Sazuna/UAT_keywords huggingface dataset:
Formation of Polar Crown Filament Magnetic Fields by Supergranular Helicity Injection. To understand the magnetic fields of the polar crown filaments (PCFs) at high latitudes near polar regions of the Sun, we perform magnetofrictional numerical simulations on the long-term magnetic evolution of bipolar fields with roughly east–west polarity inversion lines (PILs) in a 3D spherical wedge domain near polar regions. The Coriolis-effect-induced vortical motions at the boundaries of several supergranular cells inject magnetic helicity from the photospheric boundary into the solar atmosphere. Supergranular-scale helicity injection, transfer, and condensation produce strongly sheared magnetic fields. Magnetic reconnections at footpoints of the sheared fields produce magnetic flux ropes (MFRs) with helicity signs consistent with the observed hemispheric helicity rule. The cross-sectional area of MFRs exhibits an uneven distribution, resembling a "foot-node-foot" periodic configuration. Experiments with different tilt directions of PILs indicate that the PCFs preferably form along PILs with the western end close to the polar region. The bending of PILs caused by supergranular flows, forming S-shape (Z-shape) PIL segments, promotes the formation of dextral (sinistral) MFRs. The realistic magnetic models we obtained can serve as starting points for the study of the plasma formation and eruption of PCFs.

Keywords: Supergranulation, Solar prominences, Quiescent solar prominence, Solar magnetic fields, Magnetohydrodynamical simulations
Assessment of SDSS-derived Galaxy Morphologies Using HST Imaging. The Sloan Digital Sky Survey (SDSS) was foundational to the study of galaxy evolution, having revealed the bimodality of galaxies and the relationship between their structure and star-forming activity. However, ground-based optical surveys like SDSS are limited in resolution and depth, which may lead to biases or poor quality in the derived morphological properties, potentially impacting our understanding of how and why galaxies cease their star formation (quench). We use archival Hubble Space Telescope (HST) imaging of ∼2000 SDSS objects to assess the reliability of SDSS-derived morphologies, taking advantage of both SDSS statistical samples and HST's superior resolution and sensitivity. Single Sérsic fitting and bulge-disk decomposition is performed on HST images for direct comparison with SDSS results. Of the three catalogs of SDSS-derived morphologies considered, none is significantly more accurate or precise than the others. For disk-dominated galaxies (n &lt; 2.5), global Sérsic indices (n) from Meert et al. (hereafter, M15) are preferred. For bulge-dominated galaxies (n &gt; 2.5), Simard et al. (hereafter, S11) and M15 overestimate n by ∼20%, and derived global n from Blanton et al. are preferred. We provide an empirical relation to correct S11 global Sérsic indices. Global R eff from S11 overestimates R eff for the largest galaxies by 0.1 dex. Despite these moderate biases, SDSS-derived single-component parameters are generally significantly more robust than SDSS-derived two-component parameters. The bulge Sérsic index (n bulge) cannot be reliably constrained from SDSS imaging at all, whereas the bulge-to-total (B/T) ratio can be inferred from SDSS (provided that n bulge = 4 is enforced) but has a large random error of ∼0.2.

Keywords: Late-type galaxies, Quenched galaxies, Disk galaxies, Hubble Space Telescope, Galaxy structure, Galaxy bulges, Early-type galaxies, Galaxy classification systems, Galactic and extragalactic astronomy, Galaxy evolution, Galaxy quenching, Galaxies
The Reservoir of the Per-emb-2 Streamer. Streamers bring gas from outer regions to protostellar systems and could change the chemical composition around protostars and protoplanetary disks. We have carried out mapping observations of carbon-chain species (HC3N, HC5N, CCH, and CCS) in the 3 mm and 7 mm bands toward the streamer flowing to the Class 0 young stellar object (YSO) Per-emb-2 with the Nobeyama 45 m radio telescope. A region with a diameter of ∼0.04 pc is located to the north at a distance of ∼20,500 au from the YSO. The streamer connects to this northern region, which is its origin. The reservoir has high density and low temperature ( ${n}_{{{\rm{H}}}_{2}}\approx 1.9\times {10}^{4}$ cm‑3, T kin = 10 K), which are similar to those of early-stage starless cores. By comparison of the observed abundance ratios of CCS/HC3N to the chemical simulations, the reservoir and streamer are found to be chemically young. The total mass available for the streamer is derived to be 24–34 M ⊙. It has been estimated that, if all of the gas in the reservoir were to accrete onto the Per-emb-2 protostellar system, the lifetime of the streamer would be (1.1–3.2) × 105 yr, suggesting that the mass accretion via the streamer would continue until the end of the Class I stage.

Keywords: Young stellar objects, Star formation, Low mass stars, Astrochemistry
Fermi Large Area Telescope Detection of Gamma Rays from the NGC 6251 Radio Lobe. We report the detection of extended γ-ray emission from lobes in the radio galaxy NGC 6251 using observation data from the Fermi Large Area Telescope. The maximum likelihood analysis results show that a radio morphology template provides a better fit than a pointlike source description for the observational data at a confidence level of 8.1σ, and the contribution of lobes constitutes more than 50% of the total γ-ray flux. Furthermore, the γ-ray energy spectra show a significant disparity in shape between the core and lobe regions, with a curved log-parabola shape observed in the core region and a power-law form observed in the lobes. Neither the core region nor the northwest (NW) lobe displays significant flux variations in the long-term γ-ray light curves. The broadband spectral energy distributions of the core region and the NW lobe can be explained with a single-zone leptonic model. The γ-rays of the core region are due to the synchrotron-self-Compton process, while the γ-rays from the NW lobe are interpreted as inverse Compton emission of the cosmic microwave background.

Keywords: Active galaxies, Non-thermal radiation sources, Galaxy jets, Gamma-rays
Beyond the Background: Gravitational-wave Anisotropy and Continuous Waves from Supermassive Black Hole Binaries. Pulsar timing arrays have found evidence for a low-frequency gravitational-wave background (GWB). Assuming that the GWB is produced by supermassive black hole binaries (SMBHBs), the next gravitational-wave (GW) signals astronomers anticipate are continuous waves (CWs) from single SMBHBs and their associated GWB anisotropy. The prospects for detecting CWs and anisotropy are highly dependent on the astrophysics of SMBHB populations. Thus, information from single sources can break degeneracies in astrophysical models and place much more stringent constraints than the GWB alone. We simulate and evolve SMBHB populations, model their GWs, and calculate their anisotropy and detectability. We investigate how varying components of our semianalytic model, including the galaxy stellar mass function, the SMBH–host galaxy relation (M BH–M bulge), and the binary evolution prescription, impact the expected detections. The CW occurrence rate is greatest for few total binaries, high SMBHB masses, large scatter in M BH–M bulge, and long hardening times. The occurrence rate depends most on the binary evolution parameters, implying that CWs offer a novel avenue to probe binary evolution. The most detectable CW sources are in the lowest frequency bin for a 16.03 yr PTA, have masses from ∼109 to 1010 M ⊙, and are ∼1 Gpc away. The level of anisotropy increases with frequency, with the angular power spectrum over multipole modes ℓ varying in low-frequency C  ℓ&gt;0/C 0 from ∼5 × 10‑3 to ∼2 × 10‑1, depending on the model; typical values are near current upper limits. Observing this anisotropy would support SMBHB models for the GWB over cosmological models, which tend to be isotropic.

Keywords: Supermassive black holes, Gravitational waves, Galaxies
The Initial Conditions of Clustered Core Collapse: Multiwavelength Analysis of Oph A SM1N and N6 at 100 au Resolution. We present new Atacama Large Millimeter/submillimeter Array (ALMA) continuum and NH2D, N2D+, and H2D+ line emission at matched, ∼100 au resolution toward the dense star-forming cores SM1N and N6 within the Ophiuchus molecular cloud. We determine the density and temperature structure of SM1N based on radiative transfer modeling and simulated observations of the multiwavelength continuum emission at 0.8, 2, and 3 mm. We show that SM1N is best fit by either a broken power-law or Plummer-like density profile with high central densities (n ∼ 108 cm‑3), and an inner transition radius of only ∼80–300 au. The free-fall time of the inner region is only a few ×103 yr. The continuum modeling rules out the presence of an embedded first hydrostatic core (FHSC) or protostar. SM1N is therefore a dynamically unstable but still starless core. We find that NH2D is likely depleted at high densities within SM1N. The nonthermal velocity dispersions increase from NH2D to N2H+ and H2D+, possibly tracing increasing (but still subsonic) infall speeds at higher densities as predicted by some models of starless core contraction. Toward N6, we confirm the previous ALMA detection of a faint, embedded point source (N6-mm) in 0.8 mm continuum emission. NH2D and N2D+ avoid N6-mm within ∼100 au, while H2D+ is not strongly detected toward N6. The distribution of these tracers is consistent with heating by a young, warm object. N6-mm thus remains one of the best candidate FHSCs detected so far, although its observed (sub)millimeter luminosity remains below predictions for FHSCs.

Keywords: Chemical abundances, Astrochemistry, Young stellar objects, Star formation, Protostars
Joint Observations of Energy Transport and Dissipation during Plasma Flow Vortex in the Terrestrial Magnetotail. Plasma flow vorticity is ubiquitous in space and plays a key role in material mixing and energy transfer. The five THEMIS satellites orbiting in different regions of the terrestrial magnetotail provide an unprecedented opportunity to study the temporal–spatial evolution characteristics of a plasma flow vortex on large spatial scales. We present an analysis of the flow vorticity that occurred between 05:50 and 06:30 UT on 2009 March 23 during a quiet time of the terrestrial magnetotail. The uneven distributions of the density and temperature of the vortex observed by the three near-Earth satellites (THA, THD, and THE) indicate that the plasma in the solar wind gradually mixed into the near-Earth magnetotail through a series of nonequilibrium processes. Both the flow vortices and dipolarization observed by the three near-Earth satellites were about 10 minutes earlier than those observed by the two satellites (THB and THC) in the mid-magnetotail. Further analysis of the relationship between vorticity, field-aligned current, and energy transport reveals that the flow vortex interacted with the surrounding plasma during its tailward propagation. The field-aligned current related to the vorticity could only generate a pseudo-breakup of the aurora in the ionosphere. Thus, we speculate that this flow vortex mainly transports mass and energy from the solar wind to the near-magnetotail, propagates tailward to the mid-magnetotail, and heats the encountered plasma by dissipating its bulk flow and dominant thermal energy. These results shed light on the mass mixing, energy transport, and dissipation of the plasma flow vortex during quiet levels of geomagnetic activity on large spatial scales.

Keywords: Geomagnetic fields, Magnetohydrodynamics
The X-Ray Emission Reveals the Coronal Activities of Semi-detached Binaries. X-ray emission is an important tracer of stellar magnetic activity. We carried out a systematic correlation analysis for the X-ray luminosity  logLX , bolometric luminosity  logLbol , and X-ray activity level  log(LX /L bol) versus the binary parameters including orbital period P, Rossby number R O, effective temperature T eff, metallicity [Fe/H], the surface gravity  logg , stellar mass M, and radius R, by assembling a large sample of semi-detached (EB-type) binaries with X-ray emission (EBXs). The fact that both  logLX  and  logLbol  change in accordance with  logP  indicates that X-ray emission originates from the convection zone, while  logLX  is proportional to the convection zone area. We found that EBXs with main-sequence components exhibit an upward and then a downward trend in both the  logTeff – logLX  and M– logLX  relations, which is different from the monotonically decreasing trend shown by EBXs containing sub-giant and giant components. The magnetic activity level is negatively correlated with  logTeff  and stellar mass. Based on the magnetic dynamo model, the variations in the size and thickness of the surface convection zones can explain the observed relations. EBXs with main-sequence components have a similar R O– log(LX/Lbol)  relationship to that of the binaries in the clusters as Praesepe and Hyade. We compared the X-ray radiation properties of EBXs with those of the X-ray-emitting contact binaries and found that EBXs have broader value ranges for  logLX  and  log(LX /L bol).

Keywords: Binary stars, Stellar activity, Variable stars, Beta Lyrae stars, Eclipsing binary stars, Semi-detached binary stars
Cloud Formation by Supernova Implosion. The deposition of energy and momentum by supernova explosions has been subject to numerous studies in the past few decades. However, while there has been some work that focused on the transition from the adiabatic to the radiative stage of a supernova remnant (SNR), the late radiative stage and merging with the interstellar medium (ISM) have received little attention. Here, we use three-dimensional, hydrodynamic simulations, focusing on the evolution of SNRs during the radiative phase, considering a wide range of physical explosion parameters ( ${n}_{{\rm{H}},\mathrm{ISM}}\in \left[0.1,100\right]{\mathrm{cm}}^{-3}$ and ${E}_{\mathrm{SN}}\in \left[1,14\right]\times {10}^{51}\,\mathrm{erg}$ ). We find that the radiative phase can be subdivided in four stages: A pressure-driven snowplow phase, during which the hot overpressurized bubble gas is evacuated and pushed into the cold shell; a momentum-conserving snowplow phase that is accompanied by a broadening of the shell; an implosion phase where cold material from the back of the shell is flooding the central vacuum; and a final cloud phase, during which the imploding gas is settling as a central, compact overdensity. The launching timescale for the implosion ranges from a few 100 kyr to a few Myr, while the cloud formation timescale ranges from a few to about 10 Myr. The highly chemically enriched clouds can become massive (M cl ∼ 103–104 M ⊙) and self-gravitating within a few Myr after their formation, providing an attractive, novel pathway for supernova-induced star and planet formation in the ISM.

Keywords: Hydrodynamical simulations, Interstellar dynamics, Dense interstellar clouds, Supernova remnants, Interstellar medium, Shocks
EPOCHS. II. The Ultraviolet Luminosity Function from 7.5 &lt; z &lt; 13.5 Using 180 arcmin<SUP>2</SUP> of Deep, Blank Fields from the PEARLS Survey and Public JWST Data. We present an analysis of the ultraviolet luminosity function (UV LF) and star formation rate density of distant galaxies (7.5 &lt; z &lt; 13.5) in the "blank" fields of the Prime Extragalactic Areas for Reionization and Lensing Science (PEARLS) survey combined with Early Release Science data from the CEERS, GLASS, and NGDEEP surveys/fields and the first data release of JADES. We use strict quality cuts on EAZY photometric redshifts to obtain a reliable selection and characterization of high-redshift (z &gt; 6.5) galaxies from a consistently processed set of deep, near-infrared imaging. Within an area of 180 arcmin2, we identify 1046 candidate galaxies at redshifts z &gt; 6.5 and we use this sample to study the UV LF in four redshift bins between 7.5 &lt; z &lt; 13.5. The measured number density of galaxies at z = 8 and z = 9 matches those of past observations undertaken by the Hubble Space Telescope (HST). Our z = 10.5 measurements lie between early James Webb Space Telescope (JWST) results and past HST results, indicating cosmic variance may be the cause of previous high density measurements. However, the number densities of UV-luminous galaxies at z = 12.5 are high compared to predictions from simulations. When examining the star formation rate density of galaxies at this period, our observations are still largely consistent with a constant star formation efficiency, are slightly lower than previous early estimations using JWST, and support galaxy driven reionization at z ≤ 8.

Keywords: Luminosity function, Galaxy photometry, Reionization, Lyman-break galaxies, High-redshift galaxies
Comparison of Solar Multifrequency Microwave Data with Other Solar Indices for Understanding Solar and Stellar Microwave Data. Thermal microwave emissions detected from stellar atmospheres contain information on stellar activity. However, even for the Sun, the relationship between multifrequency microwave data and other activity indices remains unclear. We investigated the relationships among the thermal microwave fluxes with 1, 2, 3.75, and 9.4 GHz, their circular polarizations, and several activity indices recorded during recent solar cycles and observed that these relationships can be categorized into two groups. In the first group, the relationship between the microwave fluxes and solar indices, which are strongly related to the active regions, can be well-fitted by using a linear function. In the second group, the fitting function is dependent on frequency. Specifically, the microwave fluxes at 1 and 2 GHz can be well-fitted to the total unsigned magnetic and extreme ultraviolet fluxes by employing a power-law function. The trend changes around 3.75 GHz, and the trend for the 9.4 GHz fluxes can be fitted by using a linear function. For the first time, we present the relationship between circular polarization and solar indices. Moreover, we extrapolated these relationships of the solar microwave fluxes to higher values and compared them with the solar-type stars. We found that ϵ Eri, whose microwave emission originates from thermal plasma, follows the extrapolated relationship. However, to date, only one star's emission at 1─10 GHz has been confirmed as thermal emission. More solar-type stars should be observed with future radio interferometers to confirm that relationships based on solar data can be applied to stellar microwave data.

Keywords: Solar cycle, Solar atmosphere, Solar radio emission, Stellar atmospheres
Fossil Signatures of Main-sequence Convective Core Overshoot Estimated through Asteroseismic Analyses. Some physical processes that occur during a star's main-sequence evolution also affect its post-main-sequence evolution. It is well known that stars with masses above approximately 1.1 M ⊙ have well-mixed convective cores on the main sequence; however, the structure of the star in the neighborhood of the convective core regions is currently underconstrained. We use asteroseismology to study the properties of the stellar core, in particular convective boundary mixing through convective overshoot, in such intermediate-mass stars. These core regions are poorly constrained by the acoustic (p) mode oscillations observed for cool main-sequence stars. Consequently, we seek fossil signatures of main-sequence core properties during the subgiant and early first-ascent red giant phases of evolution. During these stages of stellar evolution, modes of mixed character that sample the deep interior can be observed. These modes sample the parts of the stars that are affected by the main-sequence structure of these regions. We model the global and near-core properties of 62 subgiant and early first-ascent red giant branch stars observed by the Kepler, K2, and TESS space missions. We find that the effective overshoot parameter, α ov,eff, increases from M = 1.0 M ⊙ to M = 1.2 M ⊙ before flattening out, although we note that the relationship between α ov,eff and mass will depend on the incorporated modeling choices of internal physics and nuclear reaction network. We also situate these results within existing studies of main-sequence convective core boundaries.

Keywords: Stellar convective zones, Subgiant stars, Stellar physics, Asteroseismology, Stellar evolution
High-resolution X-Ray Spectroscopy of Interstellar Iron toward Cygnus X-1 and GX 339-4. We present a high-resolution spectral study of Fe L-shell extinction by the diffuse interstellar medium (ISM) in the direction of the X-ray binaries Cygnus X-1 and GX 339─4, using the XMM-Newton reflection grating spectrometer. The majority of interstellar Fe is suspected to condense into dust grains in the diffuse ISM, but the compounds formed from this process are unknown. Here, we use the laboratory cross sections from Kortright &amp; Kim (2000) and Lee et al. (2005) to model the absorption and scattering profiles of metallic Fe, and the crystalline compounds fayalite (Fe2SiO4), ferrous sulfate (FeSO4), hematite (α-Fe2O3), and lepidocrocite (γ-FeOOH), which have oxidation states ranging from Fe0 to Fe3+. We find that the observed Fe L-shell features are systematically offset in energy from the laboratory measurements. An examination of over two dozen published measurements of Fe L-shell absorption finds a 1─2 eV scatter in energy positions of the L-shell features. Motivated by this, we fit for the best energy-scale shift simultaneously with the fine structure of the Fe L-shell extinction cross sections. Hematite and lepidocrocite provide the best fits (≈ + 1.1 eV shift), followed by fayalite (≈ + 1.8 eV shift). However, fayalite is disfavored, based on the implied abundances and knowledge of ISM silicates gained by infrared astronomical observations and meteoritic studies. We conclude that iron oxides in the Fe3+ oxidation state are good candidates for Fe-bearing dust. To verify this, new absolute photoabsorption measurements are needed on an energy scale accurate to better than 0.2 eV.

Keywords: Dust composition, Interstellar medium, X-ray binary stars
The Effect of Spatially Varying Collision Frequency on the Development of the Rayleigh–Taylor Instability. The Rayleigh–Taylor (RT) instability is ubiquitously observed, yet has traditionally been studied using ideal fluid models. Collisionality can vary strongly across the fluid interface, and previous work demonstrates the necessity of kinetic models to completely capture dynamics in certain collisional regimes. Where previous kinetic simulations used spatially and temporally constant collision frequency, this work presents five-dimensional (two spatial, three velocity dimensions) continuum-kinetic simulations of the RT instability using a more realistic spatially varying collision frequency. Three cases of collisional variation are explored for two Atwood numbers: low to intermediate, intermediate to high, and low to high. The low-to-intermediate case exhibits no RT instability growth, while the intermediate-to-high case is similar to a fluid-limit kinetic case with interface widening biased toward the lower-collisionality region. A novel contribution of this work is the low-to-high collisionality case that shows significantly altered instability growth through an upward movement of the interface and damped spike growth due to increased free-streaming particle diffusion in the lower region. Contributions to the energy flux from the non-Maxwellian portions of the distribution function are not accessible to fluid models and are greatest in magnitude in the spike and regions of low collisionality. Increasing the Atwood number results in greater RT instability growth and reduced upward interface movement. Deviation of the distribution function from Maxwellian is inversely proportional to collision frequency and concentrated around the fluid interface. The linear phase of RT instability growth is well described by theoretical linear growth rates accounting for viscosity and diffusion.

Keywords: Astrophysical fluid dynamics, Hydrodynamics, Plasma physics