Sazuna/UAT_keywords huggingface dataset:
RXTE Observation of the Nonthermal Emission from the Early Stage Merger in A1750. We make the first observation-based calculation of the energy that goes into cosmic ray protons versus cosmic ray electrons in shock acceleration during structure formation. We find a ratio of energy in cosmic ray protons to energy in cosmic ray electrons of 0.86. This value, calculated from the nonthermal X-ray component reported here from RTXE and the Fermi LAT upper limit for gamma-ray emission, is significantly lower than theoretical estimates that place most of the nonthermal energy in protons. Our estimate is based on the detection of nonthermal X-ray emission using the 3-20 keV RXTE spectrum, which shows residual emission not well modeled by a single thermal component. The statistical significance of adding a nonthermal, power-law component is 96%. The significance of adding a second thermal component is 90%. The addition of a component consisting of full cosmic X-ray background fluctuation to an isothermal model is significant with 92% confidence. The cumulative probability for the two-thermal-component model is 81% and 90% for the thermal plus power law. Thus the model with nonthermal emission is the preferred description of the data. Evidence of shock heating between the clusters in the spectro-imaging data of XMM, Chandra, and Suzaku indicates that a cosmic ray component should also be present and supports a nonthermal interpretation for the additional component. The bolometric nonthermal X-ray luminosity is 1.6 × 1044 ergs s-1, 36% of the total X-ray emission in the 0.1-100 keV band.

Keywords: Galaxy clusters, Non-thermal radiation sources
Laboratory Measurements of Stretching Band Strengths of Deuterated Quenched Carbonaceous Composites. The observed large variation in the abundance of deuterium (D) in the interstellar medium suggests that a significant fraction of D may be depleted into polycyclic aromatic hydrocarbons (PAHs). Signatures of the deuteration of PAHs are expected to appear most clearly through the C-D stretching modes at 4.4-4.7 μm, whose strengths in emission spectra relative to those of the C-H stretching modes at 3.3-3.5 μm provide the relative abundance of D to hydrogen (H) in PAHs, once we have accurate relative band strengths of both stretching modes. We report experimental results of the band strengths of the C-D stretching modes relative to the C-H stretching modes. We employ a laboratory analog of interstellar carbonaceous dust, Quenched Carbonaceous Composite (QCC), and synthesize deuterated QCC (D-QCC) by replacing the QCC starting gas of CH4 with mixtures of CH4 and CD4 with various ratios. Infrared spectra of D-QCC are taken to estimate the relative band strengths of the stretching modes, while the D/H ratios in the D-QCC samples are measured with a nanoscale secondary ion mass spectrometer. We obtain relative strengths of aromatic and aliphatic C-D to C-H stretches as 0.56 ± 0.04 and 0.38 ± 0.01 per D/H, respectively. The ratio for the aromatic stretches is in good agreement with the results of theoretical calculations, while that for the aliphatic stretches is smaller than that for the aromatic stretches. The present results do not significantly change the D/H ratios in interstellar PAHs that have previously been estimated from observed spectra.

Keywords: Interstellar dust, Isotopic abundances, Polycyclic aromatic hydrocarbons, Infrared astronomy, Interstellar medium
The Jet and Resolved Features of the Central Supermassive Black Hole of M87 Observed with the Event Horizon Telescope (EHT). We report the result of our independent image reconstruction of the M87 from the public data of the Event Horizon Telescope Collaborators (EHTC). Our result is different from the image published by the EHTC. Our analysis shows that (a) the structure at 230 GHz is consistent with those of lower-frequency very long baseline interferometry observations, (b) the jet structure is evident at 230 GHz extending from the core to a few milliarcsecond, although the intensity rapidly decreases along the axis, and (c) the "unresolved core" is resolved into three bright features presumably showing an initial jet with a wide opening angle of ~70°. The ring-like structures of the EHTC can be created not only from the public data but also from the simulated data of a point image. Also, the rings are very sensitive to the field-of-view (FOV) size. The u-v coverage of the Event Horizon Telescope (EHT) lacks ~ 40 μas fringe spacings. Combining with a very narrow FOV, it created the ~40 μas ring structure. We conclude that the absence of the jet and the presence of the ring in the EHTC result are both artifacts owing to the narrow FOV setting and the u-v data sampling bias effect of the EHT array. Because the EHTC's simulations only take into account the reproduction of the input image models, and not those of the input noise models, their optimal parameters can enhance the effects of sampling bias and produce artifacts such as the ~40 μas ring structure, rather than reproducing the correct image.

Keywords: Supermassive black holes, Very long baseline interferometry
Variable Active Galactic Nuclei in the Galaxy Evolution Explorer Time Domain Survey. We searched the northern hemisphere fields of the Galaxy Evolution Explorer Time Domain Survey for galaxies with UV variability indicative of active galactic nuclei (AGNs). We identified 48 high-probability candidate AGNs from a parent sample of 1819 galaxies in the NASA Sloan Atlas catalog. We further characterized these systems using optical spectroscopic diagnostics, Wide-field Infrared Survey Explorer IR color selection criteria, and spectral energy distribution modeling. Of the 48 candidates, eight were identified as AGNs from optical emission lines, two were identified by their IR colors, and 28 were identified through spectral energy decomposition. Observational biases of each selection method are discussed in connecting these AGN subsamples to another. By selecting AGNs based on UV variability, we also identified six low-mass AGN candidates, all of which would have been missed by spectroscopic selection.

Keywords: Intermediate-mass black holes, Supermassive black holes, Active galaxies, Active galactic nuclei, Time domain astronomy, Ultraviolet photometry
Evolution of Main-sequence-like Surviving Companions in Type Ia Supernova Remnants. Recent theoretical and numerical studies of Type Ia supernovae (SNe Ia) explosions within the single-degenerate scenario suggest that the nondegenerate companions could survive during the supernova impact and could be detectable in nearby supernova remnants. However, observational efforts show less promising evidence of the existence of surviving companions from the standard single-degenerate channels. The spin-up/spin-down models are possible mechanisms to explain the nondetection of surviving companions. In these models, the spin-up phase could increase the critical mass for explosion, leading to a super-Chandrasekhar-mass explosion, and the spin-down phase could lead to extra mass loss and angular momentum redistribution. Since the spin-down timescale for the delayed explosion of a rotating white dwarf is unclear, in this paper we explore a vast parameter space of main-sequence-like surviving companions via two-dimensional hydrodynamic simulations of supernova impact and the subsequent stellar evolution of surviving companions. Tight universal relations to describe the mass-stripping effect, supernova kick, and depth of supernova heating are provided. Our results suggest that the not-yet-detected surviving companions from observations of nearby SN Ia remnants might favor low-mass companions, short binary separation, or stronger supernova explosion energies than the standard single-degenerate channels.

Keywords: Hydrodynamical simulations, Type Ia supernovae, Stellar evolution
The Role of Inner H I Mass in Regulating the Scatter of the Mass-Metallicity Relation. We use 789 disk-like, star-forming galaxies (with 596 H I detections) from H I follow-up observations for the SDSS-IV MaNGA survey to study the possible role of inner H I gas in causing secondary dependences in the mass-gas-phase metallicity relation. We use the gas-phase metallicity derived at the effective radii of the galaxies. We derive the inner H I mass within the optical radius, but also use the total H I mass and star formation rate (SFR) for a comparison. We confirm the anticorrelation between the total H I mass and gas-phase metallicity at fixed stellar mass, but the anticorrelation is significantly strengthened when the total H I mass is replaced by the inner H I mass. Introducing a secondary relation with the inner H I mass can produce a small but noticeable decrease (16%) in the scatter of the mass-gas-phase metallicity relation, in contrast to the negligible effect with the SFR. The correlation with the inner H I mass is robust when using different diagnostics of metallicity, but the correlation with SFR is not. The correlation with the inner H I mass becomes much weaker when the gas-phase metallicity is derived in the central region instead of at the effective radius. These results support the idea that the scatter in the mass-metallicity relation is regulated by gas accretion, and not directly by the SFR, and stress the importance of deriving the gas mass and the metallicity from roughly the same region. The new relation between inner H I mass and gas-phase metallicity will provide new constraints for chemical and galaxy evolution models.

Keywords: Galaxy formation, Galaxy abundances, Metallicity, Galaxy evolution
Dense Gas Formation via Collision-induced Magnetic Reconnection in a Disk Galaxy with a Bisymmetric Spiral Magnetic Field. Recently, a collision-induced magnetic reconnection (CMR) mechanism was proposed to explain a dense filament formation in the Orion A giant molecular cloud. A natural question is whether CMR works elsewhere in the Galaxy. As an initial attempt to answer the question, this paper investigates the triggering of CMR and the production of dense gas in a flat-rotating disk with a modified Bisymmetric spiral (BSS) magnetic field. Cloud-cloud collisions at field reversals in the disk are modeled with the Athena++ code. Under the condition that is representative of the warm neutral medium, the cloud-cloud collision successfully triggers CMR at different disk radii. However, dense gas formation is hindered by the dominating thermal pressure, unless a moderately stronger initial field ≳5 μG is present. The strong-field model, having a larger Lundquist number S L and lower plasma β, activates the plasmoid instability in the collision midplane, which is otherwise suppressed by the disk rotation. We speculate that CMR can be common if more clouds collide along field reversals. However, to witness the CMR process in numerical simulations, we need to significantly resolve the collision midplane with a spatial dynamic range ≳106. If Milky Way spiral arms indeed coincide with field reversals in BSS, it is possible that CMR creates or maintains dense gas in the arms. High-resolution, high-sensitivity Zeeman/Faraday rotation observations are crucial for finding CMR candidates that have helical fields.

Keywords: Computational astronomy, Theoretical models, Disk galaxies, Milky Way magnetic fields, Astrophysical fluid dynamics, Molecular clouds, Milky Way disk, Star formation, Interstellar medium, Warm neutral medium, Magnetic fields, Magnetohydrodynamical simulations
The Extreme Scarcity of Dust-enshrouded Red Supergiants: Consequences for Producing Stripped Stars via Winds. Quiescent mass loss during the red supergiant (RSG) phase has been shown to be far lower than prescriptions typically employed in single-star evolutionary models. Importantly, RSG winds are too weak to drive the production of Wolf-Rayet (WR) stars and stripped-envelope supernovae (SE-SNe) at initial masses of roughly 20-40 M ⊙. If single stars are to make WR stars and SE-SNe, this shifts the burden of mass loss to rare dust-enshrouded RSGs (DE-RSGs), objects claimed to represent a short-lived, high-mass-loss phase. Here, we take a fresh look at the purported DE-RSGs. By modeling the mid-IR excesses of the full sample of RSGs in the Large Magellanic Cloud, we find that only one RSG has both a high mass-loss rate ( $\dot{M}$ ≥ 10-4 M ⊙ yr-1) and a high optical circumstellar dust extinction (7.92 mag). This RSG is WOH G64, and it is the only one of the 14 originally proposed DE-RSGs that is actually dust enshrouded. The rest appear to be either normal RSGs without strong IR excess, or lower-mass asymptotic giant branch stars. Only one additional object in the full catalog of RSGs (not previously identified as a DE-RSG) shows strong mid-IR excess. We conclude that if DE-RSGs do represent a pre-SN phase of enhanced $\dot{M}$ in single stars, it is extremely short-lived, only capable of removing ≤2 M ⊙ of material. This rules out the single-star post-RSG pathway for the production of WR stars, luminous blue variables, and SE-SNe. Single-star models should not employ $\dot{M}$ -prescriptions based on these extreme objects for any significant fraction of the RSG phase.

Keywords: Massive stars, Stellar mass loss, Core-collapse supernovae, Stellar evolution
Characterizing the Optical Nature of the Blazar S5 1803+784 during Its 2020 Flare. We report the results from our study of the blazar S5 1803+784 carried out using quasi-simultaneous B, V, R, and I observations from 2020 May to 2021 July on 122 nights. Our observing campaign detected a historically bright optical flare during MJD 59,063.5-MJD 59,120.5. We also found the source in its brightest (R mag = 13.617) and faintest (R mag = 15.888) states to date. On 13 nights, covering both flaring and nonflaring periods, we searched for intraday variability using the power-enhanced F-test and the nested ANOVA test. We found significant variability in 2 of these 13 nights. However, no such variability was detected during the flaring period. From correlation analysis, we observed that the emission in all optical bands were strongly correlated with a time lag of ~0 days. To get insights into its dominant emission mechanisms, we generated the optical spectral energy distributions of the source on 79 nights and estimated the spectral indices by fitting a simple power law. The spectral index varied from 1.392 to 1.911 and showed significant variations with time and R-band magnitude. We detected a mild bluer-when-brighter (BWB) trend during the whole monitoring period and a much stronger BWB trend during the flare. We also carried out a periodicity search using four different methods and found no significant periodicity during our observation period. Based on the analysis during the flaring state of the source one can say that the emissions most likely originate from the jet rather than from the accretion disk.

Keywords: Blazars, Active galactic nuclei, Active galaxies, BL Lacertae objects
Density and Velocity Fluctuations of Alpha Particles in Magnetic Switchbacks. Magnetic switchbacks, or sudden reversals in the magnetic field's radial direction, are one of the more striking observations of the Parker Solar Probe (PSP) in its mission thus far. While their precise production mechanisms are still unknown, the two main theories are via interchange reconnection events and in situ generation. In this work, density and abundance variations of alpha particles are studied inside and outside individual switchbacks. We find no consistent compositional differences in the alpha particle abundance ratio, n  α p , inside versus outside switchbacks, nor do we observe any signature when separating the switchbacks according to V  α p /V  pw , the ratio of the alpha-proton differential speed to the wave phase speed (the speed at which the switchback is traveling). We argue that these measurements cannot be used to rule in favor of one production mechanism over the other, due to the distance between PSP and the postulated interchange reconnection events. In addition, we examine the 3D velocity fluctuations of protons and alpha particles within individual switchbacks. While switchbacks are always associated with increases in proton velocity, alpha velocities may be enhanced, unchanged, or decrease. This is due to the interplay between V  pw  and V  α p , with the Alfvénic motion of the alpha particles vanishing as the difference ∣V  pw - V  α p ∣ decreases. We show how the Alfvénic motion of both the alphas and the protons through switchbacks can be understood as an approximately rigid arm rotation about the location of the wave frame, and illustrate that the wave frame can therefore be estimated using particle measurements alone, via sphere fitting.

Keywords: Space plasmas, Solar wind, Heliosphere
Chemical Evolution History of MaNGA Galaxies. We show the results of a study using the spectral synthesis technique study for the full MaNGA sample showing their chemical enrichment history (ChEH) as well as the evolution of the stellar mass-metallicity relation (MZR) over cosmic time. We find that the more massive galaxies became enriched first and the lower-mass galaxies did so later, producing a change in the MZR that becomes shallower in time. Separating the sample into morphology and star-forming status bins, some particularly interesting results appear: The mass dependence of the MZR becomes less relevant for later morphological types, to the extent that it inverts for Sd/Irr galaxies, suggesting that morphology is at least as important a factor as mass in the chemical evolution. The MZR for the full sample shows a flattening at the high-mass end and another in the low-mass range, but the former only appears for retired galaxies, while the latter only appears for star-forming galaxies. We also find that the average metallicity gradient is currently negative for all mass bins, but for low-mass galaxies, it was inverted at some point in the past, before which all galaxies had a positive gradient. We also compare how diverse the ChEHs are in the different bins we considered, as well as what primarily drives the diversity: By how much galaxies become enriched, or how quickly they do so.

Keywords: Galaxy chemical evolution, Chemical abundances, Galaxies
Extreme Solar Flare-driven Short-wave Fadeout Observed by SuperDARN ZHO Radar. Based on the observations from the Super Dual Auroral Radar Network at the Zhongshan Station (-74.9 MLAT, 97.2 MLON) and GOES satellites X-ray sensor, we present the first statistical study of the dayside ionospheric short-wave fadeout (SWF) events on the Southern Hemispheric high latitude from the years 2010-2019 and provide a normal characteristic of SWF with onset of 6 minutes 54 s, blackout of 20 minutes 24 s, and recovery of 39 minutes 36 s, respectively. All the SWF events in this work are selected to be caused by extreme flares. The statistical analysis shows both short-type and long-type SWF onset phases. Onset/blackout phase duration of long events is highly correlated with flare duration (0.79, 0.60), the SWF is mainly driven by the flare radiation profile, and the soft X-ray flux rise rate is higher for short-onset events than for most long-onset events, which is the main reason for the difference between the two types of events. In addition, the effect of ionospheric sluggishness on long-onset events also needs to be considered. The relationship between each phase's durations of long SWFs and the effective peak X-ray flux is not obvious. However, the correlation between the integrated effective X-ray flux and the onset/blackout phase duration of long events is significant.

Keywords: Photoionization, Earth ionosphere, Solar x-ray flares
Intermediate and Power-law Inflation in the Tachyon Model with Constant Sound Speed. By adopting the intermediate and power-law scale factors, we study the tachyon inflation with constant sound speed. We perform some numerical analysis on the perturbation and non-Gaussianity parameters in this model and compare the results with observational data. By using the constraints on the scalar spectral index and tensor-to-scalar ratio obtained from Planck2018 TT, TE, and EE+lowE+lensing+BAO+BK14 data; the constraints on the running of the scalar spectral index obtained from Planck2018 TT, TE, and EE+lowEB+lensing data; and the constraints on tensor spectral index obtained from Planck2018 TT, TE, and EE+lowE+lensing+BK14+BAO+LIGO and Virgo2016 data, we find the observationally viable ranges of the model's parameters at both 68% CL and 95% CL. We also analyze the non-Gaussian features of the model in the equilateral and orthogonal configurations. Based on Planck2018 TTT, EEE, TTE, and EET data, we find constraints on the sound speed of 0.276 ≤ c  s  ≤ 1 at 68% CL, 0.213 ≤ c  s  ≤ 1 at 95% CL, and 0.186 ≤ c  s  ≤ 1 at 97% CL.

Keywords: Observational cosmology, Inflationary universe, Early universe
The Exploration of Local VolumE Satellites (ELVES) Survey: A Nearly Volume-limited Sample of Nearby Dwarf Satellite Systems. We present the final sample of the Exploration of Local VolumE Satellites (ELVES) survey, a survey of the dwarf satellites of a nearly volume-limited sample of Milky Way (MW)-like hosts in the Local Volume. Hosts are selected simply via a cut in luminosity ( ${M}_{{K}_{s}}\lt -22.1$ mag) and distance (D &lt; 12 Mpc). We cataloged the satellites of 25 of the 31 such hosts, with another five taken from the literature. All hosts are surveyed out to at least 150 projected kpc ( ~ R vir/2), with the majority surveyed to 300 kpc ( ~ R vir). Satellites are detected using a consistent semiautomated algorithm specialized for low surface brightness dwarfs. As shown through extensive tests with injected galaxies, the catalogs are complete to M  V  ~ -9 mag and μ 0,V  ~ 26.5 mag arcsec-2. Candidates are confirmed to be real satellites through distance measurements including redshift, tip of the red giant branch, and surface brightness fluctuations. Across all 30 surveyed hosts, there are 338 confirmed satellites with M  V  &lt; -9 mag, with a further 106 candidates awaiting distance measurement. For the vast majority of these, we provide consistent multiband Sérsic photometry. We show that satellite abundance correlates with host mass, with the MW being quite typical among comparable systems, and that satellite quenched fraction rises steeply with decreasing satellite mass, mirroring the quenched fraction for the MW and M31. The ELVES survey represents a massive increase in the statistics of surveyed systems with known completeness, and the provided catalogs are a unique data set to explore various aspects of small-scale structure and dwarf galaxy evolution.

Keywords: Local Group, Dwarf galaxies, Galaxy groups, Low surface brightness galaxies
Correlations of Dark Matter, Gas, and Stellar Profiles in Dark Matter Halos. Halos of similar mass and redshift exhibit a large degree of variability in their differential properties, such as dark matter, hot gas, and stellar mass density profiles. This variability is an indicator of diversity in the formation history of these dark matter halos that is reflected in the coupling of scatters about the mean relations. In this work, we show that the strength of this coupling depends on the scale at which halo profiles are measured. By analyzing the outputs of the IllustrisTNG hydrodynamical cosmological simulations, we report the radial- and mass-dependent couplings between the dark matter, hot gas, and stellar mass radial density profiles utilizing the population diversity in dark matter halos. We find that for the same mass halos, the scatters in the density of baryons and dark matter are strongly coupled at large scales (r &gt; R 200), but the coupling between gas and dark matter density profiles fades near the core of halos (r &lt; 0.3R 200). We then show that the correlation between halo profile and integrated quantities induces a radius-dependent additive bias in the profile observables of halos when halos are selected on properties other than their mass. We discuss the impact of this effect on cluster abundance and cross-correlation cosmology with multiwavelength cosmological surveys.

Keywords: Galaxy clusters, Galaxy dark matter halos, Cold dark matter, Galaxy structure, Galactic and extragalactic astronomy, Circumgalactic medium