Sazuna/UAT_keywords huggingface dataset:
Solar Eruptions Triggered by Flux Emergence below or near a Coronal Flux Rope. Observations have shown a clear association of filament/prominence eruptions with the emergence of magnetic flux in or near filament channels. Magnetohydrodynamic (MHD) simulations have been employed to systematically study the conditions under which such eruptions occur. These simulations to date have modeled filament channels as 2D flux ropes or 3D uniformly sheared arcades. Here we present MHD simulations of flux emergence into a more realistic configuration consisting of a bipolar active region containing a line-tied 3D flux rope. We use the coronal flux-rope model of Titov et al. as the initial condition and drive our simulations by imposing boundary conditions extracted from a flux emergence simulation by Leake et al. We identify three mechanisms that determine the evolution of the system: (i) reconnection displacing footpoints of field lines overlying the coronal flux rope, (ii) changes of the ambient field due to the intrusion of new flux at the boundary, and (iii) interaction of the (axial) electric currents in the preexisting and newly emerging flux systems. The relative contributions and effects of these mechanisms depend on the properties of the preexisting and emerging flux systems. Here we focus on the location and orientation of the emerging flux relative to the coronal flux rope. Varying these parameters, we investigate under which conditions an eruption of the latter is triggered.

Keywords: Solar physics, Solar coronal mass ejections, Solar magnetic flux emergence, Solar magnetic fields
Segregation and Collisions in Galactic Nuclei: Rates of Destructive Events Near a Supermassive Black Hole. The centers of galaxies host a supermassive black hole (SMBH) surrounded by a dense stellar cluster. The cluster is expected to develop mass segregation, in which gravitational scatterings among the stars cause heavier objects to sink closer to the central black hole, while lighter objects will tend to be overconcentrated in the outer regions. This work focuses on the implications of mass segregation on the different channels for violent destruction of stars in the cluster: tidal disruptions, gravitational-wave-driven inspirals and high-velocity destructive collisions between stars. All such events occur close to the central black hole, where the heavier objects congregate. The analysis is based on a simplified Monte Carlo simulation, which evolves a two-mass population in a cluster surrounding a Milky Way–like SMBH. The simulation is based on the single-mass scheme used by Sari &amp; Fragione and Balberg &amp; Yassur, which has been extended to allow for the dynamical friction effects typical of unequal-mass populations. The effects of mass segregation on the rates of the different destruction channels are analyzed self-consistently in the overall evolution of the cluster. Also considered are stars which are injected into the cluster after being disrupted from a binary system by the SMBH. Such stars are captured in the inner regions of the cluster, and so their orbital evolution, as well as their destruction rate, are therefore influenced by heavy objects that might be abundant in the vicinity of the SMBH.

Keywords: Supermassive black holes, Galactic center, Stellar dynamics, Transient sources, Analytical mathematics, Computational methods
Prospects for Detecting Gaps in Globular Cluster Stellar Streams in External Galaxies with the Nancy Grace Roman Space Telescope. Stellar streams form through the tidal disruption of satellite galaxies or globular clusters orbiting a host galaxy. Globular cluster streams are exciting since they are thin (dynamically cold) and therefore sensitive to perturbations from low-mass subhalos. Since the subhalo mass function differs depending on the dark matter composition, these gaps can provide unique constraints on dark matter models. However, current samples are limited to the Milky Way. With its large field of view, deep imaging sensitivity, and high angular resolution, the upcoming Nancy Grace Roman Space Telescope (Roman) presents a unique opportunity to increase the number of observed streams and gaps significantly. This paper presents a first exploration of the prospects for detecting gaps in streams in M31 and other nearby galaxies with resolved stars. We simulate the formation of gaps in a Palomar 5–like stream and generate mock observations of these gaps with background stars in M31 and foreground Milky Way stellar fields. We assess Roman's ability to detect gaps out to 10 Mpc through visual inspection and with the gap-finding tool FindTheGap. We conclude that gaps of ≈1.5 kpc in streams that are created from subhalos of masses ≥5 × 106 M ⊙ are detectable within a 2–3 Mpc volume in exposure times of 1000 s to 1 hr. This volume contains ≈150 galaxies, including ≈eight galaxies with luminosities &gt;109 L ⊙. Large samples of stream gaps in external galaxies will open up a new era of statistical analyses of gap characteristics in stellar streams and help constrain dark matter models.

Keywords: Stellar streams, Galaxy structure, Space telescopes, Andromeda Galaxy, Dark matter
Black Hole Mass and Eddington-ratio Distributions of Less-luminous Quasars at z ∼ 4 in the Subaru Hyper Suprime-Cam Wide Field. We investigate the black hole mass function (BHMF) and Eddington-ratio distribution function (ERDF) of broad-line active galactic nuclei (AGNs) at z = 4, based on a sample of 52 quasars with i &lt; 23.2 at 3.50 ≤ z ≤ 4.25 from the Hyper Suprime-Cam Subaru Strategic Program S16A-Wide2 data set, and 1462 quasars with i &lt; 20.2 in the same redshift range from the Sloan Digital Sky Survey data release 7 quasar catalog. Virial black hole (BH) masses of quasars are estimated using the width of the CIV 1549 Å line and the continuum luminosity at 1350 Å. To obtain the intrinsic broad-line AGN BHMF and ERDF, we correct for the incompleteness in the low-mass and/or low-Eddington-ratio ranges caused by the flux-limited selection. The resulting BHMF is constrained down to $\mathrm{log}{M}_{\mathrm{BH}}/{M}_{\odot }\sim 7.5$ . In comparison with broad-line AGN BHMFs at z ∼ 2 in the literature, we find that the number density of massive SMBHs peaks at higher redshifts, consistent with the downsizing evolutionary scenario. Additionally, the resulting ERDF shows a negative dependence on BH mass, suggesting more massive SMBHs tend to accrete at lower-Eddington ratios at z = 4. With the derived intrinsic broad-line AGN BHMF, we also evaluate the active fraction of broad-line AGNs among the entire SMBH population at z = 4. The resulting active fraction may suggest a positive dependence on BH mass. Finally, we examine the time evolution of broad-line AGN BHMF between z = 4 and 6 through solving the continuity equation. The results suggest that the broad-line AGN BHMFs at z = 4–6 only show evolution in their normalization, but with no significant changes in their shape.

Keywords: Supermassive black holes, Active galaxies, High-redshift galaxies, Galaxy evolution
Soft X-Ray Energy Spectra in the Wide-field Galactic Disk Area Revealed with HaloSat. We analyzed data from HaloSat observations for five fields in the Galactic disk located far away from the Galactic center (135° &lt; l &lt; 254°) to understand the nature of soft X-ray energy emission in the Galactic disk. The fields have 14° diameter and were selected to contain no significant high-flux X-ray sources. All five HaloSat soft X-ray energy spectra (0.4─7 keV with energy resolution of &lt; 100 eV below 1 keV) show a possibility of the presence of unresolved high-temperature plasma in the Galactic disk (UHTPGD) with a temperature of 0.8─1.0 keV and an emission measure of (8─11) × 10−4 cm−6 pc in addition to the soft X-ray diffuse background components mainly studied at higher Galactic latitudes (solar wind charge exchange emission, Local Hot Bubble, Milky Way halo emission, and the cosmic X-ray background). This suggests that the UHTPGD is present across the whole Galactic disk. We also observed UHTPGD emission in a region with no bright sources in an XMM-Newton field contained within one of the HaloSat fields. The temperature and emission measure are consistent with those measured with HaloSat. Moreover, the stacked spectra of the X-ray pointlike sources and near-infrared-identified point sources such as stars in the XMM-Newton field also show a spectral feature similar to the UHTPGD emission. This suggests that the UHTPGD may partly originate from pointlike sources such as stars.

Keywords: X-ray astronomy, Galaxy stellar disks, Galaxy disks, Diffuse x-ray background, Milky Way Galaxy
On the Evolutionary History of a Simulated Disk Galaxy as Seen by Phylogenetic Trees. Phylogenetic methods have long been used in biology and more recently have been extended to other fields—for example, linguistics and technology—to study evolutionary histories. Galaxies also have an evolutionary history and fall within this broad phylogenetic framework. Under the hypothesis that chemical abundances can be used as a proxy for the interstellar medium's DNA, phylogenetic methods allow us to reconstruct hierarchical similarities and differences among stars—essentially, a tree of evolutionary relationships and thus history. In this work, we apply phylogenetic methods to a simulated disk galaxy obtained with a chemodynamical code to test the approach. We found that at least 100 stellar particles are required to reliably portray the evolutionary history of a selected stellar population in this simulation, and that the overall evolutionary history is reliably preserved when the typical uncertainties in the chemical abundances are smaller than 0.08 dex. The results show that the shapes of the trees are strongly affected by the age–metallicity relation, as well as the star formation history of the galaxy. We found that regions with low star formation rates produce shorter trees than regions with high star formation rates. Our analysis demonstrates that phylogenetic methods can shed light on the process of galaxy evolution.

Keywords: Interdisciplinary astronomy, Galaxy abundances, Galaxy stellar content, Galaxy chemical evolution
First High-resolution Spectroscopy of X-Ray Absorption Lines in the Obscured State of NGC 5548. Multiwavelength spectroscopy of NGC 5548 revealed remarkable changes due to the presence of an obscuring wind from the accretion disk. This broadened our understanding of obscuration and outflows in active galactic nuclei. Swift monitoring of NGC 5548 shows that over the last 10 yr, the obscuration has gradually declined. This provides a valuable opportunity for analyses that have not been feasible before because of too much obscuration. The lowered obscuration, together with the high-energy spectral coverage of Chandra HETG, facilitates the first study of X-ray absorption lines in the obscured state. The comparison of the lines (Mg XI, Mg XII, Si XIII, and Si XIV) between the new and historical spectra reveals interesting changes, most notably the He-like absorption being significantly diminished in 2022. Our study finds that the changes are caused by an increase in both the ionization parameter and the column density of the warm-absorber outflow in the obscured state. This is contrary to the shielding scenario that is evident in the appearance of the UV lines, where the inner obscuring wind shields outflows that are farther out, thus lowering their ionization. The X-ray absorption lines in the HETG spectra appear to be unaffected by the obscuration. The results suggest that the shielding is complex because various components of the ionized outflow are affected differently. We explore various possibilities for the variability behavior of the X-ray absorption lines and find that the orbital motion of a clumpy ionized outflow traversing our line of sight is the most likely explanation.

Keywords: High resolution spectroscopy, Seyfert galaxies, X-ray active galactic nuclei, Quasar absorption line spectroscopy
Investigating the Star Formation Rates of Active Galactic Nucleus Hosts Relative to the Star-forming Main Sequence. A fundamental question in galaxy and black hole evolution remains how galaxies and their supermassive black holes have evolved together over cosmic time. Specifically, it is still unclear how the position of X-ray active galactic nucleus (AGN) host galaxies with respect to the star-forming main sequence (MS) may change with the X-ray luminosity (L X) of the AGN or the stellar mass (M ⋆) of the host galaxy. We use data from the XMM-Spitzer Extragalactic Representative Volume Survey (XMM-SERVS) to probe this issue. XMM-SERVS is covered by the largest medium-depth X-ray survey (with superb supporting multiwavelength data) and thus contains the largest sample to date for study. To ensure consistency, we locally derive the MS from a large reference galaxy sample. In our analysis, we demonstrate that the turnover of the galaxy MS does not allow reliable conclusions to be drawn for high-mass AGNs, and we establish a robust safe regime where the results do not depend upon the choice of MS definition. Under this framework, our results indicate that less massive AGN host galaxies ( $\mathrm{log}{M}_{\star }\sim 9.5\mbox{--}10.5\,{M}_{\odot }$ ) generally possess enhanced star formation rates compared to their normal-galaxy counterparts while the more massive AGN host galaxies ( $\mathrm{log}{M}_{\star }\sim 10.5\mbox{--}11.5\,{M}_{\odot }$ ) lie on or below the star-forming MS. Further, we propose an empirical model for how the placement of an AGN with respect to the MS (SFRnorm) evolves as a function of both M ⋆ and L X.

Keywords: AGN host galaxies, X-ray active galactic nuclei, Galaxies
Heating of the Atmospheres of Short-orbit Exoplanets by Their Rapid Orbital Motion through an Extreme Space Environment. Exoplanets with short orbit periods reside very close to their host stars. They transition very rapidly between different sectors of the circumstellar space environment along their orbit, leading to large variations of the magnetic field in the vicinity of the planet on short timescales. This rapid change of the magnetic flux through the conducting and resistive layer of the planetary upper atmosphere may drive currents that dissipate in the form of Joule heating (JH). Here, we estimate the amount of JH dissipation in the upper atmosphere of Trappist-1e, and two hypothetical planets orbiting the Sun in close-in orbits. We find that the rapid orbital motion could drive a significant amount of atmospheric heating and could significantly affect the planetary atmosphere escape rate. Thus, the process should be accounted for when studying the long-term evolution of exoplanetary atmospheres.

Keywords: Planetary ionospheres, Exoplanet atmospheres, Exoplanet atmospheric evolution
Amplification and Saturation of Turbulent Magnetic Fields in Collapsing Primordial Gas Clouds. Recent numerical studies suggest that magnetic fields play an important role in primordial star formation in the early Universe. However, the detailed evolution of the magnetic field in the collapse phase still has uncertainties because of the complicated physics associated with turbulence in a collapsing magnetized system. Here, we perform a suite of numerical MHD simulations that follow the collapse of magnetized, turbulent primordial gas clouds to investigate the evolution of the magnetic field associated with the turbulence, assuming a polytropic equation of state with exponent γ eff and with various numerical resolutions. In addition, we generalize the analytic theory of magnetic field growth/saturation so that it can deal with various exponents γ eff and turbulence energy spectra. We find that the numerical results are well reproduced by the theory for various γ eff through the collapse phase during the formation of the first stars. The magnetic field is eventually amplified by a factor of 1012–1015 due to kinematic and nonlinear turbulent dynamo effects and reaches 3%–100% of the equipartition level, depending on γ eff. We also find that the transition between the kinematic and nonlinear stages can be analytically estimated. These results indicate that the strong magnetic field accompanied by supersonic turbulence is a general property and suggest that it can play a crucial role in the formation of the first stars.

Keywords: Early universe, Population III stars, Hydrodynamics, Magnetohydrodynamical simulations, Magnetic fields, Collapsing clouds
Three-dimensional Velocity Diagnostics to Constrain the Type Ia Origin of Tycho's Supernova Remnant. While various methods have been proposed to disentangle the progenitor system for Type Ia supernovae, their origin is still unclear. A circumstellar environment is key to distinguishing between the double-degenerate and single-degenerate (SD) scenarios since a dense wind cavity is expected only in the case of the SD system. We perform spatially resolved X-ray spectroscopy of Tycho's supernova remnant (SNR) with XMM-Newton and reveal the three-dimensional velocity structure of the expanding shock-heated ejecta measured from Doppler-broadened lines of intermediate-mass elements. Obtained velocity profiles are fairly consistent with those expected from a uniformly expanding ejecta model near the center, whereas we discover a rapid deceleration (∼4000 to ∼1000 km s−1) near the edge of the remnant in almost every direction. The result strongly supports the presence of a dense wall entirely surrounding the remnant, which is confirmed also by our hydrodynamical simulation. We thus conclude that Tycho's SNR is likely of SD origin. Our new method will be useful for understanding progenitor systems of Type Ia SNRs in the era of high-angular/energy-resolution X-ray astronomy with microcalorimeters.

Keywords: Supernova remnants
Multispacecraft Energetic Particle Enhancements Associated with a Single Corotating Interaction Region. The radial evolution of particles accelerated at corotating interaction regions (CIRs) is not fully understood, particularly the distance range over which this particle acceleration occurs and how the energy spectra are modulated by transport through the inner heliosphere. Here, we present observations of energetic proton enhancements associated with a CIR observed by Parker Solar Probe on 2021 April 25 during the inbound leg of its orbit near ∼46 R s (∼0.21 au). The CIR is identified at additional spacecraft (Solar Terrestrial Relations Observatory, STEREO-A; Solar Orbiter, SolO; and Advanced Composition Explorer, ACE) using a corotation time delay estimation, and energetic proton spectra from each spacecraft are compared. We find that (1) energetic protons are observed near 46 R s streaming sunward ahead of the CIR; (2) the CIR persists for at least one solar rotation and the corresponding energetic proton enhancements are observed at STEREO-A, SolO, and ACE; and (3) the proton energy spectrum is steeper near the Sun and hardens near 1 au. This observation presents the closest in situ energetic particle observation of a CIR to the Sun ever recorded. Results presented here suggest that particles can be accelerated by CIR structures within 1 au and these particles can penetrate very deep into the inner heliosphere.

Keywords: Interplanetary particle acceleration, Corotating streams
On the Particle Acceleration Mechanisms in a Double Radio Relic Galaxy Cluster, Abell 1240. We present a 368 ks deep Chandra observation of Abell 1240, a binary merging galaxy cluster at a redshift of 0.195 with two brightest cluster galaxies that may have passed each other 0.3 Gyr ago. Building upon previous investigations involving Giant Metrewave Radio Telescope, Very Large Array, and LOFAR data, our study focuses on two prominent extended radio relics at the northwest (NW) and southeast (SE) of the cluster core. By leveraging the high-resolution Chandra imaging, we have identified two distinct surface-brightness edges at ∼1 Mpc and 1.2 Mpc NW and SE of the cluster center, respectively, coinciding with the outer edges of both relics. Our temperature measurements suggest the edges to be shock front edges. The Mach numbers, derived from the gas density jumps, yield ${{ \mathcal M }}_{\mathrm{SE}}$ = ${1.49}_{-0.24}^{+0.22}$ for the SE shock and ${{ \mathcal M }}_{\mathrm{NW}}$ = ${1.41}_{-0.19}^{+0.17}$ for the NW shock. Our estimated Mach numbers are remarkably smaller compared to those derived from radio observations ( ${{ \mathcal M }}_{\mathrm{SE}}$ = 2.3 and ${{ \mathcal M }}_{\mathrm{NW}}$ = 2.4), highlighting the prevalence of a reacceleration scenario over direct acceleration of electrons from the thermal pool. Furthermore, we compare the observed temperature profiles across both shocks with those of predictions from collisional versus collisionless models. Both shocks favor the Coulomb collisional model, but we could not rule out a purely collisionless model due to pre-shock temperature uncertainties.

Keywords: Galaxy clusters
A Physically Motivated Framework to Compare Pair Fractions of Isolated Low- and High-mass Galaxies across Cosmic Time. Low-mass galaxy pair fractions are understudied, and it is unclear whether low-mass pair fractions evolve in the same way as more massive systems over cosmic time. In the era of JWST, Roman, and Rubin, selecting galaxy pairs in a self-consistent way will be critical to connect observed pair fractions to cosmological merger rates across all mass scales and redshifts. Utilizing the Illustris TNG100 simulation, we create a sample of physically associated low-mass (108 &lt; M * &lt; 5 × 109 M ⊙) and high-mass (5 × 109 &lt; M * &lt; 1011 M ⊙) pairs between z = 0 and 4.2. The low-mass pair fraction increases from z = 0 to 2.5, while the high-mass pair fraction peaks at z = 0 and is constant or slightly decreasing at z &gt; 1. At z = 0 the low-mass major (1:4 mass ratio) pair fraction is 4× lower than high-mass pairs, consistent with findings for cosmological merger rates. We show that separation limits that vary with the mass and redshift of the system, such as scaling by the virial radius of the host halo (r sep &lt; 1R vir), are critical for recovering pair fraction differences between low-mass and high-mass systems. Alternatively, static physical separation limits applied equivalently to all galaxy pairs do not recover the differences between low- and high-mass pair fractions, even up to separations of 300 kpc. Finally, we place isolated mass analogs of Local Group galaxy pairs, i.e., Milky Way (MW)–M31, MW–LMC, LMC–SMC, in a cosmological context, showing that isolated analogs of LMC–SMC-mass pairs and low-separation (&lt;50 kpc) MW–LMC-mass pairs are 2–3× more common at z ≳ 2–3.

Keywords: Local Group, Interacting galaxies, Galaxy pairs, Galaxy evolution