Sazuna/UAT_keywords huggingface dataset:
Turbulent Gas-rich Disks at High Redshift: Bars and Bulges in a Radial Shear Flow. Recent observations of high-redshift galaxies (z ≲ 7) reveal that a substantial fraction have turbulent, gas-rich disks with well-ordered rotation and elevated levels of star formation. In some instances, disks show evidence of spiral arms, with bar-like structures. These remarkable observations have encouraged us to explore a new class of dynamically self-consistent models using our AGAMA/RAMSES hydrodynamic N-body simulation framework that mimic a plausible progenitor of the Milky Way at high redshift. We explore disk gas fractions of f gas = 0%, 20%, 40%, 60%, 80%, and 100% and track the creation of stars and metals. The high gas surface densities encourage vigorous star formation, which in turn couples with the gas to drive turbulence. We explore three distinct histories: (i) there is no ongoing accretion and the gas is used up by the star formation, (ii) the star-forming gas is replenished by cooling in the hot halo gas, and (iii) in a companion paper, we revisit these models in the presence of a strong perturbing force. At low f disk (≲0.3), where f disk is the baryon mass fraction of the disk relative to dark matter within 2.2 R disk, a bar does not form in a stellar disk; this remains true even when gas dominates the inner disk potential. For a dominant baryon disk (f disk ≳ 0.5) at all gas fractions, the turbulent gas forms a strong radial shear flow that leads to an intermittent star-forming bar within about 500 Myr; turbulent gas speeds up the formation of bars compared to gas-free models. For f gas ≲ 60%, all bars survive, but for higher gas fractions, the bar devolves into a central bulge after 1 Gyr. The star-forming bars are reminiscent of recent discoveries in high-redshift Atacama Large Millimeter/submillimeter Array observations of gaseous disks.

Keywords: Starburst galaxies, Protogalaxies, Late-type galaxies, Disk galaxies, Spiral galaxies, Active galaxies, Primordial galaxies, Galaxy evolution, High-redshift galaxies, Post-starburst galaxies
Impacts of Bar-driven Shear and Shocks on Star Formation. Bars drive gas inflow. As the gas flows inward, shocks and shear occur along the bar dust lanes. Such shocks and shear can affect the star formation (SF) and change the gas properties. For four barred galaxies, we present Hα velocity gradient maps that highlight bar-driven shocks and shear using data from the PHANGS-MUSE and PHANGS-ALMA surveys, which allow us to study bar kinematics in unprecedented detail. Velocity gradients are enhanced along the bar dust lanes, where shocks and shear are shown to occur in numerical simulations. Velocity gradient maps also efficiently pick up H II regions that are expanding or moving relative to the surroundings. We put pseudo-slits on the regions where velocity gradients are enhanced and find that Hα and CO velocities jump up to ∼170 km s−1, even after removing the effects of circular motions due to the galaxy rotation. Enhanced velocity gradients either coincide with the peak of CO intensity along the bar dust lanes or are slightly offset from CO intensity peaks, depending on the objects. Using the Baldwin─Philips─Terlevich BPT diagnostic, we identify the source of ionization on each spaxel and find that SF is inhibited in the high-velocity gradient regions of the bar, and the majority of those regions are classified as a low-ionization nuclear emission-line region (LINER) or composite. This implies that SF is inhibited where bar-driven shear and shocks are strong. Our results are consistent with the results from the numerical simulations that show SF is inhibited in the bar where the shear force is strong.

Keywords: Spiral galaxies, Galaxy structure, Star formation, Galaxy kinematics, Barred spiral galaxies
Accretion Funnel Reconfiguration during an Outburst in a Young Stellar Object: EX Lupi. EX Lupi, a low-mass young stellar object, went into an accretion-driven outburst in 2022 March. The outburst caused a sudden phase change of ∼112° ± 5° in periodically oscillating multiband lightcurves. Our high-resolution spectra obtained with the High Resolution Spectrograph (HRS) on board the Southern African Large Telescope also revealed a consistent phase change in the periodically varying radial velocities (RVs), along with an increase in the RV amplitude of various emission lines. The phase change and increase in RV amplitude morphologically translates to a change in the azimuthal and latitudinal location of the accretion hotspot over the stellar surface, which indicates a reconfiguration of the accretion funnel geometry. Our three-dimensional magnetohydrodynamic simulations reproduce the phase change for EX Lupi. To explain the observations, we explored the possibility of forward shifting of the dipolar accretion funnel as well as the possibility of the emergence of a new accretion funnel. During the outburst, we also found evidence of the hotspot's morphology extending azimuthally asymmetrically with a leading hot edge and cold tail along the stellar rotation. Further, our high-cadence photometry showed that the accretion flow has clumps. We also detected possible clumpy accretion events in the HRS spectra that showed episodically highly blueshifted wings in the Ca II IR triplet and Balmer H lines.

Keywords: Burst astrophysics, Young stellar objects, FU Orionis stars
Microgalaxies in LCDM. A fundamental prediction of the Lambda cold dark matter cosmology is the centrally divergent cuspy density profile of dark matter haloes. Density cusps render cold dark matter haloes resilient to tides, and protect dwarf galaxies embedded in them from full tidal disruption. The hierarchical assembly history of the Milky Way may therefore give rise to a population of "microgalaxies"; i.e., heavily stripped remnants of early accreted satellites, which can reach arbitrarily low luminosity. Assuming that the progenitor systems are dark matter dominated, we use an empirical formalism for tidal stripping to predict the evolution of the luminosity, size, and velocity dispersion of such remnants, tracing their tidal evolution across multiple orders of magnitude in mass and size. The evolutionary tracks depend sensitively on the progenitor distribution of stellar binding energies. We explore three cases that likely bracket most realistic models of dwarf galaxies: one where the energy distribution of the most tightly bound stars follows that of the dark matter, and two where stars are defined by either an exponential density or surface brightness profile. The tidal evolution in the size–velocity dispersion plane is quite similar for these three models, although their remnants may differ widely in luminosity. Microgalaxies are therefore best distinguished from globular clusters by the presence of dark matter; either directly, by measuring their velocity dispersion, or indirectly, by examining their tidal resilience. Our work highlights the need for further theoretical and observational constraints on the stellar energy distribution in dwarf galaxies.

Keywords: Tidal disruption, Cold dark matter, Star clusters, Dwarf spheroidal galaxies, N-body simulations, Milky Way Galaxy, Low surface brightness galaxies
HaloFlow. I. Neural Inference of Halo Mass from Galaxy Photometry and Morphology. We present HaloFlow, a new machine-learning approach for inferring the mass of host dark matter halos, M  h , from the photometry and morphology of galaxies (https://github.com/changhoonhahn/haloflow/). HaloFlow uses simulation-based inference with normalizing flows to conduct rigorous Bayesian inference. It is trained on state-of-the-art synthetic galaxy images from Bottrell et al. that are constructed from the IllustrisTNG hydrodynamic simulation and include realistic effects of the Hyper Suprime-Cam Subaru Strategy Program observations. We design HaloFlow to infer M  h  and stellar mass, M *, using grizy band magnitudes, morphological properties quantifying characteristic size, concentration and asymmetry, total measured satellite luminosity, and number of satellites. We demonstrate that HaloFlow infers accurate and unbiased posteriors of M  h . Furthermore, we quantify the full information content in the photometric observations of galaxies in constraining M  h . With magnitudes alone, we infer M  h  with  σlogMh∼0.115  and 0.182 dex for field and group galaxies. Including morphological properties significantly improves the precision of M  h  constraints, as does total satellite luminosity:  σlogMh∼0.095  and 0.132 dex. Compared to the standard approach using the stellar-to-halo mass relation, we improve M  h  constraints by ∼40%. In subsequent papers, we will validate and calibrate HaloFlow with galaxy–galaxy lensing measurements on real observational data.

Keywords: Cosmology, Galaxy clusters, Bayesian statistics, Neural networks, Large-scale structure of the universe, Galaxy groups
Star Formation Rates in [Ne V] 3426 Å Selected Active Galactic Nuclei: Evidence for a Decrease along the Main Sequence?. Studying the behavior along the galaxy main sequence is key in furthering our understanding of the possible connection between active galactic nucleus (AGN) activity and star formation. We select a sample of 1215 AGN from the catalog of Sloan Digital Sky Survey galaxy properties from the Portsmouth group by detection of the high-ionization [Ne V] 3426 Å emission line. Our sample extends from 1040 to 1042.5 erg s‑1 in [Ne V] luminosity in a redshift range z = 0.17 to 0.57. We compare the specific star formation rates (sSFRs; SFR scaled by galaxy mass) obtained from the corrected [O II] and Hα luminosities, and the spectral energy distribution (SED)–determined values from Portsmouth. We find that the emission-line-based sSFR values are unreliable for the [Ne V] sample due to the AGN contribution, and proceed with the SED sSFRs for our study of the main sequence. We find evidence for a decrease in sSFR along the main sequence in the [Ne V] sample, which is consistent with results from the hard X-ray Burst Alert Telescope AGN sample, which extends to lower redshifts than our [Ne V] sample. Although we do not find evidence that the concurrent AGN activity is suppressing star formation, our results are consistent with a lower gas fraction in the host galaxies of the AGN as compared to that of the star-forming galaxies. If the evacuation of gas, and therefore suppression of star formation, is due to AGN activity, it must have occurred in a previous epoch.

Keywords: Starburst galaxies, Active galaxies, Star formation
VODKA-JWST: A 3.8 kpc Dual Quasar at Cosmic Noon in a Powerful Starburst Galaxy with JWST/MIRI Integral Field Unit. Dual quasars—two active supermassive black holes at galactic scales—represent crucial objects for studying the impact of galaxy mergers and quasar activity on the star formation rate (SFR) within their host galaxies, particularly at cosmic noon when SFR peaks. We present JWST/MIRI mid-infrared integral field spectroscopy of J074922.96+225511.7, a dual quasar with a projected separation of 3.8 kpc at a redshift z = 2.17. We detect spatially extended [Fe II] 5.34 μm and polycyclic aromatic hydrocarbon (PAH) 3.3 μm emissions from the star formation activity in its host galaxy. We derive the SFR of 103.0±0.2 M ⊙ yr‑1 using PAH 3.3 μm, which is 5 times higher than that derived from the knee of the infrared luminosity function for galaxies at z ∼ 2. While the SFR of J0749+2255 agrees with that of star-forming galaxies of comparable stellar mass at the same redshifts, its molecular gas content falls short of expectations based on the molecular Kennicutt–Schmidt law. This discrepancy may result from molecular gas depletion due to the longer elevated stage of star formation, even after the molecular gas reservoir is depleted. We do not observe any quasar-driven outflow that impacts PAH and [Fe II] in the host galaxy based on the spatially resolved maps. From the expected flux in PAH-based star formation, the [Fe II] line likely originates from the star-forming regions in the host galaxy. Our study highlights the extreme stardust nature of J0749+2255, indicating a potential connection between the dual quasar phase and intense star formation activities.

Keywords: Double quasars, Polycyclic aromatic hydrocarbons, Infrared astronomy, Active galactic nuclei, Galaxy mergers, Star formation
Effects of Alpha Particle Fraction on Kinetic Plasma Turbulence. Solar activities have an extraordinary impact on interplanetary space, enriching the plasma dynamics including turbulent heating of various species. The small fraction of alpha particles is believed to play a significant role in the turbulent dynamics of the solar wind. Here we present fully kinetic particle-in-cell simulations to reveal the influences of the alpha particles in decaying plasma turbulence. Multiple run cases with different controlled variations of proton and alpha density are performed to compare and evaluate the energy conversion processes. It is found that the alpha particles can suppress the energy conversion rate with increasing density. Besides, the alpha particles show more heating intermittency than the proton species. Interestingly, on the other hand, the electrons do not show any change in their dynamics, including overall heating. These two positive charge species have more correlation in temperature anisotropy as their densities are comparable. Our results provide valuable insights on the turbulence with different species compositions to a certain extent, especially with abundant heavy particles.

Keywords: Space plasmas, Plasma physics, Interplanetary turbulence, Solar wind, Plasma astrophysics
The Distance to the S147 Supernova Remnant. In the absence of a parallax distance to a pulsar or a surviving binary in a supernova remnant (SNR), distances to Galactic SNRs are generally very uncertain. However, by combining Gaia data with wide-field, multifiber echelle spectroscopy, it is now possible to obtain accurate distances to many SNRs with limited extinction by searching for the appearance of high-velocity Ca II or Na I absorption lines in hot stars as a function of distance. We demonstrate this for the SNR S147 using the spectra of 259 luminous blue stars. We obtain a median distance of 1.37 kpc (1.30–1.47 kpc at 90% confidence), which is consistent with the median parallax distance to the pulsar of 1.46 kpc (1.12–2.10 kpc at 90% confidence) but with significantly smaller uncertainties. Our distance is also consistent with the distance to the candidate unbound binary companion in this SNR, HD 37424 at a photogeometric distance of 1.45 kpc (1.40–1.50 kpc at 1σ). The presence of high-velocity absorption lines is correlated with the Hα/O [III] emission-line flux of the SNR but not with the radio flux.

Keywords: Supernova remnants, Interstellar line absorption, Distance measure
Phase-dependent Spectral Shape Changes in the Ultraluminous X-Ray Pulsar NGC 5907 ULX1. The discovery of coherent pulsations from several ultraluminous X-ray pulsars (ULXPs) has provided direct evidence of a supercritical accretion flow. However, the geometrical structure of such an accretion flow onto the central neutron star remains poorly understood. NGC 5907 ULX1 is one of the most luminous ULXPs, with a luminosity exceeding 1041 erg s−1. Here we present a broadband X-ray study of this ULXP using the data from simultaneous observations with XMM-Newton and NuSTAR conducted in 2014 July. The phase-resolved spectra are well reproduced by a model consisting of a multicolor disk blackbody emission with a temperature gradient of p = 0.5 (T ∝ r −p ) and a power law with an exponential cutoff. The disk component is phase-invariant and has an innermost temperature of ∼ 0.3 keV. Its normalization suggests a relatively low inclination angle of the disk, in contrast to the previous claims in other literature. The power-law component, attributed to the emission from the accretion flow inside the magnetosphere of the neutron star, indicates phase-dependent spectral shape changes; the spectrum is slightly harder in the pre-peak phase than in the post-peak phase. This implies that the magnetosphere has an asymmetric geometry around the magnetic axis and that hotter regions close to the magnetic pole become visible before the pulse peak.

Keywords: Accretion, X-ray binary stars, Ultraluminous x-ray sources, Pulsars
On the Origin of the Variety of Velocity Dispersion Profiles of Galaxies. Observed and simulated galaxies exhibit a significant variation in their velocity dispersion profiles. We examine the inner and outer slopes of stellar velocity dispersion profiles using integral field spectroscopy data from two surveys, SAMI (for z &lt; 0.115) and CALIFA (for z &lt; 0.03), comparing them with results from two cosmological hydrodynamic simulations: Horizon-AGN (for z = 0.017) and NewHorizon (for z ≲ 1). The simulated galaxies closely reproduce the variety of velocity dispersion slopes and stellar mass dependence of both inner and outer radii (0.5 r 50 and 3 r 50) as observed, where r 50 stands for half-light radius. The inner slopes are mainly influenced by the relative radial distribution of the young and old stars formed in situ: a younger center shows a flatter inner profile. The presence of accreted (ex situ) stars has two effects on the velocity dispersion profiles. First, because they are more dispersed in spatial and velocity distributions compared to in situ formed stars, it increases the outer slope of the velocity dispersion profile. It also causes the velocity anisotropy to be more radial. More massive galaxies have a higher fraction of stars formed ex situ and hence show a higher slope in outer velocity dispersion profile and a higher degree of radial anisotropy. The diversity in the outer velocity dispersion profiles reflects the diverse assembly histories among galaxies.

Keywords: Galaxy formation, Galaxy dynamics, Galaxy kinematics, Galaxy evolution
The CO-to-H<SUB>2</SUB> Conversion Factor in the Barred Spiral Galaxy M83. We analyze the CO-to-H2 conversion factor (α CO) in the nearby barred spiral galaxy M83. We present new H I observations from the VLA and single-dish GBT in the disk of the galaxy, and combine them with maps of CO(1-0) integrated intensity and dust surface density from the literature. α CO and the gas-to-dust ratio (δ GDR) are simultaneously derived in annuli of 2 kpc width from R = 1–7 kpc. We find that α CO and δ GDR both increase radially, by a factor of ∼2–3 from the center to the outskirts of the disk. The luminosity-weighted averages over the disk are α CO = 3.14 (2.06, 4.96)  M⊙pc‑2[Kkms‑1]‑1  and δ GDR = 137 (111, 182) at the 68% (1σ) confidence level. These are consistent with the α CO and δ GDR values measured in the Milky Way. In addition to possible variations of α CO due to the radial metallicity gradient, we test the possibility of variations in α CO due to changes in the underlying cloud populations, as a function of galactic radius. Using a truncated power-law molecular cloud CO luminosity function and an empirical power-law relation for cloud mass and luminosity, we show that the changes in the underlying cloud population may account for a factor of ∼1.5–2.0 radial change in α CO.

Keywords: Interstellar dust, Gas-to-dust ratio, Molecular gas, Galactic and extragalactic astronomy, Interstellar medium, CO line emission
CLASSY. IX. The Chemical Evolution of the Ne, S, Cl, and Ar Elements. To study the chemical evolution across cosmic epochs, we investigate Ne, S, Cl, and Ar abundance patterns in the Cosmic Origins Spectrograph Legacy Archive Spectroscopic SurveY (CLASSY). CLASSY comprises local star-forming galaxies (SFGs; 0.02 &lt; z &lt; 0.18) with enhanced star formation rates, making them strong analogues to high-z SFGs. With direct measurements of electron temperature, we derive accurate ionic abundances for all elements and assess ionization correction factors (ICFs) to account for unseen ions and derive total abundances. We find Ne/O, S/O, Cl/O, and Ar/O exhibit constant trends with gas-phase metallicity for 12+log(O/H) &lt; 8.5 but significant correlation for Ne/O and Ar/O with metallicity for 12+log(O/H) &gt; 8.5, likely due to ICFs. Thus, the applicability of the ICFs to integrated spectra of galaxies could bias results, underestimating true abundance ratios. Using CLASSY as a local reference, we assess the evolution of Ne/O, S/O, and Ar/O in galaxies at z &gt; 3, finding no cosmic evolution of Ne/O, while the lack of direct abundance determinations for S/O and Ar/O can bias the interpretation of the evolution of these elements. We determine the fundamental metallicity relationship (FMR) for CLASSY and compare to the high-redshift FMR, finding no evolution. Finally, we perform the first mass─neon relationship analysis across cosmic epochs, finding a slight evolution to high Ne at later epochs. The robust abundance patterns of CLASSY galaxies and their broad range of physical properties provide essential benchmarks for interpreting the chemical enrichment of the early galaxies observed with the JWST.

Keywords: Dwarf galaxies, Compact dwarf galaxies, Gaseous nebulae, Galaxy abundances, H II regions, High-redshift galaxies
Detection of 49 Weak Dispersed Radio Pulses in a Parkes Observation of the X-Ray Pulsar PSR J0537–6910. I conducted a new search for dispersed radio pulses from the X-ray pulsar PSR J0537‑6910 in the Large Magellanic Cloud (LMC) in a long (11.6 hr) archival 1.4 GHz Parkes search observation. I searched dispersion measures (DMs) between 0 and 10,000 pc cm‑3 and detected 49 pulses with a signal-to-noise ratio (S/N) greater than 7 at a wide range of DMs using the HEIMDALL and FETCH pulse detection and classification packages. All of the pulses were weak, with none having an S/N above 8.5. There was a significant excess of pulses observed in the DM range of the known pulsar population in the LMC, suggesting that these pulses may originate from LMC pulsars. Three repeat pulses, each having widths ≲1 ms, were detected in a single DM trial of 103.412 pc cm‑3, which is in the LMC DM range. This is unlikely to occur by chance in a single DM trial in this search at the (marginally significant) 4.3σ level. It remains unclear whether any of the detected pulses in the sample are from PSR J0537‑6910 itself.

Keywords: Radio transient sources, Pulsars
On the Width of a Collisionless Shock and the Index of the Cosmic Rays It Accelerates. Despite being studied for many years, the structure of collisionless shocks is still not fully determined. Such shocks are known to be accelerators of cosmic rays (CRs), which, in turn, modify the shock structure. The shock width λ is known to be connected to the CR spectral index a. Here, we use an instability analysis to derive the shock width in the presence of CRs. We obtain an analytical expression connecting the shock width to the CR index and to the fraction of upstream particles that are accelerated. We find that when this fraction becomes larger than ∼30%, a new instability becomes dominant. The shock undergoes a transition where its width increases by a factor ∼8–10, and the CR acceleration effectively ends. Our analysis is valid for strong, nonrelativistic, and unmagnetized shocks. We discuss the implication of these results on the expected range of CR spectra and flux observed and on the structure of nonrelativistic collisionless shocks.

Keywords: Shocks