Sazuna/UAT_keywords huggingface dataset:
Multiband Weighting of X-Ray Polarization Data. An optimal estimate for Stokes parameters is derived for the situation in X-ray astronomy where the instrument has a modulation factor that varies significantly with energy but the signals are very weak or mildly polarized. For such sources, the band of analysis may be broadened in order to obtain a significant polarization measurement. Optimal estimators are provided for the cases of binned and unbinned data and applied to data such as might be obtained for faint or weakly polarized sources observed using the Imaging X-ray Polarimetry Explorer. For a sample situation, the improvement in the minimum detectable polarization is 6%-7% using a count-weighted rms of the modulation factor, when compared to a count-weighted average. Improving the modulation factor, such as when using a neural network approach to Imaging X-ray Polarimetry Explorer event tracks, can provide additional improvement up to 10%-15%. The actual improvement depends on the spectral shape and the details of the instrument response functions.

Keywords: Polarimetry, Astronomy data analysis, High energy astrophysics
Interaction of Large- and Small-scale Dynamos in Isotropic Turbulent Flows from GPU-accelerated Simulations. Magnetohydrodynamical (MHD) dynamos emerge in many different astrophysical situations where turbulence is present, but the interaction between large-scale dynamos (LSDs) and small-scale dynamos (SSDs) is not fully understood. We performed a systematic study of turbulent dynamos driven by isotropic forcing in isothermal MHD with magnetic Prandtl number of unity, focusing on the exponential growth stage. Both helical and nonhelical forcing was employed to separate the effects of LSD and SSD in a periodic domain. Reynolds numbers ( ${\mathrm{Re}}_{{\rm{M}}}$ ) up to ≈250 were examined and multiple resolutions used for convergence checks. We ran our simulations with the Astaroth code, designed to accelerate 3D stencil computations on graphics processing units (GPUs) and to employ multiple GPUs with peer-to-peer communication. We observed a speedup of ≈35 in single-node performance compared to the widely used multi-CPU MHD solver Pencil Code. We estimated the growth rates from both the averaged magnetic fields and their power spectra. At low ${\mathrm{Re}}_{{\rm{M}}}$ LSD growth dominates, but at high ${\mathrm{Re}}_{{\rm{M}}}$ SSD appears to dominate in both helically and nonhelically forced cases. Pure SSD growth rates follow a logarithmic scaling as a function of ${\mathrm{Re}}_{{\rm{M}}}$ . Probability density functions of the magnetic field from the growth stage exhibit SSD behavior in helically forced cases even at intermediate ${\mathrm{Re}}_{{\rm{M}}}$ . We estimated mean field turbulence transport coefficients using closures like the second-order correlation approximation (SOCA). They yield growth rates similar to the directly measured ones and provide evidence of α quenching. Our results are consistent with the SSD inhibiting the growth of the LSD at moderate ${\mathrm{Re}}_{{\rm{M}}}$ , while the dynamo growth is enhanced at higher ${\mathrm{Re}}_{{\rm{M}}}$ .

Keywords: Magnetohydrodynamics, Magnetic fields, Computational methods, GPU computing, Astrophysical fluid dynamics
A Catalog of High-velocity C IV Mini-broad Absorption Lines in the VLT-UVES and Keck-HIRES Archives. We present a catalog of high-velocity C IV λ1548,1551 mini-broad absorption lines (mini-BALs) in the archives of the Very Large Telescope-UV Visual Echelle Spectrograph and Keck-High Resolution Echelle Spectrometer. We identify C IV mini-BALs based on smooth rounded BAL-like profiles with velocity blueshifts &lt;-4000 km s-1 and widths in the range 70 ≲ FWHM(1548) ≲ 2000 km s-1. We find 105 mini-BALs in 44 quasars from a total sample of 638 quasars. The fraction of quasars with at least one mini-BAL meeting our criteria is roughly ∼9% after correcting for incomplete velocity coverage. All of the systems are highly ionized based on the strong presence of N V and O VI and/or the absence of Si II and C II when within the wavelength coverage. Two of the mini-BAL systems in our catalog, plus three others at smaller velocity shifts, have P V λ1118,1128 absorption indicating highly saturated C IV absorption and total hydrogen column densities ≳1022 cm-2. Most of the mini-BALs are confirmed to have optical depths ≳1 with partial covering of the quasar continuum source. The covering fractions are as small as 0.06 in C IV and 0.03 in Si IV, corresponding to outflow absorbing structures &lt;0.002 pc across. When multiple lines are measured, the lines of less abundant ions tend to have narrower profiles and smaller covering fractions indicative of inhomogeneous absorbers where higher column densities occur in smaller clumps. This picture might extend to BAL outflows if the broader and generally deeper BALs form in either the largest clumps or collections of many mini-BAL-like clumps that blend together in observed quasar spectra.

Keywords: High resolution spectroscopy, Broad-absorption line quasar, Quasar absorption line spectroscopy, Quasars
The SAGA Survey. II. Building a Statistical Sample of Satellite Systems around Milky Way-like Galaxies. We present the Stage II results from the ongoing Satellites Around Galactic Analogs (SAGA) Survey. Upon completion, the SAGA Survey will spectroscopically identify satellite galaxies brighter than Mr,o = -12.3 around 100 Milky Way (MW) analogs at z ∼ 0.01. In Stage II, we have more than quadrupled the sample size of Stage I, delivering results from 127 satellites around 36 MW analogs with an improved target selection strategy and deep photometric imaging catalogs from the Dark Energy Survey and the Legacy Surveys. We have obtained 25,372 galaxy redshifts, peaking around z = 0.2. These data significantly increase spectroscopic coverage for very low redshift objects in 17 &lt; ro &lt; 20.75 around SAGA hosts, creating a unique data set that places the Local Group in a wider context. The number of confirmed satellites per system ranges from zero to nine and correlates with host galaxy and brightest satellite luminosities. We find that the number and luminosities of MW satellites are consistent with being drawn from the same underlying distribution as SAGA systems. The majority of confirmed SAGA satellites are star-forming, and the quenched fraction increases as satellite stellar mass and projected radius from the host galaxy decrease. Overall, the satellite quenched fraction among SAGA systems is lower than that in the Local Group. We compare the luminosity functions and radial distributions of SAGA satellites with theoretical predictions based on cold dark matter simulations and an empirical galaxy-halo connection model and find that the results are broadly in agreement.

Keywords: Luminosity function, Galaxy dark matter halos, Galaxy physics, Dwarf galaxies, Redshift surveys
Ion Acceleration in Driven Magnetic Reconnection during High-energy-Density Plasma Interaction. Strongly driven magnetic reconnection occurs in astrophysical events and also in laboratory experiments with laser-produced plasma. We have performed 2.5D particle-in-cell simulations of collisions of two high-energy-density plasmas resulting in strongly driven magnetic reconnection that demonstrates significant non-thermal ion acceleration. Such acceleration is significant only when the plasma beta is sufficiently low that the Alfvén speed at the reconnection inflow exceeds the thermal speed. Under these conditions, the most energetic ions are primarily accelerated by the Hall electric field in the reconnection outflow, especially at the trailing edge of an emerging plasmoid in the outflow. Laboratory experiments in the near future should be able to confirm these predictions and their applicability to astrophysical situations.

Keywords: Laboratory astrophysics, Plasma astrophysics, High energy astrophysics
The Evolution of a Newborn Millisecond Magnetar with a Propeller-recycling Disk. A rapidly rotating and highly magnetized neutron star (NS) could be formed from explosive phenomena such as superluminous supernovae and gamma-ray bursts. This newborn NS can substantially influence the emission of these explosive transients through its spin-down. The spin-down evolution of the NS can sometimes be affected by fallback accretion, although it is usually regulated by the magnetic dipole radiation and gravitational wave radiation of the NS. Under appropriate conditions, the accreting material can be first ejected and subsequently recycled back, so that the accretion disk can remain in a quasi-steady state for a long time. Here we describe the interaction of the NS with such a propeller-recycling disk and their coevolution. Our result shows that the spin-down of the NS can be initially dominated by the propeller, which prevents the disk material from falling onto the NS until hundreds or thousands of seconds later. It is suggested that the abrupt fall of the disk material onto the NS could significantly suppress the magnetic dipole radiation and then convert the NS from a normal magnetar to a low-field magnetar. This evolution behavior of the newborn NS can help us understand the very different influence of the NS on the early GRB afterglows and the late supernova/kilonova emission.

Keywords: Neutron stars, Magnetars, Stellar accretion disks, Gamma-ray bursts
JCMT POL-2 and BISTRO Survey Observations of Magnetic Fields in the L1689 Molecular Cloud. We present 850 μm polarization observations of the L1689 molecular cloud, part of the nearby Ophiuchus molecular cloud complex, taken with the POL-2 polarimeter on the James Clerk Maxwell Telescope (JCMT). We observe three regions of L1689: the clump L1689N which houses the IRAS 16293-2433 protostellar system, the starless clump SMM-16, and the starless core L1689B. We use the Davis-Chandrasekhar-Fermi method to estimate plane-of-sky field strengths of 366 ± 55 μG in L1689N, 284 ± 34 μG in SMM-16, and 72 ± 33 μG in L1689B, for our fiducial value of dust opacity. These values indicate that all three regions are likely to be magnetically transcritical with sub-Alfvénic turbulence. In all three regions, the inferred mean magnetic field direction is approximately perpendicular to the local filament direction identified in Herschel Space Telescope observations. The core-scale field morphologies for L1689N and L1689B are consistent with the cloud-scale field morphology measured by the Planck Space Observatory, suggesting that material can flow freely from large to small scales for these sources. Based on these magnetic field measurements, we posit that accretion from the cloud onto L1689N and L1689B may be magnetically regulated. However, in SMM-16, the clump-scale field is nearly perpendicular to the field seen on cloud scales by Planck, suggesting that it may be unable to efficiently accrete further material from its surroundings.

Keywords: Star forming regions, Molecular clouds, Interstellar magnetic fields, Star formation, Interstellar medium, Submillimeter astronomy, Polarimetry
From Starspots to Stellar Coronal Mass Ejections—Revisiting Empirical Stellar Relations. Upcoming missions, including the James Webb Space Telescope, will soon characterize the atmospheres of terrestrial-type exoplanets in habitable zones around cool K- and M-type stars by searching for atmospheric biosignatures. Recent observations suggest that the ionizing radiation and particle environment from active cool planet hosts may be detrimental to exoplanetary habitability. Since no direct information on the radiation field is available, empirical relations between signatures of stellar activity, including the sizes and magnetic fields of starspots, are often used. Here, we revisit the empirical relation between the starspot size and the effective stellar temperature and evaluate its impact on estimates of stellar flare energies, coronal mass ejections, and fluxes of the associated stellar energetic particle events.

Keywords: Solar energetic particles, Starspots, Stellar coronal mass ejections
Quality Metric for Spitzer-Braginskii and Grad 8 Moment Heat Flux Closures. Quality metrics for Spitzer-Härm and Grad closures are presented based on the percentage of the heat flux moment supported only by nonnegative, physical, phase space densities ${\mathbb{F}}\gt 0$ underlying the closure. The Spitzer and Grad qualities exceed 95% for the perturbative regimes where Spitzer's formulation is analytically known to be convergent. Beyond this regime both heat flux qualities fall about 30% per decade increase of ɛ &gt; 0.01. In the solar corona the first decade's decrease in quality straddles the radius of the coronal temperature maximum and spans the initial acceleration of the solar wind. By the end of the second decade of increase of ɛ the observer is between 5 and 10R⊙, already in conditions comparable to those at 1 au with ≃60% degradation of quality. These strong radial decays of closure quality show that integrating the fluid equations using such closures must represent a very poor assay of the role and effects of ∇ · q had the heat flux been described throughout with a uniformly high quality closure procedure. For small ɛ, $\,{\mathbb{F}}\lt 0$ occurs for cosine of pitch angle μ &lt; 0 opposed to q at speeds above 2 thermal speeds and are omnipresent (but ignorable) for truly perturbative closures. Above a computed threshold in ɛ unphysical ${\mathbb{F}}\lt 0$ occurs for speeds below 2 thermal speeds with μ &gt; 0. The present work graphically shows ${\mathbb{F}}\lt 0$ regimes becoming increasingly pervasive as ɛ increases, first crossing ≃4 thermal speeds at μ &lt; 0 and then representing ever larger unphysical incursions within the needed velocity sphere required to accurately determine the heat flux.

Keywords: Hydrodynamical simulations, Astronomical models, Plasma physics, Solar coronal heating, Solar wind, Stellar winds, Solar corona, Main sequence stars, Astrophysical fluid dynamics
HAZMAT. VII. The Evolution of Ultraviolet Emission with Age and Rotation for Early M Dwarf Stars. The ultraviolet (UV) emission from the most numerous stars in the universe, M dwarfs, impacts the formation, chemistry, atmospheric stability, and surface habitability of their planets. We have analyzed the spectral evolution of UV emission from M0-M2.5 (0.3-0.6 M⊙) stars as a function of age, rotation, and Rossby number using Hubble Space Telescope observations of Tucana-Horologium (40 Myr), Hyades (650 Myr), and field (2-9 Gyr) objects. The quiescent surface flux of their C II, C III, C IV, He II, N V, Si III, and Si IV emission lines, formed in the stellar transition region, remains elevated at a constant level for 240 ± 30 Myr before declining by 2.1 orders of magnitude to an age of 10 Gyr. The Mg II and far-UV pseudocontinuum emission, formed in the stellar chromosphere, exhibits more gradual evolution with age, declining by 1.3 and 1.7 orders of magnitude, respectively. The youngest stars exhibit a scatter of 0.1 dex in far-UV line and pseudocontinuum flux attributable only to rotational modulation, long-term activity cycles, or an unknown source of variability. Saturation-decay fits to these data can predict an M0-M2.5 star's quiescent emission in UV lines and the far-UV pseudocontinuum with an accuracy of 0.2-0.3 dex, the most accurate means presently available. Predictions of UV emission will be useful for studying exoplanetary atmospheric evolution and the destruction and abiotic production of biologically relevant molecules and interpreting infrared and optical planetary spectra measured with observatories like the James Webb Space Telescope.

Keywords: Ultraviolet astronomy, M dwarf stars, Stellar evolution, Stellar activity
Properties of Neutrino Transfer in a Deformed Remnant of a Neutron Star Merger. We study properties of neutrino transfer in a remnant of a neutron star merger, consisting of a massive neutron star and a surrounding torus. We perform numerical simulations of the neutrino transfer by solving the Boltzmann equation with momentum-space angles and energies of neutrinos for snapshots of the merger remnant having elongated shapes. The evaluation of the neutrino distributions in multiple dimensions enables us to provide detailed information on the angle and energy spectra and neutrino reaction rates. We demonstrate features of asymmetric neutrino fluxes from the deformed remnant and investigate the neutrino emission region by determining the neutrinosphere for each energy. We examine the emission and absorption of neutrinos to identify important ingredients of heating rates through neutrino irradiation. We show that the contributions of μ- and τ-type neutrinos are important for the heating in the region above the massive neutron star. We also examine the angle moments and the Eddington tensor calculated directly from the neutrino distribution functions and compare them with those obtained by a moment closure approach, which is often used in the study of neutrino-radiation hydrodynamics. We show that the components of the Eddington tensor have non-monotonic behaviors, and the approximation of the closure relation may become inaccurate for high-energy neutrinos, whose fluxes are highly aspherical due to the extended merger remnant.

Keywords: Neutron stars, High energy astrophysics, Neutrino astronomy, Radiative transfer, Compact objects
On the Collisional Disalignment of Dust Grains in Illuminated and Shaded Regions of IC 63. Interstellar dust grain alignment causes polarization from UV to mm wavelengths, allowing the study of the geometry and strength of the magnetic field. Over the last couple of decades, observations and theory have led to the establishment of the radiative alignment torque mechanism as a leading candidate to explain the effect. With a quantitatively well constrained theory, polarization can be used not only to study the interstellar magnetic field, but also the dust and other environmental parameters. Photodissociation regions, with their intense, anisotropic radiation fields, consequent rapid H2 formation, and high spatial density-contrast provide a rich environment for such studies. Here we discuss an expanded optical, NIR, and mm-wave study of the IC 63 nebula, showing strong H2 formation-enhanced alignment and the first direct empirical evidence for disalignment due to gas-grain collisions using high-resolution HCO+(J = 1-0) observations. We find that a relative amount of polarization is marginally anticorrelated with column density of HCO+. However, separating the lines of sight of optical polarimetry into those behind, or in front of, a dense clump as seen from γ Cas, the distribution separates into two well defined sets, with data corresponding to "shaded" gas having a shallower slope. This is expected if the decrease in polarization is caused by collisions since collisional disalignment rate is proportional to ${R}_{C}\propto n\sqrt{T}$ . Ratios of the best-fit slopes for the "illuminated" and "shaded" samples of lines of sight agrees, within the uncertainties, with the square root of the two-temperature H2 excitation in the nebula seen by Thi et al.

Keywords: Interstellar dust, Polarimetry
The Explosion in Orion-KL as Seen by Mosaicking the Magnetic Field with ALMA. We present the first linear-polarization mosaicked observations performed by the Atacama Large Millimeter/submillimeter Array (ALMA). We mapped the Orion-KLeinmann-Low (Orion-KL) nebula using super-sampled mosaics at 3.1 and 1.3 mm as part of the ALMA Extension and Optimization of Capabilities program. We derive the magnetic field morphology in the plane of the sky by assuming that dust grains are aligned with respect to the ambient magnetic field. At the center of the nebula, we find a quasi-radial magnetic field pattern that is aligned with the explosive CO outflow up to a radius of approximately 12″ (∼5000 au), beyond which the pattern smoothly transitions into a quasi-hourglass shape resembling the morphology seen in larger-scale observations by the James-Clerk-Maxwell Telescope (JCMT). We estimate an average magnetic field strength $\left\langle B\right\rangle =9.4$ mG and a total magnetic energy of 2 × 1045 erg, which is three orders of magnitude less than the energy in the explosive CO outflow. We conclude that the field has been overwhelmed by the outflow and that a shock is propagating from the center of the nebula, where the shock front is seen in the magnetic field lines at a distance of ∼5000 au from the explosion center.

Keywords: Interstellar dust, Shocks, Astrochemistry, Interstellar magnetic fields, Young stellar objects, Star formation, Dust continuum emission, Protostars, Polarimetry
MOSEL and IllustrisTNG: Massive Extended Galaxies at z = 2 Quench Later Than Normal-size Galaxies. Using the TNG100 (100 Mpc)3 simulation of the IllustrisTNG project, we demonstrate a strong connection between the onset of star formation quenching and the stellar size of galaxies. We do so by tracking the evolutionary history of extended and normal-size galaxies selected at z = 2 with $\mathrm{log}({M}_{* }/{\text{}}{M}_{\odot })$ $=\,10.2\mbox{--}11$ and stellar-half-mass-radii above and within 1σ of the stellar size-stellar mass relation, respectively. We match the stellar mass and star formation rate distributions of the two populations. By z = 1, only 36% of the extended massive galaxies have quenched, in contrast to a quenched fraction of 69% for the normal-size massive galaxies. We find that normal-size massive galaxies build up their central stellar mass without a significant increase in their stellar size between $z=2\mbox{--}4$ , whereas the stellar size of the extended massive galaxies almost doubles in the same time. In IllustrisTNG, lower black hole masses and weaker kinetic-mode feedback appears to be responsible for the delayed quenching of star formation in the extended massive galaxies. We show that relatively gas-poor mergers may be responsible for the lower central stellar density and weaker supermassive black hole feedback in the extended massive galaxies.

Keywords: Hydrodynamical simulations, Galaxy formation, Galaxy evolution, Galaxies
Improving Damped Random Walk Parameters for SDSS Stripe 82 Quasars with Pan-STARRS1. We use the Panoramic Survey Telescope and Rapid Response System 1 Survey (Pan-STARRS1, PS1) data to extend the Sloan Digital Sky Survey (SDSS) Stripe 82 quasar light curves. Combining PS1 and SDSS light curves provides a 15 yr baseline for 9248 quasars—5 yr longer than prior studies that used only SDSS. We fit the light curves with the damped random walk (DRW) model—a statistical description of their variability. We correlate the resulting DRW model parameters: asymptotic variability amplitude SF∞, and characteristic timescale τ, with quasar physical properties—black hole mass, bolometric luminosity, and redshift. Using simulated light curves, we find that a longer baseline allows us to better constrain the DRW parameters. After adding PS1 data, the variability amplitude is a stronger function of the black hole mass and has a weaker dependence on quasar luminosity. In addition, the characteristic timescale τ dependence on quasar luminosity is marginally weaker. We also make predictions for the fidelity of DRW model parameter retrieval when light curves will be further extended with Zwicky Transient Facility and Rubin Observatory Legacy Survey of Space and Time data. Finally, we show how updated DRW parameters offer an independent method of discovering changing-look quasar candidates (CLQSOs). The candidates are outliers in terms of differences in magnitude and scatter between the SDSS and PS1 segments. We identify 40 objects (35 newly reported) with a tenfold increase in the variability timescale between SDSS and SDSS-PS1 data due to a large change in brightness (over 0.5 mag)—characteristic for CLQSOs.

Keywords: Light curves, Active galactic nuclei, Quasars