Sazuna/UAT_keywords huggingface dataset:
The XMM-Newton Line Emission Analysis Program (X-LEAP). II. The Multiscale Temperature Structures in the Milky Way Hot Gas. This paper presents the multiscale temperature structures in the Milky Way (MW) hot gas, as part of the XMM-Newton Line Emission Analysis Program, surveying the O VII, O VIII, and Fe-L band emission features in the XMM-Newton archive. In particular, we define two temperature tracers, I OVIII/I OVII (O87) and I FeL/(I OVII + I OVIII) (FeO). These two ratios cannot be explained simultaneously using single-temperature collisional ionization models, which indicates the need for multitemperature structures in hot gas. In addition, we show three large-scale features in the hot gas: the eROSITA bubbles around the Galactic center (GC), the disk, and the halo. In the eROSITA bubbles, the observed line ratios can be explained by a log-normal temperature distribution with a median of $\mathrm{log}T/{\rm{K}}\approx 6.4$ and a scatter of σ  T  ≈ 0.2 dex. Beyond the bubbles, the line ratio dependence on the Galactic latitude suggests higher temperatures around the midplane of the MW disk. The scale height of the temperature variation is estimated to be ≈2 kpc assuming an average distance of 5 kpc for the hot gas. The halo component is characterized by the dependence on the distance to the GC, showing a temperature decline from $\mathrm{log}\,T/{\rm{K}}\,\approx 6.3$ to 5.8. Furthermore, we extract the autocorrelation and cross-correlation functions to investigate the small-scale structures. O87 and FeO ratios show a consistent autocorrelation scale of ≈5° (i.e., ≈400 pc at 5 kpc), which is consistent with the expected physical sizes of X-ray bubbles associated with star-forming regions or supernova remnants. Finally, we examine the cross-correlation between the hot and UV-detected warm gas and show an intriguing anticorrelation.

Keywords: Milky Way Galaxy fountains, Hot ionized medium, Circumgalactic medium, Diffuse x-ray background
Leaving No Branches Behind: Predicting Baryonic Properties of Galaxies from Merger Trees. Galaxies play a key role in our endeavor to understand how structure formation proceeds in the Universe. For any precision study of cosmology or galaxy formation, there is a strong demand for huge sets of realistic mock galaxy catalogs, spanning cosmologically significant volumes. For such a daunting task, methods that can produce a direct mapping between dark matter halos from dark matter-only simulations and galaxies are strongly preferred, as producing mocks from full-fledged hydrodynamical simulations or semi-analytical models is too expensive. Here, we present a graph-neural-network-based model that is able to accurately predict key properties of galaxies such as stellar mass, g ‑ r color, star formation rate, gas mass, stellar metallicity, and gas metallicity, purely from dark matter properties extracted from halos along the full assembly history of the galaxies. Tests based on the TNG300 simulation of the IllustrisTNG project show that our model can recover the baryonic properties of galaxies to high accuracy, over a wide redshift range (z = 0–5), for all galaxies with stellar masses more massive than 109 M ⊙ and their progenitors, with strong improvements over the state-of-the-art methods. We further show that our method makes substantial strides toward providing an understanding of the implications of the IllustrisTNG galaxy formation model.

Keywords: Galaxy dark matter halos, Galaxy formation, Neural networks, Galaxy physics, Astrostatistics
Measuring the Magnetic Dipole Moment and Magnetospheric Fluctuations of SXP 18.3 with a Kalman Filter. The magnetic dipole moment μ of an accretion-powered pulsar in magnetocentrifugal equilibrium cannot be inferred uniquely from time-averaged pulse period and aperiodic X-ray flux data, because the radiative efficiency η 0 of the accretion is unknown, as are the mass, radius, and distance of the star. The degeneracy associated with the radiative efficiency is circumvented if fluctuations of the pulse period and aperiodic X-ray flux are tracked with a Kalman filter, whereupon μ can be measured uniquely up to the uncertainties in the mass, radius, and distance. Here, the Kalman filter analysis is demonstrated successfully in practice for the first time on Rossi X-ray Timing Explorer observations of the X-ray transient SXP 18.3 in the Small Magellanic Cloud (SMC), which is monitored regularly. The analysis yields $\mu ={8.0}_{-1.2}^{+1.3}\,\times \,{10}^{30}\,{\rm{G}}\,{\mathrm{cm}}^{3}$ and ${\eta }_{0}={0.04}_{-0.01}^{+0.02}$ , compared to $\mu ={5.0}_{-1.0}^{+1.0}\times {10}^{30}\,{\rm{G}}\,{\mathrm{cm}}^{3}$ as inferred traditionally from time-averaged data assuming η 0 = 1. The analysis also yields time-resolved estimates of two hidden state variables, the mass accretion rate and the Maxwell stress at the disk–magnetosphere boundary. The success of the demonstration confirms that the Kalman filter analysis can be applied in the future to study the magnetic moments and disk–magnetosphere physics of accretion-powered pulsar populations in the SMC and elsewhere.

Keywords: Neutron stars, Accretion, Magnetic fields
GOALS-JWST: Gas Dynamics and Excitation in NGC 7469 Revealed by NIRSpec. We present new JWST NIRSpec integral field spectroscopy (IFS) data for the luminous infrared galaxy NGC 7469, a nearby (70.6 Mpc) active galaxy with a Seyfert 1.5 nucleus that drives a highly ionized gas outflow and a prominent nuclear star-forming ring. Using the superb sensitivity and high spatial resolution of the JWST instrument NIRSpec IFS, we investigate the role of the Seyfert nucleus in the excitation and dynamics of the circumnuclear gas. Our analysis focuses on the [Fe II], H2, and hydrogen recombination lines that trace the radiation/shocked-excited molecular and ionized interstellar medium around the active galactic nucleus (AGN). We investigate gas excitation through H2/Brγ and [Fe II]/Paβ emission line ratios and find that photoionization by the AGN dominates within the central 300 pc of the galaxy except in a small region that shows signatures of shock-heated gas; these shock-heated regions are likely associated with a compact radio jet. In addition, the velocity field and velocity dispersion maps reveal complex gas kinematics. Rotation is the dominant feature, but we also identify noncircular motions consistent with gas inflows as traced by the velocity residuals and the spiral pattern in the Paα velocity dispersion map. The inflow is 2 orders of magnitude higher than the AGN accretion rate. The compact nuclear radio jet has enough power to drive the highly ionized outflow. This scenario suggests that the inflow and outflow are in a self-regulating feeding–feedback process, with a contribution from the radio jet helping to drive the outflow.

Keywords: Galaxy dynamics, Galaxy nuclei, Seyfert galaxies, Active galactic nuclei, Galaxy winds, Galaxy kinematics, Luminous infrared galaxies
Latent Stochastic Differential Equations for Modeling Quasar Variability and Inferring Black Hole Properties. Quasars are bright and unobscured active galactic nuclei (AGN) thought to be powered by the accretion of matter around supermassive black holes at the centers of galaxies. The temporal variability of a quasar's brightness contains valuable information about its physical properties. The UV/optical variability is thought to be a stochastic process, often represented as a damped random walk described by a stochastic differential equation (SDE). Upcoming wide-field telescopes such as the Rubin Observatory Legacy Survey of Space and Time (LSST) are expected to observe tens of millions of AGN in multiple filters over a ten year period, so there is a need for efficient and automated modeling techniques that can handle the large volume of data. Latent SDEs are machine learning models well suited for modeling quasar variability, as they can explicitly capture the underlying stochastic dynamics. In this work, we adapt latent SDEs to jointly reconstruct multivariate quasar light curves and infer their physical properties such as the black hole mass, inclination angle, and temperature slope. Our model is trained on realistic simulations of LSST ten year quasar light curves, and we demonstrate its ability to reconstruct quasar light curves even in the presence of long seasonal gaps and irregular sampling across different bands, outperforming a multioutput Gaussian process regression baseline. Our method has the potential to provide a deeper understanding of the physical properties of quasars and is applicable to a wide range of other multivariate time series with missing data and irregular sampling.

Keywords: Neural networks, Quasars, Irregular cadence, Active galactic nuclei, Time series analysis
Multiphase Gas in Elliptical Galaxies: The Role of Type Ia Supernovae. Massive elliptical galaxies harbor large amounts of hot gas (T ≳ 106 K) in their interstellar medium (ISM) but are typically quiescent in star formation. The jets of active galactic nuclei (AGNs) and Type Ia supernovae (SNe Ia) inject energy into the ISM, which offsets its radiative losses and keeps it hot. SNe Ia deposit their energy locally within the galaxy compared to the larger few ×10 kiloparsec-scale AGN jets. In this study, we perform high-resolution (5123) hydrodynamic simulations of a local (1 kpc3) density-stratified patch of the ISM of massive galaxies. We include radiative cooling and shell-averaged volume heating, as well as randomly exploding SN Ia. We study the effect of different fractions of supernova (SN) heating (with respect to the net cooling rate), different initial ISM density/entropy (which controls the growth time t ti of the thermal instability), and different degrees of stratification (which affect the freefall time t ff). We find that SNe Ia drive predominantly compressive turbulence in the ISM with a velocity dispersion of σ  v  up to 40 km s‑1 and logarithmic density dispersion of σ  s  ∼ 0.2–0.4. These fluctuations trigger multiphase condensation in regions of the ISM, where $\min ({t}_{\mathrm{ti}})/{t}_{\mathrm{ff}}\lesssim 0.6\exp (6{\sigma }_{s})$ , in agreement with theoretical expectations that large density fluctuations efficiently trigger multiphase gas formation. Since the SN Ia rate is not self-adjusting, when the net cooling drops below the net heating rate, SNe Ia drive a hot wind which sweeps out most of the mass in our local model. Global simulations are required to assess the ultimate fate of this gas.

Keywords: Interstellar medium, Type Ia supernovae, Early-type galaxies, Cooling flows
Evolved Massive Stars at Low Metallicity. VII. The Lower Mass Limit of the Red Supergiant Population in the Large Magellanic Cloud. The precise definition of the lower mass limit of red supergiant stars (RSGs) is an open question in astrophysics and does not attract much attention. Here, we assemble a spectroscopic evolved cool star sample with 6602 targets, including RSGs, asymptotic giant branch stars, and red giant branch stars, in the Large Magellanic Cloud based on Gaia DR3 and Sloan Digital Sky Survey IV/APOGEE-2. The reference spectrum of each stellar population is built according to the quantile range of relative intensity (1% ∼ 99%). Five different methods, e.g., χ 2, cosine similarity, machine learning (ML), equivalent width, and line ratio, are used in order to separate different stellar populations. ML and χ 2 provide the best and relatively consistent prediction of a certain population. The derived lower limit of the RSG population is able to reach the K  s -band tip of the red giant branch (K  s  ≈12.0 mag), indicating a luminosity as low as about 103.5 L ⊙, which corresponds to a stellar radius of only about 100 R ⊙. Given the mass–luminosity relation of $L/{L}_{\odot }=f{(M/{M}_{\odot })}^{3}$ with f ≈ 15.5 ± 3 and taking into account the mass loss of faint RSGs up to now, the minimal initial mass of the RSG population would be about 6.1 ± 0.4 M ⊙, which is much lower than the traditional threshold of 8 M ⊙ for the massive stars. This is the first spectroscopic evidence, indicating that the lower mass limit of the RSG population is around 6 M ⊙. However, the destinies of such faint RSGs are still elusive and may have a large impact on stellar evolutionary and supernova models.

Keywords: Stellar populations, Stellar classification, Red supergiant stars
Imaging a Large Coronal Loop Using Type U Solar Radio Burst Interferometry. Solar radio U-bursts are generated by electron beams traveling along closed magnetic loops in the solar corona. Low-frequency (&lt;100 MHz) U-bursts serve as powerful diagnostic tools for studying large-sized coronal loops that extend into the middle corona. However, the positive frequency drift component (descending leg) of U-bursts has received less attention in previous studies, as the descending radio flux is weak. In this study, we utilized LOFAR interferometric solar imaging data from a U-burst that has a significant descending leg component, observed between 10 and 90 MHz on 2020 June 5th. By analyzing the radio source centroid positions, we determined the beam velocities and physical parameters of a large coronal magnetic loop that reached just about 1.3 R ⊙ in altitude. At this altitude, we found the plasma temperature to be around 1.1 MK, the plasma pressure around 0.20 mdyn, cm‑2, and the minimum magnetic field strength around 0.07 G. The similarity in physical properties determined from the image suggests a symmetric loop. The average electron beam velocity on the ascending leg was found to be 0.21c, while it was 0.14c on the descending leg. This apparent deceleration is attributed to a decrease in the range of electron energies that resonate with Langmuir waves, likely due to the positive background plasma density gradient along the downward loop leg.

Keywords: Solar coronal radio emission, Solar energetic particles, Solar coronal loops, Solar corona, Solar particle emission
ALMA Lensing Cluster Survey: Full Spectral Energy Distribution Analysis of z ∼ 0.5–6 Lensed Galaxies Detected with millimeter Observations. Sub/millimeter galaxies are a key population for the study of galaxy evolution because the majority of star formation at high redshifts occurred in galaxies deeply embedded in dust. To search for this population, we have performed an extensive survey with Atacama Large Millimeter/submillimeter Array (ALMA), called the ALMA Lensing Cluster Survey (ALCS). This survey covers 133 arcmin2 area and securely detects 180 sources at z ∼ 0.5–6 with a flux limit of ∼0.2 mJy at 1.2 mm. Here, we report the results of multiwavelength spectral energy distribution analysis of the whole ALCS sample, utilizing the observed-frame UV to millimeter photometry. We find that the majority of the ALCS sources lie on the star-forming main sequence, with a smaller fraction showing intense starburst activities. The ALCS sample contains high infrared-excess sources ( $\mathrm{IRX}=\mathrm{log}({L}_{\mathrm{dust}}/{L}_{\mathrm{UV}})\gt 1$ ), including two extremely dust-obscured galaxies (IRX &gt; 5). We also confirm that the ALCS sample probes a broader range in lower dust mass than conventional submillimeter galaxy samples in the same redshift range. We identify six heavily obscured active galactic nucleus (AGN) candidates that are not detected in the archival Chandra data in addition to the three X-ray AGNs reported by Uematsu et al. (2023). The inferred AGN luminosity density shows a possible excess at z = 2–3 compared with that determined from X-ray surveys below 10 keV.

Keywords: Active galactic nuclei, Spectral energy distribution, Galaxy evolution, Submillimeter astronomy, High-redshift galaxies
Persistent Upflows and Downflows at Active Region Boundaries Observed by SUTRI and AIA. Upflows and downflows at active region (AR) boundaries have been frequently observed with spectroscopic observations at extreme ultraviolet passbands. In this paper, we report the coexistence of upflows and downflows at the AR boundaries with imaging observations from the Solar Upper Transition Region Imager (SUTRI) and the Atmospheric Imaging Assembly (AIA). With their observations from 2022 September 21 to 2022 September 30, we find 17 persistent opposite flows occurring along the AR coronal loops. The upflows are prominent in the AIA 193 Å images with a velocity of 50–200 km s‑1, while the downflows are best seen in the SUTRI 465 Å and AIA 131 Å images with a slower velocity of tens of kilometers per second (characteristic temperatures (log T(K)) for 193, 465, and 131 Å are 6.2, 5.7, and 5.6, respectively). We also analyze the center-to-limb variation of the velocities for both upflows and downflows. The simultaneous observations of downflows and upflows can be explained by the chromosphere–corona mass-cycling process, in which the localized chromospheric plasma is impulsively heated to coronal temperature forming a upflow and then these upflows experience radiative cooling producing a downflow with the previously heated plasma returning to the lower atmosphere. In particular, the persistent downflows seen by SUTRI provide strong evidence of the cooling process in the mass cycle. For upflows associated with open loops, part of the plasma is able to escape outward and into the heliosphere as solar wind.

Keywords: Solar ultraviolet emission, Solar chromosphere, Solar corona, Solar transition region
Observability of Substructures in the Planet-forming Disk in the (Sub)centimeter Wavelength with SKA and ngVLA. Current imaging observations of protoplanetary disks using the Atacama Large Millimeter/submillimeter Array (ALMA) primarily focus on the submillimeter wavelength, leaving a gap in effective observational approaches for centimeter-sized dust, which is crucial to the issue of planet formation. The forthcoming Square Kilometre Array (SKA) and ngVLA may rectify this deficiency. In this paper, we employ multifluid hydrodynamic numerical simulations and radiative transfer calculations to investigate the potential of SKA1-Mid, ngVLA, and SKA2 for imaging protoplanetary disks at subcentimeter/centimeter wavelengths. We create mock images with ALMA/SKA/ngVLA at multiwavelengths based on the hydrodynamical simulation output and test different sensitivity and spatial resolutions. We discover that both SKA and ngVLA will serve as excellent supplements to the existing observational range of ALMA, and their high resolution enables them to image substructures in the disk's inner region (∼5 au from the stellar). Our results indicate that SKA and ngVLA can be utilized for more extended monitoring programs in the centimeter wave band. While in the subcentimeter range, ngVLA possesses the capability to produce high-fidelity images within shorter observation times (∼1 hr on source time) than previous research, holding potential for future survey observations. We also discuss for the first time the potential of SKA2 for observing protoplanetary disks at a 0.7 cm wavelength.

Keywords: Hydrodynamics, Astronomical simulations, Protoplanetary disks, Astrophysical fluid dynamics, Planet formation
Compton Scattering of Electrons in the Intergalactic Medium. This paper investigates the distribution and implications of cosmic-ray electrons within the intergalactic medium (IGM). Utilizing a synthesis model of the extragalactic background, we evolve the spectrum of Compton-included cosmic rays. The energy density distribution of cosmic-ray electrons peaks at redshift z ≈ 2, and peaks in the ∼MeV range. The fractional contribution of cosmic-ray pressure to the general IGM pressure progressively increases toward lower redshift. At mean density, the ratio of cosmic-ray electron to thermal pressure in the IGM ${P}_{\mathrm{CRe}}/{P}_{\mathrm{th}}$ is 0.3% at z = 2, rising to 1.0% at z = 1, and 1.8% at z = 0.1 (considering only the cosmic rays produced locally by Compton scattering). We compute the linear Landau damping rate of plasma oscillations in the IGM caused by the ∼MeV cosmic-ray electrons, and find it to be of order ∼10‑6 s‑1 for wavenumbers 1.2 ≲ ck/ω p ≲ 5 at z = 2 and mean density (where ω p is the plasma frequency). This strongly affects the fate of TeV e + e ‑ pair beams produced by blazars, which are potentially unstable to oblique instabilities involving plasma oscillations with wavenumber ${ck}/{\omega }_{{\rm{p}}}\approx \sec \theta $ (θ being the angle between the beam and wavevector). Linear Landau damping is at least thousands of times faster than either pair beam instability growth or collisional effects; it thus turns off the pair beam instability except for modes with very small θ (ck/ω p → 1, where linear Landau damping is kinematically suppressed). This leaves open the question of whether the pair beam instability is turned off entirely, or can still proceed via the small-θ modes.

Keywords: Cosmic magnetic fields theory, Intergalactic gas, Cosmic rays
XMM─NuSTAR Observation and Multiwavelength Spectral Energy Distribution Modeling of Blazar 4FGL J1520.8─0348. Active galactic nuclei (AGNs) can power relativistic jets, which are called blazars when pointed close to our line of sight. Depending on the presence or absence of emission lines in their optical spectra, blazars are categorized into flat spectrum radio quasars (FSRQs) or BL Lacertae (BL Lac) objects. According to the "blazar sequence," as synchrotron peak frequency ( ${\nu }_{\mathrm{pk}}^{\mathrm{sy}}$ ) shifts to higher energies, the synchrotron peak luminosity decreases. This means that BL Lac objects as luminous as FSRQs, and with synchrotron peak frequencies ${\nu }_{\mathrm{pk}}^{\mathrm{sy}}\gt {10}^{15}$ Hz, should not exist. Detected as a high-synchrotron peak (HSP; ${\nu }_{\mathrm{pk}}^{\mathrm{sy}}\gt {10}^{15}$ Hz) BL Lac object, 4FGL J1520.8-0348 shows high γ-ray luminosity (L  γ  &gt; 1046 erg s−1), being at a high redshift of z = 1.46. Since it is an outlier in the "blazar sequence," the process of its jet acceleration and power may be different from bona fide BL Lac objects. In this work, we constrain its spectral energy distribution (SED) by modeling the multiwavelength data from infrared to γ-ray regime. Simultaneous X-ray data were obtained from X-ray Multi-Mirror Mission and Nuclear Spectroscopic Telescope Array to constrain the synchrotron emission and underlying electron distribution. On undertaking the SED modeling of the source, including the effect of extragalactic background light, we conclude that the source is more likely to be a "blue FSRQ" or "masquerading BL Lac" where the BL Lac object is actually an FSRQ in disguise.

Keywords: Astronomy data modeling, BL Lacertae objects, Blazars, Active galaxies, Active galactic nuclei, High-redshift galaxies
Bell Instability–mediated Diffusive Shock Acceleration at Supernova Blast Wave Shock Propagating in the Interstellar Medium. Supernova blast wave shock is a very important site of cosmic-ray acceleration. However, the detailed physical process of acceleration, in particular, nonlinear interplay between cosmic-ray streaming and magnetic field amplification, has not been studied under a realistic environment. In this paper, using a unique and novel numerical method, we study cosmic-ray acceleration at supernova blast wave shock propagating in the interstellar medium with well-resolved magnetic field amplification by nonresonant hybrid instability (or Bell instability). We find that the magnetic field is mildly amplified under typical interstellar medium conditions that leads to maximum cosmic-ray energy ≃30 TeV for supernova remnants with age ≃1000 yr consistent with gamma-ray observations. The strength of the amplified magnetic field does not reach the so-called saturation level because the cosmic-ray electric current toward the shock upstream has a finite spatial extent, by which Bell instability cannot experience many e-folding times.

Keywords: Supernova remnants, Cosmic rays