Sazuna/UAT_keywords huggingface dataset:
High-mass Starless Clumps: Dynamical State and Correlation between Physical Parameters. In order to study the initial conditions of massive star formation, we have previously built a sample of 463 high-mass starless clumps (HMSCs) across the inner Galactic plane covered by multiple continuum surveys. Here, we use 13CO(2-1) line data from the SEDIGISM survey, which covers 78° in longitude (-60° &lt; l &lt; 18°, ∣b∣ &lt; 0.°5) with 30″ resolution, to investigate the global dynamical state of these parsec-scale HMSCs (207 sources with good-quality data, mass 102-105 M ☉, size 0.1-3.6 pc). We find that most HMSCs are highly turbulent with a median Mach number ${{ \mathcal M }}_{{ \mathcal S }}\sim 8.2$ , and 44%-55% of them are gravitationally bound (with virial parameter α vir ≲ 2) if no magnetic fields are present. A median magnetic field strength of 0.33-0.37 mG would be needed to support these bound clumps against collapse, in agreement with previous observations of magnetic fields in regions of massive star formation. Luminosity-to-mass ratio, an important tracer of evolutionary stage, is strongly correlated with dust temperature. Magnetic field strength is also correlated with density. The Larson line width-size scaling does not hold in HMSCs. This study advances our understanding of the global properties of HMSCs, and our high-resolution observations with the Atacama Large Millimeter/submillimeter Array are in progress to study the resolved properties.

Keywords: Interstellar dynamics, Molecular clouds, Interstellar magnetic fields, Star formation, Interstellar medium
Stellar-reddening-based Extinction Maps for Cosmological Applications. Cosmological surveys must correct their observations for the reddening of extragalactic objects by Galactic dust. Existing dust maps, however, have been found to have spatial correlations with the large-scale structure of the Universe. Errors in extinction maps can propagate systematic biases into samples of dereddened extragalactic objects and into cosmological measurements such as correlation functions between foreground lenses and background objects and the primordial non-Gaussianity parameter f NL. Emission-based maps are contaminated by the cosmic infrared background, while maps inferred from stellar reddenings suffer from imperfect removal of quasars and galaxies from stellar catalogs. Thus, stellar-reddening-based maps using catalogs without extragalactic objects offer a promising path to making dust maps with minimal correlations with large-scale structure. We present two high-latitude integrated extinction maps based on stellar reddenings, with a point-spread functions of FWHMs 6.'1 and 15'. We employ a strict selection of catalog objects to filter out galaxies and quasars and measure the spatial correlation of our extinction maps with extragalactic structure. Our galactic extinction maps have reduced spatial correlation with large-scale structure relative to most existing stellar-reddening-based and emission-based extinction maps.

Keywords: Large-scale structure of the universe, Interstellar extinction
The Chemodynamical Nature of the Triangulum-Andromeda Overdensity. We present a chemodynamical study of the Triangulum-Andromeda overdensity (TriAnd) employing a sample of 31 candidate stars observed with the GRACES high-resolution (R = 40,000) spectrograph at the Gemini North (8.1 m) telescope. TriAnd is a stellar substructure found toward the outer disk of the Milky Way, located at R GC ~ 18 kpc from the Sun, toward Galactic latitude b ~ 25°. Most stars in our sample have dynamical properties compatible with a disk stellar population. In addition, by applying an eccentricity cut, we are able to detect a stellar contamination that seems to be consistent with an accreted population. In chemical abundance space, the majority of our TriAnd candidates are similar to the outer thin-disk population, suggesting that the overdensity has an in situ origin. Finally, the found accreted halo interlopers spatially overlapping with TriAnd should explain the historical discussion of the overdensity's nature due to its complex chemical patterns.

Keywords: High resolution spectroscopy, Galactic archaeology, Chemical abundances, Milky Way disk, Milky Way stellar halo, Galaxy kinematics
A Chandra X-Ray Survey of Optically Selected Close Galaxy Pairs: Unexpectedly Low Occupation of Active Galactic Nuclei. High-resolution X-ray observations offer a unique tool for probing the still-elusive connection between galaxy mergers and active galactic nuclei (AGNs). We present an analysis of nuclear X-ray emission in an optically selected sample of 92 close galaxy pairs (with projected separations ≲20 kpc and line-of-sight velocity offsets &lt;500 km s-1) at low redshift ( $\bar{z}\sim 0.07$ ), based on archival Chandra observations. The parent sample of galaxy pairs is constructed without imposing an optical classification of nuclear activity, thus it is largely free of selection effect for or against the presence of an AGN. Nor is this sample biased for or against gas-rich mergers. An X-ray source is detected in 70 of the 184 nuclei, giving a detection rate of $38{ \% }_{-5 \% }^{+5 \% }$ , down to a 0.5-8 keV limiting luminosity of ≲1040 erg s-1. The detected and undetected nuclei show no systematic difference in their host galaxy properties such as galaxy morphology, stellar mass, and stellar velocity dispersion. When potential contamination from star formation is avoided (i.e., L 2-10 keV &gt; 1041 erg s-1), the detection rate becomes $18{ \% }_{-3 \% }^{+3 \% }$ (32/184), which shows no excess compared to the X-ray detection rate of a comparison sample of optically classified single AGNs. The fraction of pairs containing dual AGN is only $2{ \% }_{-2 \% }^{+2 \% }$ . Moreover, most nuclei at the smallest projected separations probed by our sample (a few kiloparsecs) have an unexpectedly low apparent X-ray luminosity and Eddington ratio, which cannot be solely explained by circumnuclear obscuration. These findings suggest that close galaxy interaction is not a sufficient condition for triggering a high level of AGN activity.

Keywords: X-ray active galactic nuclei, Interacting galaxies, Galaxy mergers, Galaxy nuclei
Electron-Ion Temperature Ratio in Astrophysical Shocks. Collisionless shock waves in supernova remnants and the solar wind heat electrons less effectively than they heat ions, as is predicted by kinetic simulations. However, the values of T  e /T  p  inferred from the Hα profiles of supernova remnant shocks behave differently as a function of Mach number or Alfvén Mach number than what is measured in the solar wind or predicted by simulations. Here we determine T  e /T  p  for supernova remnant shocks using Hα profiles, shock speeds from proper motions, and electron temperatures from X-ray spectra. We also improve the estimates of sound speed and Alfvén speed used to determine Mach numbers. We find that the Hα determinations are robust and that the discrepancies among supernova remnant shocks, solar wind shocks, and computer-simulated shocks remain. We discuss some possible contributing factors, including shock precursors, turbulence, and varying preshock conditions.

Keywords: Supernova remnants, Shocks, Plasma astrophysics
Stellar Cycles in Fully Convective Stars and a New Interpretation of Dynamo Evolution. An αΩ dynamo, combining shear and cyclonic convection in the tachocline, is believed to generate the solar cycle. However, this model cannot explain cycles in fast rotators (with minimal shear) or in fully convective stars (no tachocline); an analysis of these stars could therefore provide key insights into how these cycles work. We reexamine ASAS data for 15 M dwarfs, 11 of which are presumed fully convective; the addition of newer ASAS-SN data confirms cycles in roughly 12 of them, while presenting new or revised rotation periods for 5 stars. The amplitudes and periods of these cycles follow ${A}_{\mathrm{cyc}}\propto {P}_{\mathrm{cyc}}^{0.94\pm 0.11}$ , with P cyc/P rot ∝ Ro -1.02±0.06 (where Ro is the Rossby number), very similar to P cyc/P rot ∝ Ro -0.81±0.17 that we find for 40 previously studied FGK stars, although P cyc/P rot and α are a factor of ~20 smaller in the M stars. The very different P cyc/P rot-Ro relation seen here compared to previous work suggests that two types of dynamo, with opposite Ro dependences, operate in cool stars. Initially, a (likely α 2 or α 2Ω) dynamo operates throughout the convective zone in mid- to late-M and fast-rotating FGK stars, but once magnetic breaking decouples the core and convective envelope, a tachocline αΩ dynamo begins and eventually dominates in older FGK stars. A change in α in the tachocline dynamo generates the fundamentally different P cyc/P rot-Ro relation.

Keywords: M dwarf stars, Stellar rotation, Stellar magnetic fields, Stellar activity
The "Blazar Sequence" in the TeV Band. The "blazar sequence" has been proposed for more than 20 yr, yet its nature is still unclear. In this work, for the first time we expand this topic to the TeV band by using a sample of 58 TeV blazars, including 48 blazars in the quiescent state and 21 blazars in the flaring state (11 blazars show in both quiescent and flaring state). We investigate the correlation between the TeV luminosity, which has been compensated for attenuation from extragalactic background light, and the synchrotron peak frequency. We note that there is no correlation between TeV luminosity and peak frequency in the quiescent state and a strong anticorrelation in the flaring state for the observed value. However, there is a strong positive correlation in both the quiescent state and the flaring state for the intrinsic value. This indicates that the blazar sequence is shown in the flaring state rather than in the quiescent state for the observed value and the blazar sequence is not present in both states after removing the beaming effect. In addition, to confirm whether the beaming effect results in the blazar sequence, we compare the Fermi γ-ray luminosity between the quiescent state and the flaring state. We find the Fermi γ-ray luminosity in the flaring state is greater than that in the quiescent state, and the Doppler factor in the flaring state is greater. We suggest the blazar sequence in the flaring state may be due to a stronger beaming effect.

Keywords: Flat-spectrum radio quasars, BL Lacertae objects
On the Origin of the Split Main Sequences of the Young Massive Cluster NGC 1856. The detection of split main sequences (MSs) associated with young clusters (≲600 Myr) has attracted a lot of attention. A prevailing scenario is that a bimodality of stellar rotation distribution drives the bifurcation of the MS. Nevertheless, the origin of the stellar rotation dichotomy remains unclear. Hypotheses involving tidally locked binaries or blue straggler stars (BSSs) have been proposed to explain the observed split MSs. This work examines if the long-term dynamical evolution of star clusters can produce the observed split MSs, through high-performance N-body simulation. For example, the young massive cluster NGC 1856 exhibits an apparent MS bifurcation. Our simulation reports that at the age of NGC 1856, tidally locked binaries are fully mixed with single stars. This is consistent with the observation that there is no significant spatial difference between blue MS and red MS stars. However, we find that only high-mass-ratio binaries can evolve to the tidally locked phase at the age of the NGC 1856. These tidally locked binaries will populate a much redder sequence than the MS of single stars rather than a blue MS, which is inconsistent with the hypothesis. The number of tidally locked binaries cannot account for the observation. Our simulation shows that BSSs produced by binary interactions do populate in the blue periphery as shown in a color-magnitude diagram, and their spatial distribution shows a similar pattern of single stars. However, the number of BSSs does not fit the observation.

Keywords: Close binary stars, Blue straggler stars, N-body simulations, Star clusters
Three-dimensional, Time-dependent MHD Simulation of Disk-Magnetosphere-Stellar Wind Interaction in a T Tauri, Protoplanetary System. We present a three-dimensional, time-dependent MHD simulation of the short-term interaction between a protoplanetary disk and the stellar corona in a T Tauri system. The simulation includes the stellar magnetic field, self-consistent coronal heating and stellar wind acceleration, and a disk rotating at sub-Keplerian velocity to induce accretion. We find that, initially, as the system relaxes from the assumed initial conditions, the inner part of the disk winds around and moves inward and close to the star as expected. However, the self-consistent coronal heating and stellar wind acceleration build up the original state after some time, significantly pushing the disk out beyond 10R ⋆. After this initial relaxation period, we do not find clear evidence of a strong, steady accretion flow funneled along coronal field lines, but only weak, sporadic accretion. We produce synthetic coronal X-ray line emission light curves, which show flare-like increases that are not correlated with accretion events nor with heating events. These variations in the line emission flux are the result of compression and expansion due to disk-corona pressure variations. Vertical disk evaporation evolves above and below the disk. However, the disk-stellar wind boundary stays quite stable, and any disk material that reaches the stellar wind region is advected out by the stellar wind.

Keywords: Protoplanetary disks
Vibrational, Rotational, and Electronic Spectroscopy for Possible Interstellar Detection of AlNH<SUB>2</SUB> and HAlNH. We obtained accurate vibrational frequencies, rotational constants, and vertical transition energy for AlNH2(X1A1) and HAlNH(X1A') isomers using ab initio calculations at various levels of theory. These two isomers are potential candidates for astronomical observation. AlNH2 and HAlNH are thermodynamically stable, with Al-NH2 and HAl-NH bond dissociation energies predicted to be 4.39 and 3.60 eV, respectively. The two isomers are characterized by sizable dipole moments of 1.211 and 3.64 D, respectively. The anharmonic frequencies and spectroscopic constants reported for the two isomers should facilitate their experimental differentiation. In addition, we evaluated the evolution of the low-lying electronic states along the stretching coordinates, as well as the absorption cross sections. AlNH2 absorbs strongly around 287, 249, and 200 nm, whereas the HAlNH absorption is centered around 370 and 233 nm.

Keywords: Circumstellar envelopes, Computational methods, Interstellar medium, Astrochemistry
Multifrequency Microwave Imaging of Weak Transients from the Quiet Solar Corona. Understanding the dynamics of the quiet solar corona is important for answering key questions including the coronal heating problem. Multiple studies have suggested small-scale magnetic-reconnection events may play a crucial role. These reconnection events are expected to involve acceleration of electrons to suprathermal energies, which can then produce nonthermal observational signatures. However, due to the paucity of sensitive high-fidelity observations capable of probing these nonthermal signatures, most studies were unable to quantify their nonthermal nature. Here we use joint radio observations from the Very Large Array (VLA) and the Expanded Owens Valley Solar Array (EOVSA) to detect transient emissions from the quiet solar corona in the microwave (GHz) domain. While similar transients have been reported in the past, their nonthermal nature could not be adequately quantified due to the unavailability of broadband observations. Using a much larger bandwidth available now with the VLA and EOVSA, in this study, we are able to quantify the nonthermal energy associated with two of these transients. We find that the total nonthermal energy associated with some of these transients can be comparable to or even larger than the total thermal energy of a nanoflare, which underpins the importance of nonthermal energy in the total coronal energy budget.

Keywords: Solar coronal radio emission, Solar coronal transients, Solar coronal heating, Quiet solar corona
Measuring the Speed of Light with Updated Hubble Diagram of High-redshift Standard Candles. The possible time variation of the fundamental constants of nature has been an active subject of research in modern physics. In this paper, we propose a new method to investigate such possible time variation of the speed of light c using the updated Hubble diagram of high-redshift standard candles including Type Ia Supernovae (SNe Ia) and high-redshift quasars (based on UV-X relation). Our findings show that the SNe Ia Pantheon sample, combined with currently available sample of cosmic chronometers, would produce robust constraints on the speed of light at the level of c/c 0 = 1.03 ± 0.03. For the Hubble diagram of UV+X-ray quasars acting as a new type of standard candle, we obtain c/c 0 = 1.19 ± 0.07. Therefore, our results confirm that there is no strong evidence for deviation from a constant speed of light up to z ~ 2. Moreover, we discuss how our technique might be improved at much higher redshifts (z ~ 5), focusing on future measurements of the acceleration parameter X(z) with gravitational waves (GWs) produced by binary neutron star mergers. In particular, in the framework of the second-generation space-based GW detector, DECi-hertz Interferometer Gravitational Wave Observatory, the speed of light is expected to be constrained with a precision of Δc/c = 10-3.

Keywords: Cosmological parameters, Type Ia supernovae, Gravitational waves, Quasars
Multifluid Simulation of Solar Chromospheric Turbulence and Heating Due to Thermal Farley-Buneman Instability. Models fail to reproduce observations of the coldest parts of the Sun's atmosphere, where interactions between multiple ionized and neutral species prevent an accurate MHD representation. This paper argues that a meter-scale electrostatic plasma instability develops in these regions and causes heating. We refer to this instability as the Thermal Farley-Buneman Instability (TFBI). Using parameters from a 2.5D radiative MHD Bifrost simulation, we show that the TFBI develops in many of the colder regions in the chromosphere. This paper also presents the first multifluid simulation of the TFBI and validates this new result by demonstrating close agreement with theory during the linear regime. The simulation eventually develops turbulence, and we characterize the resulting wave-driven heating, plasma transport, and turbulent motions. These results all contend that the effects of the TFBI contribute to the discrepancies between solar observations and radiative MHD models.

Keywords: Solar chromospheric heating, Solar chromosphere, Astronomical simulations, Plasma physics
Mass-Metallicity Relationship of SDSS Star-forming Galaxies: Population Synthesis Analysis and Effects of Star Burst Length, Extinction Law, Initial Mass Function, and Star Formation Rate. We investigate the mass-metallicity relationship of star-forming galaxies by analyzing the absorption line spectra of ~200,000 galaxies in the Sloan Digital Sky Survey. The galaxy spectra are stacked in bins of stellar mass, and a population synthesis technique is applied yielding the metallicities, ages, and star formation history of the young and old stellar population together with interstellar reddening and extinction. We adopt different lengths of the initial starbursts and different initial mass functions for the calculation of model spectra of the single stellar populations contributing to the total integrated spectrum. We also allow for deviations of the ratio of extinction to reddening R  V  from 3.1 and determine the value from the spectral fit. We find that burst length and R  V  have a significant influence on the determination of metallicities, whereas the effect of the initial mass function is small. The R  V  values are larger than 3.1. The metallicities of the young stellar population agree with extragalactic spectroscopic studies of individual massive supergiant stars and are significantly higher than those of the older stellar population. This confirms galaxy evolution models where metallicity depends on the ratio of gas to stellar mass and where this ratio decreases with time. Star formation history is found to depend on galaxy stellar mass. Massive galaxies are dominated by stars formed at early times.

Keywords: Galaxy stellar content, Galaxy abundances, Galaxy evolution, Spectroscopy
Investigating Coronal Holes and CMEs as Sources of Brightness Depletion Detected in PSP/WISPR Images. The Parker Solar Probe (PSP) mission provides a unique opportunity to observe the solar corona from distances below 20 R ☉. In this work, we utilize white light images from the Wide-field Imager for Solar PRobe aboard the PSP from solar encounters 10 through 13 to examine the causes of brightness depletions of the corona during the rapid transit of PSP through the perihelia of its orbit. We analyze the effect of (1) coronal holes (CHs) and (2) energetic coronal mass ejection (CME) events on the observed brightness of the images. We speculate on the causes of the brightness depletions, ascribing them to the evacuation of (1) free electrons (reduced K-corona) and (2) interplanetary dust (reduced F-corona). In particular, we show that (1) the presence of CHs in all of the orbits is directly correlated with the depletion of the global white light emission recorded, and (2) a huge CME event in encounter 13 caused a very deep depletion in its wake that removed the electron content as well as some of the interplanetary dust.

Keywords: Solar K corona, Solar wind, Solar F corona, Solar coronal mass ejections, Solar coronal holes, Interplanetary dust
Constraining Fundamental Parameters in Modified Gravity Using Gaia-DR2 Massive White Dwarf Observations. Various experiments and observations have led researchers to suggest different bounds on fundamental constants like the fine-structure constant and the proton-to-electron mass ratio. These bounds differ mostly due to the energy scale of the systems where the experiments are performed. In this article, we obtain bounds on these parameters in the modified gravity context using Gaia-DR2 massive white dwarf data and show that the bounds alter as the gravity theory changes. This exploration not only indicates strong support for nonnegligible influences of modified gravity in astrophysical scenarios in high-density regimes but also reveals that the bounds on the fundamental parameters can be much stronger under alternate gravity theories.

Keywords: Stellar structures, Scalar-tensor-vector gravity, White dwarf stars, Chandrasekhar limit, Mass ratio, Stellar masses
An Unbiased CO Survey Toward the Northern Region of the Small Magellanic Cloud with the Atacama Compact Array. II. CO Cloud Catalog. The nature of molecular clouds and their statistical behavior in subsolar metallicity environments are not fully explored yet. We analyzed data from an unbiased CO (J = 2-1) survey at the spatial resolution of ~2 pc in the northern region of the Small Magellanic Cloud with the Atacama Compact Array to characterize the CO cloud properties. A cloud-decomposition analysis identified 426 spatially/velocity-independent CO clouds and their substructures. Based on the cross-matching with known infrared catalogs by Spitzer and Herschel, more than 90% CO clouds show spatial correlations with point sources. We investigated the basic properties of the CO clouds and found that the radius-velocity linewidth (R-σ  v ) relation follows the Milky Way-like power-law exponent, but the intercept is ~1.5 times lower than that in the Milky Way. The mass functions (dN/dM) of the CO luminosity and virial mass are characterized by an exponent of ~1.7, which is consistent with previously reported values in the Large Magellanic Cloud and in the Milky Way.

Keywords: Local Group, Small Magellanic Cloud, Molecular clouds, Young stellar objects, Star formation, Interstellar medium