Papers for Thursday, May 22 2025

Enceladus is among the most intriguing bodies in the solar system due to its astrobiological potential. Determining the extent and duration of sustainable habitability requires characterizing the interior properties, and in particular, the extent and distribution of the tidal heating. The intensity of any inferred geophysical activity in the core has direct implications for understanding the hydrothermal activity and the budget of biologically useful species. We build a statistical framework using an MCMC approach to constrain the interior based on currently available observations of libration, shape, heat budget, and mass. We use this framework to examine the extent that geodetic measurements can constrain the interior structure, with an emphasis on determining the partitioning of tidal dissipation between the shell and the core. We quantify plausible ranges of gravitational and displacement tidal Love numbers consistent with existing observations. We demonstrate that measuring the amplitude and phase of $k_2$ alone can only constrain the total tidally dissipated energy, without a sensitivity to the distribution of heat. However, measuring the amplitude and phase of $h_2$ or $l_2$ facilitates determination of the shell rheology. We provide the precisions required for measuring $k_2$, $h_2$, and/or $l_2$ that enable distinguishing between the two main scenarios of tidal heating, i.e., in the shell versus the core. We also investigate the effect of the structural heterogeneities of the shell on the tidal response. Lastly, we evaluate the efficacy of a suite of future geodetic measurements to constrain key interior properties essential to instantaneous and sustained habitability at Enceladus.

We report the detection of a spin-down glitch with a fractional frequency change of $\Delta\nu/\nu=-3.46(6)\times10^{-9}$ in the rotation-powered pulsar PSR J1835$-$1106 at MJD 55813, based on timing observations collected with the Nanshan 26-m and Parkes 64-m radio telescopes from January 2000 to July 2022. A comparison of the average pulse profiles within $\pm300$ d of the event reveals no significant morphological changes. We also estimate the angular velocity lag between the normal and superfluid components at the time of the glitch, demonstrating that one of the spin-down glitch models proposed by Kantor & Gusakov (2014) is not applicable to PSR J1835$-$1106.

We present the X-ray analysis of seven local compact elliptical galaxies (cEGs), selected for their morphological resemblance to high-redshift red nuggets. As likely descendants of the red nugget population, cEGs offer a unique window into the early Universe, enabling the study of early galaxy evolution and the interplay between black holes, stellar bulges, and dark matter halos. Using data from Chandra and XMM-Newton, we investigate the properties of the hot gaseous halos in cEGs. Two galaxies - MRK 1216 and PGC 32873 - host luminous, spatially extended X-ray atmospheres, allowing us to derive radial thermodynamic profiles. For MRK 1216, we performed high-resolution spectral modeling with RGS data, which hints at super-solar $\alpha/\rm{Fe}$ abundance ratios. The remaining galaxies show either faint or undetected X-ray halos, though several display AGN-like (active galactic nucleus) power-law emission. In the context of local scaling relations, cEGs show only mild deviations from the general galaxy population, exhibiting a slightly steeper $M_{\star}-L_{X}$ relation and occupying the lower boundary of the $M_{\star}$-$M_{\rm vir}$ relation. These trends suggest that high-redshift red nuggets may also host a diverse range of X-ray atmospheres. We speculate that the compactness of cEGs may trace back to the population of `little red dots' (LRDs), hinting at a potential link between LRDs, red nuggets, and compact relic galaxies in the local Universe.

The evolution of interstellar ices can be studied with thermal tracers such as the vibrational modes of CO$_2$ ice that show great diversity depending on their local chemical and thermal environment. In this work we present JWST observations of the 15.2 $\mu$m bending mode, the 4.39 $\mu$m stretching mode and the 2.70 $\mu$m combination mode of $^{12}$CO$_2$ and $^{13}$CO$_2$ ice in the high-mass protostar IRAS 20126 and the low-mass protostar Per-emb 35. The 15.2 $\mu$m bending mode of both protostars shows the characteristic double peak profile that is associated with pure CO$_2$ ice and a sharp short-wavelength peak is observed at 4.38 $\mu$m in the $^{13}$CO$_2$ bands of the two sources. Furthermore, a narrow short-wavelength feature is detected at 2.69 $\mu$m in the $^{12}$CO$_2$ combination mode of Per-emb 35. We perform a consistent profile decomposition on all three vibrational modes and show that the profiles of all three bands can be reproduced with the same linear combination of CO$_2$ ice in mixtures with mostly CH$_3$OH and H$_2$O ices when the ices undergo segregation due to heating. The findings show that upon heating, CO$_2$ ice is likely segregating from mostly the water-rich ice layer and the CO$_2$-CH$_3$OH component becomes dominant in all three vibrational modes. Additionally, we find that the contribution of the different CO$_2$ components to the total absorption band is similar for both $^{12}$CO$_2$ and $^{13}$CO$_2$. This indicates that fractionation processes must not play a significant role during the different formation epochs, H$_2$O-dominated and CO-dominated. We quantify the $^{12}$CO$_2$ and $^{13}$CO$_2$ ice column densities and derive $^{12}$C/$^{13}$C$_{ice}$ = 90 $\pm$ 9 in IRAS 20126. Finally, we report the detection of the $^{13}$CO$_2$ bending mode of pure CO$_2$ ice at 15.64 $\mu$m in both IRAS 20126 and Per-emb 35.

Compact elliptical (cE) galaxies are compact stellar systems with stellar masses of $10^8 \leq M_*/M_\odot \leq 10^{10}$ and radii typically < 0.6 kpc. Here we investigate the properties of 13 cE galaxies in the Coma cluster, six newly identified. Our goal in this paper is to explore whether these cEs form directly in the cluster environment or are pre-processed in small groups before infalling. We find that pre-processing in groups significantly contributes to the cE population in the Coma cluster. We analyze Hyper Suprime-Cam (HSC) g band Coma images and validate our photometric measurements through comparison with Hubble Space Telescope (HST) data. We also analyze spectroscopic data from the Dark Energy Spectroscopic Instrument (DESI). We significantly expand the known cE population in the Coma cluster through joint photometric and spectroscopic selection. We identify a subpopulation of cEs that likely formed in infalling groups, through their association with host galaxies, their positions on the caustic diagram, and their projected phase-space trajectories. We estimate that the central cE population will increase by 30% within the next 0.4 Gyr, highlighting the important role of pre-processing in cE evolution.

The nature of magnetic fields in the voids of the large-scale structure of the Universe has been a multifaceted open puzzle for decades. On one hand, their origin is not clear with most of the magnetogenesis models using physics beyond the standard model in the early Universe, and on the other hand, their existence and potential role in explaining the spectra of TeV blazars have been intensely debated in the past decade. Here, we show that void fields must exist and can be generated using classical electrodynamics in the late Universe. Specifically, we use the dipole component of the galactic fields, decaying as $r^{-3}$, and show that this generates space-filling magnetic fields in voids with sufficient amplitude to explain the blazar spectra and the lack of GeV halos observed by Fermi-LAT. Our results also show that the void fields might be too strong even for Cherenkov Telescope Array to observe the GeV halos. While primordial magnetic fields could still have been generated through some non-standard physics in the early Universe, our results show that the need for primordial magnetic fields is not strengthened by the presence of void magnetic fields.

We have analyzed publicly available optical spectra of PMN J0948+0022 obtained with the Sloan Digital Sky Survey, X-Shooter, and the Multi Unit Spectroscopic Explorer (MUSE). Initially, PMN J0948+0022 was classified as a jetted narrow-line Seyfert 1 galaxy, but X-Shooter and MUSE observations, which have better spectral resolution, revealed a different profile for the H$\beta$ line, from Lorentzian to a composite one (a combination of a broad and a narrow Gaussian), more typical of intermediate Seyfert galaxies. According to the unified model, intermediate Seyferts are viewed at larger angles. However, we show that, in this case, the composite line profile results from the interaction of the powerful relativistic jet with the narrow-line region. The jet transfers part of its kinetic energy to the narrow-line region, producing flux changes in the H$\beta$ narrow component (drop by a factor of 3.4 from SDSS to X-Shooter), [O III]$\lambda$5007 core component (which nearly doubled from X-Shooter to MUSE), and its blue wing ($\Delta$v$\sim$200 km s$^{-1}$), which we interpret as evidence of an outflow. We also recalculated the physical parameters of this AGN, obtaining a black hole mass of $10^{7.8}$ M$_{\odot}$ and an Eddington ratio of $\sim$0.21 (weighted mean).

Supermassive black hole binary (SMBHB) systems are expected to form as a consequence of galaxy mergers. At sub-parsec separations, SMBHBs are difficult to resolve, but can be identified as quasars with periodic variability. Previous periodicity searches have identified statistically significant candidates, but focused primarily on sinusoidal signals. However, theoretical models and hydrodynamical simulations predict that binaries produce more complex non-sinusoidal pulse shapes. Here we examine the efficacy of the Lomb-Scargle periodogram (LSP; one of the most popular tools for periodicity searches in unevenly sampled lightcurves) to detect periodicities with a saw-tooth shape mimicking results of hydrodynamical simulations. We simulate quasar lightcurves with damped random walk (DRW) variability and inject periodic signals. Our mock sample of 12,400 quasars consists either of idealised well-sampled lightcurves, or mimics the data in the Palomar Transient Factory (PTF) analyzed in Charisi et al, 2016. We assess the statistical significance of recovering two types of periodic signals, i.e. with sinusoidal and sawtooth pulse shapes. We find that the LSP detects 39.1% and 28.1% of the sinusoidal signals, in the PTF-like and idealised lightcurves, respectively. The fraction is significantly reduced for sawtooth periodicity, with only 7.5% and 1.1% detected in PTF-like and idealised lightcurves, respectively. These low recovery rates imply that previous searches have missed the large majority of binaries. Therefore, significant improvements are required beyond simple LSPs to successfully uncover SMBHBs in upcoming time-domain surveys.

Dark matter (DM) spikes around supermassive black holes (SMBHs) may lead to interesting physical effects such as enhanced DM annihilation signals or dynamical friction within binary systems, shortening the merger time and possibly addressing the `final parsec problem'. They can also be promising places to study the collisionality of DM because their velocity dispersion is higher than in DM halos allowing us to probe a different velocity regime. We aim to understand the evolution of isolated DM spikes for self-interacting dark matter (SIDM) and compute the BH accretion rate as a function of the self-interaction cross-section per unit DM mass ($\sigma/m_\chi$). We have performed the first $N$-body simulations of SIDM spikes around supermassive black holes (SMBH) and studied the evolution of the spike with an isolated BH starting from profiles similar to the ones that have been shown to be stable in analytical calculations. We find that the analytical profiles for SIDM spikes remain stable over the time-scales of hundreds of years that we have covered with our simulations. In the long-mean-free-path (LMFP) regime, the accretion rate onto the BHs grows linearly with the cross-section and flattens when we move towards the short-mean-free-path (SMFP) regime. In both regimes, our simulations match analytic expectations, which are based on the heat conduction description of SIDM. A simple model for the accretion rate allows us to calibrate the heat conduction in the gravothermal fluid prescription of SIDM. Using this prescription, we determine the maximum allowed accretion rate which occurs when $r_{\rm isco} \rho(r_{\rm isco}) \sigma/m_\chi \sim 1$, where $r_{\rm isco}$ the radius of the innermost stable orbit. Our calibrated DM accretion rates could be used for statistical analysis of SMBH growth and incorporated into subgrid models to study BH growth in cosmological simulations.

Galaxy evolution is driven by spatially distributed processes with varying timescales. Integral field spectroscopy provides spatially-resolved information about these processes. Nevertheless, disentangling these processes, which are related to both the underlying stellar populations and the interstellar medium can be challenging. We present a case study on NGC~613, observed with MUSE (Multi-Unit Spectroscopic Explorer) for the TIMER (Time Inference with MUSE in Extragalactic Rings) project, a local barred galaxy, which shows several gas ionisation mechanisms and is rich in both large and inner-scale stellar structures. We develop a set of steps to overcome fundamental problems in the modelling of emission lines with multiple components, together with the characterisation of the stellar populations. That results in the disentanglement of the gas ionisation mechanisms and kinematics, along with an optimal parametrisation for star formation history recovery. Our analysis reveals evidence of gas inflows, which are associated with the bar dust lanes traced with \textit{Hubble} Space Telescope (HST). In addition, we show the gas kinematics in a central biconical outflow, which is aligned with a radio jet observed with Very Large Array (VLA). The emission line provides estimates of electron density, gas-phase metallicity, and the mass outflow rate, allowing us to distinguish intertwined ionisation mechanisms and to identify a part of the multiphase gas cycle in NGC 613. It traces the gas kinematics from the bar lanes to inner scale gas reservoirs, where it can eventually trigger star formation or AGN activity, as observed in the outflow.

We develop and present the Descriptive Parametric Model (DPM), a tool for generating profiles of gaseous halos (pressure, electron density, and metallicity) as functions of radius, halo mass, and redshift. The framework assumes spherically symmetric, volume-filling warm/hot gas, and the DPM framework enables mock observations of the circumgalactic medium (CGM), group halos, and clusters across a number of wavebands including X-ray, sub-millimeter/millimeter, radio, and ultraviolet (UV). We introduce three model families calibrated to reproduce cluster profiles while having different extrapolations to the CGM -- (i) self-similar halos, (ii) a reduced gas model for lower halo masses, and (iii) a model with shallower radial slopes at lower masses. We demonstrate how our z = 0.0 - 0.6 models perform when applied to stacked and individual X-ray emission profiles, measurements of the thermal and kinetic Sunyaev-Zel'dovich Effect, electron dispersion measures from fast radio bursts, O VI absorption, and UV-derived pressures. Our investigation supports models that remove baryons from halos more effectively and have shallower profiles at lower halo mass. We discuss biases and systematics when modelling observables using consistent hot gaseous halo models for all wavebands explored. We release the DPMhalo code to encourage the use of our framework and new formulations in future investigations. Included with the DPMhalo distribution is a set of recent observations that allow the reproduction of most plots in this paper.

The Fornax dwarf spheroidal galaxy has five massive globular clusters (GCs). They are often used for testing different dark matter and modified gravity theories, because it is difficult to reconcile their old stellar ages with the short time they need to settle in the center of the galaxy due to dynamical friction. Using high resolution $N$-body simulations with the Phantom of Ramses code, we investigate whether the GCs of Fornax can be reconciled with the modified Newtonian dynamics (MOND), namely its QUMOND formulation. Observational data interpreted in MOND indicate that Fornax is a tidal dwarf galaxy formed at redshift $z=0.9$ in a flyby of the Milky Way (MW) and Andromeda galaxies, and that its GCs were initially massive star clusters in the disk of the MW. This helps us to set up and interpret the simulations. In the simulations, a point-mass GC orbits Fornax, and they both orbit the MW. When we ran multiple simulations with varying initial conditions for the GC, we found a 20% probability of Fornax being observed with five unsunk GCs. The unsunk GCs have the observed radial distribution. Moreover, we found: 1) In MOND, Fornax has an orbit around the MW such that the pericenters coincide with the observed peaks in the star formation history of Fornax; 2) The simulations reproduce the observed ``diffuse stellar halo'' of Fornax; 3) The simulations predict that Fornax has a stellar stream, which could be detectable in the existing data. 4) An extra simulation shows that if Fornax was initially a rotating disky tidal dwarf galaxy, the gravitational influence of the MW would be able to transform it into a nonrotating spheroidal. 5) Sometimes Phantom of Ramses does not conserve angular momentum. This makes the GC sink too fast if it is simulated as an $N$-body object.

Astrometry from the Gaia mission has revealed a large population of white dwarf (WD) + main sequence (MS) binaries with periods of $100 - 1000\,$d. Such systems have separations intermediate to predictions from standard binary evolution scenarios, challenging models of binary interaction and mass transfer. Because the selection function of Gaia astrometric catalogs is complex, the underlying population demographics of WD+MS binaries remain imperfectly understood. We present a forward-model of the au-scale WD+MS binary population probed by Gaia that begins with a realistic binary population and incorporates a full model of Gaia mock observations and astrometric model fitting, as well as cuts employed in producing the Gaia astrometric catalog and selecting WD+MS binary candidates. Our model allows us to constrain the intrinsic population demographics of intermediate-separation WD+MS binaries. The inferred period distribution is close to flat, with ${\rm d}N/{\rm d}P_{\rm orb}\propto P_{\rm orb}^{-0.25}$, while the WD mass distribution is sharply peaked at $0.6\,M_{\odot}$. We model the formation of au-scale WD+MS binaries as the result of interaction when the WD progenitor is an AGB star. Explaining the mass distributions of both components requires two key assumptions: (1) the mass growth of the WD is terminated when its AGB progenitor overflows its Roche lobe, and (2) post-AGB binaries binaries remain wide only if the accretor-to-donor mass ratio exceeds a critical threshold, $q_{\rm crit} \approx 0.4$. Systems with more unequal mass ratios likely shrink to shorter periods and become classical post-common envelope binaries or merge. The model implies that $\sim 1\%$ of solar-type stars have WD companions with periods of $100 - 1000\,$d, consistent with complementary constraints from self-lensing binaries.

In this paper we present the stellar Value-Added Catalogue (VAC) based on the DESI Data Release 1. This VAC contains stellar parameter, abundance and radial velocity measurements for more than 4 million stars. It also contains, for the first time, measurements from individual epochs for more than a million stars with at least two observations. The main contribution to the catalogue comes from the bright program of the main survey, which includes $\sim $2.5 million stars, and the backup program, which includes $\sim $ 1 million stars. The combined magnitude range for the stars in the catalogue extends from Gaia G $\sim 12$ to G $\sim 21$. For the magnitude range $17.5<G<21$ this catalogue represents a factor of 10 increase in the number of stars with radial velocity and abundance measurements compared to existing surveys. Despite DESI's resolution (R $\sim 2500-5000$), the median radial velocity random error for stars in the catalogue is better than 1 km s$^{-1}$. The stellar parameters and abundances of stars in DESI are measured by two independent pipelines, and after applying a temperature-dependent calibration, [Fe/H] abundances of high signal-to-noise stars are accurate to better than $\sim$ 0.1 dex when compared to high-resolution surveys. The catalogue probes different Galactic components including a particularly large number of distant stars: tens of thousands of stars further than 10 kpc, and thousands further than 50 kpc. The catalogue also contains several thousand extremely metal-poor stars with ${\rm [Fe/H]}<-3$. The released sample of stars includes measurements for thousands of stars that are members of dwarf galaxies, open and globular clusters as well as members of several dozen stellar streams. The next public DESI data release is expected in two years and will contain three times as many stars as DR1.

We investigate the structural and dynamical properties of Open Clusters (OCs) classified as single, in pairs, or in groups. By analysing their mass, size, age, fractality, and mass segregation, we aim to identify systematic differences among these categories and evaluate the role of the Galactic environment in their evolution. Our sample comprises 420 single OCs, 415 in pairs, and 317 in groups. To characterise their structure, we apply the Q-parameter, which distinguishes fractal from radial distributions. We also compute the local density ratio to quantify mass segregation and explore its dependence on environment. Grouped OCs tend to be the youngest, followed by those in pairs, while single OCs generally exhibit older ages. Although sizes are comparable, OCs in pairs and groups tend to be less concentrated. Structurally, grouped OCs show the highest fractality, which decreases with age as clusters evolve towards more radial configurations. Mass segregation is detected in ~80% of OCs, with a slightly higher incidence in single clusters. Some older single OCs show inverse segregation, with massive stars at larger radii. Spatially, single OCs are more dispersed, whereas paired and grouped ones are concentrated in spiral arms and star-forming regions. OC evolution appears to be shaped by both internal dynamics and environmental influences. Single OCs tend to exhibit signs of more advanced dynamical evolution, whereas those in pairs and groups may retain features reflecting their formation environment. Substructures and high fractality in younger clusters suggest that early interactions play a key role in their long-term development. More massive OCs evolve towards radial configurations, while less massive ones may retain fractal properties for longer. These findings highlight the interplay between intrinsic properties and external conditions in shaping OC evolution.

The pairwise Kinematic Sunyaev-Zel'dovich (kSZ) measures both the pairwise motion between massive groups and the amount of gas within them, providing a tracer for the cosmic growth. To interpret the cosmological information in kSZ, it is crucial to understand the optical cluster selection bias on the kSZ observables. Line-of-sight structures that contribute to both the optical observable (e.g. richness) and the kSZ signal can induce a correlation between these two quantities at fixed cluster mass. The selection bias arising from this correlation is a key systematic effect for cosmological analyses and has the potential to resolve the tension between the cosmological constraints from the DES-Y1 cluster counts, lensing, and Planck. In order to test for a kSZ equivalent of such a bias, we adopt an alternative mock richness based on galaxy counts within cylindrical volumes along the line-of-sight. We apply the cylindrical count method to hydrodynamical simulations across a wide range of galaxy selection criteria, assigning richness consistent with DES-Y1 to the mock clusters. We find no significant bias on pairwise kSZ, pairwise velocities, or optical depth, when comparing optically selected clusters to mass-selected halos, within our uncertainty limits of approximately 16, 10, and 8 per cent, respectively.

Stellar streams -- formed from tidally stripped globular clusters or dwarf galaxies -- are sensitive tracers of a galaxy's accretion history and gravitational potential. While numerous streams are known in the Milky Way (MW), the formation and evolution of stellar streams have been primarily studied in isolated settings. The impact of subsequent galaxy interactions on stellar streams remains largely unexplored. Understanding merger-induced effects is however, crucial given the accretion of the Large Magellanic Cloud (LMC) onto the MW, and the fact that for example M31 and Cen A have experienced recent mergers. We analyze the detailed evolution of 1024 stellar streams during a complete MW--LMC-like merger, systematically varying initial stream properties and considering various orbits for the infalling perturber. We find that an MW--LMC mass-ratio merger significantly alters stellar stream properties, including energy, angular momentum, orbit, and morphology. Some streams exhibit dramatic morphological changes or develop complex substructures, while others see substantial shifts in energy and/or angular momentum, or re-orient their orbital plane. Interestingly, strong morphological alterations do not necessarily correlate with large changes in energy or orbit. A few streams split apart with parts moving to different orbits, appearing disconnected in position and kinematics despite their common origin. Strong effects correlate with close encounters between stream particles and the infalling perturber at various times during the merger. Our findings highlight the considerable impact of significant accretion events on the properties of stellar streams, and the challenge to recover the initial orbits of streams from their appearance at the present-day. Visualizations of the detailed evolution of all 1024 stellar streams are available at this https URL.

Tidal deformability of a 1.4 $M_\odot$ neutron star provides a pivotal window into the physics of dense nuclear matter, bridging gravitational-wave(GW), electromagnetic observations and nuclear physics. In this work, we present a novel, data-driven approach to constrain $\Lambda_{1.4}$ without invoking specific equation-of-state(EOS) models. By interpolating directly over the mass--tidal-deformability posteriors from GW170817, we obtain an EOS-independent constraint of $ \Lambda_{1.4} \;=\; 222.89_{-98.85}^{+420.33}. $ We further combine these GW-based results with the X-ray EOS-independent constraint from \cite{Huang_2025}, deriving a multimessenger limit of $ \Lambda_{1.4} \;=\; 265.18_{-104.38}^{+237.88}, $ which remains largely EOS agnostic. This framework demonstrates that higher-order terms neglected in linear expansion methods do not significantly affect $\Lambda_{1.4}$ estimates under current observational uncertainties. As gravitational-wave detectors improve in sensitivity and more binary neutron-star mergers are discovered, our purely data-driven strategy can serve as a robust standard baseline for extracting neutron-star interior properties without relying on unverified EOS models.

Measuring the distribution of spin tilts-the angles between the spin vectors and the binary orbital angular momentum-in stellar-mass binary black holes detected by LIGO-Virgo-KAGRA would provide valuable insight into their astrophysical origins. Analyses of the 69 binary black holes detected through LIGO-Virgo-KAGRA's third observing run yielded model-dependent conclusions, particularly regarding whether the spin tilt distribution exhibits a peak near alignment, as expected for binaries formed in galactic fields. In this work, we simulate populations of up to 1500 binary black hole systems with parameters consistent with the default GWTC-3 analysis, while introducing a correlation that favors small spin tilts for binaries with mass ratios near unity. We find that: (a) spurious peaks away from perfect alignment are possible even with catalogs of up to 300 sources; (b) establishing a definitive peak at alignment remains difficult even with 1500 detections; (c) integrated measurements -- such as the fraction of events with tilt angles smaller than $10^\circ$ or greater than $90^\circ$ -- are more robust and should be preferred, achieving relative 90\% credible uncertainties of $\sim20\%-80\%$ with 1500 sources; and (d) even with the largest simulated catalogs, evidence for a mass ratio-tilt correlation remains inconclusive. Our results suggest that identifying the formation channels of merging black holes using spin tilts will remain challenging, but that model-independent measurements may yield more informative insights over model parameters themselves.

We present a comprehensive study of formaldehyde (H2CO) absorption and radio recombination line (H110a) emission in 215 molecular clouds from the Bolocam Galactic Plane Survey (BGPS), observed using the Nanshan 25-m radio telescope. H2CO was detected in 88 sources (40.93 percent) with 59 being new detections, while H110a emission was found in only 11 sources (5.12 percent), all coincident with H2CO absorption. There exists a correlation of H2CO fluxes with millimeter fluxes below a 3 Jy threshold and an increased dispersion above it, suggesting the sub-CMB cooling of H2CO. Cross-matching with kinematic distance catalogs revealed H2CO spanning galactocentric distances from 0.216 to 10.769 kpc, with column densities ranging from 7.82 x 10^11 to 6.69 x 10^14 cm-2. A significant inverse correlation was observed between H2CO detection fraction and galactocentric distance, suggesting enhanced star forming activity closer to the Galactic Center. These findings challenge traditional Galactic Habitable Zone (GHZ) models by demonstrating the presence of biogenic precursors in the inner Galaxy, shielded within dense molecular clouds. Our results underscore the importance of incorporating chemical tracers like H2CO, alongside physical constraints, to refine the boundaries of the GHZ and advance the research of prebiotic chemistry in the Milky Way.

Linear polarimetry of unresolved stars is a powerful method for discerning or constraining the geometry of a source and its environment, since spherical sources produce no net polarization. However, a general challenge to interpreting intrinsic stellar polarization is the contribution to the signal by interstellar polarization (ISP). Here, we review methodologies for distinguishing the stellar signal from the interstellar contribution in the context of massive stars. We first characterize ISP with distance using a recent compilation of starlight polarization catalogs. Several scenarios involving Thomson scattering, rapidly rotating stars, optically thick winds, and interacting binaries are considered specifically to contrast the wavelength-dependent effects of ISP in the ultraviolet versus optical bands. ISP is recognizable in the stellar polarization from Thomson scattering in the polarization position angle rotations. For hot stars with near-critical rotation rates, the ISP declines whereas the stellar continuum polarization sharply increases. In the case of quite dense winds, strong ultraviolet lines trace the ISP, which is not always the case in the optical. In the binary case, temporal and chromatic effects illustrate how the ISP displaces variable polarization with wavelength. This study clarifies the impacts of ISP in relation to new ultraviolet spectropolarimetry efforts such as Polstar and Pollux.

Accretion disks surrounding supermassive black holes can potentially form stars within the self-gravitating region. These stars undergo high accretion rates because of the dense environment of the active galactic nuclei (AGN) accretion disk. The vorticity of the AGN disk may influence the ultimate mass feeding rate toward the star. In our study, we simulate mass feeding rates onto stars at different AGN disk thicknesses through 3D numerical models to explore the relationship between feeding rates and the thermal mass of the star ($q_{\rm th}$), defined as the ratio of the star's Bondi radius to the AGN disk thickness. Our findings indicate that disk shearing with angular momentum can notably decrease the feeding rate, and we provide an approximate formula that links the feeding rate based on the angular momentum of the surrounding gas and the thermal mass $q_{\rm th}$. Lastly, we examine the potential feedback of the rapidly accreting stars on the AGN disk and their subsequent evolution.

We present an analysis of the molecular and atomic gas properties of 10 spatially resolved galaxies in the A2626 cluster (z = 0.055), observed as part of the SYMPHANY project. Using CO(2-1) observations from ALMA and SMA, together with HI data from MeerKAT, we examine the interplay between gas phases and environmental influences. A joint morphological and kinematic analysis reveals that while the kinematic behavior of HI and CO are often similar, morphologically the atomic gas is more extended compared to centrally concentrated CO distributions, making it more susceptible to environmental stripping. However, we also find evidence for molecular gas asymmetries, disturbed velocity fields, and H2 deficiencies in some galaxies, indicating that H2 reservoirs can also be disrupted in dense environments. Compared to Virgo-a dynamically unrelaxed, non-cool-core cluster-A2626's relaxed, cool-core structure likely results in less intense ram-pressure stripping. This may allow galaxies to retain more atomic gas, while local interactions or pre-processing may still affect the molecular phase, causing relatively low HI deficiencies but high H2 deficiencies in A2626 galaxies. This is also reflected in the higher gas fractions, slightly elevated SFRs, along with shorter depletion timescales (0.3-3 Gyr), implying moderately enhanced star formation efficiency A2626 galaxies. Moreover, the lack of correlation between H2 deficiency and cluster-centric distance or velocity suggests that molecular gas evolution in A2626 may be shaped more by early infall or local interactions than by current cluster location.

Galaxies undergoing ram-pressure stripping develop gaseous tails that can extend several kiloparsecs outside the galaxy disc. We used far-ultraviolet and H$\alpha$ imaging from the GASP survey to investigate how different stages of stripping affect star formation properties in the tail and disc of 13 galaxies undergoing stripping. These galaxies have different stripping strengths, as identified from the MUSE integral field spectroscopy. The star-forming knots in the disc and tails show a good correspondence between the measured FUV and H$\alpha$ flux. This is especially true for strong and extreme cases of stripping, which have developed extended ionized gaseous tails featuring clumpy structures. The mechanism behind the H$\alpha$ emission on the tails of these regions, which correlates well with FUV emission, is photoionization caused by young massive stars. The optical emission line ratio maps enable us to understand the emission mechanism, which can be attributed to star formation, LINER activity, or a combination of both phenomena and AGN. The star-forming regions in the emission line maps correspond well to the areas with significant FUV flux in these galaxies. Six galaxies exhibit minimal star formation in their tails, with two cases star formation is limited to the central regions and their discs are truncated. In galaxies with truncated discs, star formation is confined to a smaller region on the disc, as indicated by the FUV flux, compared to H$\alpha$. Galaxies with strong stripping are undergoing recent star formation and are likely recent infalls. Galaxies with truncated discs confine star formation to the center, likely because they have completed a cluster crossing that depleted most of their outer gaseous disc. Galaxies with minimal FUV flux along their tails exhibit unresolved H$\alpha$ emission which may be attributed to processes other than star formation.

We present velocity-resolved reverberation lags of H-beta for 20 active galactic nuclei (AGNs) from the Seoul National University AGN Monitoring Project. We detect unambiguous velocity-resolved structures in 12 AGNs, among which eight objects exhibit symmetric structures, two objects show inflow-like characteristics, and two objects display outflow-like signatures. For two AGNs, we successfully measure the velocity-resolved lags in different years, revealing evidence of evolving broad-line region (BLR) kinematics. By combining our sample with the literature velocity-resolved lags, we find that the symmetric velocity-resolved lags are the most common (40%) type among this sample. The frequency of inflow kinematics is also notable (20%), while outflow kinematics are less common (11%). Our sample significantly expands the previous velocity-resolved reverberation mapping sample in the high-luminosity regime, enabling us to constrain BLR kinematics across a large dynamic range of luminosity.

We investigate how statistical anisotropy (SA) in matter distributions affects the shapes and orientations of cluster-sized halos, using cosmological $N$-body simulations that incorporate SA. While the three-dimensional halo shape parameters show little dependence on SA, we find that halo orientations are significantly influenced, with halos tending to align either perpendicular or parallel to the SA direction. This SA-induced alignment becomes more prominent for more massive halos. Our findings suggest that observational measurements of projected halo shapes, such as those derived from galaxy cluster-galaxy lensing, could provide a novel probe of SA in the universe.

We compute the cross-correlation between the anisotropies of the cosmological gravitational wave background (CGWB) and the galaxy density contrast. We show that the cross-correlation is non-zero due to the {\it late} integrated Sachs-Wolfe (ISW) effect experienced by tensor modes. We study the detection prospects of the cross-correlation signal against cosmic variance (CV), and in the light of incoming LSS and GW surveys, where we found that the signal under certain conditions could be distinguishable from noise. In addition, by considering a CGWB sourced by scalar-induced gravitational waves, and the inclusion of a scale-dependent galaxy bias, we use the cross-correlation to forecast local primordial non-Gaussianity, where we find $\sigma(f_\text{NL}^\text{loc})\sim10$ for CV only and a LSST-like survey. Moreover, by combining the Fisher information of CGWB$\times$LSS with LSS, we are able to improve the constraints by 4\% compared to an LSS-only analysis. Our results imply that a cross-correlation between GW anisotropies and LSS can indeed come from a stochastic background of cosmological origin and could be used to distinguish it from an astrophysical one.

LiteBIRD is a JAXA-led international project aimed at measuring the cosmic microwave background (CMB) polarization with high sensitivity to detect polarization $B$ modes. This detection would provide evidence of inflation. LiteBIRD will observe the full sky for three years at the L2 Lagrange point of the Earth-Sun system across 34-448 GHz, and is expected to launch in the Japanese fiscal year of 2032. The Low-Frequency Telescope (LFT) will observe in the 34-161 GHz range implementing a modified crossed Dragone (MCD) reflective optical design optimized for high optical performance across a wide $18^{\circ} \times 9^{\circ}$ field-of-view (FOV). In this paper, we report the LFT optical design details including its optimization and optical performance assessed using optical simulations. The MCD design consists of a paraboloidal primary and a hyperboloidal secondary reflector with polynomial correction terms up to 7th order, achieving Strehl ratios $\ge 0.97$ at 161 GHz across the FOV. The Mueller QU (UQ) cross-polarization response is $\le -26.9$ dB at 34 GHz. The simulated beam sizes are $< 78^{\prime}$ at 34 GHz. The simulated sidelobe response for the direct and diffuse triple reflection sidelobes are estimated to be $< -57$ dB, and for the focused triple reflection sidelobe $< -37$ dB at 34 GHz. The LFT optical design satisfies all the optical requirements and specifications for the project, and is compatible with the LiteBIRD science goals.

The role of large-scale environment in shaping the structural and kinematic properties of stellar halos remains an open question. We investigate whether the cosmic web environments affect the spatial and velocity anisotropies of stellar halos in Milky Way-mass galaxies. Using high-resolution data from the TNG50 simulation, we analyze 29 stellar halos from each environment and quantify their spatial and kinematic anisotropies as a function of halo-centric radius. We find that stellar halos across all environments generally exhibit increasing spatial anisotropy with radius, with fluctuations corresponding to bound substructures. The velocity anisotropy profiles show radially dominated orbits on average, but also display significant local variation, including tangentially dominated regions. However, no statistically significant differences are observed in the mean spatial or velocity anisotropy profiles across environments, for either the total stellar halo population or for the in situ and ex situ components individually. The large scatter within each environment suggests that the formation of stellar halos is primarily driven by stochastic, small-scale processes such as satellite merger histories, rather than the large-scale geometry of the cosmic web. Our results imply that, at fixed halo mass, the influence of cosmic web environment on the structure of stellar halo is weak or highly non-deterministic. Possible environmental effects may be more prominent at higher masses where accretion is more anisotropic. Exploring this regime will require simulations with both larger volume and higher resolution.

Petabytes of archival high time resolution observations have been captured with the Murchison Widefield Array. The search for Fast Radio Bursts within these using established software has been limited by its inability to scale on supercomputing infrastructure, necessary to meet the associated computational and memory requirements. Hence, past searches used a coarse integration time, in the scale of seconds, or analysed an insufficient number of hours of observations. This paper introduces BLINK, a novel radio interferometry imaging software for low-frequency FRB searches to be run on modern supercomputers. It is implemented as a suite of software libraries executing all computations on GPU, supporting both AMD and NVIDIA hardware vendors. These libraries are designed to interface with each other and to define the BLINK imaging pipeline as a single executable program. Expensive I/O operations between imaging stages are not necessary because the stages now share the same memory space and data representation. BLINK is the first imaging pipeline implementation able to fully run on GPUs as a single process, further supporting AMD hardware and enabling Australian researchers to take advantage of Pawsey's Setonix supercomputer. In the millisecond-scale time resolution imaging test case illustrated in this paper, representative of what is required for FRB searches, the BLINK imaging pipeline achieves a 3687x speedup compared to a traditional MWA imaging pipeline employing WSClean.

The Cold Dark Matter (CDM) model successfully explains large-scale structure formation, but challenges remain at smaller scales, leading to interest in Warm Dark Matter (WDM) as an alternative. The abundance of Milky Way subhalos depends on the mass of WDM particles, allowing constraints to be obtained by comparing observations and theoretical models. However, high-resolution simulations of heavier WDM particle masses are computationally demanding, making semi-analytical approaches valuable. In this study, we evaluate the ability of the Semi-Analytical Sub-Halo Inference Modeling for WDM (SASHIMI-W) to reproduce subhalo mass functions for heavier WDM particle masses. We perform high-resolution cosmological N-body simulations for CDM and WDM with particle masses of 1 keV, 3 keV, and 10 keV, and compare the ratio of the subhalo mass function between WDM and CDM cases. Our results show that SASHIMI-W successfully reproduces the simulation results over redshifts z = 0 to z = 2. Furthermore, both simulations and the semi-analytical model show a slight redshift dependence in the subhalo suppression ratio. However, a direct comparison of the differential subhalo mass functions shows discrepancies in the mid- and low-mass regions, suggesting that the tidal stripping effects implemented in SASHIMI-W may be too strong for WDM subhalos, or that the removal of spurious subhalos in the simulations is insufficient. These results validate the use of SASHIMI-W in constraining WDM properties, and highlight the need for refinements in both tidal effect modeling and spurious subhalo filtering to improve subhalo abundance predictions.

Millimetre-compact dust disks are thought to have efficient radial drift of icy dust pebbles, which has been hypothesised to produce an enhanced cold ($T<$400 K) H$_2$O reservoir in their inner disks. Mid-infrared spectral surveys, now with the James Webb Space Telescope (JWST), pave the way to explore this hypothesis. In this work, we test this theory for 8 compact disks ($R_\mathrm{dust}<$60 au) with JWST-MIRI/MRS observations. We analyse the different reservoirs that can be probed with the pure rotational lines ($>$10 $\mathrm{\mu}$m) through parametric column density profiles, multiple component slab models, and line flux ratios. We find that not all compact disks show strong enhancements of the cold H$_2$O reservoir, instead we propose three different classes of inner disk H$_2$O distributions. Four of our disks appear to have similar H$_2$O distributions as many of the large and structured disks (Type N or ``Normal'' disks), as is indicated by the slab model fitting and the line flux ratios. These disks have a small cold reservoir, suggesting the inward drift of dust, but it is not as efficient as hypothesised before. Only two disks do show a strong enhancement of the cold H$_2$O emission (Type E or cold H$_2$O enhanced disks), agreeing with the original hypothesis. The two remaining disks are found to be very H$_2$O-poor (Type P or H$_2$O-poor disks), yet show emission from either the hot or immediate reservoirs (depending on the fit) in addition to emission from the cold one. We find that different parametrisations are able to provide a good description of the observed H$_2$O spectra, with the multiple component analysis yielding similar results. Finally, we also report the detection of other molecules in these disks, including a tentative detection of CH$_4$ in CY Tau.

Chandrasekhars $H(\mu)$-function has long been a cornerstone of radiative transfer theory in semi-infinite, isotropically scattering atmospheres subjected to external illumination. However, this classical formulation does not account for thermal emission arising from internal heat sources, which is critical in a variety of astrophysical contexts such as hot Jupiters, brown dwarfs, and irradiated exoplanets, where the re-radiation of absorbed stellar energy significantly alters the emergent intensity. To address this limitation, we extend the diffuse reflection framework to incorporate both isotropic scattering and intrinsic thermal emission, leading to a generalized function known as the $M(\mu)$-function. Building on the formalism of Chandrashekhar (1960) combined with the recent work by Sengupta(2021), we derive the governing integral equations for the $M$-function and express it in terms of three key physical parameters: the radiation direction cosine $\mu$, the thermal emission coefficient $U(T) = B(T)/F$, and the single scattering albedo $\tilde{\omega}_0$. We implement a numerically stable iterative scheme, using Gaussian quadrature method to compute high-precision values of $M(\mu, U, \tilde{\omega}_0)$ across a broad parameter space. In the zero-emission limit, our results recover the classical $H$-function, thus validating the this http URL provide comprehensive values of $M$-function for $\mu \in [0, 1]$, $U < 0.7$, and $\tilde{\omega}_0 < 1$, enabling direct application to modeling diffusely reflected intensities from thermally emitting this http URL a case study, we apply this formalism to exoplanet K2-137b and identify the wavelength range (0.85 -2.5 $\mu$m) where the model is most applicable, highlighting its relevance to the observation range of the telescopes JWST, HST, ARIEL.

Over the past century, the Sun's activity -- which exhibits significant variations -- went through a phase known as the Modern Maximum. Notably, the strongest sunspot cycle on record during this period, and indeed since direct sunspot observations began, was cycle 19; this was followed by a significantly weaker cycle 20. Understanding and reconstructing this extreme variability has remained elusive. Utilizing data-driven, coupled models of magnetic field evolution on the Sun's surface and within its convection zone, here we show that random deviations in the tilt angle and polarity orientation of bipolar sunspot pairs is sufficient to explain these observed, extreme fluctuations during the modern maximum in solar activity. Our results support the theory that perturbation in the poloidal field source of the dynamo mechanism -- mediated via the emergence of anomalously tilted solar active regions - is the primary driver of extreme variations in the Sun's activity. This study has implications for understanding how the Sun may switch from a phase of extreme activity to quiescent, low activity phases -- such as the Maunder Minimum.

In this manuscript, considering evolution of fallback accreting debris in a central Tidal Disruption Event (TDE), the outer boundary increased with time of the disk-like broad emission line regions (BLRs) lying into central accretion disk will lead expected broad emission lines changed from double-peaked to single-peaked. Considering common elliptical orbitals for the accreting fallback TDEs debris, based on simulated results through the preferred standard elliptical accretion disk model, a probability about 3.95\% can be estimated for cases with double-peaked profile changed to single-peaked profile in multi-epoch broad emission lines, indicating such unique profile variability could be indicator for BLRs related to TDE debris. Meanwhile, among the reported optical TDE candidates with apparent broad lines, such profile changes in broad H$\alpha$ can be found in the AT 2018hyz. After accepted the outer boundaries of the disk-like BLRs increased with time, the observed multi-epoch broad H$\alpha$ can be described in AT 2018hyz. Moreover, the elliptical accretion disk model determined time dependent ratios of the outer boundaries of the disk-like BLRs are well consistent with the TDE model expected ratios of the outer boundaries of the fallback TDE debris. Furthermore, the evolution properties of disk-like BLRs can be applied to estimate the locations of the disk-like BLRs of which outer boundary could be about one sixth of the outer boundary of the fallback TDE debris in AT 2018hyz. Such unique profile changes from double-peaked to single-peaked could be applied as further clues to support a central TDE.

We demonstrate that general relativistic corrections to the accretion of relativistic matter onto primordial black holes (PBHs) can significantly enhance their mass growth during the early Universe. Contrary to previous Newtonian treatments, our analysis reveals that PBH masses can increase by an order of magnitude before evaporation, leading to substantial modifications of their lifetime and cosmological imprints. We quantify the resulting shifts in the minimum PBH mass constrained by Big Bang Nucleosynthesis (BBN), the revised lower bound for PBHs surviving today, and the dark matter parameter space allowed by PBH evaporation. Furthermore, we show that the enhanced accretion alters the high-frequency gravitational wave spectrum from PBH evaporation, potentially within the reach of future detectors. Our results provide a comprehensive, relativistically consistent framework to delineate the role of PBHs in early-universe cosmology and dark matter phenomenology.

Flares are short-lived but energetic manifestations of stellar activity. Studying them is crucial, as they emit intense high-energy radiation that can impact the circumstellar environment, especially the atmospheres of orbiting planets. This is particularly relevant for M dwarfs, which frequently flare and often host planets within their habitable zones. Flare-driven photoevaporation and photochemical processes may significantly affect planetary evolution. In this work, we analyzed the flaring properties of a volume-limited, unbiased sample of nearby M dwarfs using data from the Transiting Exoplanet Survey Satellite (TESS). We selected stars within 10 pc from Gaia DR3 and used an iterative Gaussian process to remove long-term stellar variability from the light curves, isolating impulsive flare events. For each flare, we measured amplitude, duration, and total emitted energy. Our sample includes 173 stars and 17,229 detected flares, ranging from 0 to 76 flares per TESS sector. We focused on three representative stars to highlight the diversity in flare activity. Detected flares had energies above 10^29 erg and durations from 2 to 8000 seconds. We modeled cumulative energy distributions with one- and two-slope power-law fits, finding average slopes of -0.79 +/- 0.64 and -1.23 +/- 1.32, respectively. We introduced the Flare Energy Index (GF.01) to describe flare frequency, identifying two populations: fainter stars tend to produce fewer high-energy flares, while brighter stars exhibit more frequent low-energy flares. Finally, we investigated two highly active stars, G 227-22 and G 258-33, observed across many sectors, to study long-term flare behavior and energy trends.

A detailed understanding of cosmic-ray transport in galactic halos is essential for explaining various observations, such as the radio continuum measurements of synchrotron radiation from energetic electrons. Of central importance is the spatial diffusion tensor of cosmic rays, which can be computed in an ab initio manner if the turbulence in the background medium is known. The study aimed to establish a suitable framework to compute the evolution of magnetohydrodynamic (MHD) turbulence and, hence, the diffusion tensor in the dynamical halos of galaxies. The Reynolds-averaged single-fluid MHD equation were solved numerically on a cylindrical grid, assuming axial symmetry and fixed boundary conditions on a central ellipsoid representing the galaxy. The physical properties of both large-scale MHD and small-scale turbulent quantities, including the coefficients of parallel and perpendicular diffusion, were extracted from the resulting steady state. Hydrodynamic validation revealed a persistent instability of the near-axis flow, which could be traced to the galaxy's gravitating mass. The results for the evolution of MHD turbulence in a galactic halo - using parameters approximating those of NGC4631 - enabled an ab initio computation of the spatial diffusion tensor of cosmic rays through the application of a state-of-the-art nonlinear theory. The simulation results reveal variation in turbulence quantities, (i.e., fluctuation energy, correlation scale, and cross helicity) in a dynamical halo. Furthermore, the corresponding diffusion tensor of cosmic rays exhibits significant variation throughout such a halo.

We present the measurements and constraints of intrinsic alignments (IA) in the Physics of the Accelerating Universe Survey (PAUS) deep wide fields, which include the W1 and W3 fields from the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) and the G09 field from the Kilo-Degree Survey (KiDS). Our analyses cover 51deg$^{2}$, in the photometric redshift (photo-$z$) range $0.1 < z_{\mathrm{b}} < 1$ and a magnitude limit $i_{\mathrm{AB}}<22$. The precise photo-$z$s and the luminosity coverage of PAUS enable robust IA measurements, which are key for setting informative priors for upcoming stage-IV surveys. For red galaxies, we detect an increase in IA amplitude with both luminosity and stellar mass, extending previous results towards fainter and less massive regimes. As a function of redshift, we observe strong IA signals at intermediate ($z_{\mathrm{b}}\sim0.55$) and high ($z_{\mathrm{b}}\sim0.75$) redshift bins. However, we find no significant trend of IA evolution with redshift after accounting for the varying luminosities across redshift bins, consistent with the literature. For blue galaxies, no significant IA signal is detected, with $A_{1}=0.68_{-0.51}^{+0.53}$ when splitting only by galaxy colour, yielding some of the tightest constraints to date for the blue population and constraining a regime of very faint and low-mass galaxies.

Context. Integrating the motion of stars in a smoothed potential is necessary in many stellar and galactic studies. Previous works have often used numerical integrators that alternate between linear drifts and velocity kicks (such as the Leapfrog scheme). This approach contrasts with the sophisticated methods developed in planetary dynamics, for which integrators alternate between Keplerian drifts and velocity kicks. Aims. Inspired by the splitting methods used in planetary dynamics, we aim to build an integration scheme dedicated to stellar and galactic dynamics. Methods. We took advantage of the properties of Hénon's isochrone potential to design a symplectic splitting scheme that can be used to integrate the motion of stars in any gravitational potential. This scheme alternates between isochrone drifts and velocity kicks. As a first application, we consider the motion of a star in a Plummer potential -- an essential constituent of galactic potentials -- and determine integration parameters that provide the best efficiency (i.e. best conservation of energy for lowest computational cost). Results. We derive the analytical solution for all kinds of orbits in Hénon's isochrone potential (bound and unbound trajectories) as needed in our integration scheme. Our experiments for stars in a Plummer potential show excellent performances in the inner and outer parts of the gravity field, that is, where the motion of stars is well approximated by isochrone trajectories (with perturbations of order $10^{-3}$ or less). For highly elongated orbits that cross the characteristic length of the Plummer potential, the performance is equivalent to that of previous methods. Conclusions. The splitting scheme presented here is a good alternative to previous methods: it performs at least as well, and up to orders of magnitude better, depending on the dynamical regime of the star.

Most stars end their main-sequence (MS) lives by evolving through the red-giant and asymptotic-giant branches before ending as a quiescent, stable white dwarf. Therefore, it is imperative to model the post-MS as it relates to long-term stability of environments potentially suitable for life. Recent work has shown that gas giants can exist in the habitable zone (HZ) during the red giant phase and around a white dwarf remnant. Icy moons represent large reservoirs of water and will evolve through sublimation and melting when exposed to higher instellation, where the relatively lower surface gravity could lead to the rapid loss of all surface water. We model the surface evolution of Europa when initially exposed to habitable zone instellation in the red giant branch. Modeling the diurnal and yearly flux variations on a 2D map we show that, due to Jupiter's increased albedo, the sub-Jovian hemisphere of Europa largely sublimates while only the anti-Jovian equatorial band sublimates. With the increasing instellation of the red giant branch, both hemispheres sublimate substantially. We then model the evolution of a tenuous water-vapor atmosphere and show it is stable against atmospheric loss for at least 0.2 Gyr in the red giant branch habitable zone. We then present three ways to observe a sublimating Europan-like exomoon and potential spectra. Extending the results of this work to different planets and moons could open up a new pathway by which life could persist beyond the death of a star.

Coronal mass ejections (CMEs) represent the most extreme solar products, showing complex and dynamic structures when detected in situ. They are often preceded by a shock and carry a magnetic cloud organised as a flux rope, surrounded and permeated by turbulent fluctuations, and whose radial size expands during propagation. We investigate the internal dynamics of the 2D section of a cylindrical flux rope propagating at constant velocity in the spherically expanding solar wind, employing the expanding box model, which allows for high spatial resolution. Our setting is simplified, with uniform and non-magnetised solar wind, to which we superpose turbulent fluctuations. We find that the spherically expanding geometry alone perturbs the flux rope equilibrium, producing a radial head-tail velocity profile and a radial size increase. The ratio between the expansion and Alfvén timescales, associated respectively to propagation and internal crossing time, controls the resistance to transverse stretching and the increase of the flux rope radial extent; the plasma beta controls the overall size of the structure. Turbulent fluctuations mainly affect the flux rope transverse structure, spreading its axial field at distances comparable to its size; on the contrary, dynamics along the radial direction remains coherent and the increase in radial size is still consistently observed. We validate our results by comparison with statistical observations and dimensionless estimates, such as the expansion parameter and the radial size scaling exponent, suggesting that the ratio between internal and propagation timescales might help in better classifying different kinds of radial expansions for flux ropes.

Stellar streams are essential tracers of the gravitational potential of the Milky Way, with key implications to the problem of dark matter (DM) model distributions, either within or beyond phenomenological $\Lambda$CDM halos. For the first time in the literature, a DM halo model based on first physical principles such as quantum statistical mechanics and thermodynamics is used to try to reproduce the 6D observations of the Sagittarius (Sgr) stream. We model both DM haloes, the one of Sgr dwarf and the one of its host with a spherical self-gravitating system of neutral fermions which accounts for the effects of particles escape and fermion degeneracy, the latter causing a high-density core at the center of the halo. Full baryonic components for each galaxy are also considered. We use a spray algorithm with $\sim 10^{5}$ particles to generate the Sgr tidal debris, which evolves in the gravitational potential of the host-progenitor system, to compare with the full phase-space data of the stream. We repeat this kind of simulations for different parameter setups of the fermionic model including the particle mass, with special attention to test different DM halo morphologies allowed by the physics. We find that across the different families of fermionic halo models, they can only reproduce the trailing arm of the Sgr stream. Within the observationally allowed span of enclosed masses where the stream moves, neither the power-law like, nor the polytropic behaviour of the fermionic halo models can answer for the observed trend of the leading tail. A conclusion which is shared by former analysis using other type of spherically symmetric haloes. We conclude that further model sophistications such as abandoning spherical symmetry and including the Large Magellanic Cloud perturber are needed for a proper modelisation of the overall Milky Way potential within this kind of first principle halo models.

In a systematic search for eclipsing white dwarfs using Zwicky transient facility (ZTF) data, we found seven eclipsing double white dwarfs with orbital periods ranging from 45 minutes to 3 hours. We collected high-speed light curves, archival multi-wavelength data, and optical spectra for all systems and determined the binary parameters for each of them. We show that six of the systems are low-mass, double helium-core white dwarf binaries, with the last one a carbon-oxygen -- helium core white dwarf binary. These binaries slowly spiral inwards due to gravitational wave energy losses and are expected to merge within 36Myr--1.2Gyr, and we predict that the shortest orbital period binary will show a measurable eclipse arrival time delay within a decade. The two longest systems show a delay in the arrival time of the secondary eclipse, which we attribute to a small eccentricity of $\approx 2\times10^{-3}$. This is the first time that a non-zero eccentricity is measured in a compact double white dwarf binary. We suggest that these systems emerged from the common envelope with this small eccentricity, and because of the relatively long orbital period, gravitational wave emission has not yet circularised the binaries. Finally, we predict that relativistic apsidal precession will result in a change in the delay of the secondary eclipse that is measurable within a decade.

We developed a new model for the production and propagation of spectrally resolved primary and secondary Cosmic Ray (CR) nuclei elements within the framework of the Cosmic Ray Energy Spectrum (CRESP) module of the PIERNIK MHD code. We extend the algorithm to several CR nuclei and demonstrate our code's capability to model primary and secondary CR species simultaneously. Primary C, N, and O are accelerated in supernova (SN) remnants. In contrast, the spallation collisions of the primary nuclei against the thermal ISM protons lead to secondary Li, Be, and B products. All the CR species evolve according to the momentum-dependent Fokker-Planck equations that are dynamically coupled to the MHD system of equations governing the evolution of the ISM. We demonstrate the operation of this system in the gravity-stratified box, reproducing the Milky Way conditions in the Sun's local environment. We perform a parameter study by investigating the impact of the SN rate, CR parallel diffusion coefficient $D_\parallel$, and the rigidity-dependent diffusion coefficient power index $\delta$. A novel result of our investigation is that the Secondary to Primary flux ratio \BtoC grows when the diffusion coefficient grows, due to the weaker vertical magnetic field resulting from CR buoyancy effects. Moreover, a higher SN rate leads to lower values of \BtoC because of stronger winds and the shorter residence of primary CR particles in dense disk regions.

Future third-generation gravitational wave detectors like the Einstein Telescope (ET) and Cosmic Explorer (CE) are expected to detect millions of binary black hole (BBH) mergers. Alongside these advances, upcoming radio surveys, such as the Square Kilometer Array Observatory (SKAO) will provide new sets of cosmological tracers. These include mapping the large-scale distribution of neutral hydrogen (HI) using intensity mapping (IM), HI galaxies and radio continuum galaxies. In this work, we will investigate synergies between gravitational waves (GW) and radio tracers through a multi-tracer approach. We first forecast the precision on the clustering bias of GWs by cross-correlating data from an ET-like detector with an SKAO IM survey. Our results indicate that this approach can constrain the GW clustering bias to within $2\%$ up to $z = 2.5$. Additionally, we explore the potential of a triple cross-correlation using GWs, IM, and photometric galaxies from a survey like LSST. This multi-tracer method enhances constraints on the magnification lensing effect, achieving percent-level precision, and allows for a measurement of the Doppler effect with approximately $15\%$ uncertainty. Furthermore we show for the first time that this method could achieve the precision required to measure subdominant gravitational potential contributions to the relativistic corrections, which had thought to be below cosmic variance. Our analysis highlights the potential of cross-correlations between GWs and radio tracers to improve constraints on astrophysical properties of BBHs, measure relativistic effects, and perform null tests of GR in cosmological scales.

The Hubble tension, as a persistent discrepancy between early-time and late-time measurements of the Hubble constant, motivates explorations of new physics in the early Universe. In a recent early dark energy (EDE) model, we introduced a scalar field interacting with the radiation sector at early-time before recombination. We showed that such a scalar-photon coupling can lead to an accelerated expansion phase in which the energy density of scalar component dilutes faster than radiation does, a crucial feature for a successful EDE model. In the present work, we extend our analysis to investigate how this scalar-photon coupling affects the CMB temperature-redshift law and CMB anisotropies. We demonstrate that the temperature-redshift law deviates from the standard relation $T(z)\propto (1+z)$ due to the scalar-photon coupling. This deviation is controlled by a model parameter $\epsilon$, which quantifies the rate of energy transfer between the scalar field and radiation. We also argue that a positive value of $\epsilon$ shifts the acoustic peaks to larger scales, which potentially alleviates the Hubble tension. These findings suggest that scalar-photon coupling is a testable mechanism for reconciling different cosmological observations.

We conducted a spectroscopic study of 39 blue straggler stars in the globular cluster NGC 3201. The spectra of these stars were collected from the literature. We determined the radial velocity, atmospheric parameters (Teff, log g), and the abundance of Mg, as well as the metallicity ([Fe/H]) of the blue straggler population. The mean radial velocity and [Fe/H] are determined to be 498.0 $\pm$ 5.3 km/s and -1.42 $\pm$ 0.27, respectively, for the blue straggler stars. The derived [Fe/H] is consistent, within uncertainties, with the cluster's [Fe/H] of -1.59 dex. The mean [Mg/Fe] for the blue straggler stars is estimated to be 0.36 $\pm$ 0.73. Importantly, this study first estimates [Mg/Fe] for the blue straggler stars in the cluster NGC 3201.

We update our stellar population models for the time evolution of the number and mass of massive remnants - neutron stars and black holes - with a new initial mass-remnant mass relation for core collapse supernovae. The calculations are based on hydrodynamical simulations and induced explosions of a subset of previously published pre-supernovae models spanning a wide range of stellar mass, metallicity and different values for rotation velocity. The resulting stellar population models predict lower numbers of neutron stars (by up to 0.3 dex) and higher numbers of black holes (by up to 0.8 dex), especially when stellar rotation is considered. The mass fraction locked in neutron stars and black holes is lowest in high-metallicity populations, with the largest number of remnants found at about half-solar metallicity. This mirrors the amount of available gas, ranging from 35 per cent to 45 per cent. We then apply our new models to IFU spectra for ~10,000 galaxies from the SDSS-IV/MaNGA survey for which we previously published spatially-resolved star formation histories. This allows us to probe spatially-resolved graveyards in galaxies of different types. The number and radial distribution of remnants depend on a galaxy's mass, star formation history and metal content. More massive and hence more metal-rich galaxies are found to host fewer remnants. Radial gradients in the number of remnants depend on galaxy mass mostly because of the mass-dependent profiles in mass density: the gradients are flat in low-mass galaxies, and negative in high-mass galaxies, particularly in Milky Way analogues.

The Fermi Gamma ray Space Telescope, launched in 2008, has over 16 years of operations providing gamma ray (8 keV to 300 Gev) spectra science observations of cosmic phenomena. It continues to provide invaluable research for the astrophysics community which include the study of pulsars, cosmic rays, gamma ray bursts, and coordination with gravity wave observations for neutron star mergers. The Fermi Earth orbit at a 500 x 512 km altitude is subject to collision warnings due to new constellations deployed near Fermi: currently over 7,000 satellites and growing. This paper presents analysis concerning changing Fermi's orbit and associated operational flight dynamics considerations. The cadence of burns and expected fuel use for a proposed orbit raise scenario is examined, ensuring that Fermi should have sufficient fuel for end of life operations. In addition, a Monte Carlo design is presented to capture single maneuver model uncertainty.

We present high-resolution near-ultraviolet (NUV) and far-ultraviolet (FUV) deep imaging of the field around the Seyfert galaxy IC~4329A based on five observations performed with the Ultra-Violet Imaging Telescope (UVIT), onboard AstroSat. The long exposures of 82.9 ks in NUV (N245M; $\lambda_{mean}=2447$Å ; $\Delta\lambda = 270$Å) and 92.2~ks in FUV (F154W; $\lambda_{mean} = 1541$Å; $\Delta\lambda=380$Å) bands constitute the deepest observations with $5\sigma$ detection limits of AB magnitudes $m_{NUV}= 26.2$ and $m_{FUV} = 25.7$. Leveraging UVIT's excellent angular resolution (FWHM $\sim 1.2-1.8^{\prime \prime}$), we performed a detailed analysis of the IC~4329A field and detected (above 5$\sigma$ significance level) a total of 4437 and 456 sources in the NUV and FUV bands, respectively. A large number of these detected sources were unknown previously. We performed astrometry and photometry on all detected sources. By cross-matching our catalogue with Gaia-DR3 and XMM-Newton DR12 catalogues, we found 651 optical and 97 X-ray counterparts of our sources. Additionally, we explored UV variability of point sources, identifying 28 NUV sources as variable with a significance above the $2.5\sigma$ level. Of these, only three sources exhibited variability in the FUV band. Utilising the NUV and Gaia fluxes, we determined that two previously catalogued white dwarf candidates are misclassified. Furthermore, we highlight galaxies with atypical morphology, including ring-like structures, multiple compact central sources, bifurcating spiral arms, etc. Follow-up optical spectroscopy and multi-wavelength observations are imperative to further investigate the nature of the sources within this field.

Quasars, powered by gas accretion onto supermassive black holes, rank among the most energetic objects of the Universe. While they are thought to be ignited by galaxy mergers and affect the surrounding gas, observational constraints on both processes remain scarce. Here we unveil a major merging system at redshift $z \approx 2.7$, and demonstrate that radiation from the quasar in one galaxy directly alters the gas properties in the other galaxy. Our findings reveal that the galaxies, with centroids separated by only a few kiloparsecs and approaching each other at speed $\approx550\,$km$\,$s$^{-1}$, are massive, form stars, and contain a substantial molecular mass. Yet, dusty molecular gas seen in absorption against the quasar nucleus is highly excited and confined within cloudlets with densities $\sim 10^5$ - $10^6$ cm$^{-3}$ and sizes $<$0.02 pc, several orders of magnitude more compact than those observed in intervening (non-quasar) environments. This is also approximately 10$^5$ times smaller than currently resolvable through molecular-line emission at high redshifts. We infer that, wherever exposed to the quasar radiation, molecular gas is disrupted, leaving behind surviving dense clouds too small to give birth to new stars. Our results not only underscore the role of major galaxy mergers in triggering quasar activity, but also reveal localized negative feedback as a profound alteration of internal gas structure which likely hampers star formation.

One of the most crucial tests of the standard cosmological model consists on testing possible variations on fundamental physical constants. In frameworks such as the minimally extended varying speed of light model (meVSL), the relationship between the luminosity distance ($D_{\text{L}}$) and the angular diameter distance ($D_{\text{A}}$), namely the cosmic distance duality relation (CDDR), is expected to deviate from $\eta(z) \equiv D_{\text{L}}(z)/D_{\text{A}}(z) = (1+z)^{2}$, making it a powerful probe of a potential variation of such a fundamental constant. Hence, we test the viability of the meVSL model through the CDDR by comparing $D_{\text{A}}$ measurements, provided by the transverse (2D) and anisotropic (3D) baryon acoustic oscillations (BAO) observations from different surveys, like SDSS, DES and DESI, in combination with $D_{\text{L}}$ measurements from Pantheon+ type Ia Supernova (SNe) compilation. The Gaussian Process reconstruction is employed on the SN data to match $D_{\text{A}}$ with $D_{\text{L}}$ at the same redshift. We find no deviation of the standard CDDR relation within 1-2$\sigma$ confidence level when considering SNe with 2D and 3D BAO samples combined together, as well as when considering SNe with 3D BAO only. However, when SNe and 2D BAO only are considered, the standard CDDR is only recovered at $\sim 4\sigma$ confidence level. However, such a result might be due to some recently discussed tensions between SN and BAO datasets, especially at low redshifts, in addition to possible inconsistencies between the BAO datasets individually. Therefore, our results show no significant evidence in favour of the meVSL model, once these potential systematics are taken into account.

We show that the Cosmic Microwave Background (CMB) lensing trispectrum is sensitive to parity violation in Large-Scale Structure (LSS). We obtain a compact expression for the reduced lensing trispectrum that is general for any input matter trispectrum. We then present as an example a simple parity-violating toy model for the latter, and explicitly compute the parity-odd lensing trispectrum, including an estimate of the Signal-to-Noise Ratio (SNR). This work serves as a proof of principle, demonstrating how future studies of more physically motivated models can be conducted. It also provides an intuitive physical explanation of why CMB lensing is sensitive to parity. Our work is the first to point out that secondary CMB anisotropies can be used to probe parity in LSS, and will be important in enabling upcoming experiments such as Simons Observatory and CMB-S4 to contribute maximal power on parity violation.

Context. A defining characteristic of active galactic nuclei (AGN) that distinguishes them from other astronomical sources is their stochastic variability, which is observable across the entire electromagnetic spectrum. Upcoming optical wide-field surveys, such as the Vera C. Rubin Observatory's Legacy Survey of Space and Time, are set to transform astronomy by delivering unprecedented volumes of data for time domain studies. This data influx will require the development of the expertise and methodologies necessary to manage and analyze it effectively. Aims. This project focuses on optimizing AGN selection through optical variability in wide-field surveys and aims to reduce the bias against obscured AGN. We tested a random forest (RF) algorithm trained on various feature sets to select AGN. The initial dataset consisted of 54 observations in the r-band and 25 in the g-band of the COSMOS field, captured with the VLT Survey Telescope over a 3.3-year baseline. Methods. Our analysis relies on feature sets derived separately from either band plus a set of features combining data from both bands, mostly characterizing AGN on the basis of their variability properties and obtained from their light curves. We trained multiple RF classifiers using different subsets of selected features and assessed their performance via targeted metrics. Results. Our tests provide valuable insights into the use of multiband and multivisit data for AGN identification. We compared our findings with previous studies and dedicated part of the analysis to potential enhancements in selecting obscured AGN. The expertise gained and the methodologies developed here are readily applicable to datasets from other ground- and space-based missions.

In this paper it is initiated the systematic study of thermal field theory for generic equilibrium density matrices, which feature arbitrary values not only of temperature and chemical potentials, but also of average angular momentum. The focus here is on scalar fields, although some results also apply to fields with arbitrary spins. A general technique to compute ensemble averages is provided. Moreover, path-integral methods are developed to study thermal Green's functions (with an arbitrary number of points) in generic theories, which cover both the real-time and imaginary-time formalism. It is shown that, while the average angular momentum, like the chemical potentials, does not contribute positively to the Euclidean action, its negative contributions can be compensated by some other contributions that are instead positive, at least in some cases. As an application of the developed general formalism, it is shown that the production of particles weakly coupled to a rotating plasma can be significantly enhanced compared to the non-rotating case. The Higgs boson production through a portal coupling to a dark sector in the early universe is studied in some detail. The findings of this paper can also be useful, for example, to investigate the physics of rotating stars, ordinary and primordial black holes and more exotic compact objects.

We present a rigorous framework for determining the equilibrium configurations of uniformly rotating, self-gravitating fluid bodies. This work addresses the classical challenge of modeling rotational deformation in celestial objects such as stars and planets. By integrating foundational theory with modern mathematical tools, we develop a unified formalism that enhances the precision and generality of shape modeling in astrophysical contexts. Our method applies Lie group theory to vector flows and solves functional equations using the Neumann series. We extend Clairaut's classical linear perturbation theory into the nonlinear regime via Lie exponential mapping, yielding a system of nonlinear functional equations for gravitational potential and fluid density. These are analytically tractable using shift operators and Neumann series summation, enabling explicit characterization of density and gravitational perturbations. This leads to an exact nonlinear differential equation for the shape function, describing equilibrium deformation without assuming slow rotation. We validate the framework through exact solutions, including the Maclaurin spheroid, Jacobi ellipsoid, and unit-index polytrope. We also introduce spectral decomposition techniques for analyzing radial harmonics and gravitational perturbations. Using Wigner's formalism for angular momentum addition, we compute higher-order nonlinear corrections efficiently. The framework includes boundary conditions for Legendre harmonics, supporting the derivation of nonlinear Love numbers and gravitational multipole moments. This work offers a comprehensive, non-perturbative approach to modeling rotational and tidal deformations in astrophysical and planetary systems.

Accurately tracking particles and determining their position along the optical axis is a major challenge in optical microscopy, especially when extremely high precision is needed. In this study, we introduce a deep learning approach using convolutional neural networks (CNNs) that can determine axial positions from dual-focal plane images without relying on predefined models. Our method achieves an axial localization accuracy of 40 nanometers - six times better than traditional single-focal plane techniques. The model's simple design and strong performance make it suitable for a wide range of uses, including dark matter detection, proton therapy for cancer, and radiation protection in space. It also shows promise in fields like biological imaging, materials science, and environmental monitoring. This work highlights how machine learning can turn complex image data into reliable, precise information, offering a flexible and powerful tool for many scientific applications.

We report on comprehensive laboratory studies of the K-shell dielectronic recombination (DR) resonances of Fe XXV - XXI ions that prominently contribute to the hard X-ray spectrum of hot astrophysical plasmas. By scanning a monoenergetic electron beam to resonantly excite trapped Fe ions in an electron beam ion trap, and achieving a high electron-ion collision energy resolution of ~7 eV, we resolve their respective KL$n$ satellites up to n'=11. By normalization to known radiative recombination cross sections we also determine their excitation cross sections and that of the continuum with uncertainties below 15%, and verify our results with an independent normalization based on previous measurements. Our experimental data excellently confirm the accuracy and suitability of distorted-wave calculations obtained with the Flexible Atomic Code (FAC) for modeling astrophysical and fusion plasmas.

Over the last two decades, machine learning models have been widely applied and have proven effective in classifying variable stars, particularly with the adoption of deep learning architectures such as convolutional neural networks, recurrent neural networks, and transformer models. While these models have achieved high accuracy, they require high-quality, representative data and a large number of labelled samples for each star type to generalise well, which can be challenging in time-domain surveys. This challenge often leads to models learning and reinforcing biases inherent in the training data, an issue that is not easily detectable when validation is performed on subsamples from the same catalogue. The problem of biases in variable star data has been largely overlooked, and a definitive solution has yet to be established. In this paper, we propose a new approach to improve the reliability of classifiers in variable star classification by introducing a self-regulated training process. This process utilises synthetic samples generated by a physics-enhanced latent space variational autoencoder, incorporating six physical parameters from Gaia Data Release 3. Our method features a dynamic interaction between a classifier and a generative model, where the generative model produces ad-hoc synthetic light curves to reduce confusion during classifier training and populate underrepresented regions in the physical parameter space. Experiments conducted under various scenarios demonstrate that our self-regulated training approach outperforms traditional training methods for classifying variable stars on biased datasets, showing statistically significant improvements.

For densities beyond nuclear saturation, there is still a large uncertainty in the equations of state (EoS) of dense matter that translate into uncertainties in the internal structure of neutron stars. The MUSES Calculation Engine provides a free and open-source composable workflow management system, which allows users to calculate the EoS of dense and hot matter that can be used, e.g. to describe neutron stars. For this work, we make use of two MUSES EoS modules, Crust Density Functional Theory and Chiral Mean Field model, with beta-equilibrium with leptons enforced in the Lepton module, then connected by the Synthesis module using different functions: hyperbolic tangent, Gaussian, bump, and smoothstep. We then calculate stellar structure using the QLIMR module and discuss how the different interpolating functions affect our results.

We present a method to identify and categorize gravitational wave candidate triggers identified by matched filtering gravitational wave searches (pipelines) caused by transient noise (glitches) in gravitational wave detectors using Support Vector Machine (SVM) classifiers. Our approach involves training SVM models on pipeline triggers which occur outside periods of excess noise to distinguish between triggers caused by random noise and those induced by glitches. This method is applied independently to the triggers produced by the GstLAL search pipeline on data from the LIGO Hanford and Livingston observatories during the second half of the O3 observing run. The trained SVM models assign scores to ambiguous triggers, quantifying their similarity to triggers caused by random fluctuations, with triggers with scores above a defined threshold being classified as glitch-induced. Analysis of these triggers reveals the distinct impact of different glitch classes on the search pipeline, including their distribution in relevant parameter spaces. We use metrics such as the Bhattacharyya coefficient and an over-representation ratio to quantify the consistency and prevalence of glitch impacts over time and across parameter spaces. Our findings demonstrate that certain glitch types disproportionately affect specific regions of the parameter space, and that certain glitch types manifest themselves in the eyes of the pipeline in consistent ways while other types vary significantly. This method provides a framework for understanding and mitigating the influence of non-Gaussian transients on gravitational wave search pipelines, with implications for improving detection sensitivity and better understanding noise populations.

We study the dynamics of odd-parity perturbations on a static and spherically symmetric black hole background with a timelike vector field based on the effective field theory (EFT) approach. We derive the quadratic Lagrangian written in terms of two master variables, corresponding to the tensor and vector gravitons, which are coupled in general, while they can be decoupled on a stealth Schwarzschild(-de Sitter) background. For the stealth Schwarzschild background, we find that the quasinormal mode frequencies for both degrees of freedom are obtained from those in general relativity by simple scaling. Nonetheless, due to the fact that the metric perturbation is a non-trivial linear combination of the two degrees of freedom with different QNM spectra, the ringdown gravitational waves may exhibit characteristic modulation that can in principle be a signature of vector-tensor gravity.

In this paper, we consider a symmetric teleparallel gravity model that extends the general relativity equivalent model by several parity violating interactions between the gravitational field and a scalar field. We derive three different families of background solutions in flat FRW universe, with three classes of different connections. Through investigations on the linear cosmological perturbations, we show that one of the vector modes of this model will evolve into a ghost field at high energy, and the ghost instability can be cancelled only under specific combinations of the coefficients. On two of three families of backgrounds, such combination remains the same as the one we have investigated in our previous work; while on the other family of background, one additional condition should be taken into consider.

In this Letter, we numerically present the possibility of the first-order phase transition occurring through the thermal fluctuation in the early universe. We find that when the temperature is slightly higher than the mass scale of the background field, the bubble-like field configurations appear proceeded by oscillons, which expand and collide to finish the phase transition. We provide the false vacuum decay rate and the accompanied gravitational waves. We also present the vacuum phase transition comparison of the quantum tunneling case and thermal fluctuation case.

Primordial black holes (PBHs), envisioned as a compelling dark matter candidate and a window onto early-Universe physics, may contribute to the part of the gravitational-wave (GW) signals detected by the LIGO-Virgo-KAGRA network. Traditional hierarchical Bayesian analysis, which relies on precise GW-event posterior estimates, for extracting the information of potential PBH population from GW events become computationally prohibitive for catalogs of hundreds of events. Here, we present a fast deep-learning framework, leveraging Transformer and normalizing flows, that maps GW-event posterior samples to joint posterior distributions over the hyperparameters of the PBH population. Our approach yields accurate credible intervals while reducing end-to-end inference time to $\mathcal{O}(1)$ s on a single GPU. These results underscore the potential of deep learning for fast, high-accurately PBH population studies in the era of next-generation GW detectors.

Paleo detectors are emerging dark matter detection technology that exploits ancient minerals as passive, time-integrated detectors. Unlike conventional real-time experiments, they search for permanent damage tracks-typically tens of nanometers to micrometers long-left in crystal lattices by rare particle interactions, most notably dark matter induced nuclear recoils accumulated over millions to billions of years. In this paper I propose a direct detection strategy for cosmic walls-either bubble walls produced by a late-time first-order phase transition or domain walls in a scaling regime-using paleo detectors as the target medium. Because the cosmic wall is expected to traverse Earth at most $\mathcal{O}(1)$ time(s) in cosmic history, an ancient, continuously exposed detector is the only feasible way to observe it directly. By calculating the target recoils, I find that the smoking-gun signature would be parallel damage tracks found worldwide in minerals older than the wall-crossing epoch. I derive the limit on the wall-target coupling by assuming that a wall passed through the Earth within the last 0.5 Gyr. I also mention a novel indirect detection of ultra-relativistic cosmic walls by noting the induced cosmic rays.