Sazuna/UAT_keywords huggingface dataset:
Evolution of the M<SUB>∗</SUB>–M<SUB>BH</SUB> Relation from z ∼ 6 to the Present Epoch. The ratio between the stellar mass of a galaxy, M*, and that of its central supermassive black hole (SMBH), M•, the "Magorrian" relationship, traces their coevolution. JWST observations have suggested significant evolution in M•/M* relative to local scaling relationships both in low-mass galaxies and in quasars at z ≥ 4. We test this possibility by (1) determining the preferred M•/M* scaling relation among those proposed locally, and (2) providing uniform estimates of host galaxy stellar mass. These steps reduce the prominence of the reported evolution. We then apply Monte Carlo simulations to account for observational biases. We still find a significant increase over the local scaling relation in M•/M* for z ≥ 4 SMBHs in very low-mass galaxies ( ). However, similarly high values of M•/M* are also found in low-mass galaxies at z ∼ 0.5–3, which may be common at cosmic noon. Nonetheless, galaxies with similar behavior are rare locally and not accounted for in the local scaling relations. In contrast, z ∼ 6 quasars can have M•/M* well above the value given by the local relation, but they can be explained as extreme cases still within the scaling relation for their higher-mass host galaxies. Black holes in some of them and in the low-mass systems may be undergoing episodes of very high accretion that result in high M•/M* but that will be followed by quiescent periods when growth of the host drives the systems toward more typical M•/M* values.

Keywords: Active galactic nuclei, Galaxy evolution
Recovering Cosmic Structure with a Simple Physical Constraint. Radio observation of the large-scale structure (LSS) of our Universe faces major challenges from foreground contamination, which is many orders of magnitude stronger than the cosmic signal. While other foreground removal techniques struggle with complex systematics, methods like foreground avoidance emerge as effective alternatives. However, this approach inevitably results in the loss of Fourier modes and a reduction in cosmological constraints. We present a novel method that, by enforcing the non-negativity of the observed field in real space, allows us to recover some of the lost information, particularly phase angles. We demonstrate that the effectiveness of this straightforward yet powerful technique arises from the mode mixing from the nonlinear evolution of LSS. Since the non-negativity is ensured by mass conservation—one of the key principles of the cosmic dynamics— we can restore the lost modes without explicitly expressing the exact form of the mode mixing. Unlike previous methods, our approach utilizes information from highly nonlinear scales and has the potential to revolutionize the analysis of radio observational data in cosmology. Crucially, we demonstrate that in long-baseline interferometric observations, such as those from the Square Kilometre Array, it is still possible to recover the baryonic acoustic oscillation signature despite not directly covering the relevant scales. This opens up potential future survey designs for cosmological detection.

Keywords: Cosmology, Observational cosmology, Large-scale structure of the universe
Polar Circumtriple Planets and Disks around Misaligned Hierarchical Triple Stars. Observations of hierarchical triple-star systems show that misalignments are common both between the angular momentum vector of the inner binary and the outer companion orbit, and between the outer binary orbit and a circumtriple gas disk. With analytic methods and n-body simulations, we explore the dynamics of circumtriple orbits around a misaligned hierarchical triple star. Circumtriple test-particle orbits nodally precess either about the outer binary angular momentum vector (circulating orbits) or about a stationary inclination that depends upon the binary properties (librating orbits). For a coplanar (or retrograde coplanar) triple star, the apsidal precession rate is maximal and the critical orbital radius outside of which all orbits are circulating is minimal. Polar alignment of a circumtriple gas disk requires nodal libration, and therefore it can be more likely if there is a large misalignment between the inner and outer binary orbits. There are two values of the mutual misalignment, ic and 180° ‑ ic, for which the apsidal precession rate of the triple star is zero and polar alignment is possible at all orbital radii. For a circular inner binary orbit ic = 55°, and it changes with the eccentricity of the inner binary while being insensitive to other triple-star parameters.

Keywords: Exoplanet dynamics, Celestial mechanics, Trinary stars, Protoplanetary disks
Polarized Signatures of the Earth Through Time: An Outlook for the Habitable Worlds Observatory. The search for life beyond the solar system remains a primary goal of current and near-future missions, including NASA's upcoming Habitable Worlds Observatory (HWO). However, research into determining the habitability of terrestrial exoplanets has been primarily focused on comparisons to modern-day Earth. Additionally, current characterization strategies focus on the unpolarized flux from these worlds, taking into account only a fraction of the informational content of the reflected light. Better understanding the changes in the reflected-light spectrum of the Earth throughout its evolution, as well as analyzing its polarization, will be crucial for mapping its habitability and providing comparison templates to potentially habitable exoplanets. Here we present spectropolarimetric models of the reflected light from the Earth at six epochs across all four geologic eons. We find that the changing surface albedos and atmospheric gas concentrations across the different epochs allow the habitable and nonhabitable scenarios to be distinguished, and diagnostic features of clouds and hazes are more noticeable in the polarized signals. We also discuss how using Mie scattering for naturally nonspherical particles, which is a common simplification for exoplanet modeling, affects the resulting planetary signals. Finally, our results suggest that pushing the HWO planet-to-star flux contrast limit down to 1 × 10‑13 could allow for the characterization in both unpolarized and polarized light of an Earth-like planet at any stage in its history.

Keywords: Spectropolarimetry, Exoplanets, Planetary atmospheres, Radiative transfer, Polarimetry, Habitable planets
Multifrequency Very Long Baseline Interferometry Study of Emission and Absorption in the Two-sided Jets of NGC 3998. We present the multifrequency, multi-epoch very long baseline interferometry (VLBI) study of the two-sided jets in the low-luminosity active galactic nucleus NGC 3998, where physical properties of the jets on parsec scales remain poorly understood. Using Very Long Baseline Array data observed at 1.4, 1.7, 2.3, and 5 GHz, we detect symmetric twin jets aligned along the north–south direction, with a total extent of ∼5.3 pc. Notably, the position angle of the parsec-scale jets differs by 26°–30° from that of the kiloparsec-scale jets, suggesting the possibility of jet precession. Based on the frequency-dependent core shift and north/south jet brightness ratio, we identify the northern jet as the approaching jet and the southern jet as the counterjet. Measurements of the radial intensity profile on both sides indicate a change in the counterjet emission from rapid fading to a slower decline at 1.4, 1.7, and 2.3 GHz. Spectral analysis shows that the approaching jet exhibits an optically thin spectrum, while the counterjet is dominated by an optically thick, inverted spectrum. These findings tentatively suggest free–free absorption in NGC 3998, which should be verified in future studies. Finally, our observations also reveal a flat-spectrum VLBI core, showing significant radio variability that is likely linked to a jet ejection event.

Keywords: Very long baseline interferometry, Low-luminosity active galactic nuclei, Radio jets, High angular resolution
Potential Contribution of Young Pulsar Wind Nebulae to Galactic High-energy Neutrino Emission. Pulsar wind nebulae (PWNe), especially the young ones, are among the most energetic astrophysical sources in the Galaxy. It is usually believed that the spin-down energy injected from the pulsars is converted into magnetic field and relativistic electrons, but the possible presence of proton acceleration inside PWNe cannot be ruled out. Previous works have estimated the neutrino emission from PWNe using various source catalogs measured in gamma rays. However, some sources may be unresolved due to the limited sensitivity of TeV gamma-ray observations, while part of the unidentified sources may be related to off-beam pulsars. Here, we estimate the potential neutrino emission from a synthetic population of PWNe in the Galaxy with a focus on the ones that are still in the free expansion phase. In the calculation, we model the temporal evolution of the free-expanding PWNe and consider the transport of protons inside the PWNe. The Crab Nebula is treated as a standard template for young PWNe to evaluate some model parameters, such as the energy conversion fraction of relativistic protons and the target gas density for the hadronic process, which are relevant to neutrino production. In the optimistic case, the neutrino flux from the simulated young PWNe may constitute to 5% of the measured flux by IceCube around 100 TeV. At higher energy around 1 PeV, the neutrino emission from the population highly depends on the injection spectral shape, and also on the emission of the nearby prominent sources.

Keywords: High energy astrophysics, Neutrino astronomy, Pulsars, Pulsar wind nebulae
Observations of Temporal Variations in the 5303 Å Emission Line During a Coronal Mass Ejection Without Any Associated Solar Flare. Reports using total solar eclipse data indicate that the 5303 Å emission line is a promising tool for observing the thermodynamic changes due to coronal mass ejections (CMEs) close to the Sun. The Visible Emission Line Coronagraph (VELC) on board ADITYA-L1, the recently launched first Indian space solar mission, has now provided an opportunity to regularly observe the solar corona in the 5303 Å emission line. We present the first long-duration temporal observations of activity associated with a flareless CME from an active region at the west limb of the Sun, with the VELC. The observations were in the sit-and-stare mode for ≈7 hr. Our analysis shows a steady increase in the intensity of the line by ≈57%, followed by a gradual decrease to the initial level. The width of the line also showed changes, but opposite to that in the intensity. The width slowly decreased from 0.97 ± 0.01 Å to 0.87 ± 0.01 Å and then increased back. The change is ≈10%. The effective temperatures corresponding to each of the above two widths are 3.39 ± 0.1 × 106 K and 2.74 ± 0.1 × 106 K, respectively. The Doppler velocity changed gradually from 0 ± 0.5 km s‑1 to ‑3 ± 0.5 km s‑1 during the abovementioned intensity increase phase. It slowly reverted to 0 ± 0.5 km s‑1 when the intensity decreased.

Keywords: The Sun, Solar coronal lines, Solar coronal mass ejections, Solar corona, Solar activity
Mechanical Torque Disruption of Dust Grains Induced by Supernova Shock Waves. The feedback from massive stars drives the evolution of interstellar dust grains by altering their physical properties via a number of radiative and mechanical processes. Through these interactions, interstellar grains can achieve high rotational velocities due to unbalanced torques, potentially leading to their disruption. Mechanical torque disruption (METD) occurs when gas–grain collisions, induced by the passage of shocks, spin grains to critical rotational velocities. This study aims to investigate the effects of stochastic METD on both preexistent and supernova-condensed dust grains located within wind-blown bubbles. The impact of METD on supernova-condensed dust and dust grains in wind-blown bubbles is investigated through postprocessing of three-dimensional hydrodynamical simulation outputs. The associated timescale is then compared to those of kinetic sputtering and grain shattering. Before the supernova explosion, dust grain disruption timescales within wind-driven bubbles are on the order of millions of years due to the low-density environment. The timescales for METD are longer than those for kinetic sputtering and comparable to those of grain shattering, primarily due to the high grain drift velocities typical of these regions.

Keywords: Interstellar dust, Hydrodynamical simulations, Dust physics, Gas-to-dust ratio, Dust destruction, Stellar wind bubbles, Astrophysical dust processes, Supernova remnants, Interstellar dust processes
Identifying Catastrophic Outlier Photometric Redshift Estimates in the COSMOS Field with Machine Learning Methods. We present the result of two binary classifier ensembled neural networks to identify catastrophic outliers for photo-z estimates within the COSMOS field utilizing only eight and five photometric bandpasses, respectively. Our neural networks can correctly classify 55.6% and 33.3% of the true positives with few to no false positives. These methods can be used to reduce the errors caused by the errors in redshift estimates, particularly at high redshift. When applied to a larger data set with only photometric data available, our eight bandpass network increased the number of objects with a photo-z greater than five from 0.1% to 1.6%, and our five bandpass network increased the number of objects with a photo-z greater than five from 0.2% to 1.8%.

Keywords: Classification, High-redshift galaxies, Galaxies, Neural networks
The Dependence of Polarization Degree of Blazars on Particle Energy Distributions. We present a formalism to predict the polarization degree (PD) for synchrotron emission from particles having a specified energy distribution in the presence of an ordered and random magnetic field configuration. The broadband spectral energy distribution and the X-ray and optical PD data for Mrk 501 have been fitted using the formalism. As reported earlier, we find that for a broken power-law particle energy distribution the PD cannot be explained, unless it is assumed that the higher-energy particles experience a higher ordered magnetic field compared to the lower-energy ones. On the other hand, a log parabola particle energy distribution can explain the observed higher X-ray PD compared to the optical, even when all the particles experience the same magnetic configuration. We discuss the possibility of distinguishing the two scenarios using future observations.

Keywords: Blazars, Active galactic nuclei, Jets, BL Lacertae objects
Searching for Internal Absorption Signatures in High-redshift Blazars. The γ-ray emission from flat spectrum radio quasars (FSRQs), a subclass of blazars, is believed to be generated through interactions of high-energy leptons and/or hadrons in the jet with the ambient photon fields, including those from the accretion disk, the broad line region (BLR), and the dusty torus. However, these same photon fields can also attenuate γ-rays through internal photon─photon (γ─γ) absorption, imprinting characteristic spectral features. Investigating the internal absorption is crucial for unraveling the complex structure of FSRQs and constraining the poorly known location of the γ-ray emission region. In this study, we select a sample of γ-ray detected FSRQs with high redshift (z ≳ 3) to search for absorption features appearing at lower photon energies due to a substantial redshift. We extract the Fermi Large Area Telescope γ-ray spectra of these sources and perform physical modeling using a detailed γ─γ opacity model, assuming that the BLR photon field dominates the absorption and focusing on the energy range ∼25 GeV/(1 + z), where the absorption feature due to Lyα photons is expected. Our analysis reveals a hint of internal absorption for one source (the lowest redshift object in our sample, z ≃ 3) and provides constraints on the location of its γ-ray emitting region along the jet. For the remaining, higher-redshift sources, the limited photon statistics prevent a reliable detection of internal opacity features.

Keywords: High energy astrophysics, Blazars, Flat-spectrum radio quasars, Active galactic nuclei, Gamma-rays
The Signatures of Density Fluctuations and Mixing Gas in Circumgalactic Absorption Systems. We investigate the prospects for detecting and constraining density and temperature inhomogeneities in the circumgalactic medium using absorption measurements of metal ions. Distributions in the gas thermal properties could arise from turbulence, gas cooling from the hot phase, and mixing between the cool and hot phases. Focusing on these physically motivated models, we parameterize each with a single parameter for simplicity and provide empirical and theoretical estimates for reasonable parameter values. We then construct the probability distribution functions for each of these scenarios, calculate the effective ion fractions, and fit our models to the COS-Halos absorption measurements to infer the gas densities and metallicities. We find that the models we consider (i) produce similarly good fits to the observations with or without distributions in the gas thermal properties, and (ii) result in detectable changes in the column densities only at the boundaries of reasonable parameter values. We show that He II self-shielding can have a larger effect on the ion fractions than density and temperature fluctuations. As a result, uncertainties in cloud geometry and their spatial distribution, affecting the details of radiation transfer, may obscure the effect of inhomogeneities.

Keywords: Circumgalactic medium, Quasar absorption line spectroscopy, Intergalactic medium
Once a Giant, (Almost) Always a Giant: Partial Tidal Disruption Events of Giant Stars. Tidal disruption events (TDEs) of giant stars by supermassive black holes (SMBH) differ significantly from those of main-sequence ones. Most (all for SMBH of more than a few ×105m⊙) giant TDEs are partial: only a fraction of the envelope is torn apart. The dense stellar core and the rest of the envelope remain intact. In this work we explore, using the stellar evolution code MESA, the fate of the remnants. We find that after a short period, comparable to the thermal timescale, the remnant returns to a giant structure with a radius comparable to the progenitor giant one, a slightly larger luminosity (as compared with a regular giant with the same mass), and a comparable lifetime until it collapses to a white dwarf. If such a giant with a mass less than ≈0.9m⊙ is discovered, it can be identified as an outlier—a giant that is too light for the current age of the Universe. If the remnant orbit is not perturbed significantly during the encounter, the remnant will undergo successive partial tidal disruptions until its mass is 0.6–0.7m⊙. We expect a few dozen to a few hundred such remnants in the Galactic nucleus.

Keywords: Tidal disruption, Galactic center, Red giant stars, Astrophysical black holes
Detection of Anisotropies in the Circumgalactic Medium of Disk Galaxies: Supermassive Black Hole Activity or Star Formation-driven Outflows?. Gamma and X-ray observatories have revealed spectacular structures in the emission of the tenuous hot gas surrounding the Milky Way (MW), known as the Fermi and extended ROentgen Survey with an Imaging Telescope Array (eROSITA) bubbles. Galaxy formation simulations suggest that MW-like bubbles could be ubiquitous, but their emission may be too faint to detect with today's instruments in individual external galaxies. In this paper, we present an analysis of stacked Chandra observations of 93 nearby galaxies. We detected soft, diffuse X-rays from the circumgalactic medium (CGM), extending up to 14 kpc, with a luminosity of (4.2 ± 0.7) × 1039 erg s‑1 in the 0.3‑2 keV band. To probe its spatial distribution, we constructed an azimuthal profile and found a significant enhancement along the galactic minor axis. When dividing our sample by stellar mass, central supermassive black hole (SMBH) mass, and star formation rate (SFR), we found that only high-SFR galaxies exhibit significant anisotropies in the CGM emission. To investigate whether the observed anisotropies could be attributed to MW-like bubbles, we compared our results with TNG50 simulations. In these simulations, X-ray bubbles are strongly correlated with mass of the central SMBH and typically extend to much larger, ∼50 kpc, scales. We conclude that the observed anisotropies are either caused by active galactic nucleus–driven MW-like bubbles confined to smaller, ∼10 kpc, scales or by star formation– or starburst-driven bubbles/outflows.

Keywords: X-ray astronomy, Circumgalactic medium, High energy astrophysics, Galaxy nuclei
The Emission Geometry of Pulsars with Interpulses. We present polarization profiles of 23 pulsars exhibiting interpulse (IP) emissions using the Five-hundred-meter Aperture Spherical Radio Telescope. By applying the rotating vector model (RVM), we measured the inclination and impact angles for 16 pulsars, allowing us to investigate their beam geometries. Our analysis indicates that for five pulsars, the IP emissions likely originate from the same magnetic pole as the main pulse (MP), whereas for the remaining 11 pulsars, the IP and MP emissions originate from opposite magnetic poles. For the seven pulsars that do not conform to the RVM, we are unable to determine whether the IP emissions originate from the same or opposite magnetic pole as the MPs. By analyzing the beam configurations of pulsars, we found that the emission within the beam is not fully active across both longitude and latitude. Filling factors ranging from 0.27 to 0.99 were obtained for pulsars with opposite pole IP emissions, suggesting an underestimation of emission height when applying the geometrical method. The emissions for MPs and IPs occur at different heights in the pulsar magnetosphere, with the difference in emission height ranging from tens to thousands of kilometers. We also found that some pulsars have wide emission beams, indicating that radio emissions may occur in regions of high altitude within the pulsar magnetosphere.

Keywords: Radio pulsars, Pulsars
Interplanetary Magnetic Field Curvature and Its Role in Particle Acceleration: Magnetospheric Multiscale and Solar Orbiter Observations. The curvature of the magnetic field plays a crucial role in magnetic confinement, magnetic reconnection, particle heating, and acceleration. Though the magnetic field curvature has been sufficiently investigated in the terrestrial magnetosheath, there is a lack of research in the more extensive interplanetary space. This study, combining the Magnetospheric Multiscale and Solar Orbiter (SolO) observations, investigates the magnetic field curvature in the near-Earth and interplanetary space. The spatial distributions and probability distribution functions (PDFs) of the curvature are revealed in the solar wind, magnetosheath, and magnetosphere. It shown that the field curvature in the solar wind follows a two-power-law PDF, similar to that in the magnetosheath but with distinct exponents. We then extend the research to a heliocentric distance of [0.3, 1.0] au, with the aid of an indirect estimation method of magnetic field curvature that can be applied to the SolO data. The average curvature, as a function of heliocentric distance, exhibits a U-shape variation with the minimum curvature appearing at 0.5 au. A possible explanation for such a variation is also given and supported by the spacecraft data. This work could improve our understanding of the turbulent environment in the interplanetary space and demonstrate the universality of a recently proposed acceleration scenario of electrons due to the interaction of shocks and curved magnetic field lines.

Keywords: Interplanetary magnetic fields