Sazuna/UAT_keywords huggingface dataset:
Galaxy Cluster Mass Estimation through the Splashback Radius. We present an analysis of the splashback radius (Rsp) and the associated splashback mass (Msp) for a sample of galaxy clusters using Sloan Digital Sky Survey spectroscopic data and mock simulations. Rsp marks a physical boundary between the virialized core and the outer infall regions of clusters, providing a robust measure of cluster mass accretion history without being affected by pseudo-evolution. We model the cumulative galaxy number profile of clusters, testing different halo density models and considering the impact of cluster properties, such as center definitions, magnitude limits, galaxy colors, and field contamination, on the estimation of splashback features. Our results show that observed splashback radii, measured in projection (2D), are consistently smaller than predicted by dark matter simulations, with Rsp/R200m ≈ 1, supporting previous discrepancies in the literature. We also explore the relationship between Msp and Rsp, proposing a new scaling relation for future cosmological studies, as Rsp is easily observable. Our findings indicate that splashback masses strongly correlate with radii, with a dispersion of ≈0.15 dex, competitive with other mass-observable relations. However, the fitted relation diverges from the constant density expectations of galaxy clusters around Rsp. Additionally, the Msp–Rsp relation shows significant redshift evolution, though the predominantly low-redshift range of our sample limits our ability to confirm this trend conclusively. The approach developed here may play a key role in cluster characterization and cosmology in the era of large galaxy surveys.

Keywords: Galaxy clusters, Observational cosmology, Large-scale structure of the universe
Concealing Circumbinary Planets with Tidal Shrinkage. Of the 14 transiting planets that have been detected orbiting eclipsing binaries ("circumbinary planets"), none have been detected with stellar binary orbital periods shorter than 7 days, despite such binaries existing in abundance. The eccentricity–period data for stellar binaries indicate that short-period (&lt;7 days) binaries have had their orbits tidally circularized. We examine here to what extent tidal circularization and shrinkage can conceal circumbinary planets, i.e. whether planets actually exist around short-period binaries, but are not detected because their transit probabilities drop as tides shrink the binary away from the planet. We carry out a population synthesis by initializing a population of eccentric stellar binaries hosting circumbinary planets, and then circularizing and tightening the host orbits using stellar tides. To match the circumbinary transit statistics, stellar binaries must form with eccentricities ≳ 0.2 and periods ≳ 6 days, with circumbinary planets emplaced on exterior stable orbits before tidal circularization; moreover, tidal dissipation must be efficient enough to circularize and shrink binaries out to ∼6–8 days. The resultant binaries that shrink to sub-7 day periods no longer host transiting planets. However, this scenario cannot explain the formation of nearly circular, tight binaries, brought to their present sub-7 day orbits from other processes like disk migration. Still, tidal shrinkage can introduce a bias against finding transiting circumbinary planets, and predicts a population of KIC 3853259 (AB)b analogs consisting of wide-separation, nontransiting planets orbiting tight binaries.

Keywords: Tides, Transit photometry, Eclipsing binary stars
Modeling of Ionization and Recombination Processes in Plasma with Arbitrary Non-Maxwellian Electron Distribution. In astronomical environments, the high-temperature emission of plasma mainly depends on ion charge states, requiring accurate analysis of the ionization and recombination processes. For various phenomena involving energetic particles, non-Maxwellian distributions of electrons exhibiting high-energy tails can significantly enhance the ionization process. Therefore, accurately computing ionization and recombination rates with non-Maxwellian electron distributions is essential for emission diagnostic analysis. In this work, we report two methods for fitting various non-Maxwellian distributions by using the Maxwellian decomposition strategy. For standard κ-distributions, the calculated ionization and recombination rate coefficients show comparable accuracy to other public packages. Additionally, our methods support arbitrary electron distributions and can be easily extended to updated atomic databases. We apply the above methods to two specific non-Maxwellian distribution scenarios: (i) accelerated electron distributions due to magnetic reconnection revealed in a combined MHD─particle simulation; and (ii) the high-energy truncated κ-distribution predicted by the exospheric model of the solar wind. During the electron acceleration process, we show that the ionization rates of high-temperature iron ions increase significantly compared to their initial Maxwellian distribution, while the recombination rates may decrease due to the electron distribution changes in low-energy ranges. This can potentially lead to an overestimation of the plasma temperature when analyzing the Fe emission lines under the Maxwellian distribution assumption. For the truncated κ-distribution in the solar wind, our results show that the ionization rates are lower than those for the standard κ-distribution, while the recombination rates remain similar. This leads to an overestimation of the plasma temperature when assuming a κ-distribution.

Keywords: Solar magnetic reconnection, Recombination, Solar wind, Non-thermal radiation sources, Ionization, Astronomical simulations
Connecting the Small Solar Wind Transients Observed Remotely to Their In Situ Measurement near 1 au. Based on the two-vantage observations by the COR2 coronagraphs on board the two STEREO spacecraft between 2010 January 1 and 2010 July 15, we reconstruct the three-dimensional (3D) structures of small solar wind transients in the extended corona and determine their velocities by using the CORrelation-Aided Reconstruction technique. From this data set, we select three small transient events that are predicted to arrive at the L1 point after extrapolating their 3D trajectories in the heliosphere. We find that the predicted trajectories are consistent with the heliospheric observations, and the transients are likely to have also been detected by in situ instruments at L1. The case 1 event is a streamer blob associated with high-density regions across the heliospheric current sheet detected 2 days before the occurrence of a stream interaction region (SIR). The case 2 transient is identified as the bright core of a streamer blowout coronal mass ejection entrained by an SIR, and the case 3 event is merged with the SIR-compressed outflow. The in situ properties related to these events and their ambient plasma flows are consistent with the properties of their source regions, identified after tracing their motion back to the solar surface. This work is an attempt to establish an exact connection between the coronal observations of a small solar wind transient and its in situ measurement at near 1 au and to understand the evolution of solar wind transients in the heliosphere.

Keywords: Slow solar wind, Solar corona, Heliosphere
A Multi-wavelength Characterization of the 2023 Outburst of MAXI J1807+132: Manifestations of Disk Instability and Jet Emission. Several phenomenological aspects of low-luminosity neutron star transients, such as atolls, remain poorly understood. One such source, MAXI J1807+132, entered its latest outburst in 2023 July. To thoroughly characterize this outburst, we conducted an extensive observational campaign spanning radio to X-ray wavelengths. Here we present the results of this campaign, which covered the period from before the outburst to the return to quiescence. We detected a delay between the X-ray and optical rise times, which is consistent with the predictions of the disk instability model with a truncated disk. The color evolution and optical/X-ray correlations, along with infrared and radio detections, support the presence of jet synchrotron emission during the gradual decay phase following the peak. We also report for the first time in an X-ray binary a near-orthogonal rotation of the optical polarization just before a small flare, after which the jet is thought to be quenched. The main outburst is followed by several high-amplitude, rapid reflares in the optical, ultraviolet, and X-ray bands, the origin of which remains difficult to constrain.

Keywords: Low-mass x-ray binary stars, Neutron stars, Accretion, Jets
Ensemble Modeling of the Solar Wind Flow with Boundary Conditions Governed by Synchronic Photospheric Magnetograms. I. Multipoint Validation in the Inner Heliosphere. The solar wind (SW) is a vital component of space weather, providing a background for solar transients such as coronal mass ejections, stream interaction regions, and energetic particles propagating toward Earth. Accurate prediction of space weather events requires a precise description and thorough understanding of physical processes occurring in the ambient SW plasma. Ensemble simulations of the 3D SW flow are performed using an empirically driven magnetohydrodynamic heliosphere model implemented in the Multi-Scale Fluid-Kinetic Simulation Suite (MS-FLUKSS). The effect of uncertainties in the photospheric boundary conditions on the simulation outcome is investigated. The MS-FLUKSS simulation results are in good overall agreement with the observations from the Parker Solar Probe, Solar Orbiter, Solar Terrestrial Relations Observatory, and OMNI data at Earth, specifically during 2020–2021. This makes it possible to shed more light on the properties of the SW propagating through the heliosphere and perspectives for improving space weather forecasts.

Keywords: Heliosphere, Space weather, Solar wind, Interplanetary magnetic fields, Magnetohydrodynamical simulations
The XMAGNET Exascale MHD Simulations of SMBH Feedback in Galaxy Groups and Clusters: Overview and Preliminary Cluster Results. We present initial results from extremely well-resolved 3D magnetohydrodynamical simulations of idealized galaxy clusters, conducted using the AthenaPK code on the Frontier exascale supercomputer. These simulations explore the self-regulation of galaxy groups and cool-core clusters by cold gas-triggered active galactic nucleus (AGN) feedback incorporating magnetized kinetic jets. Our simulation campaign includes simulations of galaxy groups and clusters with a range of masses and intragroup and intracluster medium properties. In this paper, we present results that focus on a Perseus-like cluster. We find that the simulated clusters are self-regulating, with the cluster cores staying at a roughly constant thermodynamic state and AGN jet power staying at physically reasonable values (≃1044–1045 erg s–1) for billions of years without a discernible duty cycle. These simulations also produce significant amounts of cold gas, with calculations having strong magnetic fields generally both promoting cold gas formation and allowing cold gas out to much larger cluster-centric radii (≃100 kpc) than simulations with weak or no fields (≃10 kpc), and also having more filamentary cold gas morphology. We find that AGN feedback significantly increases the strength of magnetic fields at the center of the cluster. We also find that the magnetized turbulence generated by the AGN results in turbulence where the velocity power spectra are tied to AGN activity, whereas the magnetic energy spectra are much less impacted after reaching a stationary state.

Keywords: Galaxy clusters, Galaxy jets, Intracluster medium, Magnetic fields, Magnetohydrodynamical simulations
All-sky Kinematics of the Distant Halo: The Reflex Response to the LMC. The infall of the Large Magellanic Cloud (LMC) is predicted to displace the inner Milky Way (MW), imprinting an apparent "reflex motion" on the observed velocities of distant halo stars. We construct the largest all-sky spectroscopic data set of luminous red giant stars from 50–160 kpc, including a new survey of the southern celestial hemisphere. We fit the full 6D kinematics of our data to measure the amplitude and direction of the inner MW's motion toward the outer halo. The observed velocity grows with distance such that, relative to halo stars at 100 kpc, the inner MW is lurching at ≈40 km s‑1 toward a recent location along the LMC's past orbit. Our measurements align with N-body simulations of the halo's response to a 1.8 × 1011 M⊙ LMC on first infall, suggesting that the LMC is at least 15% as massive as the MW. Our findings highlight the dramatic disequilibrium of the MW outskirts, and will enable more accurate measurements of the total mass of our Galaxy.

Keywords: Stellar kinematics, Milky Way stellar halo, Milky Way dynamics, Large Magellanic Cloud
XMM-Newton Conclusively Identifies an Active Galactic Nucleus in a Green Pea Galaxy. Green Pea galaxies are a class of compact, low-mass, low-metallicity star-forming galaxies in the relatively local Universe. They are believed to be analogs of high-redshift galaxies that reionized the Universe, and, indeed, the James Webb Space Telescope (JWST) is now uncovering such populations at record redshifts. Intriguingly, JWST finds evidence suggestive of active galactic nuclei (AGN) in many of these distant galaxies, including the elusive Little Red Dots, which broadly lack any detectable X-ray counterparts. Intuitively, one would expect to detect an AGN in their low-redshift analogs with X-rays, yet no study to date has conclusively identified an X-ray AGN within a Green Pea galaxy. Here we present the deepest X-ray campaign of a Green Pea galaxy performed to date, obtained with the goal of discerning the presence of a (potentially low-luminosity) AGN. The target—SDSS J082247.66+224144.0 (hereafter J0822+2241)—was previously found to display a comparable X-ray spectral shape to more local AGN (Γ ∼ 2) and a high luminosity (L2−10 keV ∼ 1042 erg s−1). We show that over 6.2 yr (rest frame) the 2─10 keV luminosity of J0822+2241 is constant, whereas the soft 0.5─2 keV flux has decreased significantly by ∼60%. We discuss possible scenarios to explain the X-ray properties of J0822+2241, finding transient low column density obscuration surrounding an AGN to be the only plausible scenario. J0822+2241 thus provides further evidence that low-luminosity AGN activity could have contributed to the epoch of reionization and that local analogs are useful to derive a complete multiwavelength picture of black hole growth in high-redshift, low-luminosity AGNs. *Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.

Keywords: Starburst galaxies, Active galaxies, X-ray active galactic nuclei, Compact galaxies
The Optimal Padé Polynomial for Reconstruction of Luminosity Distance Based on 10-fold Cross Validation. The cosmography known as the Padé polynomials has been widely used in the reconstruction of luminosity distance, and the orders of Padé polynomials influence the reconstructed result derived from Padé approximation. In this paper, we present a more general scheme of selecting optimal Padé polynomial for reconstruction of luminosity distance based on 10-fold cross validation. Then the proposed scheme is applied to Pantheon+ data set. The numerical results clearly indicate that the proposed procedure has a remarkable ability to distinguish Padé approximations with different orders for the reconstruction of the luminosity distance. We conclude that the (2,1) Padé approximation is the optimal approach that can well explain Pantheon+ data at low and high redshifts. Future applications of this scheme could help choose the optimal model that is more suitable for cosmological observation data at hand and gain a deeper understanding of the Universe.

Keywords: Bayesian information criterion, Cross-validation , Observational cosmology, Akaike information criterion
Residual Test to Search for Microlensing Signatures in Strongly Lensed Gravitational Wave Signals. When a gravitational wave signal encounters a massive object, such as a galaxy or galaxy cluster, it undergoes strong gravitational lensing, producing multiple copies of the original signal. These strongly lensed signals exhibit identical waveform morphology in the frequency domain, allowing analysis without the need for complex lens models. However, stellar fields and dark matter substructures within the galactic lens introduce microlensing effects that alter individual signal morphologies. Identifying these microlensing signatures is computationally challenging within Bayesian frameworks. In this study, we propose a residual test to efficiently search for microlensing signatures by leveraging the fact that current Bayesian inference pipelines are optimized solely for the strong lensing hypothesis. Using cross-correlation techniques, we investigate the microlensing-induced deviations from the strong hypothesis, which are imprinted in the residuals. Most simulated signals from our realistic microlensing populations exhibit small mismatches (MMs) between the microlensed and unlensed waveforms, but a fraction show significant deviations. We find that 28% (52%) and 34% (66%) of microlensed events with MM ≥0.03 and ≥0.1, respectively, can be discerned with O4 (O5) detector sensitivities, which demonstrates that high-MM events are more likely to be identified as microlensed. Including all events from a realistic population, 11% (21.5%) are identifiable with O4 (O5) sensitivity using our approach.

Keywords: Bayesian statistics, Strong gravitational lensing, Gravitational wave astronomy, Gravitational lensing, Gravitational waves, Gravitational microlensing
Self-similar Decomposition of the Hierarchical Merger Tree of Dark Matter Halos. In the ΛCDM universe, structure formation is generally not a self-similar process, while some self-similarity remains in certain statistics, which can greatly simplify our description and understanding of the cosmic structures. In this work, we show that the merger tree of dark matter halos is approximately self-similar by investigating the universality of the subhalo peak mass function (PMF) describing the mass distribution of progenitor halos. Using a set of cosmological simulations and identifying subhalos of different merger levels with HBT+, we verify that the level-1 subhalo PMF is close to universal across halo mass, redshift, and cosmology. This approximate self-similarity allows us to analytically derive the subhalo PMF for subhalos accreted at any level (i.e., for sub-subhalos) through self-convolutions of the level-1 PMF, and the resulting model shows good agreement with simulation measurements. We further derive a number of analytical properties of the hierarchical origin of subhalos. We show that higher-level subhalos dominate at progressively lower peak mass in the PMF and are more likely to originate from major mergers than lower-level ones. At a given merger mass ratio, the subhalo accretion rates at each level track the growth rate of the host halo. At a fixed final mass ratio, however, subhalos of higher-level, higher-mass-ratio, and in more massive haloes tend to be accreted more recently. Matching subhalo peak mass to galaxy mass, these results have direct implications on the hierarchical origin of satellite galaxies.

Keywords: Galaxy dark matter halos, Dark matter
Globular Clusters GMRT Pulsar Search (GCGPS). I. Survey Description, Discovery and Timing of the First Pulsar in NGC6093 (M80). This paper describes the new Globular Clusters GMRT Pulsar Search survey. This survey aims to find millisecond pulsars (MSPs) in the globular clusters (GCs) of the Milky Way using the upgraded Giant Metrewave Radio Telescope (uGMRT). Using the uGMRT's Band-4 (550─750 MHz) and Band-3 (300─500 MHz) receivers, this survey will eventually cover the GCs accessible to the uGMRT sky, avoiding GCs visible to the Five-hundred-meter Aperture Spherical Radio Telescope (i.e., −53° &lt; δ &lt; −17°), and targeting GCs that have not been targeted with the sensitivity of this survey. In this paper, we present the discovery and follow-up study of the first pulsar from this survey, J1617─2258A, a 4.32 ms binary MSP, the first to be discovered in the GC NGC 6093. We localized this MSP with arcsecond precision from imaging and obtained the unique timing solution from more than one year of timing observations with the uGMRT Band-4 (550─750 MHz) receivers. This revealed an unusual binary MSP, with a ∼19 hr, highly eccentric (e ∼ 0.54) orbit having a low-mass companion. This orbital eccentricity allowed the measurement of the rate of advance of the periastron for this system, which led to the derivation of its total mass, 1.67 ± 0.06 M⊙; this together with the system's mass function implies, for the pulsar and the companion, Mp &lt; 1.60 M⊙ and Mc &gt; 0.072 M⊙. The system is most likely a perturbed MSP─helium white dwarf system seen at a low orbital inclination.

Keywords: Globular star clusters, Neutron stars, Millisecond pulsars, Surveys, Radio astronomy, Binary pulsars
Constraining Resolved Extragalactic R<SUB>21</SUB> Variation with Well-calibrated ALMA Observations. CO(1─0) and CO(2─1) are commonly used as bulk molecular gas tracers. The CO line ratios (especially CO(2─1)/CO(1─0)─R21) vary within and among galaxies, yet previous studies on R21 and alike often rely on measurements constructed by combining data from facilities with substantial relative calibration uncertainties that have the same order as physical line ratio variations. Hence, robustly determining systematic R21 variations is challenging. Here, we compare CO(1─0) and CO(2─1) mapping data from ALMA for 14 nearby galaxies, at a common physical resolution of 1.7 kpc. Our data set includes new ALMA (7 m+TP) CO(1─0) maps of 12 galaxies. We investigate R21 variation to understand its dependence on global galaxy properties, kiloparsec-scale environmental factors, and its correlation with star formation rate (SFR) surface density and metallicity. We find that the galaxy-to-galaxy scatter is 0.05 dex. This is lower than previous studies, which reported over 0.1 dex variation, likely reflecting significant flux calibration uncertainties in single-dish surveys. Within individual galaxies, R21 has a typical mean value of ∼0.64 and 0.1 dex variation, with an increase to ∼0.75 toward galactic centers. We find strong correlations between R21 and various galactic parameters, particularly SFR surface density, which shows a power-law slope of 0.10─0.11 depending on the adopted binning/fitting methods. Our findings suggest that, for studies covering main-sequence galaxy samples, assuming a fixed R21 = 0.64 does not significantly bias kiloparsec-scale molecular gas mass estimates from CO(2─1). Instead, systematic uncertainties from flux calibration and the CO-to-H2 conversion factor account for more systematic scatter of CO-derived molecular gas properties.

Keywords: Molecular gas, Spiral galaxies, Millimeter-wave spectroscopy, Interstellar medium, Radio interferometry
Radio Observation of the Pulsar Wind Nebula in Supernova Remnant G11.2‑0.3. Pulsar wind nebulae (PWNe) are important sources for understanding galactic high-energy processes, but it is controversial until now how high-energy particles in PWNe are accelerated and transported. Lacking radio counterparts of X-ray PWNe (the proposed acceleration sites) introduces difficulties to better understand questions about multiwavelengths. Our recent 3, 6, and 16 cm high-resolution observations of G11.2‑0.3 PWN with the Australia Telescope Compact Array uniquely show morphological similarity with its X-ray PWN (a torus/jet feature). Spectral indices of the radio torus and jet are around ‑0.09 and ‑0.10, respectively. Meanwhile, for the jet region, the spectral break between radio and X-ray spectra implies particle acceleration mechanisms other than a diffusive shock acceleration. Polarization results suggest a helical B-field inside the jet, the equipartition B-field strength of which is below 100 μG.

Keywords: Supernova remnants, Polarimetry, Pulsar wind nebulae