Sazuna/UAT_keywords huggingface dataset:
On the Maximum Mass of Neutron Stars and GW190814. Motivated by the recent discovery of a compact object with mass in the range 2.5-2.67 M⊙ in the binary merger GW190814, we revisit the question of the maximum mass of neutron stars (NSs). We use a Markov Chain Monte Carlo approach to generate about two million phenomenological equations of state with and without first-order phase transitions. We fix the crust equation of state and only assume causality at higher densities. We show how a strict upper bound on the maximum NS mass can be inferred from upcoming observation of NS radii and masses. The derived upper bounds depend only on relativity and causality, so it is not affected by nuclear physics uncertainties. We show how a lower limit on the maximum mass of NSs, in combination with upcoming measurements of NS radii by LIGO/Virgo and NICER, would constrain the equation of state of dense matter. Finally, we discuss the implications for GW190814.

Keywords: Neutron stars, Nuclear astrophysics
The SAMI Galaxy Survey: Kinematics of Stars and Gas in Brightest Group Galaxies—The Role of Group Dynamics. We study the stellar and gas kinematics of the brightest group galaxies (BGGs) in dynamically relaxed and unrelaxed galaxy groups for a sample of 154 galaxies in the SAMI galaxy survey. We characterize the dynamical state of the groups using the luminosity gap between the two most luminous galaxies and the BGG offset from the luminosity centroid of the group. We find that the misalignment between the rotation axis of gas and stellar components is more frequent in the BGGs in unrelaxed groups, although with quite low statistical significance. Meanwhile, galaxies whose stellar dynamics would be classified as "regular rotators" based on their kinemetry are more common in relaxed groups. We confirm that this dependency on group dynamical state remains valid at fixed stellar mass and Sérsic index. The observed trend could potentially originate from a differing BGG accretion history in virialized and evolving groups. Among the halo relaxation probes, the group BGG offset appears to play a stronger role than the luminosity gap on the stellar kinematic differences of the BGGs. However, both the group BGG offset and luminosity gap appear to roughly equally drive the misalignment between the gas and stellar component of the BGGs in one direction. This study offers the first evidence that the dynamical state of galaxy groups may influence the BGG's stellar and gas kinematics, and we call for further studies using a larger sample with higher signal-to-noise.

Keywords: Galaxy dynamics, Galaxy rotation, Galaxy kinematics, Galaxy evolution, Galaxy mergers, Galaxy groups
Constraining the Quasar Radio-loud Fraction at z ∼ 6 with Deep Radio Observations. We carry out a series of deep Karl G. Jansky Very Large Array (VLA) S-band observations of a sample of 21 quasars at z ∼ 6. The new observations expand the searches of radio continuum emission to the optically faint quasar population at the highest redshift with rest-frame $4400\,\mathring{\rm A} $ luminosities down to $3\times {10}^{11}\ {L}_{\odot }$ . We report the detections of two new radio-loud quasars: CFHQS J2242+0334 (hereafter J2242+0334) at z = 5.88 and CFHQS J0227-0605 (hereafter J0227-0605) at z = 6.20, detected with 3 GHz flux densities of $87.0\pm 6.3\ \mu \mathrm{Jy}$ and $55.4\pm 6.7\ \mu \mathrm{Jy}$ , respectively. Their radio loudnesses are estimated to be 54.9 ± 4.7 and 16.5 ± 3.2, respectively. To better constrain the radio-loud fraction (RLF), we combine the new measurements with the archival VLA L-band data as well as available data from the literature, considering the upper limits for non-detections and possible selection effects. The final derived RLF is 9.4 ± 5.7% for the optically selected quasars at z ∼ 6. We also compare the RLF to that of the quasar samples at low redshift and check the RLF in different quasar luminosity bins. The RLF for the optically faint objects is still poorly constrained due to the limited sample size. Our results show no evidence of significant quasar RLF evolution with redshift. There is also no clear trend of RLF evolution with quasar UV/optical luminosity due to the limited sample size of optically faint objects with deep radio observations.

Keywords: Radio continuum emission, High-redshift galaxies, Quasars
Harmonic Radio Emission in Randomly Inhomogeneous Plasma. In the present paper, we describe a theoretical model of the generation of harmonic emissions of type III solar radio bursts. The goal of our study is to fully take into account the most efficient physical processes involved in the generation of harmonic electromagnetic emission via nonlinear coupling of Langmuir waves in randomly inhomogeneous plasma of solar wind ( $l+{l}^{{\prime} }\to t$ ). We revisit the conventional mechanism of coalescence of primarily generated and back-scattered Langmuir waves in quasihomogeneous plasma. Additionally, we propose and investigate another mechanism that generates harmonic emission only in a strongly inhomogeneous plasma: the nonlinear coupling of incident and reflected Langmuir waves inside localized regions with enhanced plasma density (clumps), in the close vicinity of the reflection point. Both mechanisms imply the presence of strong density fluctuations in plasma. We use the results of a probabilistic model of beam-plasma interaction and evaluate the efficiency of energy transfer from Langmuir waves to harmonic emission. We infer that harmonic emissions from a quasihomogeneous plasma are significantly more intense than found in previous studies. The efficiency of Langmuir wave conversion into electromagnetic harmonic emission is expected to be higher at large heliospheric distances for the mechanism operating in quasihomogeneous plasma and at small heliocentric distances for the one operating in inhomogeneous plasma. The evaluation of emission intensity in quasihomogeneous plasma may also be applied for type II solar radio bursts. The radiation pattern in both cases is quadrupolar, and we show that emission from density clumps may efficiently contribute to the visibility of harmonic radio emission.

Keywords: Interplanetary turbulence, Solar wind, Solar coronal waves
Reconciling X-Ray and λ21 cm H I Absorption Gas Column Densities toward Obscured AGN. Hydrogen column densities inferred from X-ray absorption are typically 5-30 times larger than the neutral atomic hydrogen column densities derived from λ21 cm H I absorption toward radio-loud active galactic nuclei (AGN). Some part of the difference is ascribed to uncertainty in the spin temperature Tsp = 100 K that is often used to convert λ21 cm H I absorption to N(H I). Here we propose another way to infer the gas column from H I absorption. In our Galaxy there is a nearly linear correlation between the inteferometrically measured integrated λ21 cm absorption ϒH I and reddening, ϒH I ∝ E(B-V)1.10 for ϒH I ≳ 0.7 km s-1 or E(B-V) ≳ 0.04 mag. Scaling E(B-V) then provides the total gas column density N(H) from the same dust column that is responsible for optical obscuration and X-ray absorption, without calculating N(H I). Values of N(H) so derived typically exceed N(H I) by a factor 4 because the ubiquitous Galactic λ21 cm H I absorption samples only a portion of the interstellar gas. If the well-studied case of Hydra-A is a guide, even very large disparities in X-ray and λ21 cm gas column densities can be explained by resolving the core radio continuum and inferring N(H) from λ21 cm absorption. Milky Way conditions are often invoked in discussion of obscured AGN, so the empirical relationship seen in the Milky Way should be a relevant benchmark.

Keywords: Interstellar dust extinction, Interstellar medium, Interstellar atomic gas
Spectral Line Asymmetries of Hot Fe Lines in Multiloop Models. Extreme ultraviolet emission line profiles often show asymmetries, in the form of wing enhancements, during solar flares. Various explanations, ranging from magnetic disturbances to non-Maxwellian electron distributions to plasma turbulence have been proposed to explain these features. Plasma dynamics in a single loop can also satisfactorily explain line asymmetry. However, the presence of sub-resolution structures, confirmed by increasingly high-resolution observations, and observational difficulties in isolating a monolithic loop from nearby loops, necessitate detailed modeling efforts to investigate the effect of superposed dynamics on some line asymmetries. In the present work, we design multiloop models, representative of three possible loop configurations, to study how the resultant Fe XXIII spectral line profiles differ in each case and examine the differences between these multiloop models and the single loop model. We also briefly explore the role of a constant time delay in heating successive sub-loops on the spectral line shape. We find that for a multiloop model with sub-loops of the same length, heating time delay is an important factor that alters the line profile shape from the single loop case. Whereas, multiloop models with sub-loops of varied lengths predict significantly different line profiles, such as asymmetric lines for longer durations and with large blueshifts, without the necessity of introducing time delays.

Keywords: Solar flares, Solar flare spectra
Discovery of a Damped Lyα Galaxy at z ∼ 3 toward the Quasar SDSS J011852+040644. We report the detection of the host galaxy of a damped Lyα system (DLA) with log N(H I) [cm-2] = 21.0 ± 0.10 at z ≈ 3.0091 toward the background quasar SDSS J011852+040644 using the Palomar Cosmic Web Imager at the Hale (P200) telescope. We detect Lyα emission in the dark core of the DLA trough at a 3.3σ confidence level, with Lyα luminosity of LLyα = (3.8 ± 0.8) × 1042 erg s-1, corresponding to a star formation rate of ≳2 M⊙ yr-1 (considering a lower limit on Lyα escape fraction ${f}_{\mathrm{esc}}^{\mathrm{Ly}\alpha }\sim 2 \% $ ) as typical for Lyman break galaxies at these redshifts. The Lyα emission is blueshifted with respect to the systemic redshift derived from metal absorption lines by 281 ± 43 km s-1. The associated galaxy is at very small impact parameter of ≲12 kpc from the background quasar, which is in line with the observed anticorrelation between column density and impact parameter in spectroscopic searches tracing the large-scale environments of DLA host galaxies.

Keywords: Star formation, Damped Lyman-alpha systems, Quasar absorption line spectroscopy
Growth and Morphology of Water-, Methanol-, and Ethanol-ice Dust Grains Formed in an Astrophysically Relevant Plasma Experiment. Ice dust grains composed of water, methanol, and ethanol are successfully produced in a laboratory plasma experiment operating at astrophysically relevant temperatures. Both methanol- and ethanol-ice grains grow in an elongated and branched way similar to water-ice grains formed in a plasma. The experiment reveals that methanol- and ethanol-ice grains grow faster, larger, and more branched (spikier) than water-ice grains. The observed growth features seem to be related to the fact that more source molecules and monomer grains can exist in the system at the same temperature. The observed morphology is in agreement with the characteristics of the diffusion-limited aggregation. We also find that larger and more branched ice grains form when the ambient gas pressure is low or the mass of the ambient gas is light, indicating that the aggregation of small grains is enhanced under these conditions.

Keywords: Interstellar dust, Laboratory astrophysics, Plasma astrophysics, Planetary rings, Circumstellar dust
M-subdwarf Research. II. Atmospheric Parameters and Kinematics. We applied the revised M subdwarf classification criteria discussed in Zhang et al. to Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) DR7 and combined the result with the M subdwarf sample from Savcheva et al. to construct a new M subdwarf sample for further study. The atmospheric parameters for each object were derived from fitting to the PHOENIX grid, and the sources with available astrometry and photometry from Gaia DR2 were combined for further analysis. The relationship between the gravity and metallicity was explored according to the locus both in the color-absolute magnitude diagram and the reduced proper motion diagram. Objects that have both the largest gravity and the lowest metallicity are located away from the main-sequence cloud and may be considered as the intrinsic M subdwarfs, which can be classified as luminosity class VI. Another group of objects whose spectra show typical M subdwarf characteristics have lower gravity and relatively moderate metal deficiency and occupy part of the ordinary M dwarf region in both diagrams. The Galactic U, V, W space velocity components and their dispersion show that the local Galactic halo population sampled in the solar neighborhood is represented by objects of high gravity and an inconspicuous bimodal metallicity distribution, with a fraction of prograde orbits. The other M subdwarfs seem to belong in part to the thick disk component, with a significant fraction of thin disk, moderately metal-poor objects intricately mixed with them. However, selection effects, especially the favored anticenter direction of investigation in the LAMOST subsample, as well as contamination by multiplicity and parameter coupling, could play important roles and need to be investigated further.

Keywords: M subdwarf stars
Evolution of the Nonpotential Magnetic Field in the Solar Active Region 12673 Based on a Nonlinear Force-free Modeling. Active region (AR) 12673 has produced many M-class and several X-class flares, one of which being an X9.3 flare, which is recorded as the largest solar flare in solar cycle 24. We studied the evolution of the three-dimensional flare-productive magnetic field within AR 12673, using a time series of nonlinear force-free field extrapolations of every 12 hr from 2017 September 4 00:00 UT to 6 00:00 UT. Our analysis found that three magnetic flux ropes (MFRs) formed by September 4, one of which produced the X9.3 flare on September 6. One MFR has positive magnetic twist, which is a different sign from the other two MFRs. Since the temporal evolution of the magnetic flux of the MFR accumulating the positive twist is consistent with the profile of the GOES X-ray flux well observed from September 4 to 6, we suggest that the formation of the MFR having the positive twist is closely related to the occurrence of the M-class flares, including an M5.5 flare. We further found a magnetic null in the magnetic field surrounding the MFRs, in particular above the MFR having positive twist before the M5.5 flare, which is the largest M-flare observed during this period. By comparing with Atmospheric Imaging Assembly 1600 Å images, we found that the footpoints of the overlying field lines are anchored to the area where the brightening was initially observed. Therefore, we suggest that reconnection induced by the torus instability of the positively twisted MFR at the null possibly drove the M5.5 flare.

Keywords: Solar active region magnetic fields, Magnetohydrodynamics, Solar flares, Solar magnetic reconnection, Solar magnetic fields, Active solar corona
On the Decay of Sunspot Groups and Their Internal Parts in Detail. The decay of sunspot groups is a relatively unknown field since most studies have focused mainly on the decay of sunspots or sunspot groups, but only on small samples. As an extension of the recent work of Muraközy (2020), which is based on a large verified sample, this study investigates not only the long-term behavior of the decay of sunspot groups but also the dynamics of their parts. The aim of the present work is to search for dependencies of the decay process in order to find physical conditions that modify or contribute to the decay. The investigations are based on the catalog of the SoHO Debrecen Sunspot Database (SDD) and the Greenwich Photoheliographic Results as well as the Debrecen Photoheliographic Data. Altogether more than 750 sunspot groups were considered. The decay rates have been calculated for the total, umbral, and penumbral area of the groups and in the case of the SDD's groups they have been calculated for both the leading and the following parts. The decay rates depend linearly on the maximum areas and ranged from 30 to 50 millionths of the solar hemisphere (MSH) day-1 for the sunspot groups and penumbrae and 5-10 MSH day-1 for the umbrae throughout the cycle. The decay rates fall significantly during the Gnevyshev gap and show 4 + 4 Schwabe cyclical variations in the ascending/descending phases, but it is always higher in the northern hemisphere. There is a slight decrease in the decay rates in the activity range toward higher latitudes.

Keywords: Solar active region magnetic fields, Sunspot groups, Sunspots, Solar physics, Solar magnetic fields, Sunspot cycle
Ultramassive Black Holes in the Most Massive Galaxies: M<SUB>BH</SUB>-σ versus M<SUB>BH</SUB>-R<SUB>b</SUB>. We investigate the nature of the relations between black hole (BH) mass (MBH) and the central velocity dispersion (σ) and, for core-Sérsic galaxies, the size of the depleted core (Rb). Our sample of 144 galaxies with dynamically determined MBH encompasses 24 core-Sérsic galaxies, thought to be products of gas-poor mergers, and reliably identified based on high-resolution Hubble Space Telescope imaging. For core-Sérsic galaxies, i.e., combining normal-core (Rb &lt; 0.5 kpc) and large-core galaxies (Rb ≳ 0.5 kpc), we find that MBH correlates remarkably well with Rb such that ${M}_{\mathrm{BH}}\propto {R}_{{\rm{b}}}^{1.20\pm 0.14}$ (rms scatter in log MBH of Δrms ∼ 0.29 dex), confirming previous works on the same galaxies apart from three new ones. Separating the sample into Sérsic, normal-core and large-core galaxies, we find that Sérsic and normal-core galaxies jointly define a single log-linear MBH-σ relation MBH ∝ σ4.88±0.29 with Δrms ∼ 0.47 dex; however, at the high-mass end, large-core galaxies (four with measured MBH) are offset upward from this relation by (2.5-4) × σs, explaining the previously reported steepening of the MBH-σ relation for massive galaxies. Large-core spheroids have magnitudes MV ≲ -23.50 mag, half-light radii Re ≳ 10 kpc, and are extremely massive, M* ≳ 1012 M⊙. Furthermore, these spheroids tend to host ultramassive BHs (MBH ≳ 1010 M⊙) tightly connected with their Rb rather than σ. The less popular MBH-Rb relation exhibits ∼62% less scatter in log MBH than the MBH-σ relations. Our findings suggest that large-core spheroids form via multiple major "dry" merger events involving super/ultramassive BHs, consistent with the flattening of the σ-LV relation observed at MV ≲ -23.5 mag.

Keywords: Lenticular galaxies, Supermassive black holes, cD galaxies, Galaxy structure, Galaxy nuclei, Galaxy photometry, Elliptical galaxies
The Fundamental Plane of Massive Quiescent Galaxies at z ∼ 2. We examine the Fundamental Plane (FP) and mass-to-light ratio (M/L) scaling relations using the largest sample of massive quiescent galaxies at 1.5 &lt; z &lt; 2.5 to date. The FP (re, σe, Ie) is established using 19 UVJ quiescent galaxies from COSMOS with Hubble Space Telescope HF160W rest-frame optical sizes and X-shooter absorption line-measured stellar velocity dispersions. For a very massive, $\mathrm{log}({M}_{* }/{M}_{\odot })\gt 11.26$ , subset of eight quiescent galaxies at z &gt; 2, from Stockmann et al., we show that they cannot passively evolve to the local Coma cluster relation alone and must undergo significant structural evolution to mimic the sizes of local massive galaxies. The evolution of the FP and M/L scaling relations, from z = 2 to present day, for this subset are consistent with passive aging of the stellar population and minor merger structural evolution into the most massive galaxies in the Coma cluster and other massive elliptical galaxies from the MASSIVE Survey. Modeling the luminosity evolution from minor merger-added stellar populations favors a history of merging with "dry" quiescent galaxies.

Keywords: High resolution spectroscopy, Quenched galaxies, Hubble Space Telescope, Galaxy physics, Galaxy dynamics, Scaling relations, Giant elliptical galaxies, Galaxy evolution, Galaxy mergers, Galaxy quenching, Elliptical galaxies
Intrusion of MeV-TeV Cosmic Rays into Molecular Clouds Studied by Ionization, the Neutral Iron Line, and Gamma Rays. Low-energy (∼ MeV) cosmic rays (CRs) ionize molecular clouds and create the neutral iron line (Fe I Kα) at 6.4 keV. On the other hand, high-energy (≳GeV) CRs interact with the dense cloud gas and produce gamma rays. Based on a one-dimensional model, we study the spatial correlation among ionization rates of gas, 6.4 keV line fluxes, and gamma-ray emissions from a molecular cloud illuminated by CRs accelerated at an adjacent supernova remnant. We find that the spatial distributions of these three observables depend on how CRs intrude the cloud and on the internal structure of the cloud. If the intrusion is represented by slow diffusion, the 6.4 keV line should be detected around the cloud edge where ionization rates are high. On the other hand, if CRs freely stream in the cloud, the 6.4 keV line should be observed where gamma rays are emitted. In the former, the cooling time of the CRs responsible for the 6.4 keV line is shorter than their cloud crossing time, and it is opposite in the latter. Although we compare the results with observations, we cannot conclude whether the diffusion or the free-streaming is dominantly realized. Our predictions can be checked in more detail with future X-ray missions such as XRISM and Athena and by observations of ionization rates that cover wider fields.

Keywords: Galactic cosmic rays, Gamma-ray sources, Molecular clouds, X-ray sources
FRB131104 Swift/BAT Data Revisited: No Evidence of a Gamma-Ray Counterpart. We present a reanalysis of the Swift Burst Alert Telescope (BAT) data around the radio detection of FRB 131104. Possible evidence of a gamma-ray counterpart was presented by DeLaunay et al. However, based on our analysis using all the available BAT data, no significant emission is found in either the temporal or the image domain. We place a 5σ fluence upper limit of 3.3 × 10-6 erg cm-2 and 2.7 × 10-6 erg cm-2 (15-150 keV) with an integration time of 300 s assuming a simple power-law spectrum with photon index of -1.2 and -2.0, respectively. Our result does not support the association of this FRB with a high-energy counterpart, in agreement with growing observational evidence that most FRBs are not associated with catastrophic events such as gamma-ray bursts.

Keywords: Radio transient sources
Role of Polycyclic Aromatic Hydrocarbons on the Cosmic-Ray Ionization Rate in the Galaxy. The cosmic-ray (CR) ionization rate (ζ, s-1) plays an important role in the interstellar medium. It controls ion-molecular chemistry and provides a source of heating. Here we perform a grid of calculations using the spectral synthesis code CLOUDY along nine sightlines toward, HD 169454, HD 110432, HD 204827, λ Cep, X Per, HD 73882, HD 154368, Cyg OB2 5, and Cyg OB2 12. The value of ζ is determined by matching the observed column densities of ${{\rm{H}}}_{3}^{+}$ and H2. The presence of polycyclic aromatic hydrocarbons (PAHs) affects the free electron density, which changes the ${{\rm{H}}}_{3}^{+}$ density and the derived ionization rate. PAHs are ubiquitous in the Galaxy, but there are also regions where PAHs do not exist. Hence, we consider clouds within a range of PAH abundances and show their effects on the ${{\rm{H}}}_{3}^{+}$ abundance. We predict an average CR ionization rate for H2 (ζ(H2)) = (7.88 ± 2.89) × 10-16 s-1 for models with average Galactic PAH abundances, (PAH/H = 10-6.52), except Cyg OB2 5 and Cyg OB2 12. The value of ζ is nearly 1 dex smaller for sightlines toward Cyg OB2 12. We estimate the average value of ζ(H2) = (95.69 ± 46.56) × 10-16 s-1 for models without PAHs.

Keywords: Interstellar molecules, Photodissociation regions, Interstellar medium, Astrochemistry