Sazuna/UAT_keywords huggingface dataset:
Discovery of a Double Sequence of Blue Straggler Stars in the Core-collapsed Globular Cluster NGC 6256. We used a combination of high-resolution optical images acquired with the Hubble Space Telescope and near-IR wide-field data to investigate the stellar density profile and the population of blue straggler stars (BSSs) in the Galactic globular cluster NGC 6256, with the aim of probing its current stage of internal dynamical evolution. We found that the inner stellar density profile significantly deviates from a King model, while it is well reproduced by a steep cusp with a power-law slope α cusp = -0.89, thus implying that the cluster is currently in the post-core-collapse (PCC) phase. This is also confirmed by the very high segregation level of the BSS population measured through the ${A}_{\mathrm{rh}}^{+}$ parameter. We also found that the distribution of BSSs in the color-magnitude diagram is characterized by a collimated blue sequence and a red more sparse component, as already observed in three other PCC clusters. A comparison with appropriate collisional models demonstrates that the vast majority of the BSSs lying along the collimated blue sequence is consistent with a generation of coeval (1 Gyr old) stars with different masses originated by an event that highly enhanced the collisional rate of the system (i.e., the core collapse). This study confirms that the segregation level of BSSs is a powerful dynamical diagnostic also of star cluster in a very advanced stage of dynamical evolution. Moreover, it pushes forward the possibility of using the morphology of BSSs in a color-magnitude diagram as a tracer of the core-collapse and subsequent dynamical evolutionary phases.

Keywords: Globular star clusters, Blue straggler stars, Stellar populations, Star clusters
A Selection of Hα Emitters at z = 2.1-2.5 Using the K <SUB> s </SUB>-band Photometry of ZFOURGE. Large and less-biased samples of star-forming galaxies are essential to investigate galaxy evolution. Hα emission line is one of the most reliable tracers of star-forming galaxies because its strength is directly related to recent star formation. However, it is observationally expensive to construct large samples of Hα emitters by spectroscopic or narrowband imaging survey at high redshifts. In this work, we demonstrate a method to extract Hα fluxes of galaxies at z = 2.1-2.5 from K  s  broadband photometry of ZFOURGE catalog. Combined with 25-39 other filters, we estimate the emission-line fluxes by SED fitting with stellar population models that incorporate emission-line strengths. 2005 galaxies are selected as Hα emitters by our method and their fluxes show good agreement with previous measurements in the literature. On the other hand, there are more Hα luminous galaxies than previously reported. The discrepancy can be explained by extended Hα profiles of massive galaxies and a luminosity dependence of dust attenuation, which are not taken into account in the previous work. We also find that there are a large number of low-mass galaxies with a much higher specific star formation rate (sSFR) than expected from the extrapolated star formation main sequence. Such low-mass galaxies exhibit larger ratios between Hα and UV fluxes compared to more massive high sSFR galaxies. This result implies that a "starburst" mode may differ among galaxies: low-mass galaxies appear to assemble their stellar mass via short-duration bursts, while more massive galaxies tend to experience longer-duration (&gt;10 Myr) bursts.

Keywords: Galaxy formation, Multi-color photometry, Emission line galaxies, Galaxy evolution, Broad band photometry, High-redshift galaxies, Galaxies
Constraints on Cosmological Parameters with a Sample of Type Ia Supernovae from JWST. We investigate the potential of using a sample of very high-redshift (2 ≲ z ≲ 6) (VHZ) Type Ia supernovae (SNe Ia) attainable by JWST on constraining cosmological parameters. At such high redshifts, the age of the universe is young enough that the VHZ SN Ia sample comprises the very first SNe Ia of the universe, with progenitors among the very first generation of low-mass stars that the universe has made. We show that the VHZ SNe Ia can be used to disentangle systematic effects due to the luminosity distance evolution with redshifts intrinsic to SN Ia standardization. Assuming that the systematic evolution can be described by a linear or logarithmic formula, we found that the coefficients of this dependence can be determined accurately and decoupled from cosmological models. Systematic evolution as large as 0.15 mag and 0.45 mag out to z = 5 can be robustly separated from popular cosmological models for linear and logarithmic evolution, respectively. The VHZ SNe Ia will lay the foundation for quantifying the systematic redshift evolution of SN Ia luminosity distance scales. When combined with SN Ia surveys at comparatively lower redshifts, the VHZ SNe Ia allow for the precise measurement of the history of the expansion of the universe from z ~ 0 to the epoch approaching reionization.

Keywords: Cosmological models, Hubble diagram, Cosmological parameters, Expanding universe, Type Ia supernovae, Cosmological constant, Accelerating universe, Dark energy
Observational Analysis and Numerical Modeling of the Solar Wind Fluctuation Spectra during Intervals of Plasma Instability. We perform a statistical analysis of observed magnetic spectra in the solar wind at 1 au with localized power elevations above the level of the ambient turbulent fluctuations. We show that the elevations are seen only when the intensity of the ambient fluctuations is sufficiently low. Assuming that the spectral elevations are caused by thermal-ion instabilities, this suggests that on average the effect of the solar wind background is strong enough to suppress the instability or obscure it or both. We then carry out nonlinear numerical simulations with particle ions and an electron fluid to model a thermal-ion instability coexisting with an ambient turbulence. The parameters of the simulation are taken from a known solar wind interval where an instability was assumed to exist based on the linear theory and a bi-Maxwellian fit of the observed distribution with core and secondary-beam protons. The numerical model closely matches the position of the observed spectral elevation in the wavenumber space. This confirms that the thermal-ion instability is responsible for the elevation. At the same time, the magnitude of the elevation turns out to be smaller than in the real solar wind. When higher intensity of the turbulence is used in the simulation, which is typical of solar wind in general, the power elevation is no longer seen. This is in agreement with the reduced observability of the elevations at higher intensities. However, the simulations show that the turbulence does not simply obscure the instability but also lowers its saturation level.

Keywords: Interplanetary turbulence, Space plasmas, Solar wind
Three-dimensional Simulations of Magnetospheric Accretion in a T Tauri Star: Accretion and Wind Structures Just Around the Star. We perform three-dimensional (3D) magnetohydrodynamic simulations of magnetospheric accretion in a T Tauri star to study the accretion and wind structures in the close vicinity of the star. The gas accreting onto the star consists of the gas from the magnetospheric boundary and the failed disk winds. The accreting gas is commonly found as a multi-column accretion, which is consistent with observations. A significant fraction of the angular momentum of the accreting flows is removed by the magnetic fields of conical disk winds and turbulent failed winds inside and near the magnetosphere. As a result, the accretion torque is significantly reduced compared to the simple estimation based on the mass accretion rate. The stellar spin affects the time variability of the conical disk wind by changing the stability condition of the magnetospheric boundary. However, the time-averaged magnetospheric radius only weakly depends on the stellar spin, which is unlike the prediction of classical theories that the stellar spin controls the magnetospheric radius through the magnetic torque. The ratio of the toroidal to the poloidal field strengths at the magnetospheric boundary, which is a key parameter for the magnetic torque, is also insensitive to the spin; it is rather determined by the disk dynamics. Considering newly found 3D effects, we obtain a scaling relation of the magnetospheric radius very similar to the Ghosh &amp; Lamb relation from the steady angular momentum transport equation.

Keywords: Stellar magnetic fields, Pre-main sequence stars, Star formation, Protoplanetary disks, Stellar accretion disks, Protostars, Magnetohydrodynamical simulations
ALMA Observations of CO Emission from Luminous Lyman-break Galaxies at z = 6.0293-6.2037. We present our new Atacama Large Millimeter/submillimeter Array (ALMA) observations targeting CO(6-5) emission from three luminous Lyman-break galaxies (LBGs) at z spec = 6.0293-6.2037 found in the Subaru/Hyper Suprime-Cam survey, whose [O III] 88 μm and [C II] 158 μm emissions have been detected with ALMA. We find a marginal detection of the CO(6-5) line from one of our LBGs, J0235-0532, at the ≃4σ significance level and obtain upper limits for the other two LBGs, J1211-0118 and J0217-0208. Our z = 6 luminous LBGs are consistent with the previously found correlation between the CO luminosity and the infrared luminosity. The unique ensemble of the multiple far-infrared emission lines and underlying continuum fed to a photodissociation region model reveals that J0235-0532 has a relatively high density of hydrogen nuclei n H that is comparable to those of low-z (U)LIRGs, quasars, and Galactic star-forming regions with high n H values, while the other two LBGs have lower n H consistent with local star-forming galaxies. By carefully taking account of various uncertainties, we obtain constraints on total gas mass and gas surface density from their CO luminosity measurements. We find that J0235-0532 is located below the Kennicutt-Schmidt (KS) relation, comparable to the z = 5.7 LBG, HZ10, previously detected with CO(2-1). Combined with previous results for dusty starbursts at similar redshifts, the KS relation at z = 5-6 is on average consistent with the local one.

Keywords: Molecular gas, Galaxy formation, Interstellar line emission, Millimeter astronomy, Photodissociation regions, Galactic and extragalactic astronomy, Galaxy evolution, Interstellar medium, CO line emission, Submillimeter astronomy, Lyman-break galaxies, High-redshift galaxies
The First Interferometric Measurements of NH<SUB>2</SUB>D/NH<SUB>3</SUB> Ratio in Hot Corinos. The chemical evolution of nitrogen during star and planet formation is still not fully understood. Ammonia (NH3) is a key specie in the understanding of the molecular evolution in star-forming clouds and nitrogen isotope fractionation. In this paper, we present high-spatial-resolution observations of multiple emission lines of NH3 toward the protobinary system NGC1333 IRAS4A with the Karl G. Jansky Very Large Array. We spatially resolved the binary (hereafter, 4A1 and 4A2) and detected compact emission of NH3 transitions with high excitation energies (≳100 K) from the vicinity of the protostars, indicating the NH3 ice has sublimated at the inner hot region. The NH3 column density is estimated to be ~1017-1018 cm-2. We also detected two NH2D transitions, allowing us to constrain the deuterium fractionation of ammonia. The NH2D/NH3 ratios are as high as ~0.3-1 in both 4A1 and 4A2. From comparisons with the astrochemical models in the literature, the high NH2D/NH3 ratios suggest that the formation of NH3 ices mainly started in the prestellar phase after the formation of bulk water ice finished, and that the primary nitrogen reservoir in the star-forming cloud could be atomic nitrogen (or N atoms) rather than nitrogen-bearing species such as N2 and NH3. The implications on the physical properties of IRAS4A's cores are discussed as well.

Keywords: Star formation, Astrochemistry
The Neutron Star Population in M28: A Joint Chandra/GBT Look at Pulsar Paradise. We present the results of a deep study of the neutron star (NS) population in the globular cluster M28 (NGC 6626), using the full 330 ks 2002-2015 ACIS data set from the Chandra X-ray Observatory and coordinated radio observations taken with the Green Bank Telescope (GBT) in 2015. We investigate the X-ray luminosity (L  X ), spectrum, and orbital modulation of the seven known compact binary millisecond pulsars in the cluster. We report two simultaneous detections of the redback PSR J1824-2452I (M28I) and its X-ray counterpart at L  X  = [8.3 ± 0.9] × 1031 erg s-1. We discover a double-peaked X-ray orbital flux modulation in M28I during its pulsar state, centered around pulsar inferior conjunction. We analyze the spectrum of the quiescent NS low-mass X-ray binary to constrain its mass and radius. Using both hydrogen and helium NS atmosphere models, we find an NS radius of R = 9.2-11.5 km and R = 13.0-17.5 km, respectively, for an NS mass of 1.4 M ⊙ (68% confidence ranges). We also search for long-term variability in the 46 brightest X-ray sources and report the discovery of six new variable low-luminosity X-ray sources in M28.

Keywords: Neutron stars, Low-mass x-ray binary stars, Millisecond pulsars
LoTSS Jellyfish Galaxies. IV. Enhanced Star Formation on the Leading Half of Cluster Galaxies and Gas Compression in IC3949. With Mapping Nearby Galaxies at APO integral field spectroscopy, we present a resolved analysis of star formation for 29 jellyfish galaxies in nearby clusters, identified from radio continuum imaging taken by the Low Frequency Array. Simulations predict enhanced star formation on the "leading half" (LH) of galaxies undergoing ram pressure stripping, and in this work we report observational evidence for this elevated star formation. The dividing line (through the galaxy center) that maximizes this star formation enhancement is systematically tied to the observed direction of the ram-pressure-stripped tail, suggesting a physical connection between ram pressure and this star formation enhancement. We also present a case study on the distribution of molecular gas in one jellyfish galaxy from our sample, IC3949, using Atacama Large Millimeter/submillimeter Array CO J = 1 - 0, HCN J = 1 - 0, and HCO+ J = 1 - 0 observations from the ALMA MaNGA Quenching and Star Formation Survey. The H2 depletion time (as traced by CO) in IC3949 ranges from ~1 Gyr in the outskirts of the molecular gas disk to ~11 Gyr near the galaxy center. IC3949 shows a clear region of enhanced star formation on the LH of the galaxy where the average depletion time is ~2.7 Gyr, in line with the median value for the galaxy on the whole. Dense gas tracers, HCN and HCO+, are only detected at the galaxy center and on the LH of IC3949. Our results favor a scenario in which ram pressure compresses the interstellar medium, promoting the formation of molecular gas that in turn fuels a localized increase of star formation.

Keywords: Galaxy clusters, Molecular gas, Ram pressure stripped tails, Star formation, Galaxy quenching
Galaxies at a Cosmic Ray Eddington Limit. Cosmic rays have been shown to be extremely important in the dynamics of diffuse gas in galaxies, helping to maintain hydrostatic equilibrium, and serving as a regulating force in star formation. In this paper, we address the influence of cosmic rays on galaxies by re-examining the theory of a cosmic ray Eddington limit, first proposed by Socrates et al. and elaborated upon by Crocker et al. and Huang &amp; Davis. A cosmic ray Eddington limit represents a maximum cosmic ray energy density above which the interstellar gas cannot be in hydrostatic equilibrium, resulting in a wind. In this paper, we continue to explore the idea of a cosmic ray Eddington limit by introducing a general framework that accounts for the circumgalactic environment and applying it to five galaxies that we believe to be a good representative sample of the star-forming galaxy population, using different cosmic ray transport models to determine what gives each galaxy the best chance to reach this limit. We show that, while an Eddington limit for cosmic rays does exist, for our five galaxies, the limit either falls at star formation rates that are much larger or gas densities that are much lower than each galaxy's measured values. This suggests that cosmic ray pressure is not the main factor limiting the luminosity of starburst galaxies.

Keywords: Galactic winds, Galaxy structure, Interstellar medium, Cosmic rays
STITCH: A Subgrid-scale Model for Energy Buildup in the Solar Corona. The solar corona routinely exhibits explosive activity, in particular coronal mass ejections and their accompanying eruptive flares, which have global-scale consequences. These events and their smaller counterparts, coronal jets, originate in narrow, sinuous filament channels. The key processes that form and evolve the channels operate on still smaller spatial scales and much longer timescales, culminating in a vast separation of characteristic lengths and times that govern these explosive phenomena. In this article, we describe implementation and tests of an efficient subgrid-scale model for generating eruptive structures in magnetohydrodynamics (MHD) coronal simulations. STITCH-STatistical InjecTion of Condensed Helicity-is a physics-based, reduced representation of helicity condensation: a process wherein small-scale vortical surface convection forms ubiquitous current sheets and pervasive reconnection across the sheets mediates an inverse cascade of magnetic helicity and free energy, thereby forming the filament channels. We have developed a formalism, STITCH, that abstracts these complex processes into a single term in Ohm's law and the induction equation that directly injects tangential magnetic flux into the low corona. We show that our approach is in very good agreement with a full helicity condensation calculation that treats all of the dynamics explicitly, while enabling substantial reductions in temporal duration and spatial resolution. In addition, we illustrate the flexibility of STITCH at forming localized filament channels and at energizing complex surface flux distributions that have sinuous boundaries. STITCH is simple to implement and computationally efficient, making it a powerful technique for physics-based modeling of solar eruptive events.

Keywords: Solar flares, Solar magnetic reconnection, Solar corona, Solar coronal mass ejections, Solar filament eruptions, Magnetohydrodynamical simulations
Fast Multipole Method for Gravitational Lensing: Application to High-magnification Quasar Microlensing. We introduce the use of the fast multipole method (FMM) to speed up gravitational lensing ray tracing calculations. The method allows very fast calculation of ray deflections when a large number of deflectors, N *, are involved, while keeping rigorous control on the errors. In particular, we apply this method, in combination with the inverse polygon mapping (IPM) technique, to quasar microlensing to generate microlensing magnification maps with very high workloads (high magnification, large size, and/or high resolution) that require a very large number of deflectors. Using FMM-IPM, the computation time can be reduced by a factor of ~105 with respect to standard inverse ray shooting (IRS), making the use of this algorithm on a personal computer comparable to the use of standard IRS on GPUs. We also provide a flexible web interface for easy calculation of microlensing magnification maps using FMM-IPM (see https://gloton.ugr.es/microlensing/). We exemplify the power of this new method by applying it to some challenging interesting astrophysical scenarios, including clustered primordial black holes and extremely magnified stars close to the giant arcs of galaxy clusters. We also show the performance/use of FMM to calculate ray deflection for a halo resulting from cosmological simulations composed of a large number (N ≳ 107) of elements.

Keywords: Quasar microlensing, Gravitational lensing
A Census of Outflow to Magnetic Field Orientations in Nearby Molecular Clouds. We define a sample of 200 protostellar outflows showing blue- and redshifted CO emission in the nearby molecular clouds Ophiuchus, Taurus, Perseus, and Orion, to investigate the correlation between outflow orientations and local, but relatively large-scale, magnetic field directions traced by Planck 353 GHz dust polarization. At high significance (p ~ 10-4), we exclude a random distribution of relative orientations and find that there is a preference for alignment of projected plane of sky outflow axes with magnetic field directions. The distribution of relative position angles peaks at ~30° and exhibits a broad dispersion of ~50°. These results indicate that magnetic fields have dynamical influence in regulating the launching and/or propagation directions of outflows. However, the significant dispersion around perfect alignment orientation implies that there are large measurement uncertainties and/or a high degree of intrinsic variation caused by other physical processes, such as turbulence or strong stellar dynamical interactions. Outflow to magnetic field alignment is expected to lead to a correlation in the directions of nearby outflow pairs, depending on the degree of order of the field. Analyzing this effect, we find limited correlation, except on relatively small scales ≲0.5 pc. Furthermore, we train a convolutional neural network to infer the inclination angle of outflows with respect to the line of sight and apply it to our outflow sample to estimate their full 3D orientations. We find that the angles between outflow pairs in 3D space also show evidence of small-scale alignment.

Keywords: Stellar feedback, Stellar jets, Convolutional neural networks, Molecular clouds, Interstellar magnetic fields, Star formation, Interstellar medium
Constraints on the Physics of the Prompt Emission from Distant and Energetic Gamma-Ray Burst GRB 220101A. The emission region of γ-ray bursts (GRBs) is poorly constrained. The uncertainty on the size of the dissipation site spans over 4 orders of magnitude (1012-1017 cm) depending on the unknown energy composition of the GRB jets. The joint multiband analysis from soft X-rays to high energies (up to ~1 GeV) of one of the most energetic and distant GRBs, GRB 220101A (z = 4.618), allows us to make an accurate distinction between prompt and early afterglow emissions. The enormous amount of energy released by GRB 220101A (E iso ≈ 3 × 1054 erg) and the spectral cutoff at ${E}_{\mathrm{cutoff}}={85}_{-26}^{+16}$ MeV observed in the prompt emission spectrum constrain the parameter space of the GRB dissipation site. We put stringent constraints on the prompt emission site, requiring 700 &lt; Γ0 &lt; 1160 and R  γ  ~ 4.5 × 1013 cm. Our findings further highlight the difficulty of finding a simple self-consistent picture in the electron-synchrotron scenario, favoring instead a proton-synchrotron model, which is also consistent with the observed spectral shape. Deeper measurements of the time variability of GRBs, together with accurate high-energy observations (MeV-GeV), would unveil the nature of the prompt emission.

Keywords: Gamma-ray bursts