Sazuna/UAT_keywords huggingface dataset:
Testing Model-determined Temperatures in the Hyades: A Bayesian Approach. Gains in our understanding of stellar evolution over the last century are largely due to improvements in stellar models. One key aspect in the use of these models is a reliable transformation between theoretical values (such as luminosity and temperature) to observable quantities (such as magnitude and color). To assess the current state of this transformation, we sought to compare model-determined temperatures from color-magnitude diagram fitting to temperatures obtained from photometric colors or spectroscopy. Our sample for analysis was 88 nonbinary stars in the Hyades open star cluster. By applying a sophisticated Bayesian algorithm we fit five widely available model sets to high-quality photometric data combined with Gaia parallaxes. This analysis provides specific feedback for improving temperature-color transformations, as well as practical guidance for using results based on these models.

Keywords: Fundamental parameters of stars, Hertzsprung Russell diagram, Open star clusters, Stellar astronomy
Hubble Space Telescope Proper Motion (HSTPROMO) Catalogs of Galactic Globular Clusters. VII. Energy Equipartition. We examine the degree of energy equipartition in nine Galactic globular clusters using proper motions measured with the Hubble Space Telescope. For most clusters in the sample, this is the first energy equipartition study ever performed. This study is also the largest of its kind, albeit with only nine clusters. We begin by rigorously cleaning the catalogs to remove poor-quality measurements and to ensure high signal to noise for the study. Using the cleaned catalogs, we investigate how velocity dispersion σ changes with stellar mass m. We fit two functional forms: the first, a classic power law of the form σ ∝ m -η  where η is the degree of energy equipartition, and the second from Bianchini et al. parameterized by an equipartition mass m eq where η changes with stellar mass. We find that both functions fit well but cannot distinguish with statistical significance which function provides the best fit. All clusters exhibit varying degrees of partial equipartition; no cluster is at or near full equipartition. We search for correlations of η and m eq with various cluster properties. The most significant correlation is observed with the number of core or median relaxation times ( ${N}_{\mathrm{core}}$ or N half) the cluster has experienced. Finally, we determine the radial equipartition profile for each cluster, that is, how the degree of equipartition changes with projected distance from the cluster center. We do not detect statistically significant trends in the degree of equipartition with radius. Overall, our observational findings are in broad agreement with theoretical predictions from N -body models published in recent years.

Keywords: Globular star clusters, Stellar dynamics, Proper motions, Stellar kinematics
Extremely Slow (V <SUB>sw</SUB> &lt; 300 km s<SUP>-1</SUP>) Solar Winds (ESSWs) at 1 au: Causes of Extreme Geomagnetic Quiet at Earth. A search for extremely slow (V sw &lt; 300 km s-1) solar winds (ESSWs) at 1 au has been conducted using hourly average solar wind data from 1963 through 2021. 297 ESSW events were identified with an average duration of ~2.0 ± 1.4 days. The lowest speed detected was 156 km s-1. Ten of the lowest-speed events were analyzed in detail. It was found that all 10 events were located at the ends of high-speed solar wind (HSSW) streams. The termination of the ESSWs was caused by high-density plasmas, either a corotating interaction region associated with the next HSSW stream or a heliospheric plasma sheet encounter. There was a greater occurrence of ESSW events in solar cycles 23 and 24 than in previous solar cycles. This phenomenon is associated with the much lower solar activity during these two cycles. The decrease in solar polar open magnetic fields was accompanied by an increase in low and midlatitude open magnetic fields. The ESSWs were accompanied by low interplanetary magnetic fields (4.4 ± 2.1 nT) and low negative interplanetary B z fields (-1.7 ± 1.5 nT), which led to extreme geomagnetic quiet: AE = 67 ± 78 nT and Dst = 2.2 ± 9.9 nT. We encourage magnetospheric researchers to use ESSW events to better understand the ground states of the magnetosphere and ionosphere.

Keywords: Slow solar wind, Geomagnetic fields, Solar wind, Solar coronal mass ejections
KODIAQ-Z: Metals and Baryons in the Cool Intergalactic and Circumgalactic Gas at 2.2 ≲ z ≲ 3.6. We present the KODIAQ-Z survey aimed to characterize the cool, photoionized gas at 2.2 ≲ z ≲ 3.6 in 202 H I-selected absorbers with 14.6 ≤ $\mathrm{log}{N}_{{\rm{H}}\,{\rm\small{I}}}$ &lt; 20 that probe the interface between galaxies and the intergalactic medium (IGM). We find that gas with $14.6\leqslant \mathrm{log}{N}_{{\rm{H}}\,{\rm\small{I}}}\lt 20$ at 2.2 ≲ z ≲ 3.6 can be metal-rich (-1.6 ≲ [X/H] ≲ - 0.2) as seen in damped Lyα absorbers (DLAs); it can also be very metal-poor ([X/H] &lt; - 2.4) or even pristine ([X/H] &lt; - 3.8), which is not observed in DLAs but is common in the IGM. For $16\lt \mathrm{log}{N}_{{\rm{H}}\,{\rm\small{I}}}\lt 20$ absorbers, the frequency of pristine absorbers is about 1%-10%, while for $14.6\leqslant \mathrm{log}{N}_{{\rm{H}}\,{\rm\small{I}}}\leqslant 16$ absorbers it is 10%-20%, similar to the diffuse IGM. Supersolar gas is extremely rare (&lt;1%) at these redshifts. The factor of several thousand spread from the lowest to highest metallicities and large metallicity variations (a factor of a few to &gt;100) between absorbers separated by less than Δv &lt; 500 km s-1 imply that the metals are poorly mixed in $14.6\leqslant \mathrm{log}{N}_{{\rm{H}}\,{\rm\small{I}}}\lt 20$ gas. We show that these photoionized absorbers contribute to about 14% of the cosmic baryons and 45% of the cosmic metals at 2.2 ≲ z ≲ 3.6. We find that the mean metallicity increases with N H I , consistent with what is found in z &lt; 1 gas. The metallicity of gas in this column density regime has increased by a factor ~8 from 2.2 ≲ z ≲ 3.6 to z &lt; 1, but the contribution of the $14.6\leqslant \mathrm{log}{N}_{{\rm{H}}\,{\rm\small{I}}}\lt 19$ absorbers to the total metal budget of the universe at z &lt; 1 is a quarter of that at 2.2 ≲ z ≲ 3.6. We show that FOGGIE cosmological zoom-in simulations have a similar evolution of [X/H] with N H I , which is not observed in lower-resolution simulations. In these simulations, very metal-poor absorbers with [X/H] &lt; - 2.4 at z ~ 2-3 are tracers of inflows, while higher-metallicity absorbers are a mixture of inflows and outflows.

Keywords: Quasar absorption line spectroscopy, Lyman limit systems, Damped Lyman-alpha systems, Cool intergalactic medium, Circumgalactic medium, Metallicity
Image Subtraction in Fourier Space. Image subtraction is essential for transient detection in time-domain astronomy. The point-spread function (PSF), photometric scaling, and sky background generally vary with time and across the field of view for imaging data taken with ground-based optical telescopes. Image subtraction algorithms need to match these variations for the detection of flux variability. An algorithm that can be fully parallelized is highly desirable for future time-domain surveys. Here we introduce the saccadic fast Fourier transform (SFFT) algorithm we developed for image differencing. SFFT uses a δ-function basis for kernel decomposition, and the image subtraction is performed in Fourier space. This brings about a remarkable improvement in computational performance of about an order of magnitude compared to other published image subtraction codes. SFFT can accommodate the spatial variations in wide-field imaging data, including PSF, photometric scaling, and sky background. However, the flexibility of the δ-function basis may also make it more prone to overfitting. The algorithm has been tested extensively on real astronomical data taken by a variety of telescopes. Moreover, the SFFT code allows for the spatial variations of the PSF and sky background to be fitted by spline functions.

Keywords: Transient detection, Astronomy software
Relationship between Total Solar Irradiance and Magnetic Flux during Solar Minima. What drives the small total solar irradiance (TSI) changes of ~50-100 parts per million (compared with &gt;1000 ppm solar-cycle amplitudes) during a deep solar minimum, i.e., in the practical absence of detectable sunspots and long-lasting active regions? We consider the epoch 2008 June-October and investigate multiple data sets (TSI; various Mg II line-activity indices, extreme ultraviolet fluxes, and full-disk magnetograms) to show that variations in TSI closely follow changes in total magnetic flux from sources with ∣B∣ &gt; 80 G (up to ~600 G) that persist even during extended periods with no detectable sunspots. These sources comprise the populations of (a) short-lived (&lt;20 minutes), small-scale (predominantly a single 2″ MDI pixel), ~evenly distributed regions, and (b) on average, more extended (a few MDI pixels) and longer-lived (140-260 minutes median lifetimes) magnetic areas. We ascribe the latter to ephemeral regions, finding them clustering on ~200 Mm scales. We speculate that the short-lived MDI sources are linked to the ubiquitous magnetic bright points. Our analysis of magnetic flux variations during solar cycle 23 shows that the magnetic regions present during this deep solar minimum elevate the total magnetic flux above the total flux in just the Gaussian "cores," fitted to histogram distributions of the full-disk flux. This suggests that solar irradiance during more extended, even deeper minima, such as the Maunder Minimum, may be lower than in 2008.

Keywords: Solar photosphere, Quiet sun, Solar spectral irradiance, Sunspots, Solar magnetic fields, Ephemeral active regions, Solar activity, Solar magnetic bright points
Mode Conversion of Kinetic Alfvén Waves in the Presence of Proton Beams and Its Role in Plasma Heating in the Solar Corona. The density inhomogeneity is a typical feature in various magnetoplasmas in the corona, where kinetic Alfvén waves (KAWs) are effectively generated and contribute greatly to the inhomogeneous heating of coronal plasmas. Proton beams exist widely in various space and solar plasma environments. In this paper, based on the kinetic Vlasov theory, we investigate the resonant mode conversion of Alfvén waves to KAWs in the presence of proton beams in an inhomogeneous plasma and the plasma heating of KAWs due to wave-particle interactions. It is found that the wave properties of excited KAWs are highly sensitive to the density of proton beams n  bi /n 0, the drift velocity of proton beams v  bi /v A, the proton-to-electron temperature ratio T  i /T  e , and the proton-beam-to-proton-temperature ratio T  bi /T  i . In addition, the maximum heating rate of KAWs Q  m /Q 0 obviously increases with increasing n  bi /n 0 and/or v  bi /v A. As the electron beta β  e  increases, Q  m /Q 0 decreases sharply in the region of 6 × 10-4 &lt; β  e  &lt; 10-2 and decreases slowly in the region of β  e  &gt; 10-2. In addition, the applications of KAW dissipation to plasma heating are discussed in the corona and coronal loops. The KAWs associated with perturbed electric field E  x  ~ a few V · m-1 are enough to supply the energy loss in the corona and coronal loops. The present results are of significant importance for comprehending the KAW excitation and the particle energization in the corona.

Keywords: Solar coronal loops, Solar coronal waves, Solar coronal heating, Alfven waves
Disconnecting the Dots: Re-examining the Nature of Stellar "Strings" in the Milky Way. Recent analyses of Gaia data have resulted in the identification of new stellar structures, including a new class of extended stellar filaments called stellar "strings," first proposed by Kounkel &amp; Covey. We explore the spatial, kinematic, and chemical composition of strings to demonstrate that these newfound structures are largely inconsistent with being physical objects whose members share a common origin. Examining the 3D spatial distribution of string members, we find that the spatial dispersion around the claimed string spine does not improve in the latest Gaia DR3 data release-despite tangible gains in the signal-to-noise ratio of the parallax measurements-counter to expectations of a bona fide structure. Using the radial velocity dispersion of the strings (averaging ${\sigma }_{{V}_{r}}=16\,\mathrm{km}\,{{\rm{s}}}^{-1}$ ) to estimate their virial masses, we find that all strings are gravitationally unbound. Given the finding that the strings are dispersing, the reported stellar ages of the strings are typically 120× larger than their measured dispersal times. Finally, we validate prior work that stellar strings are more chemically homogeneous than their local field stars but show it is possible to obtain the same signatures of chemical homogeneity by drawing random samples of stars from spatially, temporally, and kinematically unrelated open clusters. Our results show that while some strings may be composed of real substructures, there is no consistent evidence for larger string-like connections over the sample. These results underscore the need for caution in over-interpreting the significance of these strings and their role in understanding the star formation history of the Milky Way.

Keywords: Interstellar filaments, Stellar dynamics, Milky Way Galaxy, Star clusters
Halo Properties and Mass Functions of Groups/Clusters from the DESI Legacy Imaging Surveys DR9. Based on a large group/cluster catalog recently constructed from the DESI Legacy Imaging Surveys DR9 using an extended halo-based group finder, we measure and model the group-galaxy weak-lensing signals for groups/clusters in a few redshift bins within redshift range 0.1 ≤ z &lt; 0.6. Here, the background shear signals are obtained based on the DECaLS survey shape catalog, derived with the FOURIER_QUAD method. We divide the lens samples into five equispaced redshift bins and seven mass bins, which allow us to probe the redshift and mass dependence of the lensing signals, and hence the resulting halo properties. In addition to these sample selections, we also check the signals around different group centers, e.g., the brightest central galaxy, the luminosity-weighted center, and the number-weighted center. We use a lensing model that includes off-centering to describe the lensing signals that we measure for all mass and redshift bins. The results demonstrate that our model predictions for the halo masses, biases, and concentrations are stable and self-consistent among different samples for different group centers. Taking advantage of the very large and complete sample of groups/clusters, as well as the reliable estimations of their halo masses, we provide measurements of the cumulative halo mass functions up to redshift z = 0.6, with a mass precision at 0.03 ~ 0.09 dex.

Keywords: Weak gravitational lensing, Observational cosmology, Galaxy dark matter halos, Galaxy clusters
NuSTAR Observations of AGNs with Low Observed X-Ray to [O III] Luminosity Ratios: Heavily Obscured AGNs or Turned-off AGNs?. Type 2 active galactic nuclei (AGNs) show signatures of accretion onto a supermassive black hole through strong, high-ionization, narrow emission lines extended on scales of hundreds to thousands of parsecs, but they lack the broad emission lines from close in to the black hole that characterize type 1 AGNs. The lack of broad emission could indicate obscuration of the innermost nuclear regions, or could indicate that the black hole is no longer strongly accreting. Since high-energy X-rays can penetrate thick obscuring columns, they have the power to distinguish these two scenarios. We present high-energy NuSTAR observations of nine Seyfert 2 AGNs from the Infrared Astronomical Satellite 12 μm survey, supplemented with low-energy X-ray observations from Chandra, XMM-Newton, and Swift. The galaxies were selected to have anomalously low observed 2-10 keV luminosities compared to their [O III] optical luminosities, a traditional diagnostic of heavily obscured AGNs, reaching into the Compton-thick regime for the highest hydrogen column densities (N H &gt; 1.5 × 1024 cm-2). Based on updated [O III] luminosities and intrinsic X-ray luminosities based on physical modeling of the hard X-ray spectra, we find that one galaxy was misclassified as type 2 (NGC 5005) and most of the remaining AGNs are obscured, including three confirmed as Compton thick (IC 3639, NGC 1386, and NGC 3982). One galaxy, NGC 3627, appears to have recently deactivated. Compared to the original sample that the nine AGNs were selected from, this is a rate of approximately 1%. We also find a new X-ray changing-look AGN in NGC 6890.

Keywords: LINER galaxies, Seyfert galaxies, X-ray active galactic nuclei, Scaling relations
Mapping the Complex Kinematic Substructure in the TW Hya Disk. We present ALMA observations of CO J = 2 - 1 and CS J = 5 - 4 emission from the disk around TW Hydrae. Both molecules trace a predominantly Keplerian velocity structure, although a slowing of the rotation velocity is detected at the outer edge of the disk beyond ≍140 au in CO emission. This was attributed to the enhanced pressure support from the gas density taper near the outer edge of the disk. Subtraction of an azimuthally symmetric background velocity structure reveals localized deviations in the gas kinematics traced by each of the molecules. Both CO and CS exhibit a "Doppler flip" feature, centered nearly along the minor axis of the disk (PA ~ 60°) at a radius of 1.″35, coinciding with the large gap observed in scattered light and mm continuum. In addition, the CO emission, both through changes in intensity and its kinematics, traces a tightly wound spiral, previously seen with higher-frequency CO J = 3 - 2 observations. Through comparison with linear models of the spiral wakes generated by embedded planets, we interpret these features in the context of interactions with a Saturn-mass planet within the gap at a position angle of PA = 60°, consistent with the theoretical predictions of Mentiplay et al. The lack of a corresponding spiral in the CS emission is attributed to the strong vertical dependence on the buoyancy spirals, which are believed to only grow in the atmospheric of the disk, rather than those traced by CS emission.

Keywords: Exoplanet formation, Radio interferometry, Protoplanetary disks
Switchbacks in the Young Solar Wind: Electron Evolution Observed inside Switchbacks between 0.125 au and 0.25 au. Switchbacks are localized deviations from the nominal Parker spiral field in the solar wind. In this study, we investigate the electron distributions inside switchbacks, focusing primarily on the suprathermal (halo and strahl) populations. We explore electron parameters in relation to the angle of rotation of the magnetic field from radial to determine whether electron distributions observed within switchbacks have any differences from those outside of switchbacks. Our observations reveal several trends in the suprathermal electron populations inside switchbacks. We find that the sunward deficit in the electron velocity distribution function typically observed near the Sun is filled in at larger rotation angles. This results in the suprathermal electron density and heat flux in the antistrahl direction changing from a negative to a positive value. On many days, we also observe a positive correlation between the halo density and rotation angle, and this may suggest that the growth of the halo may fill in the sunward deficit. We also find that strahl distributions have an increased average angular spread at large magnetic field rotation angles. The increase in suprathermal electron flux in the antistrahl direction, and the increase in strahl width, together could suggest that enhanced scattering occurs inside switchbacks. Electron core beta values tend to increase with the magnetic field rotation angle, mainly due to a decrease in magnetic pressure. An increase in electron beta may favor the growth of instabilities inside switchbacks. The Parker Solar Probe observations therefore support an enhanced role for wave-particle interactions in switchbacks.

Keywords: Space plasmas, Solar wind, Solar physics, Solar corona, Solar magnetic fields
A New Census of the 0.2 &lt; z &lt; 3.0 Universe. II. The Star-forming Sequence. We use the panchromatic spectral energy distribution (SED)-fitting code Prospector to measure the galaxy logM*-logSFR relationship (the star-forming sequence) across 0.2 &lt; z &lt; 3.0 using the COSMOS-2015 and 3D-HST UV-IR photometric catalogs. We demonstrate that the chosen method of identifying star-forming galaxies introduces a systematic uncertainty in the inferred normalization and width of the star-forming sequence, peaking for massive galaxies at ~0.5 and ~0.2 dex, respectively. To avoid this systematic, we instead parameterize the density of the full galaxy population in the logM*-logSFR-redshift plane using a flexible neural network known as a normalizing flow. The resulting star-forming sequence has a low-mass slope near unity and a much flatter slope at higher masses, with a normalization 0.2-0.5 dex lower than typical inferences in the literature. We show this difference is due to the sophistication of the Prospector stellar populations modeling: the nonparametric star formation histories naturally produce higher masses while the combination of individualized metallicity, dust, and star formation history constraints produce lower star formation rates (SFRs) than typical UV+IR formulae. We introduce a simple formalism to understand the difference between SFRs inferred from SED fitting and standard template-based approaches such as UV+IR SFRs. Finally, we demonstrate the inferred star-forming sequence is consistent with predictions from theoretical models of galaxy formation, resolving a long-standing ~ 0.2-0.5 dex offset with observations at 0.5 &lt; z &lt; 3. The fully trained normalizing flow including a nonparametric description of $\rho (\mathrm{log}{M}^{* },\mathrm{logSFR},z)$ is available online 20 20 https://github.com/jrleja/sfs_leja_trained_flow to facilitate straightforward comparisons with future work.

Keywords: Galaxy masses, Galaxy formation, Galaxy photometry, Star formation
The Odd Dark Matter Halos of Isolated Gas-rich Ultradiffuse Galaxies. We analyze circular velocity profiles of seven ultradiffuse galaxies (UDGs) that are isolated and gas-rich. Assuming that the dark matter halos of these UDGs have a Navarro-Frenk-White (NFW) density profile or a Read density profile (which allows for constant-density cores), the inferred halo concentrations are systematically lower than the cosmological median, even as low as -0.6 dex (about 5σ away) in some cases. Alternatively, similar fits can be obtained with a density profile that scales roughly as 1/r 2 for radii larger than a few kiloparsecs. Both solutions require the radius where the halo circular velocity peaks ( ${R}_{\max }$ ) to be much larger than the median expectation. Surprisingly, we find an overabundance of such large- ${R}_{\max }$ halos in the IllustrisTNG dark-matter-only simulations compared to the Gaussian expectation. These halos form late and have higher spins compared to median halos of similar masses. The inner densities of the most extreme among these late-forming halos are higher than their NFW counterparts, leading to a ~1/r 2 density profile. However, the two well-resolved UDGs in our sample strongly prefer lower dark matter densities in the center than the simulated ones. Comparing to IllustrisTNG hydrodynamical simulations, we also find a tension in getting both low enough circular velocities and high enough halo mass to accommodate the measurements. Our results indicate that the gas-rich UDGs present a significant challenge for galaxy formation models.

Keywords: Dark matter, Low surface brightness galaxies