Sazuna/UAT_keywords huggingface dataset:
The Hough Stream Spotter: A New Method for Detecting Linear Structure in Resolved Stars and Application to the Stellar Halo of M31. Stellar streams from globular clusters (GCs) offer constraints on the nature of dark matter and have been used to explore the dark matter halo structure and substructure of our Galaxy. Detection of GC streams in other galaxies would broaden this endeavor to a cosmological context, yet no such streams have been detected to date. To enable such exploration, we develop the Hough Stream Spotter (HSS), and apply it to the Pan-Andromeda Archaeological Survey (PAndAS) photometric data of resolved stars in M31's stellar halo. We first demonstrate that our code can re-discover known dwarf streams in M31. We then use the HSS to blindly identify 27 linear GC stream-like structures in the PAndAS data. For each HSS GC stream candidate, we investigate the morphologies of the streams and the colors and magnitudes of all stars in the candidate streams. We find that the five most significant detections show a stronger signal along the red giant branch in color-magnitude diagrams than spurious non-stream detections. Lastly, we demonstrate that the HSS will easily detect globular cluster streams in future Nancy Grace Roman Space Telescope data of nearby galaxies. This has the potential to open up a new discovery space for GC stream studies, GC stream gap searches, and for GC stream-based constraints on the nature of dark matter.

Keywords: Globular star clusters, Galaxy dark matter halos, Dark matter distribution, Stellar streams, Cold dark matter, Galaxy structure, Galaxy dynamics, Galaxy stellar halos, Galaxy kinematics, Andromeda Galaxy
The NANOGrav 12.5 yr Data Set: Polarimetry and Faraday Rotation Measures from Observations of Millisecond Pulsars with the Green Bank Telescope. In this work, we present polarization profiles for 23 millisecond pulsars observed at 820 and 1500 MHz with the Green Bank Telescope as part of the NANOGrav pulsar timing array. We calibrate the data using Mueller matrix solutions calculated from observations of PSRs B1929+10 and J1022+1001. We discuss the polarization profiles, which can be used to constrain pulsar emission geometry, and present both the first published radio polarization profiles for nine pulsars and the discovery of very low-intensity average profile components ("microcomponents") in four pulsars. We obtain the Faraday rotation measures for each pulsar and use them to calculate the Galactic magnetic field parallel to the line of sight for different lines of sight through the interstellar medium. We fit for linear and sinusoidal trends in time in the dispersion measure and Galactic magnetic field and detect magnetic field variations with a period of 1 yr in some pulsars, but overall find that the variations in these parameters are more consistent with a stochastic origin.

Keywords: Astronomical techniques, Interstellar medium, Pulsars
Effects of Forcing on Shocks and Energy Dissipation in Interstellar and Intracluster Turbulences. Observations indicate that turbulence in the interstellar medium (ISM) is supersonic (M turb ≫ 1) and strongly magnetized (β ~ 0.01-1), while in the intracluster medium (ICM) it is subsonic (M turb ≲ 1) and weakly magnetized (β ~ 100). Here, M turb is the turbulent Mach number and β is the plasma beta. We study the properties of shocks induced in these disparate environments, including the distribution of the shock Mach number, M  s , and the dissipation of the turbulent energy at shocks, through numerical simulations using a high-order, accurate code based on the weighted essentially nonoscillatory scheme. In particular, we investigate the effects of different modes of the forcing that drives turbulence: solenoidal, compressive, and a mixture of the two. In ISM turbulence, while the density distribution looks different with different forcings, the velocity power spectrum, P  v , on small scales exhibits only weak dependence. Hence, the statistics of shocks depend weakly on forcing either. In the ISM models with M turb ≈ 10 and β ~ 0.1, the fraction of the turbulent energy dissipated at shocks is estimated to be ~15%, not sensitive to the forcing mode. In contrast, in ICM turbulence, P  v  as well as the density distribution show strong dependence on forcing. The frequency and average Mach number of shocks are greater for compressive forcing than for solenoidal forcing; so is the energy dissipation. The fraction of the ensuing shock dissipation is in the range of ~10%-35% in the ICM models with M turb ≈ 0.5 and β ~ 106. The rest of the turbulent energy should be dissipated through turbulent cascade.

Keywords: Interstellar medium, Shocks, Intracluster medium, Magnetic fields, Magnetohydrodynamical simulations
Metal-poor Stars Observed with the Southern African Large Telescope II. An Extended Sample. We present results from high-resolution (R ~ 40,000) spectroscopic observations of over 200 metal-poor stars, mostly selected from the RAVE survey, using the Southern African Large Telescope. We were able to derive stellar parameters for a total of 108 stars; an additional sample of 50 stars from this same effort was previously reported on by Rasmussen et al. Among our newly reported observations, we identify 84 very metal-poor (VMP; [Fe/H] &lt; -2.0, 53 newly identified) stars and three extremely metal-poor (EMP; [Fe/H] &lt; -3.0, one newly identified) stars. The elemental abundances were measured for carbon, as well as several other α-elements (Mg, Ca, Sc, and Ti), iron-peak elements (Mn, Co, Ni, and Zn), and neutron-capture elements (Sr, Ba, and Eu). Based on these measurements, the stars are classified by their carbon and neutron-capture abundances into carbon-enhanced metal-poor (CEMP; [C/Fe] &gt; +0.70), CEMP subclasses, and by the level of their r-process abundances. A total of 17 are classified as CEMP stars. There are 11 CEMP-r stars (eight newly identified), one CEMP-s star (newly identified), two possible CEMP-i stars (one newly identified), and three CEMP-no stars (all newly identified) in this work. We found 11 stars (eight newly identified) that are strongly enhanced in r-process elements (r-II; [Eu/Fe] &gt; +0.70), 38 stars (31 newly identified) that are moderately enhanced in r-process elements (r-I; +0.30 &lt; [Eu/Fe] ≤ + 0.70), and one newly identified limited-r star.

Keywords: Stellar abundances, R-process, Milky Way stellar halo, Population II stars, CEMP stars, Stellar atmospheres
Interstellar Scintillation of PSR J2048-1616. We report on the interstellar scintillation from pulsar J2048-1616 for the first time at 732, 1369, and 3100 MHz observed with the Parkes 64 m radio telescope. Dynamic spectra are obtained and diffractive parameters are derived from two-dimensional autocorrelation analyses. The frequency dependencies of the observed diffractive scintillation timescale and decorrelation bandwidth indicate that the electron density fluctuations in the interstellar medium (ISM) do not follow the Kolmogorov spectrum. The secondary spectra are calculated by forming the Fourier power spectra of the corresponding dynamic spectra. Prominent parabolic arcs are revealed in the secondary spectra at three frequencies, which indicate that they originated from scattering by a thin screen. The scattering screen is approximately located centrally between the pulsar and Earth assuming that the ISM is stationary.

Keywords: Radio pulsars
Spatial Structures in the Globular Cluster Distribution of Fornax Cluster Galaxies. We report the discovery of statistically significant spatial structures in the projected two-dimensional distributions of Globular Cluster (GC) systems of 10 galaxies that are among the brightest in the Fornax Cluster. We use a catalog of GCs extracted from the Hubble Space Telescope Advanced Camera for Surveys Fornax Cluster Survey imaging data. We characterize the size, shape, and location relative to the host galaxies of the GC structures and suggest a classification based on their morphology and location that is suggestive of different formation mechanisms. We also investigate the GC structures in the context of the positions of their host galaxies relative to the general spatial distributions of galaxies and intracluster GCs in the Fornax Cluster. We finally estimate the dynamical masses of the progenitors of some GC structures under the assumption that they are the relics of past accretion events of satellite galaxies by their hosts.

Keywords: Globular star clusters, Galaxy evolution
Robust Absolute Solar Flux Density Calibration for the Murchison Widefield Array. Sensitive radio instruments are optimized for observing faint astronomical sources, and usually need to attenuate the received signal when observing the Sun. There are only a handful of flux density calibrators that can comfortably be observed with the same attenuation setup as the Sun. Additionally, for wide field-of-view (FoV) instruments like the Murchison Widefield Array (MWA) calibrator observations are generally done when the Sun is below the horizon, to avoid the contamination from solar emissions. These considerations imply that the usual radio interferometric approach to flux density calibration is not applicable for solar imaging. A novel technique, relying on a good sky model and detailed characterization of the MWA hardware, was developed for solar flux density calibration for MWA. Though successful, this technique is not general enough to be extended to the data from the extended configuration of the MWA Phase II. Here, we present a robust flux density calibration method for solar observations with MWA independent of the array configuration. We use different approaches-the serendipitous presence of strong sources; detection of numerous background sources using high dynamic range images in the FoV along with the Sun; and observations of strong flux density calibrators with and without the additional attenuation used for solar observations-to obtain the flux scaling parameters required for the flux density calibration. Using the present method, we have achieved an absolute flux density uncertainty ~10% for solar observations even in the absence of dedicated calibrator observations.

Keywords: Solar radio telescopes, Solar physics, Radio telescopes, Flux calibration
Mass Accretion Rates of the HectoMAP Clusters of Galaxies. We estimate the mass accretion rate (MAR) of 321 clusters of galaxies in the HectoMAP Cluster Survey. The clusters span the redshift range 0.17-0.42 and the M 200 mass range ≈ (0.5-3.5) × 1014 M ⊙. The MAR estimate is based on the caustic technique along with a spherical infall model. Our analysis extends the measurement of MARs for 129 clusters at z &lt; 0.3 from the Cluster Infall Regions in the Sloan Digital Sky Survey and the Hectospec Cluster Survey to redshift z ~ 0.42. Averaging over redshift, low-mass clusters with masses near 0.7 × 1014 M ⊙ roughly accrete 3 × 104 M ⊙ yr-1; more massive clusters with masses near 2.8 × 1014 M ⊙ roughly accrete 1 × 105 M ⊙ yr-1. Low- and high-mass clusters increase their MAR by approximately 46% and 84%, respectively, as the redshift increases from z in the range 0.17-0.29 to z in the range 0.34-0.42. The MARs at fixed redshift increase with mass and MARs at fixed mass increase with redshift in agreement with the ΛCDM cosmological model for hierarchical structure formation. We consider the extension of MAR measurements to z ~ 1.

Keywords: Galaxy clusters, Cosmology, Dark matter distribution, Large-scale structure of the universe, Observational cosmology, Galaxy dynamics, Galaxy kinematics, Hierarchical cosmology
Constraining the CME Core Heating and Energy Budget with SOHO/UVCS. We describe the energy budget of a coronal mass ejection (CME) observed on 1999 May 17 with the Ultraviolet Coronagraph Spectrometer (UVCS). We constrain the physical properties of the CME's core material as a function of height along the corona by using the spectra taken by the single-slit coronagraph spectrometer at heliocentric distances of 2.6 and 3.1 solar radii. We use plasma diagnostics from intensity ratios, such as the O VI doublet lines, to determine the velocity, density, temperature, and nonequilibrium ionization states. We find that the CME core's velocity is approximately 250 km s-1, and its cumulative heating energy is comparable to its kinetic energy for all of the plasma heating parameterizations that we investigated. Therefore, the CME's unknown heating mechanisms have the energy to significantly affect the CME's eruption and evolution. To understand which parameters might influence the unknown heating mechanism, we constrain our model heating rates with the observed data and compare them to the rate of heating generated within a similar CME that was constructed by the MAS code's 3D MHD simulation. The rate of heating from the simulated CME agrees with our observationally constrained heating rates when we assume a quadratic power law to describe a self-similar CME expansion. Furthermore, the heating rates agree when we apply a heating parameterization that accounts for the CME flux rope's magnetic energy being converted directly into thermal energy. This UVCS analysis serves as a case study for the importance of multislit coronagraph spectrometers for CME studies.

Keywords: Solar ultraviolet emission, Plasma astrophysics, Spectrometers, Solar coronal mass ejections, Spectroscopy
Galaxy-scale Test of General Relativity with Strong Gravitational Lensing. Although general relativity (GR) has been precisely tested at the solar system scale, precise tests at a galactic or cosmological scale are still relatively insufficient. Here, in order to test GR at the galactic scale, we use the newly compiled galaxy-scale strong gravitational lensing (SGL) sample to constrain the parameter γ PPN in the parameterized post-Newtonian (PPN) formalism. We employ the Pantheon sample of Type Ia supernova observations to calibrate the distances in the SGL systems using the Gaussian Process method, which avoids the logical problem caused by assuming a cosmological model within GR to determine the distances in the SGL sample. Furthermore, we consider three typical lens models in this work to investigate the influences of the lens-mass distributions on the fitting results. We find that the choice of lens models has a significant impact on the constraints on the PPN parameter γ PPN. By using a minimum χ 2 comparison and the Bayesian information criterion as evaluation tools to make comparisons for the fitting results of the three lens models, we find that the most reliable lens model gives the result of ${\gamma }_{\mathrm{PPN}}={1.065}_{-0.074}^{+0.064}$ , which is in good agreement with the prediction of γ PPN = 1 by GR. As far as we know, our 6.4% constraint result is the best result so far among recent works using the SGL method.

Keywords: Cosmology, Strong gravitational lensing, General relativity
How Do the Galaxy Stellar Spins Acquire a Peculiar Tidal Connection?. We explore how the galaxy stellar spins acquire a peculiar tendency of being aligned with the major principal axes of the local tidal fields, in contrast to their dark matter (DM) counterparts, which tend to be perpendicular to them, regardless of their masses. Analyzing the halo and subhalo catalogs from IllustrisTNG 300 hydrodynamic simulations at z ≤ 1, we determine the cosines of the alignment angles, $\cos \alpha $ , between the galaxy stellar and DM spins. Creating four $\cos \alpha $ -selected samples of the galaxies and then controlling them to share the same density and mass distributions, we determine the average strengths of the alignments between the galaxy stellar spins and the tidal tensor major axes over each sample. It is clearly shown that at z ≤ 0.5 the more severely the galaxy stellar spin directions deviate from the DM counterparts, the stronger the peculiar tidal alignments become. Taking the ensemble averages of such galaxy properties as central black hole-to-stellar mass ratio, specific star formation rate, formation epoch, stellar-to-total mass ratio, velocity dispersions, average metallicity, and degree of the cosmic web anisotropy over each sample, we also find that all of these properties exhibit either strong correlations or anticorrelations with $\cos \alpha $ . Our results imply that the peculiar tidal alignments of the galaxy stellar spins may be caused by anisotropic occurrence of some baryonic process responsible for discharging stellar materials from the galaxies along the tidal major directions at z &lt; 1.

Keywords: Large-scale structure of the universe
Modeling Photoionized Turbulent Material in the Circumgalactic Medium. III. Effects of Corotation and Magnetic Fields. Absorption-line measurements of the circumgalactic medium (CGM) display a highly nonuniform distribution of lower ionization state species accompanied by more widespread higher ionization state material. This suggests that the CGM is a dynamic, multiphase medium, such as arises in the presence of turbulence. To better understand this evolution, we perform hydrodynamic and magnetohydrodynamic (MHD) simulations of the CGM surrounding Milky Way-like galaxies. In both cases, the CGM is initially in hydrostatic balance in a 1012 M ⊙ dark matter gravitational potential, and the simulations include rotation in the inner halo and turbulence that decreases radially. They also track ionizations, recombinations, and species-by-species radiative cooling in the presence of the redshift-zero UV background, employing the MAIHEM nonequilibrium chemistry package. We find that after 9 Gyr of evolution, the presence of a magnetic field leads to an overall hotter CGM, with cool gas in the center where magnetic pressure dominates. While the non-MHD run produces more cold clouds overall, we find similar Si IV/O VI and N V/O VI ratios between the MHD and non-MHD runs, which are both very different from their equilibrium values. The non-MHD halo develops cool, low angular momentum filaments above the central disk, in comparison to the MHD run that has more efficient angular momentum transport, especially for the cold gas, which forms a more ordered and extended disk late into its evolution.

Keywords: Magnetic fields, Circumgalactic medium, Astrochemistry
A Guide to Realistic Uncertainties on the Fundamental Properties of Solar-type Exoplanet Host Stars. Our understanding of the properties and demographics of exoplanets critically relies on our ability to determine the fundamental properties of their host stars. The advent of Gaia and large spectroscopic surveys has now made it possible, in principle, to infer the properties of individual stars, including most exoplanet hosts, to very high precision. However, we show that, in practice, such analyses are limited by uncertainties in both the fundamental scale and our models of stellar evolution, even for stars similar to the Sun. For example, we show that current uncertainties on measured interferometric angular diameters and bolometric fluxes set a systematic uncertainty floor of ≈2.4% in temperature, ≈2.0% in luminosity, and ≈4.2% in radius. Comparisons between widely available model grids suggest uncertainties of order ≈5% in mass and ≈20% in age for main-sequence and subgiant stars. While the radius uncertainties are roughly constant over this range of stars, the model-dependent uncertainties are a complex function of luminosity, temperature, and metallicity. We provide open-source software for approximating these uncertainties for individual targets and discuss strategies for reducing these uncertainties in the future.

Keywords: Stellar luminosities, Stellar properties, Stellar ages, Exoplanets, Stellar effective temperatures, Stellar masses
CHORUS. IV. Mapping the Spatially Inhomogeneous Cosmic Reionization with Subaru HSC. Spatial inhomogeneity is one of the important features for understanding the reionization process; however, it has not yet been fully quantified. To map this inhomogeneous distribution, we simultaneously detect Lyα emitters (LAEs) and Lyman-break galaxies (LBGs) at z ~ 6.6 from the Subaru/Hyper Suprime-Cam large-area (~1.5 deg2 = 34,000 cMpc2) deep survey. We estimate the neutral fraction, x HI, from the observed number density ratio of LAEs to LBGs, n(LAE)/n(LBG), using numerical radiative transfer simulations, in which model galaxies are selected to satisfy the observed selection function. While the average x HI within the field of view is found to be x HI &lt; 0.4, which is consistent with previous studies, the variation of n(LAE)/n(LBG) within the field of view for every 140 pMpc2 area is found to be as large as a factor of 3. This may suggest a spatially inhomogeneous topology of reionization, but it also leaves open the possibility that the variation is based on the inherent large-scale structure of the galaxy distribution. Based on the simulations, it may be difficult to distinguish between the two from the current survey. We also find that LAEs in the high-LAE-density region are more numerous at high EW0, supporting the fact that the observed n(LAE)/n(LBG) is more or less driven by the neutral fraction, though the statistical significance is not high.

Keywords: Early universe, Reionization, High-redshift galaxies
Constraining the Baryon Loading Factor of AGN Jets: Implication from the γ-Ray Emission of the Coma Cluster. High-energy cosmic rays (CRs) can be accelerated in the relativistic jets of active galactic nuclei (AGNs) powered by supermassive black holes. The baryon loading efficiency onto relativistic CR baryons from the accreting black holes is poorly constrained by observations so far. In this paper, we suggest that the γ-ray emission of galaxy clusters can be used to study the baryon loading factor of AGN jets, since CRs injected by AGN jets are completely confined in the galaxy clusters and sufficiently interact with the intracluster medium via a hadronic process, producing diffuse γ-rays. We study the propagation of CRs in the galaxy clusters and calculate the radial distribution of the γ-rays in the galaxy cluster with different injection rates from AGNs. By comparison with the γ-ray flux and upper limits of the Coma cluster measured by Fermi-LAT and VERITAS, we find the upper limit of the average baryon loading factor (defined as the efficiency with which the gravitational energy is converted into relativistic particles) to be η  p,grav &lt; 0.1. The upper limit is much lower than that required to account for diffuse neutrino flux in the conventional blazar models.

Keywords: Galaxy clusters, Gamma-rays, Coma Cluster, Cosmic rays