Sazuna/UAT_keywords huggingface dataset:
Implications of Different Solar Photospheric Flux-transport Models for Global Coronal and Heliospheric Modeling. The concept of surface-flux transport (SFT) is commonly used in evolving models of the large-scale solar surface magnetic field. These photospheric models are used to determine the large-scale structure of the overlying coronal magnetic field, as well as to make predictions about the fields and flows that structure the solar wind. We compare predictions from two SFT models for the solar wind, open magnetic field footpoints, and the presence of coronal magnetic null points throughout various phases of a solar activity cycle, focusing on the months of April in even-numbered years between 2012 and 2020, inclusively. We find that there is a solar-cycle dependence to each of the metrics considered, but there is not a single phase of the cycle in which all the metrics indicate good agreement between the models. The metrics also reveal large, transient differences between the models when a new active region is rotating into the assimilation window. The evolution of the surface flux is governed by a combination of large-scale flows and comparatively small-scale motions associated with convection. Because the latter flows evolve rapidly, there are intervals during which their impact on the surface flux can only be characterized in a statistical sense, thus their impact is modeled by introducing a random evolution that reproduces the typical surface flux evolution. We find that the differences between the predicted properties are dominated by differences in the model assumptions and implementation, rather than the selection of a particular realization of the random evolution.

Keywords: Solar magnetic fields, Solar wind, Solar corona
Magnetic Misalignment of Interstellar Dust Filaments. We present evidence for scale-independent misalignment of interstellar dust filaments and magnetic fields. We estimate the misalignment by comparing millimeter-wave dust-polarization measurements from Planck with filamentary structures identified in neutral-hydrogen (H I) measurements from HI4PI. We find that the misalignment angle displays a scale independence (harmonic coherence) for features larger than the HI4PI beamwidth (16.'2). We additionally find a spatial coherence on angular scales of ${ \mathcal O }(1^\circ )$ . We present several misalignment estimators formed from the auto- and cross-spectra of dust-polarization and H I-based maps, and we also introduce a map-space estimator. Applied to large regions of the high-Galactic-latitude sky, we find a global misalignment angle of ~2°, which is robust to a variety of masking choices. By dividing the sky into small regions, we show that the misalignment angle correlates with the parity-violating TB cross-spectrum measured in the Planck dust maps. The misalignment paradigm also predicts a dust EB signal, which is of relevance in the search for cosmic birefringence but as yet undetected; the measurements of EB are noisier than those of TB, and our correlations of EB with misalignment angle are found to be weaker and less robust to masking choices. We also introduce an H I-based dust-polarization template constructed from the Hessian matrix of the H I intensity, which is found to correlate more strongly than previous templates with Planck dust B modes.

Keywords: Cosmology, Interstellar dust, Interstellar filaments, Interstellar atomic gas, Milky Way magnetic fields, Astrophysical magnetism, Cosmic microwave background radiation, Neutral hydrogen clouds, Interstellar magnetic fields, Dust continuum emission, Interstellar medium, Magnetic fields
Quantification of High-dimensional Non-Gaussianities and Its Implication to Fisher Analysis in Cosmology. It is well known that the power spectrum is not able to fully characterize the statistical properties of non-Gaussian density fields. Recently, many different statistics have been proposed to extract information from non-Gaussian cosmological fields that perform better than the power spectrum. The Fisher matrix formalism is commonly used to quantify the accuracy with which a given statistic can constrain the value of the cosmological parameters. However, these calculations typically rely on the assumption that the sampling distribution of the considered statistic follows a multivariate Gaussian distribution. In this work, we follow Sellentin &amp; Heavens and use two different statistical tests to identify non-Gaussianities in different statistics such as the power spectrum, bispectrum, marked power spectrum, and wavelet scattering transform (WST). We remove the non-Gaussian components of the different statistics and perform Fisher matrix calculations with the Gaussianized statistics using Quijote simulations. We show that constraints on the parameters can change by a factor of ~2 in some cases. We show with simple examples how statistics that do not follow a multivariate Gaussian distribution can achieve artificially tight bounds on the cosmological parameters when using the Fisher matrix formalism. We think that the non-Gaussian tests used in this work represent a powerful tool to quantify the robustness of Fisher matrix calculations and their underlying assumptions. We release the code used to compute the power spectra, bispectra, and WST that can be run on both CPUs and GPUs.

Keywords: Cosmology, Large-scale structure of the universe, Cosmological parameters from large-scale structure, Astrostatistics distributions, Normal distribution, Astrostatistics strategies
Wave Conversion, Decay, and Heating in a Partially Ionized Two-fluid Magneto-atmosphere. A ray-theoretic phase-space description of linear waves in a two-fluid (charges and neutrals) magnetized plasma is used to calculate analytic decay rates and mode transmission and conversion coefficients between fast and slow waves in two dimensions due to finite ion-neutral collision frequencies at an arbitrary ionization fraction. This is relevant to partially ionized astrophysical plasmas, in particular solar and stellar atmospheres. The most important parameter governing collisional effects is the ratio of the wave frequency to the neutral-charges collision frequency, ϵ = ω/ν nc, with secondary dependence on ionization fraction and wave attack angle. Comparison is made to the one-fluid magnetohydrodynamic case, and it is found that acoustic-to-acoustic and magnetic-to-magnetic transmission through the Alfvén-acoustic equipartition layer is decreased by a term of ${ \mathcal O }({\epsilon }^{2})$ relative to one-fluid (infinite collision frequency), and correspondingly acoustic-to-magnetic and magnetic-to-acoustic conversion is increased. The neutral-acoustic mode is shown to dissipate rapidly as ν nc → ∞. Away from the mode conversion region, dissipative decay along the remaining magneto-acoustic rays scales as ${ \mathcal O }(\epsilon )$ and is found to be much more effective on magnetically dominated rays compared to acoustically dominated rays. This produces a steep jump in dissipation in mode conversion regions, where the rays change character, and can produce localized heating there and beyond. Applications to the solar chromosphere are discussed.

Keywords: Solar atmosphere, Magnetohydrodynamics, Plasma astrophysics
Classification of Blazar Candidates of Unknown Type in Fermi 4LAC by Unanimous Voting from Multiple Machine-learning Algorithms. The Fermi fourth catalog of active galactic nuclei (AGNs) data release 3 (4LAC-DR3) contains 3407 AGNs, out of which 755 are flat spectrum radio quasars (FSRQs), 1379 are BL Lacertae objects (BL Lac objects), 1208 are blazars of unknown (BCUs) type, while 65 are non-AGNs. Accurate categorization of many unassociated blazars still remains a challenge due to the lack of sufficient optical spectral information. The aim of this work is to use high-precision, optimized machine-learning (ML) algorithms to classify BCUs into BL Lac objects and FSRQs. To address this, we selected the 4LAC-DR3 Clean sample (i.e., sources with no analysis flags) containing 1115 BCUs. We employ five different supervised ML algorithms, namely, random forest, logistic regression, XGBoost, CatBoost, and neural network with seven features: photon index, synchrotron-peak frequency, pivot energy, photon index at pivot energy, fractional variability, ν F ν, at synchrotron-peak frequency, and variability index. Combining results from all models leads to better accuracy and more robust predictions. These five methods together classified 610 BCUs as BL Lac objects and 333 BCUs as FSRQs with a classification metric area under the curve &gt;0.96. Our results are significantly compatible with recent studies as well. The output from this study provides a larger blazar sample with many new targets that could be used for forthcoming multiwavelength surveys. This work can be further extended by adding features in X-rays, UV, visible, and radio wavelengths.

Keywords: BL Lacertae objects, Classification, Neural networks, Blazars, Active galaxies, Random Forests
Ba-enhanced Dwarf and Subgiant Stars in the LAMOST Galactic Surveys. Ba-enhanced stars are interesting probes of stellar astrophysics and Galactic formation history. In this work, we investigate the chemistry and kinematics of a large sample of Ba-enhanced ([Ba/Fe]&gt;1.0) dwarf and subgiant stars with 5000 &lt; T eff &lt; 6700 K from LAMOST. We find that both stellar internal evolution processes and external mass exchange due to binary evolution are responsible for the origins of the Ba enhancement of our sample stars. About one third of them exhibit C and N enhancement and an ultraviolet brightness excess, indicating they are products of binary evolution. The remaining Ba-enhanced stars with normal C and N abundances are mostly warm stars with T eff &gt; 6000 K. They are likely the consequences of stellar internal element transport processes, but they show very different element patterns to hotter Am/Fm stars. Our results reveal a substantially lack of high-[α/Fe], Ba-enhanced stars in the [Fe/H]-[α/Fe] plane, which we dub as a "high-[α/Fe] desert". We suggest it is due to a lower efficiency for producing Ba-enhanced stars by low-mass asymptotic giant branch progenitors in binary systems. Our results call for detailed modeling of these Ba-enhanced stellar peculiarities, in the context of both stellar internal element transport and external mass accretion.

Keywords: Binary stars, Stellar populations, Surveys, Chemical abundances, Barium stars, Chemically peculiar stars, Stellar evolution
Weighing the Darkness. II. Astrometric Measurement of Partial Orbits with Gaia. Over the course of several years, stars trace helical trajectories as they traverse across the sky due to the combined effects of proper motion and parallax. It is well known that the gravitational pull of an unseen companion can cause deviations to these tracks. Several studies have pointed out that the astrometric mission Gaia will be able to identify a slew of new exoplanets, stellar binaries, and compact object companions with orbital periods as short as tens of days to as long as Gaia's lifetime. Here, we use mock astrometric observations to demonstrate that Gaia can identify and characterize black hole companions to luminous stars with orbital periods longer than Gaia's lifetime. Such astrometric binaries have orbital periods too long to exhibit complete orbits, and instead are identified through curvature in their characteristic helical paths. By simultaneously measuring the radius of this curvature and the orbital velocity, constraints can be placed on the underlying orbit. We quantify the precision with which Gaia can measure orbital accelerations and apply that to model predictions for the population of black holes orbiting stars in the stellar neighborhood. Although orbital degeneracies imply that many of the accelerations induced by hidden black holes could also be explained by faint low-mass stars, we discuss how the nature of certain putative black hole companions can be confirmed with high confidence using Gaia data alone.

Keywords: Wide binary stars, Astrometric binary stars, Stellar mass black holes, Astrophysical black holes
Particle-in-cell Simulation of Energy Conversion at the Turbulent Region Downstream of the Reconnection Front. We study the energy conversion in the turbulent region (TR) downstream of the reconnection front (RF) via 2.5D particle-in-cell simulations. Our study shows that most magnetic energy is transferred into plasma in the exhaust region (ER) and the TR downstream of the RF; the latter is formed due to the electron Kelvin-Helmholtz instability (KHI). Unlike the energy conversion in the ER, the energy conversion in the TR is mainly balanced by its in-plane component (E  x  J  x +E  z  J  z ). We further find that the time evolution of the integrated energy conversion in the TR is strongly correlated with the time evolution of the electron KHI and secondary reconnection. The KHI feeds on the electron kinetic energy to grow, and electron vortices are formed, correspondently. The energy is transferred to ions through a nonideal electric field associated with those electron vortices after the KHI is well developed. Finally, the electron vortices are collapsed due to the secondary reconnection among those vortices. The power law of the magnetic energy spectra also shows a slope near -5/3 at wavenumbers larger than the ion scale when the KHI is fully developed.

Keywords: Space plasmas, Solar magnetic reconnection, Plasma physics, Interplanetary turbulence, Astronomical simulations
The Perseus ALMA Chemistry Survey (PEACHES). II. Sulfur-bearing Species and Dust Polarization Revealing Shocked Regions in Protostars in the Perseus Molecular Cloud. In protostellar cores, sulfur species are effective probes for the energetic environments, such as shocked regions. With the majority of sulfur depleted on dust grains, sulfur-bearing molecules could be liberated back to gas phase by shocks associated with accretion and outflow activities. Therefore, the gas-phase abundance of these molecules may be correlated to the change of dust properties, which can be investigated through polarization observations. Here we present a comparison study of sulfur species and dust polarization at ~100 au scale for nine protostars in the Perseus Molecular Cloud. Overall, the emission of sulfur-bearing molecules correlates with the high and disordered polarization in the extended continuum of eight sources, indicating intense physical conditions (e.g., high temperature) and/or change of dust properties within these regions, while no clear correlation is seen for Per-emb-14. For the more evolved sources with clear disk structures (Per-emb-50 and -18), the enhanced SO/SO2 emission overlaps with the stark contrast of polarization in the shocked regions near the centrifugal barriers. In the six sources with more extended CS and SO emission, such as Per-emb-11 and -5, the polarization enhancement correlates with the outer edge of outflow cavities and other filaments probed by sulfur-bearing molecules, revealing soft shocks along the outflows and envelopes. Such comparison studies could provide additional diagnostics of the physical properties and activities in star-forming processes, especially for the shocked regions.

Keywords: Interstellar molecules, Astrochemistry, Star formation, Protostars, Polarimetry
Effects of Magnetic Fields on Gas Dynamics and Star Formation in Nuclear Rings. Nuclear rings at the centers of barred galaxies are known to be strongly magnetized. To explore the effects of magnetic fields on star formation in these rings and nuclear gas flows, we run magnetohydrodynamic simulations in which there is a temporally constant magnetized inflow to the ring, representing a bar-driven inflow. The mass inflow rate is 1M ☉ yr-1, and we explore models with a range of field strength in the inflow. We adopt the TIGRESS framework developed by Kim &amp; Ostriker to handle radiative heating and cooling, star formation, and resulting supernova (SN) feedback. We find that magnetic fields are efficiently amplified in the ring due to rotational shear and SN feedback. Within a few 100 Myr, the turbulent component B trb in the ring saturates at ~35 μG (in rough equipartition with the turbulent kinetic energy density), while the regular component B reg exceeds 50 μG. Expanding superbubbles created by clustered SN explosions vertically drag predominantly toroidal fields from near the midplane to produce poloidal fields in high-altitude regions. The growth of magnetic fields greatly suppresses star formation at late times. Simultaneously, strong magnetic tension in the ring drives radially inward accretion flows from the ring to form a circumnuclear disk in the central region; this feature is absent in the unmagnetized model.

Keywords: Magnetohydrodynamics, Stellar feedback, Galaxy nuclei, Star formation, Interstellar medium, Galaxy circumnuclear disk, Barred spiral galaxies, Magnetohydrodynamical simulations
Multifluid Simulations of Upper-chromospheric Magnetic Reconnection with Helium-Hydrogen Mixture. Our understanding of magnetic reconnection (MR) under chromospheric conditions remains limited. Recent observations have demonstrated the important role of ion-neutral interactions in the dynamics of the chromosphere. Furthermore, the comparison between the spectral profiles and synthetic observations of reconnection events suggests that current MHD approaches appear to be inconsistent with observations. First, collisions and multithermal aspects of the plasma play a role in these regions. Second, hydrogen and helium ionization effects are relevant to the energy balance of the chromosphere. This work investigates the multifluid multispecies (MFMS) effects on MR in conditions representative of the upper chromosphere using the multifluid Ebysus code. We compare an MFMS approach based on a helium-hydrogen mixture with a two-fluid MHD model based on hydrogen only. The simulations of MR are performed in a Lundquist number regime high enough to develop plasmoids and instabilities. We study the evolution of the MR and compare the two approaches including the structure of the current sheet and plasmoids, the decoupling of the particles, the evolution of the heating mechanisms, and the composition. The presence of helium species leads to more efficient heating mechanisms than the two-fluid case. This scenario, which is out of reach of the two-fluid or single-fluid models, can reach transition region temperatures starting from upper-chromospheric thermodynamic conditions, representative of a quiet Sun scenario. The different dynamics between helium and hydrogen species could lead to chemical fractionation and, under certain conditions, enrichment of helium in the strongest outflows. This could be of significance for recent observations of helium enrichment in the solar wind in switchbacks and coronal mass ejections.

Keywords: Solar chromosphere, Solar magnetic reconnection
Galaxy and Mass Assembly (GAMA): Low-redshift Quasars and Inactive Galaxies Have Similar Neighbors. We explore the properties of galaxies in the proximity (within a ~2 Mpc radius sphere) of Type I quasars at 0.1 &lt;z &lt;0.35, to check whether and how an active galaxy influences the properties of its neighbors. We further compare these with the properties of neighbors around inactive galaxies of the same mass and redshift within the same volume of space, using the Galaxy and Mass Assembly spectroscopic survey. Our observations reveal no significant difference in properties such as the number of neighbors, morphologies, stellar mass, star formation rates, and star formation history between the neighbors of quasars and those of the comparison sample. This implies that quasar activity in a host galaxy does not significantly affect its neighbors (e.g., via interactions with the jets). Our results suggest that quasar host galaxies do not strongly differ from the average galaxy within the specified mass and redshift range. Additionally, the implication of the relatively minor importance of the environmental effect on and from quasars is that nuclear activity is more likely triggered by internal and secular processes.

Keywords: Supermassive black holes, Quasars, Galaxy environments, Active galaxies, Companion galaxies, Star formation, Active galactic nuclei, Galaxy evolution, Galaxy mergers, Galaxies
The Hα Luminosity Function of Galaxies at z 4.5. We present the Hα luminosity function (LF) derived from a large sample of Lyman break galaxies at z ~ 4.5 over the GOODS-South and North fields. This study makes use of the new, full-depth Spitzer/IRAC [3.6] and [4.5] imaging from the GOODS Re-ionization Era wide-Area Treasury from the Spitzer program. The Hα flux is derived from the offset between the continuum flux estimated from the best-fit spectral energy distribution, and the observed photometry in IRAC [3.6]. From these measurements, we build the Hα LF and study its evolution providing the best constraints of this property at high redshift, where spectroscopy of Hα is not yet available. Schechter parameterizations of the Hα LF show a decreasing evolution of Φ∗ with redshift, increasing evolution in L ∗, and no significant evolution in the faint-end slope at high z. We find that star formation rates (SFRs) derived from Hα are higher than those derived from the rest-frame UV for low SFR galaxies but the opposite happens for the highest SFRs. This can be explained by lower mass galaxies (also lower SFR) having, on average, rising star formation histories (SFHs), while at the highest masses the SFHs may be declining. The SFR function is steeper, and because of the excess SFR(Hα) compared to SFR(UV) at low SFRs, the SFR density estimated from Hα is higher than the previous estimates based on UV luminosities.

Keywords: Galaxy formation, High-redshift galaxies, Galaxy evolution
The Imprint of Clump Formation at High Redshift. II. The Chemistry of the Bulge. In Paper I, we showed that clumps in high-redshift galaxies, having a high star formation rate density (ΣSFR), produce disks with two tracks in the [Fe/H]-[α/Fe] chemical space, similar to that of the Milky Way's (MW's) thin+thick disks. Here we investigate the effect of clumps on the bulge's chemistry. The chemistry of the MW's bulge is comprised of a single track with two density peaks separated by a trough. We show that the bulge chemistry of an N-body + smoothed particle hydrodynamics clumpy simulation also has a single track. Star formation within the bulge is itself in the high-ΣSFR clumpy mode, which ensures that the bulge's chemical track follows that of the thick disk at low [Fe/H] and then extends to high [Fe/H], where it peaks. The peak at low metallicity instead is comprised of a mixture of in situ stars and stars accreted via clumps. As a result, the trough between the peaks occurs at the end of the thick disk track. We find that the high-metallicity peak dominates near the mid-plane and declines in relative importance with height, as in the MW. The bulge is already rapidly rotating by the end of the clump epoch, with higher rotation at low [α/Fe]. Thus clumpy star formation is able to simultaneously explain the chemodynamic trends of the MW's bulge, thin+thick disks, and the splash.

Keywords: Milky Way formation, Galaxy bulges, Milky Way dynamics, Galactic bulge, Milky Way evolution