates relevant for ESO 362-G18 ( $\dot{m}\sim 0.015$ ). This may therefore argue in favor of a scenario in which the soft excess is instead dominated by the relativistic reflection. Based on this model, we find that the data would require a compact hot corona (h ∼ 3 RHorizon) around a rapidly spinning (a⋆ &gt; 0.927) black hole.

Keywords: X-ray astronomy, Supermassive black holes, High energy astrophysics, Seyfert galaxies, Active galactic nuclei, X-ray active galactic nuclei, Spectroscopy, Astrophysical black holes
A Multiwavelength Study of the Formation of the AFGL 333-Ridge. We presented a multiwavelength study of the AFGL 333-Ridge. The molecular line data reveals that the AFGL 333-Ridge has two independent velocity components at -50.5 and -48.0 km s-1. In the position-velocity diagram, the bridge feature connects with two parts that are spatially correlated but separated in velocity. This observational evidence supports the scenario that the two velocity components have collided and merged into one molecular cloud. The majority of Class I young stellar objects (YSOs) are distributed within the collision region, suggesting that the cloud-cloud collision has induced the YSOs' formation in the ridge. Using the radio recombination line (RRL) data obtained by the Five-hundred-meter Aperture Spherical radio Telescope, the RRL velocities of three H II regions are consistent with that of the AFGL 333-Ridge. By comparing the three H II regions' dynamical ages with the collision timescale of the two components, we conclude that the influence of the three H II regions may not drive the two clouds to merge. The formation of the AFGL 333-Ridge is probably due to the expansion of the giant H II region W4.

Keywords: Star forming regions, H II regions, Interstellar filaments
FOXSI-2 Solar Microflares. II. Hard X-ray Imaging Spectroscopy and Flare Energetics. We study the nature of energy release and transfer for two sub-A class solar microflares observed during the second Focusing Optics X-ray Solar Imager (FOXSI-2) sounding rocket flight on 2014 December 11. FOXSI is the first solar-dedicated instrument to utilize focusing optics to image the Sun in the hard X-ray (HXR) regime, sensitive to energies of 4-20 keV. Through spectral analysis of the microflares using an optically thin isothermal plasma model, we find evidence for plasma heated to ∼10 MK and emission measures down to ∼1044 cm-3. Though nonthermal emission was not detected for the FOXSI-2 microflares, a study of the parameter space for possible hidden nonthermal components shows that there could be enough energy in nonthermal electrons to account for the thermal energy in microflare 1, indicating that this flare is plausibly consistent with the standard thick-target model. With a solar-optimized design and improvements in HXR focusing optics, FOXSI-2 offers approximately five times greater sensitivity at 10 keV than the Nuclear Spectroscopic Telescope Array for typical microflare observations and allows for the first direct imaging spectroscopy of solar HXRs with an angular resolution at scales relevant for microflares. Harnessing these improved capabilities to study small-scale events, we find evidence for spatial and temporal complexity during a sub-A class flare. This analysis, combined with contemporaneous observations by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory, indicates that these microflares are more similar to large flares in their evolution than to the single burst of energy expected for a nanoflare.

Keywords: The Sun, Solar flare spectra, Active sun, X-ray telescopes, Solar corona, Solar x-ray flares, Solar instruments
Circumbinary Disk Accretion into Spinning Black Hole Binaries. Supermassive black hole binaries are likely to accrete interstellar gas through a circumbinary disk. Shortly before merger, the inner portions of this circumbinary disk are subject to general relativistic effects. To study this regime, we approximate the spacetime metric of close orbiting black holes by superimposing two boosted Kerr-Schild terms. After demonstrating the quality of this approximation, we carry out very long-term general relativistic magnetohydrodynamic simulations of the circumbinary disk. We consider black holes with spin dimensionless parameters of magnitude 0.9, in one simulation parallel to the orbital angular momentum of the binary, but in another anti-parallel. These are contrasted with spinless simulations. We find that, for a fixed surface mass density in the inner circumbinary disk, aligned spins of this magnitude approximately reduce the mass accretion rate by 14% and counter-aligned spins increase it by 45%, leaving many other disk properties unchanged.

Keywords: Accretion, Supermassive black holes, Rotating black holes, Magnetohydrodynamical simulations
X-Ray Constraint on the Location of the AGN Torus in the Circinus Galaxy. The location of the obscuring "torus" in an active galactic nucleus (AGN) is still an unresolved issue. The line widths of X-ray fluorescence lines originating from the torus, particularly Fe Kα, carry key information on the radii of line-emitting regions. Utilizing XCLUMPY, an X-ray clumpy torus model, we develop a realistic model of emission line profiles from an AGN torus where we take into account line broadening due to the Keplerian motion around the black hole. Then, we apply the updated model to the best available broadband spectra (3-100 keV) of the Circinus galaxy observed with Suzaku, XMM-Newton, Nuclear Spectroscopic Telescope Array, and Chandra, including 0.62 Ms Chandra/HETG data. We confirm that the torus is Compton-thick (hydrogen column density along the equatorial plane is ${N}_{{\rm{H}}}^{\mathrm{Equ}}={2.16}_{-0.16}^{+0.24}\times {10}^{25}\ {\mathrm{cm}}^{-2}$ ), geometrically thin (torus angular width $\sigma \,={10.3}_{-0.3}^{+0.7}\,{\rm{d}}{\rm{e}}{\rm{g}}$ ), viewed edge-on (inclination $i={78.3}_{-0.9}^{+0.4}\,{\rm{d}}{\rm{e}}{\rm{g}}$ ), and has supersolar abundance ( ${1.52}_{-0.06}^{+0.04}$ times solar). Simultaneously analyzing the Chandra/HETG first-, second-, and third-order spectra with consideration of the spatial extent of the Fe Kα line-emitting region, we constrain the inner radius of the torus to be ${1.9}_{-0.8}^{+3.1}\times {10}^{5}$ times the gravitational radius, or ${1.6}_{-0.9}^{+1.5}\times {10}^{-2}\ \mathrm{pc}$ for a black hole mass of (1.7 ± 0.3) × 106 M☉. This is about three times smaller than that estimated from the dust sublimation radius, suggesting that the inner side of the dusty region of the torus is composed of dust-free gas.

Keywords: Supermassive black holes, High energy astrophysics, Seyfert galaxies, Active galactic nuclei, X-ray active galactic nuclei, Astrophysical black holes
The Cosmic Ultraviolet Baryon Survey (CUBS). II. Discovery of an H<SUB>2</SUB>-bearing DLA in the Vicinity of an Early-type Galaxy at z = 0.576. We report the serendipitous detection of an H2-bearing damped Lyα absorber at z = 0.576 in the spectrum of the QSO J0111-0316 in the Cosmic Ultraviolet Baryon Survey. Spectroscopic observations from Hubble Space Telescope-COS in the far-ultraviolet reveal a damped absorber with log[N(H I)/cm-2] = 20.1 ± 0.2 and log[N(H2)/cm-2] $={18.97}_{-0.06}^{+0.05}$ . The diffuse molecular gas is found in two velocity components separated by ∆ ν ≍ 60 km s-1, with &gt;99.9% of the total H2 column density concentrated in one component. At a metallicity of ≍50% of solar, there is evidence for Fe enhancement and dust depletion, with a dust-to-gas ratio κO ≍ 0.4. A galaxy redshift survey conducted with IMACS and LDSS-3C on Magellan reveals an overdensity of nine galaxies at projected distance d ≤ 600 proper kpc (pkpc) and line-of-sight velocity offset ∆ νg ≤ 300 km s-1 from the absorber. The closest is a massive, early-type galaxy at d = 41 pkpc that contains ≍70% of the total stellar mass identified at d ≤ 310 pkpc of the H2 absorber. The close proximity of the H2-bearing gas to the quiescent galaxy and the Fe-enhanced chemical abundance pattern of the absorber suggest a physical connection, in contrast to a picture in which DLAs are primarily associated with gas-rich dwarfs. This case study illustrates that deep galaxy redshift surveys are needed to gain insight into the diverse environments that host dense and potentially star-forming gas. * Based on data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory and the NASA/ESA Hubble Space Telescope operated by the Space Telescope Science Institute and the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

Keywords: Interstellar molecules, Quasar absorption line spectroscopy, Galaxy groups, Interstellar medium, Circumgalactic medium, Extragalactic astronomy
Magnetohydrodynamic Simulations of Spicular Jet Propagation Applied to Lower Solar Atmosphere Model. We report a series of numerical experiments for the propagation of a momentum pulse representing a chromospheric jet, simulated using an idealized magnetohydrodynamic model. The jet in a stratified lower solar atmosphere is subjected to a varied initial driver (amplitude, period) and magnetic field conditions to examine the parameter influence over jet morphology and kinematics. The simulated jet captured key observed spicule characteristics including maximum heights, field-aligned mass motions/trajectories, and cross-sectional width deformations. Next, the jet features also show a prominent bright, bulb-like apex, similar to reported observed chromospheric jets, formed due to the higher density of plasma and/or waves. Furthermore, the simulations highlight the presence of not yet observed internal crisscross/knots substructures generated by shock waves reflected within the jet structure. Therefore we suggest verifying these predicted fine-scale structures in highly localized lower solar atmospheric jets, e.g., in spicules or fibrils by high-resolution observations, offered by the Daniel K. Inoyue Solar Telescope or otherwise.

Keywords: Solar atmosphere, Jets, Solar spicules, Solar corona, Magnetohydrodynamical simulations