Sazuna/UAT_keywords huggingface dataset:
LoCuSS: The Splashback Radius of Massive Galaxy Clusters and Its Dependence on Cluster Merger History. We present the direct detection of the splashback feature using the sample of massive galaxy clusters from the Local Cluster Substructure Survey (LoCuSS). This feature is clearly detected (above 5σ) in the stacked luminosity density profile obtained using the K-band magnitudes of spectroscopically confirmed cluster members. We obtained the best-fit model by means of Bayesian inference, which ranked models including the splashback feature as more descriptive of the data with respect to models that do not allow for this transition. In addition, we have assessed the impact of the cluster dynamical state on the occurrence of the splashback feature. We exploited the extensive multiwavelength LoCuSS data set to test a wide range of proxies for the cluster formation history, finding the most significant dependence of the splashback feature location and scale according to the presence or absence of X-ray emitting galaxy groups in the cluster infall regions. In particular, we report for the first time that clusters that do not show massive infalling groups present the splashback feature at a smaller clustercentric radius rsp/r200,m = 1.158 ± 0.071 than clusters that are actively accreting groups rsp/r200,m = 1.291 ± 0.062. The difference between these two subsamples is significant at 4.2σ, suggesting a correlation between the properties of the cluster potential and its accretion rate and merger history. Similarly, clusters that are classified as old and dynamically inactive present stronger signatures of the splashback feature, with respect to younger, more active clusters. We are directly observing how fundamental dynamical properties of clusters reverberate across vastly different physical scales.

Keywords: Galaxy clusters, Observational astronomy, Large-scale structure of the universe, Galaxy groups, Galaxies
Precision Timing of PSR J0437-4715 with the IAR Observatory and Implications for Low-frequency Gravitational Wave Source Sensitivity. While observations of many high-precision radio pulsars of order ≲1 μs across the sky are needed for the detection and characterization of a stochastic background of low-frequency gravitational waves (GWs), sensitivity to single sources of GWs requires even higher timing precision. The Argentine Institute of Radio Astronomy (IAR; Instituto Argentino de Radioastronomía) has begun observations of the brightest known millisecond pulsar, J0437-4715. Even though the two antennas are smaller than other single-dish telescopes previously used for pulsar timing array (PTA) science, the IAR's capability to monitor this pulsar daily, coupled with the pulsar's brightness, allows for high-precision measurements of pulse-arrival time. While upgrades of the facility are currently underway, we show that modest improvements beyond current plans will provide IAR with unparalleled sensitivity to this pulsar. The most stringent upper limits on single GW sources come from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav). Observations of PSR J0437-4715 will provide a significant sensitivity increase in NANOGrav's "blind spot" in the sky where fewer pulsars are currently being observed. With state-of-the-art instrumentation installed, we estimate the array's sensitivity will improve by a factor of ≈2-4 over 10 yr for 20% of the sky with the inclusion of this pulsar, as compared to a static version of the PTA used in NANOGrav's most recent limits. More modest instrumentation results in factors of ≈1.4-3. We identify four other candidate pulsars as suitable for inclusion in PTA efforts. International PTA efforts will also benefit from inclusion of these data, given the potential achievable sensitivity.

Keywords: Pulsar timing method, Millisecond pulsars, Gravitational wave sources, Pulsars, Gravitational wave astronomy, Gravitational waves
Projected Rotational Velocities and Fundamental Properties of Low-mass Pre-main-sequence Stars in the Taurus-Auriga Star-forming Region. The projected stellar rotational velocity ( $v\sin i$ ) is critical for our understanding of processes related to the evolution of angular momentum in pre-main-sequence stars. We present $v\sin i$ measurements of high-resolution infrared and optical spectroscopy for 70 pre-main-sequence stars in the Taurus-Auriga star-forming region, in addition to effective temperatures measured from line-depth ratios, as well as stellar rotation periods determined from optical photometry. From the literature, we identified the stars in our sample that show evidence of residing in circumstellar disks or multiple systems. The comparison of infrared $v\sin i$ measurements calculated using two techniques shows a residual scatter of ∼1.8 km s-1, defining a typical error floor for the $v\sin i$ of pre-main-sequence stars from infrared spectra. A comparison of the $v\sin i$ distributions of stars with and without companions shows that binaries/multiples typically have a higher measured $v\sin i$ , which may be caused by contamination by companion lines, shorter disk lifetimes in binary systems, or tidal interactions in hierarchical triples. A comparison of optical and infrared $v\sin i$ values shows no significant difference regardless of whether the star has a disk or not, indicating that CO contamination from the disk does not impact $v\sin i$ measurements above the typical ∼1.8 km s-1 error floor of our measurements. Finally, we observe a lack of a correlation between the $v\sin i$ , presence of a disk, and H-R diagram position, which indicates a complex interplay between stellar rotation and evolution of pre-main-sequence stars.

Keywords: High resolution spectroscopy, Fundamental parameters of stars, Pre-main sequence stars, Low mass stars, Stellar rotation
Extinction at the Galactic Center Using Near- and Mid-infrared Broadband Photometry: A Twist on the Rayleigh-Jeans Color Excess Method. We present an extinction map of the inner ∼15' by 16' of the Galactic center (GC) with map pixels measuring 5″ × 5″ using integrated light color measurements in the near- and mid-infrared. We use a variant of the Rayleigh-Jeans color excess (RJCE) method first described by Majewski et al. as the basis of our work, although we have approached our problem with a Bayesian mindset and dispensed with point-source photometry in favor of surface photometry, turning the challenge of the extremely crowded field at the GC into an advantage. Our results show that extinction at the GC is not inconsistent with a single power-law coefficient, β = 2.03 ± 0.06, and compare our results with those using the red clump (RC) point-source photometry method of extinction estimation. We find that our measurement of β and its apparent lack of spatial variation are in agreement with prior studies, despite the bimodal distribution of values in our extinction map at the GC with peaks at 5 and 7.5 mag. This bimodal nature of extinction is likely due to the infrared dark clouds that obscure portions of the inner GC field. We present our extinction law and map of the GC region using the point-source catalog of infrared sources compiled by DeWitt et al. The dereddening is limited by the error in the extinction measurement (typically 0.6 mag), which is affected by the size of our map pixels and is not fine-grained enough to separate out the multiple stellar populations present toward the GC.

Keywords: Galactic center, Infrared excess, Interstellar reddening, Interstellar extinction, Infrared photometry, Near infrared astronomy
Effects of the Compressibility of Turbulence on the Dust Coagulation Process in Protoplanetary Disks. Planetesimals are believed to be formed by the coagulation of dust grains in the protoplanetary disk turbulence. However, the bouncing and fragmentation barriers have not been completely solved, particularly for silicate dust. To circumvent these barriers, the turbulent clustering of dust particles must be properly treated. According to the minimum-mass solar nebula (MMSN) model, the Mach number of the turbulence ranges from Mrms ≃ 0.01-0.32, and thus the turbulence is often regarded as essentially incompressible. However, it has not been quantitatively investigated whether the incompressible limit is adequate for protoplanetary disk simulations. We therefore compare in this study the motions of inertial particles in direct numerical simulations (DNSs) of the Navier-Stokes equation between weakly compressible turbulence and incompressible turbulence. In the DNSs of compressible turbulence, we use an external force to set the total dissipation and the dilatational-to-solenoidal dissipation ratio. The DNSs reveal that despite the small Mach number Mrms( ≲ 0.3), the compressible turbulence field notably differs from the incompressible field in terms of the density fluctuations, pressure fluctuations, and shocklet generation, depending on the ratio of the dilatational forcing. However, we quantitatively confirmed that these effects on the particle collision statistics are weak and that the motion of inertial particles in weakly compressible turbulence is dominated by the solenoidal velocity components. Therefore we can conclude that the incompressible assumption is appropriate for an investigation of the dust coagulation process in protoplanetary disk turbulence, as assumed in the MMSN model.

Keywords: Hydrodynamical simulations, Hydrodynamics, Interplanetary turbulence, Protoplanetary disks, Planetesimals, Astrophysical fluid dynamics, Planet formation
The Kinematics of z ≳ 6 Quasar Host Galaxies. We explore the kinematics of 27 z ≳ 6 quasar host galaxies observed in [C II] 158 μm ([C II]) emission with the Atacama Large Millimeter/submillimeter Array at a resolution of ≍0"25. We find that nine of the galaxies show disturbed [C II] emission, due to either a close companion galaxy or a recent merger. Ten galaxies have smooth velocity gradients consistent with the emission arising from a gaseous disk. The remaining eight quasar host galaxies show no velocity gradient, suggesting that the gas in these systems is dispersion dominated. All galaxies show high velocity dispersions with a mean of 129 ± 10 km s-1. To provide an estimate of the dynamical mass within twice the half-light radius of the quasar host galaxy, we model the kinematics of the [C II] emission line using our publicly available kinematic fitting code, qubefit. This results in a mean dynamical mass of 5.0 ± 0.8( ± 3.5) × 1010 M☉. Comparison between the dynamical mass and the mass of the supermassive black hole reveals that the sample falls above the locally derived bulge mass-black hole mass relation at 2.4σ significance. This result is robust even if we account for the large systematic uncertainties. Using several different estimators for the molecular mass, we estimate a gas mass fraction of &gt;10%, indicating that gas makes up a large fraction of the baryonic mass of z ≳ 6 quasar host galaxies. Finally, we speculate that the large variety in [C II] kinematics is an indication that gas accretion onto z ≳ 6 supermassive black holes is not caused by a single precipitating factor.

Keywords: Supermassive black holes, Interstellar atomic gas, Quasars, Galaxy dynamics, Galaxy kinematics, Galaxy evolution
Magnetar-driven Shock Breakout Revisited and Implications for Double-peaked Type I Superluminous Supernovae. The discovery of early bumps in some type-I superluminous supernovae (SLSNe-I) before the main peaks offers an important clue to their energy source mechanisms. In this paper, we updated an analytic magnetar-powered model for fitting the multiband light curves of double-peaked SLSNe-I. The early bump is powered by magnetar-driven shock-breakout thermal emission, and the main peak is powered by a radiative diffusion through the supernova (SN) ejecta as in the standard magnetar-powered model. Generally, the diffusive luminosity is greater than the shock-breakout luminosity at the early time, which usually makes the shock-breakout bumps unclear to observe. To obtain a clear double-peaked light curve, inefficient magnetar heating at early times is required. This model is applied to three well-observed double-peaked SLSNe-I (i.e., SN2006oz, LSQ14bdq, and DES14Xtaz). We find that a relatively massive SN ejecta with Mej ≃ 10.2-18.1M⊙ and relatively large kinetic energy of SN ejecta ${E}_{\mathrm{sn}}\simeq (3.8\mbox{--}6.5)\times {10}^{51}$ erg are required, and the thermalization efficiency of the magnetar heating is suppressed before tdelay, which is in the range of ≃15-43 days. The model can reproduce the observed light curves well, with a reasonable and similar set of physical parameters for both the early bump and the main peak, strengthening support for the magnetar-powered model. In the future, modeling of the double-peaked SLSNe-I will become more feasible as more events are discovered before the early bump.

Keywords: Magnetars, Light curves, Supernovae
Spectrum and Morphology of the Very-high-energy Source HAWC J2019+368. The MGRO J2019+37 region is one of the brightest sources in the sky at TeV energies. It was detected in the second HAWC catalog as 2HWC J2019+367 and here we present a detailed study of this region using data from HAWC. This analysis resolves the region into two sources: HAWC J2019+368 and HAWC J2016+371. We associate HAWC J2016+371 with the evolved supernova remnant CTB 87, although its low significance in this analysis prevents a detailed study at this time. An investigation of the morphology (including possible energy-dependent morphology) and spectrum for HAWC J2019+368 is the focus of this work. We associate HAWC J2019+368 with PSR J2021+3651 and its X-ray pulsar wind nebula, the Dragonfly nebula. Modeling the spectrum measured by HAWC and Suzaku reveals a ∼7 kyr pulsar and nebula system producing the observed emission at X-ray and γ-ray energies.

Keywords: Gamma-ray sources, Pulsars
GASP XXXIV: Unfolding the Thermal Side of Ram Pressure Stripping in the Jellyfish Galaxy JO201. X-ray studies of jellyfish galaxies play a crucial role in understanding the interactions between the interstellar medium (ISM) and the intracluster medium (ICM). In this paper, we focused on the jellyfish galaxy JO201. By combining archival Chandra observations, Multi Unit Spectroscopic Explorer Hα cubes, and maps of the emission fraction of the diffuse ionized gas, we investigated both its high-energy spectral properties and the spatial correlation between its X-ray and optical emissions. The X-ray emission of JO201 is provided by both the Compton-thick active galactic nucleus (L ${}_{{\rm{X}}}^{0.5-10\mathrm{keV}}$ = 2.7 · 1041 erg s-1, not corrected for intrinsic absorption) and an extended component (L ${}_{{\rm{X}}}^{0.5\mbox{--}10\,\mathrm{keV}}\,\approx $ 1.9-4.5 · 1041 erg s-1) produced by a warm plasma (kT $\approx 1$ keV), whose luminosity is higher than expected from the observed star formation (L ${}_{{\rm{X}}}\,\sim $ 3.8 · 1040erg s-1). The spectral analysis showed that the X-ray emission is consistent with the thermal cooling of hot plasma. These properties are similar to the ones found in other jellyfish galaxies showing extended X-ray emission. A point-to-point analysis revealed that this X-ray emission closely follows the ISM distribution, whereas CLOUDY simulations proved that the ionization triggered by this warm plasma would be able to reproduce the [O I]/Hα excess observed in JO201. We conclude that the galactic X-ray emitting plasma originates on the surface of the ISM as a result of the ICM-ISM interplay. This process would entail the cooling and accretion of the ICM onto the galaxy, which could additionally fuel the star formation, and the emergence of [O I]/Hα excess in the optical spectrum.

Keywords: X-ray astronomy, Galaxy clusters, Galaxy evolution
Asymmetry Revisited: The Effect of Dust Attenuation and Galaxy Inclination. Dust attenuation of an inclined galaxy can cause additional asymmetries in observations, even if the galaxy has a perfectly symmetric structure. Taking advantage of the integral field spectroscopic data observed by the Sloan Digital Sky Survey-IV Mapping Nearby Galaxies at the Apache Point Observatory survey, we investigate the asymmetries of the emission-line and continuum maps of star-forming disk galaxies. We define new parameters, Aa and Ab, to estimate the asymmetries of a galaxy about its major and minor axes, respectively. Comparing Aa and Ab in different inclination bins, we attempt to detect the asymmetries caused by dust. For the continuum images, we find that Aa increases with the inclination, while Ab is a constant as inclination changes. Similar trends are found for g - r, g - i, and r - i color images. The dependence of the asymmetry on inclination suggests a thin dust layer with a scale height smaller than the stellar populations. For the Hα and Hβ images, neither Aa nor Ab shows a significant correlation with inclination. Also, we do not find any significant dependence of the asymmetry of E(B - V)g on inclination, implying that the dust in the thick disk component is not significant. Compared to the SKIRT simulation, the results suggest that the thin dust disk has an optical depth of τV ∼ 0.2. This is the first time that the asymmetries caused by the dust attenuation and the inclination are probed statistically with a large sample. Our results indicate that the combination of the dust attenuation and the inclination effects is a potential indicator of the 3D disk orientation.

Keywords: Galaxy structure
The Effect of the Approach to Gas Disk Gravitational Instability on the Rapid Formation of Gas Giant Planets. II. Quadrupled Spatial Resolution. Observations support the hypothesis that gas disk gravitational instability might explain the formation of massive or wide-orbit gas giant exoplanets. The situation with regard to Jupiter-mass exoplanets orbiting within ∼20 au is more uncertain. Theoretical models yield divergent assessments often attributed to the numerical handling of the gas thermodynamics. Boss used the β cooling approximation to calculate three-dimensional hydrodynamical models of the evolution of disks with initial masses of 0.091 M⊙ extending from 4 to 20 au around 1 M⊙ protostars. The models considered a wide range (1-100) of β cooling parameters and started from an initial minimum Toomre stability parameter of Qi = 2.7 (gravitationally stable). The disks cooled down from initial outer disk temperatures of 180 K to as low as 40 K as a result of the β cooling, leading to fragmentation into dense clumps, which were then replaced by virtual protoplanets (VPs) and evolved for up to ∼500 yr. The present models test the viability of replacing dense clumps with VPs by quadrupling the spatial resolution of the grid once dense clumps form, sidestepping in most cases VP insertion. After at least ∼200 yr of evolution, the new results compare favorably with those of Boss: similar numbers of VPs and dense clumps form by the same time for the two approaches. The results imply that VP insertion can greatly speed disk instability calculations without sacrificing accuracy.

Keywords: Hydrodynamical simulations, Gravitational instability, Protoplanetary disks, Exoplanet formation
Detecting Reconnection Sites Using the Lorentz Transformations for Electromagnetic Fields. We take a pragmatic definition of reconnection to find locations where a reconnection electric field causes an E × B drift that carries two components of the magnetic field toward their elimination. With this in mind as our target, we observe that such locations can be found using a new indicator: the velocity of the Lorentz transformation that eliminates two components of the local magnetic field. Serendipitously, the indicator naturally becomes subluminal in the close proximity of a point where two components of the magnetic field vanish and it is hard zero at the vanishing location. Everywhere else the velocity of this Lorentz frame change far exceeds the speed of light. This property can be quickly applied in practice because computing the frame change is a local operation that requires only the knowledge of the local magnetic and electric field: it can be applied in a simulation or in observational data from a field instrument. We further show that the points identified can be classified in six categories that extend the usual types of magnetic nulls to the case of 3D reconnection in the presence of a guide field. The approach is used to identify secondary electron-scale reconnection sites in a turbulent outflow from a primary reconnection site in a highly resolved massively parallel fully kinetic particle-in-cell simulation. Numerous points are found, and their detailed analysis is reported.

Keywords: Interplanetary turbulence, Geomagnetic fields, Magnetic fields, Solar magnetic reconnection
More Variable Quasars Have Stronger Emission Lines. UV/optical variation, likely driven by accretion disk turbulence, is a defining characteristic of type 1 active galactic nuclei and quasars. In this work we investigate an interesting consequence of such turbulence using quasars in Sloan Digital Sky Survey Stripe 82 for which the measurements of the UV/optical variability amplitude are available from ∼10 yr long light curves. We discover positive correlations between the UV/optical variability amplitude σrms and equivalent widths of C IV, Mg II, and [O III]5007 emission lines. Such correlations remain statistically robust through partial correlation analyses, i.e., after controlling the effects of other variables including bolometric luminosity, central supermassive black hole mass, Eddington ratio, and redshift. This, for the first time, indicates a causal link between disk turbulence and emission line production. We propose two potential underlying mechanisms, both of which may be involved: (1) quasars with stronger disk turbulence have on average a bluer/harder broadband spectral energy distribution, an expected effect of the disk thermal fluctuation model; (2) stronger disk turbulence could lead to the launch of emission line regions with larger covering factors.

Keywords: Accretion, Supermassive black holes, Active galactic nuclei, Quasars
Broken into Pieces: ATLAS and Aliqa Uma as One Single Stream. We present the first spectroscopic measurements of the ATLAS and Aliqa Uma streams from the Southern Stellar Stream Spectroscopic Survey (S5), in combination with the photometric data from the Dark Energy Survey and astrometric data from Gaia. From the coherence of spectroscopic members in radial velocity and proper motion, we find that these two systems are extremely likely to be one stream with discontinuity in morphology and density on the sky (the "kink" feature). We refer to this entire stream as the ATLAS-Aliqa Uma stream, or the AAU stream. We perform a comprehensive exploration of the effect of baryonic substructures and find that only an encounter with the Sagittarius dwarf ∼0.5 Gyr ago can create a feature similar to the observed "kink." In addition, we also identify two gaps in the ATLAS component associated with the broadening in the stream width (the "broadening" feature). These gaps have likely been created by small mass perturbers, such as dark matter halos, as the AAU stream is the most distant cold stream known with severe variations in both the stream surface density and the stream track on the sky. With the stream track, stream distance, and kinematic information, we determine the orbit of the AAU stream and find that it has been affected by the Large Magellanic Cloud, resulting in a misalignment between the proper motion and stream track. Together with the Orphan-Chenab Stream, AAU is the second stream pair that has been found to be a single stream separated into two segments by external perturbation.

Keywords: Milky Way dark matter halo, Stellar streams, Stellar motion, Stellar kinematics, Stellar abundances, Tidal disruption, Milky Way dynamics, Metallicity, Dark matter, Stellar associations