Sazuna/UAT_keywords huggingface dataset:
COSMOS2020: Disentangling the Role of Mass and Environment in Star Formation Activity of Galaxies at 0.4 &lt; z &lt; 4. The role of internal and environmental factors in the star formation activity of galaxies is still a matter of debate, in particular at higher redshifts. Leveraging the most recent release of the COSMOS catalog, COSMOS2020, as well as density measurements from our previous study, we disentangle the impact of environment and stellar mass on the star formation rate (SFR) and specific SFR (sSFR) of a sample of ∼210,000 galaxies within a redshift range of 0.4 &lt; z &lt; 4, and present our findings in three cosmic epochs: (1) out to z ∼ 1, the average SFR and sSFR decline in extremely dense environments and at the high-mass end of the distribution, which is mostly due to the presence of the massive quiescent population; (2) at 1 &lt; z &lt; 2, the environmental dependence diminishes, while mass is still the dominant factor in star formation activity; and (3) beyond z ∼ 2, our sample is dominated by star-forming galaxies and we observe a reversal of the trends seen in the local Universe—the average SFR increases with increasing environmental density. Our analysis shows that both environmental and mass quenching efficiencies increase with stellar mass at all redshifts, with mass being the dominant quenching factor in massive galaxies compared to environmental effects. At 2 &lt; z &lt; 4, negative values of environmental quenching efficiency suggest that the fraction of star-forming galaxies in dense environments exceeds that in less-dense regions, likely due to the greater availability of cold gas, higher merger rates, and tidal effects that trigger star formation activity.

Keywords: Galaxy environments, Galaxy quenching, Galaxy evolution, Large-scale structure of the universe
Switchback Patches Evolve into Microstreams via Magnetic Relaxation. Switchbacks, defined as Alfvénic reversals in magnetic field polarity, can dissipate their magnetic energy with heliocentric distance. To further investigate this, two distinct solar wind parcels tracing back to a similar solar source region were examined during a radial alignment between Parker Solar Probe (@25.8RS) and Solar Orbiter (@152RS). The one caveat was that the two probes were located on opposite sides of the heliospheric current sheet during the alignment. The two parcels contained a multitude of switchbacks—the parcel closer to the Sun was characterized as a switchback patch (SBP), where background proton velocity (vp ) is comparable to the pristine solar wind (v sw), while the parcel farther from the Sun showed characteristics attributable to a microstream (MS; v  p  &gt; v sw). It was found that (1) MS contains, on average, 30% fewer switchbacks than SBP, and (2) dynamic and thermal pressures decreased by up to 20% across switchback boundaries in SBP and relatively unchanged in MS. Magnetic relaxation can explain the lower number of switchbacks in MS compared to SBP. Switchback relaxation inside SBP can, in turn, accelerate plasma inside SBP over time and heliocentric distance, thus resulting in vp &gt; v sw in MS. Therefore, it is hypothesized that magnetic relaxation of switchbacks may cause SBPs to evolve into MSs over time and heliocentric distance.

Keywords: The Sun, Solar wind, Solar magnetic reconnection
Signatures of Massive Black Hole Merger Host Galaxies from Cosmological Simulations. II. Unique Stellar Kinematics in Integral Field Unit Spectroscopy. Secure methods for identifying the host galaxies of individual massive black hole (MBH) binaries and mergers detected by gravitational-wave experiments such as the Laser Interferometer Space Antenna and pulsar timing arrays are currently lacking, but will be critical to a variety of science goals. Recently, in Bardati et al., we used the Romulus25 cosmological simulation to show that MBH merger host galaxies have unique morphologies in imaging, due to their stronger bulges. Here, we use the same sample of simulated MBH merger host galaxies to investigate their stellar kinematics, as probed by optical integral field unit (IFU) spectroscopy. We perform stellar population synthesis and dust radiative transfer to generate synthetic 3D optical spectral data cubes of each simulated galaxy, and produce mock stellar kinematic maps. Based on a linear discriminant analysis of a combination of kinematic parameters derived from these maps, we show that this approach can identify MBH binary and merger host galaxies with accuracies that increase with chirp mass and mass ratio. For mergers with high chirp masses (≳108.2 M ⊙) and high mass ratios (≳0.5), the accuracies reach ≳85%, and their host galaxies are uniquely characterized by slower rotation and stronger stellar kinematic misalignments. These kinematic properties are commonly associated with massive early-type galaxies that have experienced major mergers, and naturally act as signposts for MBH binaries and mergers with high chirp masses and mass ratios. These results suggest that IFU spectroscopy should also play a role in telescope follow-up of future MBH binaries and mergers detected in gravitational waves.

Keywords: Black holes, Gravitational waves, Radiative transfer simulations, N-body simulations, Galaxies
Solar Wind–Magnetosphere Coupling by the Kelvin–Helmholtz Instability at Mercury. The Kelvin–Helmholtz instability (KHI) has been considered important in the energy transfer and momentum coupling between the solar wind and planetary magnetospheres. To explore this issue, we employ a two-dimensional magnetohydrodynamic simulation to study the nonlinear evolution of the KHI at Mercury's magnetopause using the parameters derived from a global hybrid simulation of MESSENGER's first flyby of Mercury. Due to the absence of comprehensive plasma observations of Mercury's magnetosphere, two scenarios are considered: one with a heavily loaded magnetosphere and the other with a weakly loaded magnetosphere, to demonstrate the development of the KHI under distinct levels of magnetospheric plasma density. Our results indicate that the KHI with a heavily loaded magnetosphere leads to a significantly more turbulent magnetopause and grows into the nonlinear fast-mode plane waves expanding away from the magnetopause. The momentum and energy flux quantified from our simulations reveal that the KHI with a heavily loaded magnetosphere can efficiently transport momentum and energy away from the magnetopause in the presence of the fast-mode plane waves. In the cases with a heavily loaded magnetosphere, observed in the inner magnetosphere, the momentum flux can reach 10‑3 nPa, i.e., about 0.5% of the initial solar-wind dynamic pressure; the energy flux can be   and the energy density is about 1.5%–3.0% of the initial solar-wind energy. In the cases with a very thin magnetosphere, observed away from the magnetopause, the momentum flux is negligible and the energy flux is smaller without the presence of the fast-mode plane waves in the magnetosphere.

Keywords: Space plasmas, Solar wind, Solar-terrestrial interactions, Mercury (planet), Planetary magnetospheres, Magnetohydrodynamical simulations
Evolutionary Dynamics of Counterhelical Magnetic Flux Ropes. Upon interaction, a pair of magnetic flux ropes can merge to form a new pair, each consisting of opposite helicity along their axis. Magnetic helicity along such new structures may annihilate and release the energy of the azimuthal magnetic field. In this study, we model the deformation dynamics of such structures within the solar wind at 1 au. The perturbation front of deformation propagates along the rope axis at approximately the Alfvén speed. However, the process of annihilating 90% of the azimuthal components is much slower and is affected by the screw pitch of the magnetic field. Such a deformation process causes the plasma in the transition region between the two opposite chiralities to spin about the rope axis. The resulting plasma heating is discussed accordingly. Our results provide insights for estimating the lifetimes of such flux ropes, facilitating observational efforts to identify them. This process may also apply to the behavior of magnetic flux ropes in other space and astronomical plasma environments.

Keywords: Space plasmas, Solar active region magnetic fields, Interplanetary magnetic fields
Binary Stars Approaching Supermassive Black Holes: Tidal Breakup, Double Stellar Disruptions, and Stellar Collision. In galactic centers, stars and binaries can be injected into low-angular-momentum orbits, resulting in close encounters with the central supermassive black hole (SMBH). Previous works have shown that under different conditions, such close encounters can lead to the breakup of the binary, disruptions of both stars, and collision between the stars. We use three-body scattering experiments to characterize these different outcomes for a range of system parameters, such as β  b , the ratio of the binary tidal radius to the pericenter distance r  p  to the SMBH, and the compactness of the binary. We focus on stellar collisions, which occur for a range of β  b s, with a few to tens of percent probabilities (depending on the compactness of the binary). In gentle encounters (β  b  ≲ 1), stellar collisions occur after the pericenter passage, and the merger remnants are typically ejected from the SMBH at a small velocity. In deep encounters (β  b  ≳ 1), collisions occur near the pericenter, with the impact velocity a few times the escape velocity of the star, and the merger remnants are typically bound to the SMBH. We suggest that stellar collisions induced by binary–SMBH encounters may produce exotic stars in galactic centers, trigger accretion flares onto the SMBH due to the mass loss, and result in bound merger remnants causing repeated partial tidal disruption events.

Keywords: Tidal disruption, Binary stars, Black holes, Stellar dynamics
Metal-strong Inflows at the Outer-galactic-scale of a Quasar. We present an analysis of the absorption-line system in the Very Large Telescope/Ultraviolet and Visual Echelle Spectrograph spectrum at a redshift of z a = 3.1448 associated with the quasar SDSS J122040.23+092326.96, whose systematic redshift is z e = 3.1380 ± 0.0007, measured from the Hβ+[O III] emission lines in our newly acquired NIR P200/TripleSpec data. This absorbing system, detected in numerous absorption lines, including the N V, N III, C IV, C III, Si IV, Si III, and H I Lyman series, can be resolved into seven kinematic components with redshifted velocities ranging from 200 to 900 km s−1. The high-ionization N V doublet detected and the rather narrow Lyman series measured (b ≍ 14 km s−1) suggest that the absorption gas is photoionized, possibly by the quasar. A low density is inferred by the fact that N III λ989.80 is significantly detected while N III*λ991.57 ( ) is undetectably weak. A firm lower limit of a solar value to the abundance of the gas can be set based on the measurements of Si IV and H I column densities, as first proposed by F. Hamann. Detailed photoionization simulations indicate that T1, and possibly the absorber as a whole, has metallicities of Z ∼ 1.5 − 6.0 Z ☉, and is located at ∼15 kpc from the quasar nucleus. The metal-strong absorption inflows at the outskirt of the quasar host galaxy most likely originated in situ and were driven by stellar processes, such as stellar winds and/or supernova explosions. Such a relatively rare system may hold important clues to understanding the baryonic cycling of galaxies, and more cases could be picked out using relatively strong Si IV and weak Lyman absorption lines.

Keywords: Metallicity, Active galactic nuclei, Quasar absorption line spectroscopy, Quasars
Rotational Velocities and Radii Estimates of Low-mass Pre-main-sequence Stars in NGC 2264. Investigating the angular momentum evolution of pre-main-sequence (PMS) stars provides important insight into the interactions between Sun-like stars and their protoplanetary disks, and the timescales that govern disk dissipation and planet formation. We present projected rotational velocities (v sin i values) of 254 T Tauri stars (TTSs) in the ∼3 Myr old open cluster NGC 2264, measured using high-dispersion spectra from the WIYN 3.5 m telescope's Hydra instrument. We combine these with literature values of temperature, rotation period, luminosity, disk classification, and binarity. We find some evidence that weak-lined TTSs may rotate faster than their classical TTS counterparts and that stars in binary systems may rotate faster than single stars. We also combine our v sin i measurements with rotation period to estimate the projected stellar radii of our sample stars, and then use a maximum likelihood modeling technique to compare our radii estimates to predicted values from stellar evolution models. We find that starspot-free models tend to underestimate the radii of the PMS stars at the age of the cluster, while models that incorporate starspots are more successful. We also observe a mass dependence in the degree of radius inflation, which may be a result of differences in the birth-line location on the HR diagram. Our study of NGC 2264 serves as a pilot study for analysis methods to be applied to four other clusters ranging in age from 1‑14 Myr, which is the timescale over which protoplanetary disks dissipate and planetary systems begin to form.

Keywords: Early stellar evolution, Weak-line T Tauri stars, Classical T Tauri stars, T Tauri stars, Young stellar objects, Pre-main sequence stars, Low mass stars, Stellar rotation
New Radio Observations of the Supernova Remnant CTA 1. We present new radio images of the supernova remnant (SNR) CTA 1 at 1420 and 408 MHz, and in the 21 cm line of H I observed with the Dominion Radio Astrophysical Observatory Synthesis Telescope and at 1420 MHz observed with the Effelsberg 100 m telescope. We confirm previously described continuum features and elaborate further on filamentary features identified using the high-resolution (1') maps from these new observations. We investigate the abrupt change in sign of rotation measure (RM) across the SNR, using the linear polarization observations in the four bands around 1420 MHz. Following X. H. Sun et al.'s (2011) investigation, we both confirm that the distribution of signs of the RMs for extragalactic sources in the area appears to match that of the shell, as well as combine the data from the four bands to estimate the relative depolarization and the intrinsic rotation measure of the SNR. We do not conclusively reject X. H. Sun et al.'s (2011) claim of a Faraday screen in the foreground causing the distribution of RMs that we observe; however, we do suggest an alternative explanation of a swept-up stellar wind from the progenitor star with a toroidal magnetic field. Finally, we expand on the analysis of the H I observations by applying the Rolling Hough Transform to isolate filamentary structure and better identify H I emission with the SNR. Further constraining the H I velocity channels associated with CTA 1, we use more recent Galactic rotation curves to calculate an updated kinematic distance of 1.09 ± 0.2 kpc.

Keywords: Supernova remnants
A High-resolution Simulation of Protoplanetary Disk Turbulence Driven by the Vertical Shear Instability. A high-resolution fourth-order Padé scheme is used to simulate locally isothermal 3D disk turbulence driven by the vertical shear instability (VSI) using 268.4 M points. In the early nonlinear period of axisymmetric VSI, angular momentum transport by vertical jets creates correlated N-shaped radial profiles of perturbation vertical and azimuthal velocity. This implies dominance of positive perturbation vertical vorticity layers and a recently discovered angular momentum staircase with respect to radius (r). These features are present in 3D in a weaker form. The 3D flow consists of vertically and azimuthally coherent turbulent shear layers containing small vortices with all three vorticity components active. Previously observed large persistent vortices in the interior of the domain driven by the Rossby wave instability are absent. We speculate that this is due to a weaker angular momentum staircase in 3D in the present simulations compared to a previous simulation. The turbulent viscosity parameter α(r) increases linearly with r. At intermediate resolution, the value of α(r) at midradius is close to that of a previous simulation. The specific kinetic energy spectrum with respect to radial wavenumber has a power-law region with exponent −1.84, close to the value −2 expected for shear layers. The spectrum with respect to azimuthal wavenumber has a −5/3 region and lacks a −5 region reported in an earlier study. Finally, it is found that axisymmetric VSI has artifacts at late times, including a very strong angular momentum staircase, which in 3D is present weakly in the disk's upper layers.

Keywords: Accretion, Hydrodynamical simulations, Protoplanetary disks, Hydrodynamics
Separating Repeating Fast Radio Bursts Using the Minimum Spanning Tree as an Unsupervised Methodology. Fast radio bursts (FRBs) represent one of the most intriguing phenomena in modern astrophysics. However, their classification into repeaters and nonrepeaters is challenging. Here, we present the application of the graph theory minimum spanning tree (MST) methodology as an unsupervised classifier of repeater and nonrepeater FRBs. By constructing MSTs based on various combinations of variables, we identify those that lead to MSTs that exhibit a localized high density of repeaters at each side of the node with the largest betweenness centrality. Comparing the separation power of this methodology against known machine learning methods, and with the random expectation results, we assess the efficiency of the MST-based approach to unravel the physical implications behind the graph pattern. We finally propose a list of potential repeater candidates derived from the analysis using the MST.

Keywords: Astronomy data analysis, Radio transient sources
Cloud Crushing and Dissipation of Uniformly Driven Adiabatic Turbulence in Circumgalactic Media. The circumgalactic medium (CGM) is responsive to kinetic disruptions generated by nearby astrophysical events. In this work, we study the saturation and dissipation of turbulent hydrodynamics within the CGM through an extensive array of 252 numerical simulations with proper cooling mechanisms and a large parameter space spanning average gas density, metallicity, and turbulence driving strength. A dichotomy emerges in the dynamics dissipation behaviors upon turbulence driving turnoff. Hot and subsonic disturbances are characterized by weak compression and slow dissipation, while warm and supersonic turbulences are marked by significant compression shocks and subsequent rapid cooling. In the supersonic cases, the kinetic energy decay is divided into a rate-limiting phase of shock dissipation and a comparatively swift phase of thermal dissipation, predominantly occurring within the overdense regions. Dense clouds are crushed on relatively brief timescales of ∼30–100 Myr, depending on turbulence driving strength but independent from average gas density. This independence is in spite of the complex interplay between the kinetics and thermodynamics of dissipation. The brevity of such timescales relative to typical dynamical timescales within the CGM suggests turbulent clouds must be cotemporal with turbulence driving sources such as cool accretion flows or feedback from the interstellar medium. Quantitative results from this work contribute a novel data set of dissipation timescales that incorporates thermodynamics and radiative cooling in an area of study typically focused on kinematics, which may serve as a valuable asset for forthcoming simulations that aim to explore gas dynamics on galactic and cosmological scales.

Keywords: Collapsing clouds, Hydrodynamical simulations, Extragalactic astronomy, Circumgalactic medium
Deep Chandra Observations of NGC 5728. III. Probing the High-resolution X-Ray Morphology and Multiphase Interstellar Medium Interactions in the Circumnuclear Region. We present a detailed imaging analysis of 260 ks of subarcsecond resolution Chandra (ACIS-S) observations of the nearby Seyfert 2 galaxy NGC 5728. Our study focuses on the bright and diffuse soft X-ray emission within the galaxy's inner ∼1 kpc. By comparing the X-ray emission across different energy bands, we identify localized variations in the absorbing column and emission processes. We observe more X-ray absorption in the direction perpendicular to the bicone, which is co-located with an inner warped CO disk in the galaxy. The innermost region, which shows the strongest excess of hard X-ray emission, is spatially coincident with the CO (2─1) emission from the Atacama Large Millimeter/submillimeter Array and dusty spirals we find in a Hubble Space Telescope V − H color map. We detect soft extended emission associated with the circumnuclear star-forming ring at ∼1 kpc, suggestive of hot gas with kT = 0.44 keV. We derive measurements for the hot gas mass, M = 7.9 × 105 M ⊙, pressure, p = 2.0 × 10−10 dyne cm−2, and cooling times, τ  c  = 193.2 Myr. In the vicinity of the star-forming ring, we detect two X-ray point sources, with soft X-ray spectra, and 0.3─7 keV luminosities L ∼ 8 × 1038 erg s−1. These properties suggest X-ray binaries.

Keywords: AGN host galaxies, Seyfert galaxies
Interpolation Techniques for Reconstructing Galactic Faraday Rotation. The line-of-sight structure of the Galactic magnetic field (GMF) can be studied using Faraday rotation measure (RM) grids. We analyze how the choice of interpolation kernel can affect the accuracy and reliability of reconstructed RM maps. We test the following kernels: inverse distance weighting (IDW), natural neighbor interpolation (NNI), inverse multiquadric interpolation (IM), thin-plate spline interpolation (TPS), and a Bayesian rotation measure sky (BRMS); all techniques were tested on two simulated Galactic foreground RMs (one assuming the GMF has patchy structures and the other assuming it has filamentary structures) using magnetohydrodynamic simulations. Both foregrounds were sampled to form RM grids with densities of ∼40 sources deg‑2 and area ∼144 deg2. The techniques were tested on data sets with different noise levels and Gaussian random extragalactic RM contributions. The data set that most closely emulates expected data from current surveys, such as the POlarization Sky Survey of the Universe's Magnetism (POSSUM), had extragalactic contributions and a noise standard deviation of ∼1.5 rad m‑2. For this data set, the accuracy of the techniques for the patchy structures is ranked from best to worst as BRMS, NNI, TPS, IDW, and IM; in the filamentary simulated foreground, the ordering is BRMS, NNI, TPS, and IDW. IDW is the most computationally expensive technique, while TPS and IM are the least expensive. BRMS and NNI have the same, intermediate computational cost. This analysis lays the groundwork for Galactic RM studies with large radio polarization sky surveys, such as POSSUM.

Keywords: Radio astronomy, Astrostatistics, Milky Way magnetic fields