Sazuna/UAT_keywords huggingface dataset:
Quantifying Wave-Particle Interactions in Collisionless Plasmas: Theory and Its Application to the Alfvén-mode Wave. Wave-particle interactions can induce energy transfer at different timescales in collisionless plasmas, which leads to the reshaping of the particle velocity distribution function. Therefore, how to quantify wave-particle interactions is one of the fundamental problems in the heliosphere and in astrophysical plasmas. This study proposes a systematic method to quantify linear wave-particle interactions based on the Vlasov-Maxwellian model. We introduce energy transfer rates with various expressions by using perturbed electric fields and perturbed particle velocity distribution functions. Then, we use different expressions of the energy transfer rate to perform a comprehensive investigation of wave-particle interactions of the Alfvén-mode wave. We clarify the physical mechanisms responsible for the damping of the Alfvén-mode wave in wavevector space. Moreover, this study exhibits for the first time evident signatures of wave-particle interactions between Alfvén-mode waves and resonant/nonresonant particles in the velocity space. These resonant and nonresonant particles can induce energy transfer in opposite directions, which leads to self-regulation of the particle velocity distribution function. Furthermore, this study exhibits a comprehensive dependence of wave-particle interactions of the Alfvén-mode wave on the wavenumber and plasma beta (the ratio between the plasma thermal pressure and the magnetic pressure). These results illustrate that the proposed method would be very useful for quantifying different types of linear wave-particle interactions of an arbitrary wave mode.

Keywords: Space plasmas, Solar wind, Plasma astrophysics, Plasma physics
A Study of Photoionized Gas in Two H II Regions of the N44 Complex in the LMC Using MUSE Observations. We use the optical integral field observations with Multi-Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope, together with CLOUDY photoionization models, to study ionization structure and physical conditions of two luminous H II regions in the N44 star-forming complex of the Large Magellanic Cloud. The spectral maps of various emission lines reveal a stratified ionization geometry in N44 D1. The spatial distribution of [O I] λ6300 emission in N44 D1 indicates a partially covered ionization front at the outer boundary of the H II region. These observations reveal that N44 D1 is a blister H II region. The [O I] λ6300 emission in N44 C does not provide a well-defined ionization front at the boundary, while patches of [S II] λ6717 and [O I] λ6300 emission bars are found in the interior. The results of spatially resolved MUSE spectra are tested with the photoionization models for the first time in these H II regions. A spherically symmetric ionization-bounded model with a partial covering factor, which is appropriate for a blister H II region, can well reproduce the observed geometry and most of the diagnostic line ratios in N44 D1. Similarly, in N44 C we apply a low-density and optically thin model based on the observational signatures. Our modeling results show that the ionization structure and physical conditions of N44 D1 are mainly determined by the radiation from an O5 V star. However, local X-rays, possibly from supernovae or stellar wind, play a key role. In N44 C, the main contribution is from three ionizing stars.

Keywords: Interstellar line emission, Photoionization, H II regions, Large Magellanic Cloud
The Bow Shock and Kinematics of PSR J1959+2048. Pulsar Hα bow shocks provide rare opportunities to constrain the energetics and kinematics of the relativistic pulsar wind. We have acquired optical imaging and integral field unit spectroscopy of the bow shock of the millisecond pulsar PSR J1959+2048, measuring the shock symmetry axis at a position angle = 213.2 ± 0.°2 and showing that this slow nonradiative shock has a broad-to-narrow line component ratio I  b /I  n  = 4. The data show that the pulsar's velocity lies 2.°2 out of the plane of the sky. Coupled with a new fit for its timing proper motion, giving μ tot = 30.05 mas yr-1 and a Very Long Baseline Array (VLBA) interferometric parallax measurement giving $d={2.57}_{-0.77}^{+1.84}$ kpc (90% range), we have unusually complete information on the pulsar kinematics. The bow shock constraints on the wind momentum flux imply that, at the best-fit parallax distance, the pulsar moment of inertia must be very large and/or the Hα efficiency at its modest shock velocity must be very high.

Keywords: Pulsar wind nebulae
A Search for Massive Galaxy Population in a Protocluster of LAEs at z = 2.39 near the Radio Galaxy 53W002. We searched for massive galaxy population in the known large-scale high-density structure of Lyα emitters (LAEs) at z = 2.39 near the radio galaxy 53W002 by using imaging data from $B,\,V,\,i^{\prime} ,\,J,\,H,\,\mathrm{and}\,{K}_{s}$ bands taken with Suprime-Cam and MOIRCS on the Subaru telescope. We selected 62 protocluster member candidates by their JHK  s -band colors and spectral energy distribution (SED) fitting analysis (JHK  s -selected galaxies) in our survey field of $70.2\,{\mathrm{arcmin}}^{2}$ and compared their physical properties estimated from the SED fitting with a comparison sample in the COSMOS field. We found significant number density excesses for the JHK  s -selected galaxies in the 53W002 field at K  s  &lt; 22.25, J - K  s  &gt; 2, or V - K  s  &gt; 4. In particular, the number density of the JHK  s -selected galaxies with K  s  &lt; 22.25 and J - K  s  &gt; 2 in the 53W002 field is nine times higher than the comparison sample. Most of those with K  s  &lt; 22.25 and J - K  s  &gt; 2 are massive galaxies with M  s  &gt; 1011 M ☉, and their specific star formation rates (sSFRs) of 10-11-10-10 yr-1 suggest that the star formation has not yet stopped completely. We also found a density excess of quiescent galaxies with M  s  = 5 × 1010 M ☉ to 1011 M ☉ and sSFR &lt; 10-11 yr-1, as well as that of low-mass galaxies with M  s  = 109.75-1010 M ☉ and various sSFRs. The massive galaxies with M  s  &gt; 1011 M ☉ are not located at the density peaks of LAEs but widely distributed along a similar direction to the structure of LAEs over ~15-20 comoving Mpc. On the other hand, the quiescent galaxies with sSFR &lt; 10-11 yr-1 clearly avoid the structure of LAEs. Our results suggest that massive galaxies also exist in this protocluster discovered by the moderate overdensity of LAEs and their star formation activities depend on location in the protocluster.

Keywords: Galaxy formation, Galaxy evolution, High-redshift galaxy clusters
The Complexity of the Cetus Stream Unveiled from the Fusion of STREAMFINDER and StarGO. We combine the power of two stream-searching tools, STREAMFINDER and StarGO applied to the Gaia EDR3 data, to detect stellar debris belonging to the Cetus stream system that forms a complex, nearly polar structure around the Milky Way. In this work, we find the southern extensions of the northern Cetus stream as the Palca stream and a new southern stream, which overlap on the sky but have different distances. These two stream wraps extend over more than ~100° on the sky (-60° &lt; δ &lt; +40°). The current N-body model of the system reproduces both as two wraps in the trailing arm. We also show that the Cetus system is confidently associated with the Triangulum/Pisces, Willka Yaku, and the recently discovered C-20 streams. The association with the ATLAS-Aliqa Uma stream is much weaker. All of these stellar debris are very metal-poor, comparable to the average metallicity of the southern Cetus stream with [Fe/H] = -2.17 ± 0.20. The estimated stellar mass of the Cetus progenitor is at least 105.6 M ☉, compatible with Ursa Minor or Draco dwarf galaxies. The associated globular cluster with similar stellar mass, NGC 5824 very possibly was accreted in the same group infall. The multi-wrap Cetus stream is a perfect example of a dwarf galaxy that has undergone several periods of stripping, leaving behind debris at multiple locations in the halo. The full characterization of such systems is crucial to unravel the history of the assembly of the Milky Way, and importantly, to provide nearby fossils to study ancient low-mass dwarf galaxies.

Keywords: Galactic archaeology, Dwarf galaxies, Stellar streams, N-body simulations
Searching for Islands of Reionization: A Potential Ionized Bubble Powered by a Spectroscopic Overdensity at z = 8.7. We present the results from a spectroscopic survey using the MOSFIRE near-infrared spectrograph on the 10 m Keck telescope to search for Lyα emission from candidate galaxies at z ~ 9-10 in four of the CANDELS fields (GOODS-N, EGS, UDS, and COSMOS). We observed 11 target galaxies, detecting Lyα from one object in ~8.1 hr of integration, at z = 8.665 ± 0.001 with an integrated signal-to-noise ratio &gt; 7. This galaxy is in the CANDELS Extended Groth Strip (EGS) field and lies physically close (3.5 physical Mpc [pMpc]) to another confirmed galaxy in this field with Lyα detected at z = 8.683. The detection of Lyα suggests the existence of large (~1 pMpc) ionized bubbles fairly early in the reionization process. We explore the ionizing output needed to create bubbles of this size at this epoch and find that such a bubble requires more than the ionizing power provided by the full expected population of galaxies (by integrating the UV luminosity function down to M UV = -13). The Lyα we detect would be able to escape the predominantly neutral intergalactic medium at this epoch if our detected galaxy is inhabiting an overdensity, which would be consistent with the photometric overdensity previously identified in this region by Finkelstein et al. This implies that the CANDELS EGS field is hosting an overdensity at z = 8.7 that is powering one or more ionized bubbles, a hypothesis that will be imminently testable with forthcoming James Webb Space Telescope observations in this field.

Keywords: High-redshift galaxy clusters, Spectroscopy, Lyman-alpha galaxies, Reionization, Galaxy spectroscopy, High-redshift galaxies
Direct Constraints on the Extremely Metal-poor Massive Stars Underlying Nebular C IV Emission from Ultra-deep HST/COS Ultraviolet Spectroscopy. Metal-poor nearby galaxies hosting massive stars have a fundamental role to play in our understanding of both high-redshift galaxies and low-metallicity stellar populations. But while much attention has been focused on their bright nebular gas emission, the massive stars that power it remain challenging to constrain. Here we present exceptionally deep Hubble Space Telescope ultraviolet spectra targeting six local (z &lt; 0.02) galaxies that power strong nebular C IV emission approaching that encountered at z &gt; 6. We find that the strength and spectral profile of the nebular C IV in these new spectra follow a sequence evocative of resonant scattering models, indicating that the hot circumgalactic medium likely plays a key role in regulating C IV escape locally. We constrain the metallicity of the massive stars in each galaxy by fitting the forest of photospheric absorption lines, reporting measurements driven by iron that lie uniformly below 10% solar. Comparison with the gas-phase oxygen abundances reveals evidence for enhancement in O/Fe 2-4 times above solar across the sample, robust to assumptions about the absolute gas-phase metallicity scale. This supports the idea that these local systems are more chemically similar to their primordial high-redshift counterparts than to the bulk of nearby galaxies. Finally, we find significant tension between the strong stellar wind profiles observed and our population synthesis models constrained by the photospheric forest in our highest-quality spectra. This reinforces the need for caution in interpreting wind lines in isolation at high redshift, but also suggests a unique path toward validating fundamental massive star physics at extremely low metallicity with integrated ultraviolet spectra.

Keywords: Blue compact dwarf galaxies, Stellar populations, Massive stars, Ultraviolet astronomy, High-redshift galaxies
Nonlinear Electromagnetic-wave Interactions in Pair Plasma. I. Nonrelativistic Regime. High brightness-temperature radiation is observed in various astrophysical sources: active galactic nuclei, pulsars, interstellar masers, and flaring stars; the discovery of fast radio bursts renewed interest in the nonlinear interaction of intense radiation with plasma. In astronomical systems, the radiation frequency is typically well above the plasma frequency and its spectrum is broad, so nonlinear processes differ considerably from those typically studied in laboratory plasma. This paper is the first in a series devoted to the numerical study of nonlinear interactions of electromagnetic waves with plasma. We start with nonmagnetized pair plasmas, where the primary processes are induced (Compton) scattering and filamentation instability. In this paper, we consider waves in which electron oscillations are nonrelativistic. Here, the numerical results can be compared to analytical theory, facilitating the development of appropriate numerical tools and framework. We distill the analytic theory, reconciling the plasma and radiative transfer pictures of induced scattering and developing in detail the kinetic theory of modulation/filamentation instability. We carry out homogeneous numerical simulations using the particle-in-cell codes EPOCH and Tristan-MP for both monochromatic waves and wave packets. We show that simulations of both processes are consistent with theoretical predictions, setting the stage for analyzing the highly nonlinear regime.

Keywords: Radiative processes, Non-thermal radiation sources, Radiative transfer, Plasma astrophysics
Galactic Positrons from Thermonuclear Supernovae. Type Ia supernovae (SNe Ia) may originate from a wide variety of explosion scenarios and progenitor channels. They exhibit a factor of ≈10 difference in brightness and thus a differentiation in the mass of 56Ni → 56Co → 56Fe. We present a study on the fate of positrons within SNe Ia in order to evaluate their escape fractions and energy spectra. Our detailed Monte Carlo transport simulations for positrons and γ-rays include both β + decay of 56Co and pair production. We simulate a wide variety of explosion scenarios, including the explosion of white dwarfs (WDs) close to the Chandrasekhar mass (M Ch), He-triggered explosions of sub-M Ch WDs, and dynamical mergers of two WDs. For each model, we study the influence of the size and morphology of the progenitor magnetic field between 1 and 1013 G. Population synthesis based on the observed brightness distribution of SNe Ia was used to estimate the overall contributions to Galactic positrons due to escape from SNe Ia. We find that this is dominated by SNe Ia of normal brightness, where variations in the distribution of emitted positrons are small. We estimate a total SNe Ia contribution to Galactic positrons of &lt;2% and, depending on the magnetic field morphology, &lt;6-20% for M Ch and sub-M Ch, respectively.

Keywords: Type Ia supernovae, Supernovae, Galaxy chemical evolution
Thermal Equilibrium Solutions of Black Hole Accretion Flows: Outflows versus Advection. Observations and numerical simulations have shown that outflows generally exist in the accretion process. We revisit the thermal equilibrium solutions of black hole accretion flows by including the role of outflows. Our study focuses on the comparison of the cooling rate of outflows with that of advection. Our results show that, except for the inner region, outflows can dominate over advection in a wide range of flows, which is in good agreement with previous numerical simulations. We argue that an advection-dominated inner region together with an outflow-dominated outer region should be a general radial distribution for both super-Eddington accretion flows and optically thin flows with low accretion rates.

Keywords: Accretion, Hydrodynamics, Black holes, High energy astrophysics
Characterizing Protoclusters and Protogroups at z 2.5 Using Lyα Tomography. Lyα tomography surveys have begun to produce 3D maps of the intergalactic medium opacity at z ~ 2.5 with megaparsec resolution. These surveys provide an exciting new way to discover and characterize high-redshift overdensities, including the progenitors of today's massive groups and clusters of galaxies, known as protogroups and protoclusters. We use the IllustrisTNG-300 hydrodynamical simulation to build mock maps that realistically mimic those observed in the Lyα Tomographic IMACS Survey. We introduce a novel method for delineating the boundaries of structures detected in 3D Lyα flux maps by applying the watershed algorithm. We provide estimators for the dark matter masses of these structures (at z ~ 2.5), their descendant halo masses at z = 0, and the corresponding uncertainties. We also investigate the completeness of this method for the detection of protogroups and protoclusters. Compared to earlier work, we apply and characterize our method over a wider mass range that extends to massive protogroups. We also assess the widely used fluctuating Gunn-Peterson approximation applied to dark-matter-only simulations; we conclude that while it is adequate for estimating the Lyα absorption signal from moderate-to-massive protoclusters (≳1014.2 h -1 M ⊙), it artificially merges a minority of lower-mass structures with more massive neighbors. Our methods will be applied to current and future Lyα tomography surveys to create catalogs of overdensities and study environment-dependent galactic evolution in the Cosmic Noon era.

Keywords: Dark matter distribution, Galaxy environments, Lyman alpha forest, Large-scale structure of the universe, Protoclusters, Dark matter density, Intergalactic medium, Magnetohydrodynamical simulations
Variability Selected Active Galactic Nuclei from ASAS-SN Survey: Constraining the Low Luminosity AGN Population. Low luminosity active galactic nuclei (LLAGN) probe accretion physics in the low Eddington regime can provide additional clues about galaxy evolution. AGN variability is ubiquitous and thus provides a reliable tool for finding AGN. We analyze the All-Sky Automated Survey for SuperNovae light curves of 1218 galaxies with g &lt; 14 mag and Sloan Digital Sky Survey spectra in search of AGN. We find 37 objects that are both variable and have AGN-like structure functions, which is about 3% of the sample. The majority of the variability selected AGN are LLAGN with Eddington ratios ranging from 10-4 to 10-2. We thus estimate the fraction of LLAGN in the population of galaxies as 2% down to a median Eddington ratio of 2 × 10-3. Combining the BPT line ratio AGN diagnostics and the broad-line AGN, up to ~60% of the AGN candidates are confirmed spectroscopically. The BPT diagnostics also classified 10%-30% of the candidates as star-forming galaxies rather than AGN.

Keywords: Surveys, Low-luminosity active galactic nuclei, Active galactic nuclei
Clumpy Accretion in Pre-main-sequence Stars as a Source of Perturbations in Circumstellar Disks. The development of perturbations in the circumstellar disks of pre-main-sequence stars caused by clumpy accretion was investigated. Here we perform 3D smoothed particle hydrodynamics simulations of disks perturbed by a recent clump accretion event. These simulations are further explored by radiative transfer calculations to quantify the observational appearance of such disks. It was shown that the density waves in the disks were formed at the fall of the clump. After several revolutions they can transform into spirals and ring structures. Their images in millimeter wavelengths are very similar to those observed with Atacama Large Millimeter/submillimeter Array in some protoplanetary disks. We assume that clumpy accretion may be the source of such structures.

Keywords: Accretion, Hydrodynamical simulations, Pre-main sequence stars, Protoplanetary disks, Radiative transfer simulations
CO Emission Delineating the Interface between the Milky Way Nuclear Wind Cavity and the Gaseous Disk. Based on the MWISP survey, we study high-z CO emission toward the tangent points, in which the distances of the molecular clouds (MCs) are well determined. In the region of l = 12°-26° and ∣b∣ ≲ 5.°1, a total of 321 MCs with ∣z∣ ≳ 110 pc are identified, of which nearly 30 extreme high-z MCs (EHMCs at ∣z∣ ≳ 260 pc) are concentrated in a narrow region of R GC ~ 2.6-3.1 kpc. The EHMC concentrations, together with other high-z MCs at R GC ≲ 2.3-2.6 kpc, constitute molecular crater-wall structures surrounding the edges of the H I voids that are physically associated with the Fermi bubbles. Intriguingly, some large high-z MCs, which lie in the crater walls above and below the Galactic plane, show cometary structures with the head toward the plane, favoring the scenario that the entrained molecular gas moves with the multiphase flows from the plane to the high-z regions. We suggest that the Milky Way nuclear wind has a significant impact on the Galactic gaseous disk. The powerful nuclear wind at ~3-6 Myr ago is likely responsible for the observational features: (1) the enhanced CO gas lying in the edges of the H I voids, (2) the deficiency of atomic and molecular gas within R GC ≲ 3 kpc, (3) the possible connection between the EHMC concentrations and the 3 kpc arm, and (4) the elongated high-z MCs with the tail pointing away from the Galactic plane.

Keywords: Galactic winds, Interstellar dynamics, Stellar feedback, Molecular clouds, Milky Way disk, Interstellar medium
Detecting Baryon Acoustic Oscillations with Third-generation Gravitational Wave Observatories. We explore the possibility of detecting baryon acoustic oscillations (BAO) solely from gravitational wave (GW) observations of binary neutron star mergers with third-generation (3G) GW detectors such as the Cosmic Explorer and the Einstein Telescope. These measurements would provide a new independent probe of cosmology. The detection of the BAO peak with current-generation GW detectors (solely from GW observations) is not possible because i) unlike galaxies, the GW mergers are poorly localized, and ii) there are not enough merger events to probe the BAO length scale. With the 3G GW detector network, it is possible to observe $\sim { \mathcal O }(1000)$ binary neutron star mergers per year that are localized well within one square degree in the sky for redshift z ≤ 0.3. We show that 3G observatories will enable precision measurements of the BAO feature in the large-scale two-point correlation function; the effect of BAO can be independently detected at different redshifts, with a log-evidence ratio of ~23, 17, or 3, favoring a model with a BAO peak at redshift of 0.2, 0.25, or 0.3, respectively, using a redshift bin corresponding to a shell of thickness 150h -1 Mpc.

Keywords: Cosmology, Gravitational wave detectors, Large-scale structure of the universe, Gravitational wave sources, Gravitational wave astronomy, Gravitational waves, Baryon acoustic oscillations