Sazuna/UAT_keywords huggingface dataset:
Redshift Evolution of Electron Density in the Interstellar Medium at z   0-9 Uncovered with JWST/NIRSpec Spectra and Line-spread Function Determinations. We present electron densities n e in the interstellar medium (ISM) of star-forming galaxies at z = 4-9 observed by the JWST/NIRSpec GLASS, Early Release Observations, and CEERS programs. We carefully evaluate the line-spread functions of the NIRSpec instrument as a function of wavelength with the calibration data of a planetary nebula taken on board, and obtain secure [O II] λ λ3726, 3729 doublet fluxes for 14 galaxies at z = 4.02-8.68 falling on the star formation main sequence with the NIRSpec high- and medium-resolution spectra. We thus derive the electron densities of singly ionized oxygen nebulae with the standard n e indicator of the [O II] doublet, and find that the electron densities of the z = 4-9 galaxies are n e ≳ 300 cm-3 significantly higher than those of low-z galaxies at a given stellar mass, star formation rate (SFR), and specific SFR. Interestingly, the typical electron densities of the singly ionized nebulae increase from z = 0 to z = 1-3 and z = 4-9, which is approximated by the evolutionary relation of n e ∝ (1 + z) p  with p ~ 1-2. Although it is not obvious that the ISM property of n e is influenced by global galaxy properties, these results may suggest that the nebula densities of high-z galaxies are generally high due to the compact morphologies of high-z galaxies evolving by ${r}_{{\rm{e}}}\mathop{\propto }\limits_{\sim }{(1+z)}^{-1}$ (r vir ∝ (1 + z)-1) for a given stellar (halo) mass whose inverse square corresponds to the p ~ 2 evolutionary relation. The p ~ 1-2 evolutionary relation can be explained by a combination of the compact morphology and the reduction of n e due to the high electron temperature of high-z metal-poor nebulae.

Keywords: Galaxy formation, Galaxy structure, Star formation, Dwarf galaxies
Ab Initio Study of Glycine Formation in the Condensed Phase: Carbon Monoxide, Formaldimine, and Water Are Enough. Glycine is considered to be crucial in the formation of proteins and prebiotic substances. Nevertheless, the mechanism of spontaneous glycine formation under prebiotic Earth conditions or within the interstellar medium (ISM) remains a topic of debate, given the changing geochemical environment over Earth's history and the difficulty of detecting it within the ISM. Yet it is believed that its formation could be possible in interstellar water-rich ice. In this study, using molecular dynamics (MD) simulations at the ab initio level of theory enhanced with modern free energy calculations, we modeled the chemical reaction between carbon monoxide, formaldimine, and water to produce glycine. We estimated under what conditions, in condensed phase at 50, 70, 100, and 300 K, glycine is formed. We also explored the effect of different electric fields on this process. Our results show that glycine could be formed with energy barriers as low as 0.5 kcal mol-1 at 50 K. We discuss whether this reaction could be a suitable candidate for explaining the mechanism of glycine formation under conditions that resemble various astrophysical environments, such as planets, exoplanets, and Earth. This study is relevant to finding a consensus among various proposals for glycine formation. Moreover, it highlights the importance of metadynamics and Car-Parrinello MD methods as tools in finding unknown complex, multistep reaction mechanism pathways, possibly important to the astronomical phenomena.

Keywords: Interstellar molecules, Astrobiology, Interstellar medium, Molecular reactions, Pre-biotic astrochemistry
Dependence of Stellar Differential Rotation on Effective Temperature and Rotation: An Analysis from Starspot Transit Mapping. Stellar rotation is crucial for studying stellar evolution, since it provides information about age, angular momentum transfer, and magnetic fields of stars. In the case of the Sun, due to its proximity, detailed observation of sunspots at various latitudes and longitudes allows a precise estimation of the solar rotation period and its differential rotation. Here, we present for the first time an analysis of stellar differential rotation using starspot transit mapping as a means of detecting differential shear in solar-type and M stars. The aim of this study is to investigate the relationship between rotational shear, ΔΩ, and both the star's effective temperature (T eff) and its average rotation period ( $\bar{{P}}$ ). We present differential rotation profiles derived from previously collected spot transit mapping data for 13 slowly rotating stars (P rot ≥ 4.5 days), with spectral types ranging from M to F, which were observed by the Kepler and CoRoT satellites. Our findings reveal a significant negative correlation between rotational shear and the mean period of stellar rotation (correlation coefficient of -0.77), which may be an indicator of stellar age. On the other hand, a weak correlation was observed between differential rotation and the effective temperature of the stars. Overall, the study provides valuable insights into the complex relationship between stellar parameters and differential rotation, which may enhance our understanding of stellar evolution and magnetic dynamos.

Keywords: Exoplanet astronomy, Starspots, Stellar rotation, Transit photometry
What Are the Radial Distributions of Density, Outflow Rates, and Cloud Structures in the M82 Wind?. Galactic winds play essential roles in the evolution of galaxies through the feedback they provide. Despite intensive studies of winds, the radial distributions of their properties and feedback are rarely observable. Here we present such measurements for the prototypical starburst galaxy, M82, based on observations by the Subaru Telescope. We determine the radial distribution of outflow densities (n  e ) from the spatially resolved [S II] λλ6717, 6731 emission lines. We find that n  e  drops from 200 to 40 cm-3 with radius (r) between 0.5 and 2.2 kpc with a best-fit power-law index of r -1.2. Combined with resolved Hα lines, we derive mass, momentum, and energy outflow rates, which drop quite slowly (almost unchanged within error bars) over this range of r. This suggests that the galactic wind in M82 can carry mass, momentum, and energy from the central regions to a few kiloparsecs with minimal losses. We further derive outflow cloud properties, including size and column densities. The clouds we measure have pressures and densities that are too high to match those from recent theoretical models and numerical simulations of winds. By comparing with a sample of outflows in local star-forming galaxies studied with UV absorption lines, the above-derived properties for M82 outflows match well with the published scaling relationships. These matches suggest that the ionized gas clouds traced in emission and absorption are strongly related. Our measurements motivate future spatially resolved studies of galactic winds, which is the only way to map the structure of their feedback effects.

Keywords: Galactic winds, Starburst galaxies, Galaxy kinematics, Galaxy evolution
The Wave Growth, Saturation, and Electron Heating of Lower Hybrid Waves in the Magnetic Reconnection Exhaust. Lower hybrid waves are commonly observed in magnetic reconnection. Based on in situ measurements and the application of an extended quasi-linear model, we investigate the occurrence, saturation, and electron heating of lower hybrid waves in the region of magnetopause reconnection outflows. Lower hybrid waves are statistically favored when the density gradient length scale (L  n ) normalized by the ion gyroradius (ρ  i ) is small. The occurrence of lower hybrid waves is significantly higher in the regime of L  n /ρ  i  &lt; 1 and plasma beta β &lt; 1. These features of wave occurrence are consistent with the linear theory of the wave growth rate. Evidence indicates that the saturation level and the parallel electron heating of waves both increase as the normalized gradient scale L  n /ρ  i  decreases. The parallel electron temperature increases ~30%-70% as L  n /ρ  i  &lt; 1. We show that the observation of saturation and electron heating is consistent with an extended quasi-linear model. In this scenario, lower hybrid waves are driven by density gradients and then quickly saturate in tens of ion gyroperiods. The parallel electron heating from lower hybrid waves is achieved through Landau damping before the nonlinear saturation. Our results provide comprehensive evidence for an end-to-end process of electron heating through lower hybrid waves in reconnection exhausts. L  n /ρ  i  is the key parameter that determines the extent of the wave growth, saturation energy, and electron heating in this wave-particle interaction process.

Keywords: Space plasmas, Planetary magnetospheres
Generalized Harris Sheet Equilibrium in Regularized Kappa Distributed Plasmas. Harris sheet models with antiparallel magnetic field are the equilibrium solutions to the steady Vlasov-Maxwell equations, which have been widely adopted for the study of plasma instabilities and magnetic reconnection in thin current sheets. The original Harris equilibrium model assumes the Maxwellian velocity distribution, which necessarily gives rise to the isothermal current sheets. Many observations have shown that the suprathermal populations are indispensable features of particle distribution profiles, which may well be fitted by the Kappa distribution (KD) functions with the free parameter κ. The Harris equilibrium based on the standard Kappa distribution (SKD), however, may become unphysical for $\kappa \leqslant \displaystyle \frac{3}{2}$ . Alternatively, the regularized KD (RKD) with two adjustable parameters, κ and α 2, has been proposed to replace the SKD in various studies. The RKD may recover the SKD for α 2 = 0, and Maxwellian model for α 2 = 0 and κ → ∞ . This paper presents the first results of adopting the nonthermal RKDs in the Harris equilibrium models. It is shown that the new RKD-Harris equilibrium is applicable for all κ values, and exhibits a stronger magnetic field associated with higher temperature in the asymptotic region. The proposed formulations for the generalized Harris sheet equilibrium may be applied to multiple component plasmas (e.g., electrons, protons) with different RKDs and temperatures.

Keywords: Planetary magnetospheres, Space plasmas, Plasma astrophysics, Plasma physics
Dynamics of Photospheric Magnetic Flux Distribution and Variations in Solar RVs: A Study Using HARPS-N Solar and SDO Observations. The distribution and evolution of photospheric magnetic fields in sunspots, plages, and network, and variations in their relative flux content, play key roles in radial velocity (RV) fluctuations observed in Sun-as-a-star spectra. Differentiating and disentangling such magnetic contributions to RVs help in building models to account for stellar activity signals in high-precision RV exoplanet searches. In this work, as earlier authors, we employ high-resolution images of the solar magnetic field and continuum intensities from SDO/HMI to understand the activity contributions to RVs from HARPS-N solar observations. Using well-observed physical relationships between strengths and fluxes of photospheric magnetic fields, we show that the strong fields (spots, plages, and network) and the weak inter-network fields leave distinguishing features in their contributions to the RV variability. We also find that the fill factors and average unsigned magnetic fluxes of different features correlate differently with the RVs and hence warrant care in employing either of them as a proxy for RV variations. In addition, we examine disk-averaged UV intensities at 1600 and 1700 Å wavelength bands imaged by SDO/AIA and their performances as proxies for variations in different magnetic features. We find that the UV intensities provide a better measure of contributions of plage fields to RVs than the Ca II H-K emission indices, especially during high activity levels when the latter tend to saturate.

Keywords: Solar activity, Radial velocity, Solar active region magnetic fields, Solar photosphere
On the Migration Origin of the Hercules Moving Group with GAIA, LAMOST, APOGEE, and GALAH Surveys. Using Gaia DR3 data and the wavelet transformation technique, we study the substructures of the Hercules moving group (HMG): Hercules 1 (H1) and Hercules 2 (H2). Spectroscopic survey data from LAMOST, APOGEE, and GALAH are used to obtain metallicities and ages of stars belonging to the HMG. Our analysis leads to several key findings as follows: (a) the HMG is on average richer in metallicity than the Galactic disk, with H2 being metal richer than H1; (b) the HMG likely has a radial metallicity gradient distinct from that of the disk; (c) the HMG is on average older than the disk, with H2 being older than H1; (d) the HMG likely has a radial age gradient distinct from that of the disk; and (e) the metallicity and age distributions of the HMG depend mainly on the Galactic radius but show no dependence on the azimuthal velocity. Taken all together, we conclude that the HMG is composed primarily of stars undergoing radial migration. We suggest that the HMG is associated with a higher-order dynamical resonance of the bar of the Galaxy.

Keywords: Stellar kinematics, Metallicity, Milky Way dynamics
The Physical Thickness of Stellar Disks to z ∼ 2. In local disk galaxies such as our Milky Way, older stars generally inhabit a thicker disk than their younger counterparts. Two competing models have attempted to explain this result: one in which stars first form in thin disks that gradually thicken with time through dynamical heating, and one in which stars form in thick disks at early times and in progressively thinner disks at later times. We use a direct measure of the thicknesses of stellar disks at high redshift to discriminate between these scenarios. Using legacy Hubble Space Telescope imaging from the CANDELS and GOODS surveys, we measure the rest-optical scale heights of 491 edge-on disk galaxies spanning 0.4 ≤ z ≤ 2.5. We measure a median intrinsic scale height for the full sample of 0.74 ± 0.03 kpc, with little redshift evolution of both the population median and scatter. The median is consistent with the thick disk of the Milky Way today (0.6-1.1 kpc), but it is smaller than the median scale height of local disks (~1.5 kpc) that are matched to our high-redshift sample by descendant mass. These findings indicate that, while (1) disks as thick as the Milky Way's thick disk were in place at early times, (2) to explain the full disk galaxy population today, the stellar disks in galaxies need to on average physically thicken after formation.

Keywords: Disk galaxies, High-redshift galaxies, Galaxy evolution, Scale height
FAST-ASKAP Synergy: Quantifying Coexistent Tidal and Ram Pressure Strippings in the NGC 4636 Group. Combining new H I data from a synergetic survey of Australian Square Kilometre Array Pathfinder (ASKAP) Widefield ASKAP L-band Legacy All-sky Blind surveY and Five-hundred-meter Aperture Spherical radio Telescope with the Arecibo Legacy Fast ALFA data, we study the effect of ram pressure and tidal interactions in the NGC 4636 group. We develop two parameters to quantify and disentangle these two effects on gas stripping in H I-bearing galaxies: the strength of external forces at the optical-disk edge, and the outside-in extents of H I-disk stripping. We find that gas stripping is widespread in this group, affecting 80% of H I-detected nonmerging galaxies, and that 41% are experiencing both types of stripping. Among the galaxies experiencing both effects, the two types of strengths are independent, while two H I-stripping extents moderately anticorrelate with each other. Both strengths are correlated with H I-disk shrinkage. The tidal strength is related to a rather uniform reddening of low-mass galaxies (M * &lt; 109 M ☉) when tidal stripping is the dominating effect. In contrast, ram pressure is not clearly linked to the color-changing patterns of galaxies in the group. Combining these two stripping extents, we estimate the total stripping extent, and put forward an empirical model that can describe the decrease of H I richness as galaxies fall toward the group center. The stripping timescale we derived decreases with distance to the center, from ~1 Gyr beyond R 200 to ≲10 Myr near the center. Gas depletion happens ~3 Gyr since crossing 2R 200 for H I-rich galaxies, but much quicker for H I-poor ones. Our results quantify in a physically motivated way the details and processes of environmental-effects-driven galaxy evolution, and might assist in analyzing hydrodynamic simulations in an observational way.

Keywords: Galaxy environments, Galaxy evolution, Galaxies, Interstellar atomic gas
A Universal Equation to Predict Ω<SUB>m</SUB> from Halo and Galaxy Catalogs. We discover analytic equations that can infer the value of Ωm from the positions and velocity moduli of halo and galaxy catalogs. The equations are derived by combining a tailored graph neural network (GNN) architecture with symbolic regression. We first train the GNN on dark matter halos from Gadget N-body simulations to perform field-level likelihood-free inference, and show that our model can infer Ωm with ~6% accuracy from halo catalogs of thousands of N-body simulations run with six different codes: Abacus, CUBEP3M, Gadget, Enzo, PKDGrav3, and Ramses. By applying symbolic regression to the different parts comprising the GNN, we derive equations that can predict Ωm from halo catalogs of simulations run with all of the above codes with accuracies similar to those of the GNN. We show that, by tuning a single free parameter, our equations can also infer the value of Ωm from galaxy catalogs of thousands of state-of-the-art hydrodynamic simulations of the CAMELS project, each with a different astrophysics model, run with five distinct codes that employ different subgrid physics: IllustrisTNG, SIMBA, Astrid, Magneticum, SWIFT-EAGLE. Furthermore, the equations also perform well when tested on galaxy catalogs from simulations covering a vast region in parameter space that samples variations in 5 cosmological and 23 astrophysical parameters. We speculate that the equations may reflect the existence of a fundamental physics relation between the phase-space distribution of generic tracers and Ωm, one that is not affected by galaxy formation physics down to scales as small as 10 h -1 kpc.

Keywords: Cosmology, Hydrodynamical simulations, Cosmological parameters
Fleeting Small-scale Surface Magnetic Fields Build the Quiet-Sun Corona. Arch-like loop structures filled with million Kelvin hot plasma form the building blocks of the quiet-Sun corona. Both high-resolution observations and magnetoconvection simulations show the ubiquitous presence of magnetic fields on the solar surface on small spatial scales of ~100 km. However, the question of how exactly these quiet-Sun coronal loops originate from the photosphere and how the magnetic energy from the surface is channeled to heat the overlying atmosphere is a long-standing puzzle. Here we report high-resolution photospheric magnetic field and coronal data acquired during the second science perihelion of Solar Orbiter that reveal a highly dynamic magnetic landscape underlying the observed quiet-Sun corona. We found that coronal loops often connect to surface regions that harbor fleeting weaker, mixed-polarity magnetic field patches structured on small spatial scales, and that coronal disturbances could emerge from these areas. We suggest that weaker magnetic fields with fluxes as low as 1015 Mx and/or those that evolve on timescales less than 5 minutes are crucial to understanding the coronal structuring and dynamics.

Keywords: Magnetohydrodynamics, Solar magnetic reconnection, Solar photosphere, Solar extreme ultraviolet emission, Solar coronal loops, Solar coronal heating, Solar magnetic fields
Fast Radio Bursts: Electromagnetic Counterparts to Extreme Mass-ratio Inspirals. Recent observations discovered that some repeating fast radio bursts (FRBs) show a large value and complex variations of Faraday rotation measures (RMs). The binary systems containing a supermassive black hole and a neutron star can be used to explain such RM variations. Meanwhile, such systems produce low-frequency gravitational-wave (GW) signals, which are one of the primary interests of three proposed space-based GW detectors: the Laser Interferometer Space Antenna (LISA), Tianqin, and Taiji. These signals are known as extreme mass-ratio inspirals (EMRIs). Therefore, FRBs can serve as candidates of electromagnetic counterparts for EMRI signals. In this Letter, we study the EMRI signals in this binary system, which can be detected up to z ~ 0.04 by LISA and Tianqin for the most optimistic case. Assuming the cosmic comb model for FRB production, the total event rate can be as high as ~1 Gpc-3 yr-1. EMRI signals associated with FRBs can be used to reveal the progenitor of FRBs. It is also a new type of standard siren, which can be used as an independent cosmological probe.

Keywords: Magnetars, Gravitational wave sources, Radio transient sources
The NANOGrav 15 yr Data Set: Search for Anisotropy in the Gravitational-wave Background. The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) has reported evidence for the presence of an isotropic nanohertz gravitational-wave background (GWB) in its 15 yr data set. However, if the GWB is produced by a population of inspiraling supermassive black hole binary (SMBHB) systems, then the background is predicted to be anisotropic, depending on the distribution of these systems in the local Universe and the statistical properties of the SMBHB population. In this work, we search for anisotropy in the GWB using multiple methods and bases to describe the distribution of the GWB power on the sky. We do not find significant evidence of anisotropy. By modeling the angular power distribution as a sum over spherical harmonics (where the coefficients are not bound to always generate positive power everywhere), we find that the Bayesian 95% upper limit on the level of dipole anisotropy is (C  l=1/C  l=0) &lt; 27%. This is similar to the upper limit derived under the constraint of positive power everywhere, indicating that the dipole may be close to the data-informed regime. By contrast, the constraints on anisotropy at higher spherical-harmonic multipoles are strongly prior dominated. We also derive conservative estimates on the anisotropy expected from a random distribution of SMBHB systems using astrophysical simulations conditioned on the isotropic GWB inferred in the 15 yr data set and show that this data set has sufficient sensitivity to probe a large fraction of the predicted level of anisotropy. We end by highlighting the opportunities and challenges in searching for anisotropy in pulsar timing array data.

Keywords: Gravitational wave astronomy, Supermassive black holes, Gravitational waves, Pulsars