Sazuna/UAT_keywords huggingface dataset:
Small-amplitude Compressible Magnetohydrodynamic Turbulence Modulated by Collisionless Damping in Earth's Magnetosheath: Observation Matches Theory. Plasma turbulence is a ubiquitous dynamical process that transfers energy across many spatial and temporal scales and affects energetic particle transport. Recent advances in the understanding of compressible magnetohydrodynamic (MHD) turbulence demonstrate the important role of damping in shaping energy distributions on small scales, yet its observational evidence is still lacking. This study provides the first observational evidence of substantial collisionless damping (CD) modulation on the small-amplitude compressible MHD turbulence cascade in Earth's magnetosheath using four Cluster spacecraft. Based on an improved compressible MHD decomposition algorithm, turbulence is decomposed into three eigenmodes: incompressible Alfvén modes and compressible slow and fast (magnetosonic) modes. Our observations demonstrate that CD enhances the anisotropy of compressible MHD modes because CD has a strong dependence on wave propagation angle. The wavenumber distributions of slow modes are mainly stretched perpendicular to the background magnetic field ( B 0) and weakly modulated by CD. In contrast, fast modes are subjected to a more significant CD modulation. Fast modes exhibit a weak, scale-independent anisotropy above the CD truncation scale. Below the CD truncation scale, the anisotropy of fast modes enhances as wavenumbers increase. As a result, fast-mode fractions in the total energy of compressible modes decrease with the increase of perpendicular wavenumber (to B 0) or wave propagation angle. Our findings reveal how the turbulence cascade is shaped by CD and its consequences for anisotropies in the space environment.

Keywords: Space plasmas, Magnetohydrodynamics, Interplanetary turbulence, Plasma astrophysics, Interplanetary physics
Disentangling CO Chemistry in a Protoplanetary Disk Using Explanatory Machine-learning Techniques. Molecular abundances in protoplanetary disks are highly sensitive to the local physical conditions, including gas temperature, gas density, radiation field, and dust properties. Often multiple factors are intertwined, impacting the abundances of both simple and complex species. We present a new approach to understanding these chemical and physical interdependencies using machine learning. Specifically, we explore the case of CO modeled under the conditions of a generic disk and build an explanatory regression model to study the dependence of CO spatial density on the gas density, gas temperature, cosmic-ray ionization rate, X-ray ionization rate, and UV flux. Our findings indicate that combinations of parameters play a surprisingly powerful role in regulating CO abundance compared to any singular physical parameter. Moreover, in general we find the conditions in the disk are destructive toward CO. CO depletion is further enhanced in an increased cosmic-ray environment and in disks with higher initial C/O ratios. These dependencies uncovered by our new approach are consistent with previous studies, which are more modeling intensive and computationally expensive. Our work thus shows that machine learning can be a powerful tool not only for creating efficient predictive models, but also for enabling a deeper understanding of complex chemical processes.

Keywords: Regression, Chemical reaction network models, Protoplanetary disks, Astrochemistry
An Optical Search for New Outbursting Low Mass X-Ray Binaries. Transient low-mass X-ray binaries (LMXBs) are discovered largely by X-ray and gamma-ray all-sky monitors. The X-ray outburst is also accompanied by an optical brightening, which empirically can precede the detection of X-rays. Newly sensitive optical synoptic surveys may offer a complementary pathway for discovery and potential for insight into the initial onset and propagation of the thermal instability that leads to the ionization of the accretion disk. We use the Zwicky Transient Facility (ZTF) alert stream to perform a comprehensive search at optical wavelengths for previously undiscovered outbursting LMXBs. Our pipeline first crossmatches the positions of the alerts to cataloged X-ray sources, and then analyzes the 30 day lightcurve of matched alerts by thresholding on differences with an 8 day exponentially weighted moving average. In addition to a 19 month long live search, we ran our pipeline over 4 yr of ZTF archival data, recovering four known LMXBs. We also independently detected an outburst of MAXI J1957+032 in the live search and found the first outburst of Swift J1943.4+0228, an unclassified X-ray transient, in 10 yr. Using Monte Carlo simulations of the Galactic LMXB population, we estimate that 29% of outbursting LMXBs are detectable by ZTF and that 4.4% of LMXBs would be present in the crossmatched X-ray catalogs, giving an estimated Galactic population of ${3390}_{-1930}^{+3980}$ . We estimate that our current pipeline can detect 1.3% of all outbursting LMXBs, including those previously unknown, but that Rubin Observatory's Legacy Survey of Space and Time will be able to detect 43% of outbursting LMXBs.

Keywords: X-ray binary stars
First Detection of Polarization in X-Rays for PSR B0540-69 and Its Nebula. We report on X-ray polarization measurements of the extragalactic Crab-like PSR B0540-69 and its Pulsar Wind Nebula (PWN) in the Large Magellanic Cloud, using a ∼850 ks Imaging X-ray Polarimetry Explorer (IXPE) exposure. The PWN is unresolved by IXPE. No statistically significant polarization is detected for the image-averaged data, giving a 99% confidence polarization upper limit (MDP99) of 5.3% in the 2–8 keV energy range. However, a phase-resolved analysis detects polarization for both the nebula and pulsar in the 4–6 keV energy range. For the PWN defined as the off-pulse phases, the polarization degree (PD) of (24.5 ± 5.3)% and polarization angle (PA) of (78.1 ± 6.2)° is detected at 4.6σ significance level, consistent with the PA observed in the optical band. In a single on-pulse window, a hint of polarization is measured at 3.8σ with PD of (50.0 ± 13.1)% and PA of (6.2 ± 7.4)°. A "simultaneous" PSR/PWN analysis finds two bins at the edges of the pulse exceeding 3σ PD significance, with PD of (68 ± 20)% and (62 ± 20)%; intervening bins at 2–3σ significance have lower PD, hinting at additional polarization structure.

Keywords: Pulsar wind nebulae, Polarimetry, Pulsars
Active Galactic Nuclei and Host Galaxies in COSMOS-Web. I. NIRCam Images, Point-spread-function Models and Initial Results on X-Ray-selected Broad-line AGNs at 0.35 ≲ z ≲ 3.5. We present detailed and comprehensive data reduction and point-spread-function (PSF) model construction for all public JWST NIRCam imaging data from the COSMOS-Web treasury program (up to 2023 June, totaling 0.28 deg2). We show that the NIRCam PSF has significant short-timescale temporal variations and random spatial variations in all four filters (F115W, F150W, F277W, and F444W). Combining NIRCam with archival Hubble Space Telescope imaging, we perform multiwavelength active galactic nucleus (AGN)+host image decomposition to study the properties of 143 X-ray-selected (L bol = 1043.6─47.2 erg s−1) broad-line AGNs at 0.35 ≲ z ≲ 3.5. Leveraging the superb resolution, wavelength coverage, and sensitivity of NIRCam, we successfully detect host stellar emission after decomposing the central AGN point source in 142 objects. ∼2/3 AGNs are in star-forming galaxies based on the UVJ diagram, suggesting that there is no instantaneous negative AGN feedback. X-ray-selected broad-line AGN hosts follow a similar stellar mass─size relation as inactive galaxies, albeit with slightly smaller galaxy sizes. We find that although major mergers are rare (∼7%─22%) among the sample, more subtle nonaxisymmetric features from stellar bars, spiral arms, and minor mergers are ubiquitous, highlighting the importance of secular processes and minor mergers in triggering AGN activity. For a subsample of 30 AGNs at 1 &lt; z &lt; 2.5 with black hole mass measurements from single epoch spectra, they follow a similar black hole mass-stellar mass relation as local inactive early-type galaxies but reside preferentially near the upper envelope of nearby AGNs. We caution that selection biases and the intrinsic differences of AGN populations at different redshifts may significantly affect their location on the black hole mass-stellar mass plane.

Keywords: AGN host galaxies, Supermassive black holes, Sky surveys, Galaxy structure, Active galactic nuclei, Galaxy evolution
ZWCL 1856.8: A Rare Double Radio Relic System Captured within NuSTAR and Chandra Field of View. Observations of galaxy cluster mergers provide insights on the particle acceleration and heating mechanisms taking place within the intracluster medium. Mergers form shocks that propagate through the plasma, which result in shock/cold fronts in the X-ray, and radio halos and/or relics in the radio regime. The connection between these tracers and the mechanisms driving non-thermal processes, such as inverse Compton, are not well understood. ZWCL 1856.8 is one of the few known double radio relic systems that originate from nearly head-on collisions observed close to the plane of the sky. For the first time, we study NuSTAR and Chandra observations of this system, which contains both relics within their field of view. The spectro-imaging analyses results of the system suggest weak shock fronts with ${ \mathcal M }$ numbers within 2σ of the radio-derived values, and provide evidence of inverse Compton emission at both relic sites. Our findings have great uncertainties due to the shallow exposure times available. Deeper NuSTAR and Chandra data are crucial for studying the connection of the radio and X-ray emission features and for constraining the thermal versus non-thermal emission contributions in this system. We also present methods and approaches on how to investigate X-ray properties of double relic systems by taking full advantage of the complementary properties of NuSTAR and Chandra missions.

Keywords: Galaxy clusters, Shocks, Non-thermal radiation sources, High energy astrophysics
CLASSY. VIII. Exploring the Source of Ionization with UV Interstellar Medium Diagnostics in Local High-z Analogs. In the current JWST era, rest-frame UV spectra play a crucial role in enhancing our understanding of the interstellar medium (ISM) and stellar properties of the first galaxies in the epoch of reionization (z &gt; 6). Here, we compare well-known and reliable optical diagrams sensitive to the main ionization source (i.e., star formation, SF; active galactic nuclei, AGN; and shocks) to UV counterparts proposed in the literature—the so-called "UV─BPT diagrams"—using the HST COS Legacy Archive Spectroscopic SurveY (CLASSY), which is the largest high-quality, high-resolution, and broad-wavelength range atlas of far-UV spectra for 45 local star-forming galaxies. In particular, we explore where CLASSY UV line ratios are located in the different UV diagnostic plots, taking into account state-of-the-art photoionization and shock models, and, for the first time, the measured ISM and stellar properties (e.g., gas-phase metallicity, ionization parameter, carbon abundance, and stellar age). We find that the combination of C III] λ λ1907,9 He II λ1640 and O III] λ1666 can be a powerful tool to separate between SF, shocks, and AGN at subsolar metallicities. We also confirm that alternative diagrams without O III] λ1666 still allow us to define an SF-locus, with some caveats. Diagrams including C IV λ λ1548,51 should be taken with caution given the complexity of this doublet profile. Finally, we present a discussion detailing the ISM conditions required to detect UV emission lines, visible only in low gas-phase metallicity (12 + log(O/H) ≲ 8.3) and high ionization parameter (log(U) ≳ −2.5) environments. Overall, CLASSY and our UV toolkit will be crucial in interpreting the spectra of the earliest galaxies that JWST is currently revealing. *Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

Keywords: Galaxy chemical evolution, Dwarf galaxies, Emission line galaxies, Ultraviolet astronomy, Galaxy spectroscopy, High-redshift galaxies
High-spectral-resolution Observations of the Optical Filamentary Nebula Surrounding NGC 1275. We present new high-spectral-resolution observations (R = λ/Δλ = 7000) of the filamentary nebula surrounding NGC 1275, the central galaxy of the Perseus cluster. These observations have been obtained with SITELLE, an imaging Fourier transform spectrometer installed on the Canada–France–Hawai Telescope with a field of view of $11^{\prime} \times 11^{\prime} $ , encapsulating the entire filamentary structure of ionized gas despite its large size of 80 kpc × 50 kpc. Here, we present renewed fluxes, velocities, and velocity dispersion maps that show in great detail the kinematics of the optical nebula at [S II] λ6716, [S II] λ6731, [N II] λ6584, Hα (6563 Å), and [N II] λ6548. These maps reveal the existence of a bright flattened disk-shaped structure in the core extending to r ∼10 kpc and dominated by a chaotic velocity field. This structure is located in the wake of X-ray cavities and characterized by a high mean velocity dispersion of 134 km s‑1. The disk-shaped structure is surrounded by an extended array of filaments spread out to r ∼ 50 kpc that are 10 times fainter in flux, remarkably quiescent, and have a uniform mean velocity dispersion of 44 km s‑1. This stability is puzzling given that the cluster core exhibits several energetic phenomena. Based on these results, we argue that there are two mechanisms that form multiphase gas in clusters of galaxies: a first triggered in the wake of X-ray cavities leading to more turbulent multiphase gas and a second, distinct mechanism, that is gentle and leads to large-scale multiphase gas spreading throughout the core.

Keywords: AGN host galaxies, Active galaxies, Brightest cluster galaxies, Filamentary nebulae, Perseus Cluster
Quantifying the Transit Light Source Effect: Measurements of Spot Temperature and Coverage on the Photosphere of AU Microscopii with High-resolution Spectroscopy and Multicolor Photometry. AU Microscopii (AU Mic) is an active 24 ± 3 Myr pre-main-sequence M dwarf in the stellar neighborhood (d = 9.7 pc) with a rotation period of 4.86 days. The two transiting planets orbiting AU Mic, AU Mic b and c, are warm sub-Neptunes on 8.5 and 18.9 day periods and are targets of interest for atmospheric observations of young planets. Here we study AU Mic's unocculted starspots using ground-based photometry and spectra in order to complement current and future transmission spectroscopy of its planets. We gathered multicolor Las Cumbres Observatory (LCO) 0.4 m SBIG photometry to study the star's rotational modulations and LCO Network of Robotic Echelle Spectrographs high-resolution spectra to measure the different spectral components within the integrated spectrum of the star, parameterized by three spectral components and their coverage fractions. We find AU Mic's surface has at least two spectral components: a T amb = ${4003}_{-14}^{+15}$ K ambient photosphere and cool spots that have a temperature of T spot = ${3003}_{-71}^{+63}$ K, covering a globally averaged area of 39% ± 4% which increases and decreases by 5.1% ± 0.3% from the average throughout a rotation. We also detect a third flux component with a filling factor less than 0.5% and a largely uncertain temperature between 8500 and 10,000 K that we attribute to flare flux not entirely omitted when time averaging the spectra. We include measurements of spot characteristics using a two-temperature model, which we find agree strongly with the three-temperature results. Our expanded use of various techniques to study starspots will help us better understand this system and may have applications for interpreting the transmission spectra for exoplanets transiting stars of a wide range of activity levels.

Keywords: M dwarf stars, Starspots, High resolution spectroscopy, Transits, Multi-color photometry, Pre-main sequence stars, Stellar rotation, Exoplanet atmospheres
An Ensemble Study of Turbulence in Extended QSO Nebulae at z ≈ 0.5─1. Turbulent motions in the circumgalactic medium play a critical role in regulating the evolution of galaxies, yet their detailed characterization remains elusive. Using two-dimensional velocity maps constructed from spatially extended [O II] and [O III] emission, Chen et al. measured the velocity structure functions (VSFs) of four quasar nebulae at z ≈ 0.5─1.1. One of these exhibits a spectacular Kolmogorov relation. Here, we carry out an ensemble study using an expanded sample incorporating four new nebulae from three additional quasi-stellar object (QSO) fields. The VSFs measured for all eight nebulae are best explained by subsonic turbulence revealed by the line-emitting gas, which in turn strongly suggests that the cool gas (T ∼ 104 K) is dynamically coupled to the hot ambient medium. Previous work demonstrates that the largest nebulae in our sample reside in group environments with clear signs of tidal interactions, suggesting that environmental effects are vital in seeding and enhancing the turbulence within the gaseous halos, ultimately promoting the formation of the extended nebulae. No discernible differences are observed in the VSF properties between radio-loud and radio-quiet QSO fields. We estimate the turbulent heating rate per unit volume, Q turb, in the QSO nebulae to be ∼10−26─10−22 erg cm−3 s−1 for the cool phase and ∼10−28─10−25 erg cm−3 s−1 for the hot phase. This range aligns with measurements in the intracluster medium and star-forming molecular clouds but is ∼103 times higher than the Q turb observed inside cool gas clumps on scales ≲1 kpc using absorption-line techniques. We discuss the prospect of bridging the gap between emission and absorption studies by pushing the emission-based VSF measurements to below ≈10 kpc.

Keywords: AGN host galaxies, Galaxy environments, Surveys, Quasars, Circumgalactic medium
Weak-lensing Analysis of the Complex Cluster Merger A746 with Subaru/Hyper Suprime-Cam. The galaxy cluster A746 (z = 0.214), featuring a double radio relic system, two isolated radio relics, a possible radio halo, disturbed V-shaped X-ray emission, and intricate galaxy distributions, is a unique and complex merging system. We present a weak-lensing analysis of A746 based on wide-field imaging data from Subaru/Hyper Suprime-Cam observations. The mass distribution is characterized by a main peak, which coincides with the center of the X-ray emission. At this main peak, we detect two extensions toward the north and west tracing the cluster galaxy and X-ray distributions. Despite the ongoing merger, our estimate of the A746 global mass M 500 = 4.4 ± 1.0 × 1014 M ☉ is consistent with the previous results from Sunyaev-Zel'dovich and X-ray observations. We conclude that reconciling the distributions of mass, galaxies, and intracluster medium with the double radio relic system and other radio features remains challenging.

Keywords: Galaxy clusters, Abell clusters, Weak gravitational lensing
Black Hole Spin Measurements in LMC X-1 and Cyg X-1 Are Highly Model Dependent. The black hole spin parameter, a *, was measured to be close to its maximum value of 1 in many accreting X-ray binaries. In particular, a * ≳ 0.9 was found in a number of studies of LMC X-1. These measurements were claimed to take into account both statistical and systematic uncertainties. We perform new measurements using a recent simultaneous observation by NICER and NuSTAR, providing a data set of high quality. We use the disk continuum method together with improved models for coronal Comptonization. With the standard relativistic disk model and optically thin Comptonization, we obtain values of a * similar to those obtained before. We then consider modifications to the standard model. Using a color correction of 2, we find a * ≈ 0.64–0.84. We then consider disks with dissipation in surface layers. To account for that, we assume the standard disk is covered by a warm and optically thick Comptonizing layer. Our model with the lowest χ 2 then yields ${a}_{* }\approx {0.40}_{-0.32}^{+0.41}$ . In order to test the presence of such effects in other sources, we also study an X-ray observation of Cyg X-1 by Suzaku in the soft state. We confirm the previous findings of a * &gt; 0.99 using the standard model, but then we find a weakly constrained ${a}_{* }\approx {0.82}_{-0.74}^{+0.16}$ when including an optically thick Comptonizing layer. We conclude that determinations of the spin using the continuum method can be highly sensitive to the assumptions about the disk structure.

Keywords: Accretion, X-ray binary stars, Rotating black holes, X-ray sources, Be stars, Astrophysical black holes
Absorption Troughs of Lyα Emitters in HETDEX. The Hobby–Eberly Telescope Dark Energy Experiment (HETDEX) is designed to detect and measure the redshifts of more than 1 million Lyα emitting galaxies (LAEs) 1.88 &lt; z &lt; 3.52. In addition to its cosmological measurements, these data enable studies of Lyα spectral profiles and the underlying radiative transfer. Using the roughly half a million LAEs in the HETDEX Data Release 3, we stack various subsets to obtain the typical Lyα profile for the z ∼ 2–3 epoch and to understand their physical properties. We find clear absorption wings around Lyα emission, which extend ∼2000 km s‑1 both redward and blueward of the central line. Using far-UV spectra of nearby (0.002 &lt; z &lt; 0.182) LAEs in the COS Legacy Archive Spectroscopic Survey treasury and optical/near-IR spectra of 2.8 &lt; z &lt; 6.7 LAEs in the Multi Unit Spectroscopic-Wide survey, we observe absorption profiles in both redshift regimes. Dividing the sample by volume density shows that the troughs increase in higher-density regions. This trend suggests that the depth of the absorption is dependent on the local density of objects near the LAE, a geometry that is similar to damped Lyα systems. Simple simulations of Lyα radiative transfer can produce similar troughs due to absorption of light from background sources by H I gas surrounding the LAEs.

Keywords: Lyman-alpha galaxies, Diffuse radiation, High-redshift galaxies
Observations Favor the Redshift-evolutionary L <SUB>X</SUB>–L <SUB>UV</SUB> Relation of Quasars from Copula. We compare, with data from quasars, Hubble parameter measurements, and Pantheon+ type Ia supernova, three different relations between X-ray luminosity (L X) and ultraviolet luminosity (L UV) of quasars. These three relations consist of the standard and two redshift-evolutionary L X–L UV relations, which are constructed, respectively, by considering a redshift-dependent correction to the luminosities of quasars and using the statistical tool copula. By employing the PAge approximation for a cosmological model–independent description of the cosmic background evolution and dividing the quasar data into the low-redshift and high-redshift parts, we find that the constraints on the PAge parameters from the low-redshift and high-redshift data, which are obtained with the redshift-evolutionary relations, are consistent with each other, while they are not when the standard relation is considered. If the data are used to constrain the coefficients of the relations and the PAge parameters simultaneously, then the observations support the redshift-evolutionary relations at more than 3σ. The Akaike and Bayes information criteria indicate that there is strong evidence against the standard relation and mild evidence against the redshift-evolutionary relation constructed by considering a redshift-dependent correction to the luminosities of quasars. This suggests that the redshift-evolutionary L X–L UV relation of quasars constructed from copula is favored by the observations.

Keywords: Cosmology, Quasars