Papers for Friday, Nov 21 2025

The model for the Planck-mean dust opacity $\kappa_{P}$ given in Appendix C of the STARFORGE simulations methods paper does not extrapolate well to low radiation temperature $T_{\rm rad}$, so we provide an updated calculation suitable for general use. We also clarify the role of the dust and radiation temperatures in setting the dust opacity, and provide code and calculations of the Planck- and Rosseland- mean dust opacity as a function of both the dust temperature $T_{\rm d}$ and the radiation temperature $T_{\rm rad}$.

We give a preparation-invariant analytic description of image formation near microlensing caustics. After a local Weierstrass preparation at any multiple image (order $d\ge2$), the lens mapping reduces to a single geode variable $m$ satisfying $m=U\,\varphi(m)$, where $U$ is a prepared source coordinate and $\varphi$ is an image-side kernel. The coefficients of $m(U)$ obey closed Hyper-Catalan (HC) recurrences, allowing termwise derivatives and truncation control from the characteristic system. We also use the same form for a short HC predictor-corrector: evaluate the series within its certified radius and apply a brief Newton polish near the boundary. We define an HC signature (first nonzero kernel coefficients) and an HC spectrum (branch points and analyticity radius $\rho_U$), which quantify sparsity, stiffness, and safe evaluation domains. The construction covers folds and cusps of any global degree. On a binary fold and cusp, an artificial decic with a resonant unit, and two triple-lens cusps of a challenging geometry, HC seeds plus a few Newton steps recover the exact images to machine precision within the certified domain and maintain continuity under continuation. The resulting single-series templates (with $(\mathrm{Sig}_R,\rho_U)$ metadata) are ready for photometric and astrometric modeling.

The propagation of cosmic iron nuclei with energies above 10^19 eV from their sources to the Galaxy is discussed by assuming that cosmic rays at ultra-high energies are of extragalactic origin. In extragalactic space, cosmic nuclei interact with background emissions and inevitably fragment. An analysis is performed of the fraction of iron nuclei reaching the Earth and how its energy depends on the distance from cosmic ray sources. It is found that energies of iron nuclei can be used to determine restriction on the distances from their sources

Due to their different nucleosynthetic origin, a stellar population produces oxygen (O) and iron (Fe) on different timescales and their relative abundance can deviate strongly from solar. Galaxy formation models should treat these elements separately, as they play a distinct role in shaping physical phenomena. For example, oxygen mainly sets the gas cooling rate, while the iron abundance sets stellar atmosphere opacities impacting stellar evolution, spectra and feedback. Observations of star-forming galaxies usually only constrain gas-phase oxygen abundance, vastly limiting our capabilities of separating the cosmic evolution of oxygen and iron. Here, we present an observationally-motivated framework to scale the cosmic evolution of O and Fe abundances. We apply the relation between the alpha-enhancement and galaxies' specific star formation rate ([O/Fe]-sSFR; Chruslinska et al. 2024) to derive the Fe and O-dependent cosmic star formation history (cSFH). We find that star formation with near-solar O/Fe is rare: at least 70% of the integrated cosmic stellar mass forms at non-solar O/Fe. The cosmic average metallicity is generally lower in [Fe/H] than in [O/H] (by up to a factor 3), with the offset increasing from redshifts z=0 to z~3 and then approaching the core-collapse O/Fe ratio. We validate our results against samples that probe the Fe-dependent cSFH in different regimes such as absorption-derived <[Fe/H]> from long gamma-ray bursts. Our results impact the interpretations of stellar and galaxy spectra and the predicted rates of transients, especially those linked to metal-poor progenitors (e.g., black hole mergers).

Fossil groups (FGs) are groups or clusters of galaxies with a single, massive, central galaxy and with a clear lack of L* galaxies. The physical reason for their large magnitude gap (dm12) may arise from early FG formation, which allowed all L galaxies to merge with the central one, and/or it could be related to the fact that galaxies accreting on the FGs move on radial orbits, shortening their merging timescales. The latter properties could be linked with the peculiar position of FGs within the cosmic web. We determine the velocity anisotropy profile beta(r) of the fossil cluster A267, which is related to the orbital distribution of cluster galaxies. This is the first individual FG for which the orbital distribution of galaxies is determined. We aim to confirm previous findings based on stack samples that indicate that FGs, on average, host galaxies on more radial orbits than normal clusters. We started with a sample of 2315 redshifts in the field of A267 and we determined the membership for 329 of them. Of these, 174 are located within r200. We used them as tracers of the gravitational potential of the cluster to solve the Jeans equation using the MAMPOSSt algorithm. We thus obtained the cluster mass M(r) and beta(r) profiles. We also estimated M(r) from the X-ray data. A comparison of the MAMPOSSt and X-ray-determined M(r)s allows us to estimate the cluster hydrostatic mass bias, that is consistent with previous findings. The anisotropy parameter beta(r) indicates tangential orbits for the galaxies near the cluster centre and increasingly radial orbits in the external regions. We therefore confirm that FGs are characterised by more radial orbits for their member galaxies than the average cluster population. We speculate that this different orbital distribution might be an important element in creating a large dm12.

We develop a flexible one-dimensional code to model the escape of hydrogen and helium from a hot Jupiter as a result of photoionization from extreme-ultraviolet (EUV) radiation. We include stellar spectrum heating and ionization, radiative cooling by Lyman-$\alpha$ and H$_3^+$, heat conduction, tidal gravity, a H-He reaction network, and account for the secondary ionization of species by photoelectrons. For a fiducial hot Jupiter, we uncover a three-layer structure: an H$_3^+$-cooled layer of molecular hydrogen at the base, enveloped by a Lyman-$\alpha$-cooled layer of neutral hydrogen, which transitions into an ionized wind layer that is cooled by adiabatic expansion. The highest spectral energy photons are deposited in the molecular layer, where, after accounting for energy loss via photoelectrons and ionization, H$_3^+$ is a substantial radiative coolant. We run a grid of models, varying the distance of our fiducial planet from the star. We find that heat conduction at the base starts to have an effect at distances $\gtrsim 0.2$ au, increasing the H$_3^+$ cooling relative to the EUV input flux. At increasing stellocentric distances, the outflow becomes increasingly more neutral. The neutral hydrogen starts to decouple from the ionized outflow, free-streaming out. In pure H-He mini-Neptune/super-Earth simulations, the outflows are significantly cooler, allowing molecules to survive throughout the outflow, pointing toward the likely importance of molecular cooling in determining whether these planets can maintain massive atmospheres. The analysis in this paper provides a framework for understanding the impact of molecular radiative cooling on atmospheric outflows.

The classification of radio galaxies is central to understanding galaxy evolution, active galactic nuclei dynamics, and the large-scale structure of the universe. However, traditional manual techniques are inadequate for processing the massive, heterogeneous datasets generated by modern radio surveys. In this study, we present a probabilistic machine learning framework that integrates Singular Value Decomposition (SVD) for feature extraction with Bayesian ensemble learning to achieve robust, scalable radio galaxy classification. The SVD approach effectively reduces dimensionality while preserving key morphological structures, enabling efficient representation of galaxy features. To mitigate class imbalance and avoid the introduction of artefacts, we incorporate a Local Neighbourhood Encoding strategy tailored to the astrophysical distribution of galaxy types. The resulting features are used to train and optimize several baseline classifiers: Logistic Regression, Support Vector Machines, LightGBM, and Multi-Layer Perceptrons within bagging, boosting, and stacking ensembles governed by a Bayesian weighting scheme. Our results demonstrate that Bayesian ensembles outperform their traditional counterparts across all metrics, with the Bayesian stacking model achieving a classification accuracy of 99.0% and an F1-score of 0.99 across Compact, Bent, Fanaroff-Riley Type I (FR-I), and Type II (FR-II) sources. Interpretability is enhanced through SHAP analysis, which highlights the principal components most associated with morphological distinctions. Beyond improving classification performance, our framework facilitates uncertainty quantification, paving the way for more reliable integration into next-generation survey pipelines. This work contributes a reproducible and interpretable methodology for automated galaxy classification in the era of data-intensive radio astronomy.

We discuss the properties of a sample of z>6 bright (bolometric luminosity L$_{\rm bolo}$>10$^{46.25}$ erg/s) Quasars drawn from a realization of the GAlaxy Evolution and Assembly (GAEA) model coupled with the Planck Millennium Simulation. We focus on the properties and environment of host galaxies, and their evolution down to z=0, with the aim of assessing how well the bright high redshift QSOs population traces the progenitors of most massive haloes in the local Universe. Our results show that at z>6 bright QSOs live in a variety of environments, and that secular processes like disc instability are responsible for triggering roughly the same number of QSOs as galaxy mergers. Half of cubic (7.5 $h^{-1}$ cMpc size) mock fields built around these high-z QSOs include other active galaxies (with L$_{\rm bolo}$>10$^{44}$ erg/s) in sizeable number, the other host galaxies being relatively isolated. The large field-to-field variance in the the number of companions (both active and non-active) recently reported from JWST observations is fairly well reproduced by GAEA predictions. Descendants of host galaxies at z=0 cover a wide range of physical properties and environments with only a small fraction of the hosts of high-z QSOs ending up in massive galaxy clusters. Viceversa, GAEA predicts that only a small fraction of Bright Central Galaxies have a bright z>6 QSOs among their progenitors. Our results suggest that luminous high-z QSO loosely trace the progenitors of low-z galaxy clusters, and that additional information about the environment of high-z QSOs are required to identify the most promising proto-cluster candidates.

To explain the properties of the local galaxy population, theoretical models require active galactic nuclei (AGN) to inject energy into host galaxies, thereby expelling outflows of gas that would otherwise form stars. Observational tests of this scenario rely on determining outflow masses, which requires measuring the electron density ($n_e$) of ionised gas. However, recent studies have argued that the most commonly used diagnostic may underestimate electron densities (and hence overestimate outflow masses) by several orders of magnitude, casting doubt as to whether ionised AGN-driven outflows can provide the impact needed to reconcile observations with theory. Here, we investigate this by applying two different electron-density diagnostics to Sloan Digital Sky Survey (SDSS) spectroscopy of the Quasar Feedback (QSOFEED) sample of 48 nearby type-2 quasars. Accounting for uncertainties, we find that outflow masses implied by the transauroral-line electron-density diagnostic are significantly lower than those produced by the commonly-used `strong-line' [S II](6717/6731) method, indicating a different origin of these emission lines and suggesting that these doubts are justified. Nevertheless, we show that it is possible to modify the [S II](6717/6731) electron-density diagnostic for our sample by applying a correction of $\mathrm{log}_{10}(n_{e\mathrm{,\, outflow}}\mathrm{ [cm}^{-3}\mathrm{]}) = \mathrm{log}_{10}(n_{e\mathrm{,[S\,II]}}\mathrm{ [cm}^{-3}\mathrm{]}) + 0.75(\pm0.07)$ to account for this, which results in values that are statistically consistent with those produced using the transauroral-line method. The techniques that we present here will be crucial for outflow studies in the upcoming era of large spectroscopic surveys, which will also be able to verify our results and broaden this method to larger samples of AGN of different types.

[abridged] The previously inaccessible star formation tracer Pa$\alpha$ can now be spatially resolved by JWST NIRCam slitless spectroscopy in distant galaxies up to cosmic noon. In the first study of its kind, we combine JWST NGDEEP NIRISS and FRESCO NIRCam slitless spectroscopy to provide the first direct comparison of spatially resolved dust-obscured (traced by Pa$\alpha$) versus unobscured (traced by H$\alpha$) star formation across the main sequence. We stack Pa$\alpha$ and H$\alpha$ emission-line maps, along with stellar continuum images at both wavelengths of 31 galaxies at 1<z<1.8 in three bins of stellar mass. Surface brightness profiles are measured and equivalent width (EW) profiles computed. Increasing Pa$\alpha$ and H$\alpha$ EW profiles with galactocentric radius across all stellar masses probed provide direct evidence for the inside-out growth of galaxies both via dust-obscured and unobscured star formation for the first time. For galaxies on the main sequence, a weakly positive ($0.1\pm0.1$) Pa$\alpha$/H$\alpha$ line profile as a function of radius is found at $8.8\leqslant\mathrm{log}(M_{*}/\mathrm{M}_{\odot})<9.9$ with a negative ($-0.4\pm0.1$) Pa$\alpha$/H$\alpha$ line profile found at $9.9\leqslant\mathrm{log}(M_{*}/\mathrm{M}_{\odot})<11.0$. Low mass galaxies ($7.7\leqslant\mathrm{log}(M_{*}/\mathrm{M}_{\odot})<8.8$) with high sSFRs are found to have a negative ($-0.5\pm0.1$) Pa$\alpha$/H$\alpha$ line profile gradient. Our results demonstrate that while inside-out growth via star formation is ubiquitous across the main sequence just after cosmic noon, centrally concentrated dust attenuation is not. Along with other recent work in the literature, our findings motivate future studies of resolved SFR profiles in large samples of individual cosmic noon galaxies across the main sequence, to understand the intrinsic scatter in spatially resolved star formation.

The existence of dark matter (DM) is supported by various macroscopic observations, but its microscopic nature remains elusive. The Galactic Center GeV gamma-ray excess (GCE) has been a leading candidate signal for particle dark matter annihilation. However, an unresolved population of millisecond pulsars (MSPs) in the bulge provides the alternative explanation for the excess. Identifying these MSPs in electromagnetic bands is difficult due to source confusion, pulse broadening, and extinction. Gravitational waves (GWs) provide a complementary probe: a steadily rotating, non-axisymmetric MSP emits a nearly monochromatic GW signal in the sensitive band of ground-based detectors, with amplitude set by its ellipticity. In this work, we systematically investigate the GW emission from the MSP population proposed to explain the GCE and its detectability with current and future detectors. We consider three major scenarios for the origin of ellipticity and model the population properties of these MSPs. We also consider both isolated MSPs and MSPs in binary systems, as well as Doppler effects in the detection. We find that while the signal is below the reach of current interferometers, next-generation detectors such as the Einstein Telescope (ET) and Cosmic Explorer (CE) can detect a fraction of those MSPs, offering a novel test of the MSP interpretation of the GCE. Future directed searches toward the Galactic Center with continued improvements in sensitivities will either uncover this long-sought MSP population or place stringent limits on their ellipticities and abundance, with important implications for both the astrophysical and dark-matter interpretations of the GCE.

We present the deepest HI mass Function (HIMF) ever measured, outside the Local Group. The observations are part of the MeerKAT Fornax Survey and cover a 4 x 4 deg^2 field, corresponding to ~ Rvir. The 3$\sigma$ detection limit is log(MHI/Msun) = 5.7 for a 50 km/s-wide point source. We detect HI in 35 galaxies and 44 clouds with no optical counterparts. Using deep optical images from the Fornax Deep Survey, we show that the clouds are a distinct population, separated by a four magnitude gap from the faintest HI-detected galaxies. The majority (33 out of 44) of the clouds are associated with the two galaxies with the most HI in the cluster -- NGC 1365 and NGC 1427A, although the clouds contribute a negligible amount to the total MHI budget. By performing a SNR analysis and computing the Rauzy statistic on the HI detections, we demonstrate that our catalogue is complete down log(MHI/Msun) = 6, and we are therefore able to probe the HIMF down to this level. We find an abrupt drop of the number density of HI-detected galaxies at log(MHI/Msun) = 7, signifying a clear absence of galaxies between 6 < log(MHI/Msun) < 7. We use the modified maximum likelihood method to fit a Schechter function down to log(MHI/Msun) > 7, the range where the HIMF follows a power-law. The measured low-mass slope is $\alpha$ = -1.31 $\pm$ 0.13, with a characteristic knee mass of log(M*/Msun) = 10.52 $\pm$ 1.89. The low-mass slope matches the slope in the field, while the knee is defined by a single galaxy and is unconstrained. Below log(MHI/Msun) = 7, there is a sharp departure from a Schechter function, and we report the first robust measurement of the collapse of a HIMF. For the HIMF below log(MHI/Msun) = 7 to follow a power-law, tens of galaxies are needed -- a factor ~ six higher than what is observed. The collapse of the Fornax HIMF is likely due to the rapid removal of HI from low-mass galaxies.

We analyzed the spatial distribution of globular cluster (GC) systems across 37 host galaxies in a two dimensional parameter space defined by projected galactocentric distance Rg and metallicity Fe/H. We identified a universal triangular depleted region characterized by a lack of metal poor GCs in the inner parts of host galaxies. The morphology of this depleted region correlates with the luminous mass of the host galaxies; more massive galaxies consistently exhibit more extended depleted regions. We attribute this phenomenon to the combined influence of large scale galactic assembly and internal GC dynamics, particularly the initial retention of black holes within GCs. Metal poor GCs contain a more massive and compact black hole subsystem, which drives more energetic few body encounters and injects greater kinetic energy into the stellar population. This extra energy, combined with strong tidal forces in central galactic regions, accelerates the dissolution of low metallicity GCs, producing the triangular depleted pattern in the Rg - Fe/H space. Stronger tidal fields in more massive galaxies confine surviving metal poor GCs to larger radii, broadening the depleted region. The morphology of this region may serve as a potential distance indicator for host galaxies. Our results also suggest that scenarios with substantial black hole natal kicks are unlikely, as too few retained black holes would erase the metallicity dependent cluster dissolution required to form the observed depletion region.

We present observational constraints on large-scale white noise (LSWN) in the cosmic density field, a phenomenon predicted to arise from non-linear mode coupling during cosmological evolution. Building on the theoretical framework of Paper I, where we demonstrated that non-linearities inevitably redistribute power from small to large scales through mode mixing, we confront these predictions with current cosmological data. We modify the CLASS Boltzmann code to incorporate a white noise component $k_\mathrm{BH}/k$ in the primordial power spectrum and perform parameter estimation using current cosmological data. The non-detection of excess power on the largest observable scales places stringent upper bounds: $k_\mathrm{BH} \leq 1.80 \times 10^{-13}~\mathrm{Mpc}^{-1}$ at 99\% confidence. These constraints imply the primordial power spectrum must deviate from perfect scale invariance on small scales, either through a cutoff at $k_{\mathrm{cut}} \lesssim 3~\mathrm{pc}^{-1}$ or through running of the spectral index with $\alpha_s \lesssim -0.015$. Our results demonstrate that LSWN provides a powerful probe of the primordial spectrum at scales orders of magnitude smaller than directly observable, offering unique constraints on early-universe physics.

We investigate the formation and observable properties of faint satellite galaxies (M$_\rm V > -3$) in Milky Way-like halos using the semi-analytic galaxy formation model Galacticus. The ability of the smallest dark matter halos to form stars depends sensitively on the balance between gas cooling and reionization heating. To quantify how this balance shapes the abundance and properties of the faintest galaxies, we compare two model variants: a fiducial model that includes molecular hydrogen (H$_2$) cooling and UV background radiation, and a No-H$_2$ model with atomic cooling only. Both models reproduce the structural properties of brighter Milky Way satellites, but they diverge at the lowest luminosities in the hyper-faint regime. The fiducial model predicts a substantially larger population of such systems that are on average hosted in halos with lower peak masses and quenched earlier. Many of these predicted systems lie below current observational thresholds but are within reach of next-generation deep imaging surveys. The predicted size-luminosity distributions of both models overlap with the region occupied by recently discovered "ambiguous" systems, whose classification as galaxies or star clusters remains uncertain. Specifically, we find that hyper-faint satellites have line-of-sight velocity dispersions of $\sigma_{\rm los} \sim 1-3$ km/s in the fiducial model, nearly an order of magnitude higher than expected for purely self-gravitating stellar systems of the same stellar mass. This distinction underscores the diagnostic power of precise kinematic measurements for determining whether ambiguous objects are dark matter dominated dwarf galaxies or star clusters, and highlights the importance of upcoming spectroscopic campaigns in resolving the nature of the faintest satellites.

We present new measurements of the chemical abundance pattern in the core of the nearby galaxy cluster Abell~2029, based on XRISM observations with Resolve (37 ks) and Xtend (500 ks), combined with archival data from XMM-Newton (EPIC, RGS) and Chandra. Fe abundances derived from Resolve, Xtend, and EPIC are broadly consistent, while RGS gives systematically lower values. Because the XRISM gate valve remained closed during these observations, Resolve spectral fitting is restricted to the 2--10 keV band, providing reliable constraints only for elements with strong lines in this band (S, Ar, Ca, Fe, Ni). Abundances of the $\alpha$-elements are therefore derived using complementary observations from Xtend, EPIC, RGS, and Chandra. We construct an average X/Fe pattern in the cluster core by using Resolve exclusively for S/Fe, Ar/Fe, Ca/Fe, and Ni/Fe, and RGS + Xtend for O/Fe. The Ne/Fe ratio is averaged from Xtend, EPIC, RGS, and Chandra measurements; Mg/Fe from EPIC and Chandra measurements; and Si/Fe from Xtend, EPIC, and Chandra. Comparison with the supernovae yield models indicates that the observed abundance pattern in A2029 core is best reproduced by a combination of core-collapsed yields from low-metallicity progenitors ($Z_{\rm init}=0.001$) and a sub-Chandrasekhar-mass, double-degenerate Type Ia model. Additionally, we find an excess in Ca abundance in the core of A2029 that cannot be reproduced by the standard supernovae yield models.

We report the results of the optical follow-up of a sample of $\gamma$-ray-emitting active galactic nuclei (AGN). New high-quality optical spectra were obtained using Gran Telescopio Canarias with Optical System for Imaging and low- Intermediate-Resolution Integrated Spectroscopy and the European Southern Observatory Very Large Telescope Unit Telescope 1 with the FOcal Reducer and low dispersion Spectrograph 2. From the analysis of these spectra, we confirmed the previous classification as narrow-line Seyfert 1 (NLS1) for four objects and discovered two new NLS1s, bringing the total number of optically confirmed $\gamma$-NLS1s to 26. We also identified two ambiguous cases between NLS1 and intermediate Seyfert (IS), three IS, one broad-line Seyfert 1, one Seyfert 2. Based on the new spectra, we calculated black hole masses ranging from $10^{6.25}$ to $10^{9.32}$ $M_\odot$, and Eddington ratios spanning 0.05 to 2.07. This reclassification reinforces the scenario in which AGN with relatively small black hole masses are capable of launching powerful relativistic jets, contributing to our broader understanding of $\gamma$-ray-emitting AGN.

A significant amount of work has been devoted to the study of small binary solar system objects. The majority of these binaries, especially among the near-earth or main belt asteroids have small radius ratios, implying a large difference in size between the primary and its companion. Farther from the sun, the binary fraction increases, with the Kuiper Belt having many known binaries with radius ratios of order unity. In this paper, we consider the runaway growth of a binary system in an accretionary stream of small particles. We perform brute-force integrations, each with 10 million test particles and numerically compute the gravitational cross sections for each member of the binary as a function of the system's separation and mass ratio. We show that the behavior of the cross section is complex, and it can be either diminished or enhanced depending on the orbital configuration. In the regime where gravitational focusing dominates the accretion process, we show that binaries grow towards smaller mass ratios than would be expected given single-body cross sections. Finally, we provide a grid of these cross sections for use in the future study of such systems.

In this paper, we describe the SPHEREx image and spectrophotometry data processing pipeline, an infrastructure and software system designed to produce calibrated spectral images and photometric measurements for NASA's SPHEREx mission. SPHEREx is carrying out a series of four all-sky spectrophotometric surveys at 6.15 arcsecond resolution in 102 spectral channels spanning 0.75 to 5 microns. The pipeline which will deliver the flux- and wavelength-calibrated data products deriving from these surveys has been developed and is operated by the SPHEREx Science Data Center at Caltech/IPAC in collaboration with the SPHEREx Science Team. Here we describe the framework and modules used in the pipeline, along with the data products, which are available at the NASA/IPAC Infrared Science Archive.

In this work, we impose observational limits on the product of dark energy chemical potential, $\mu$, and number density, $n$, at the present time in out-of-equilibrium models, considering that particles can be created or destroyed in the fluid at a rate $\Gamma=3\alpha H(a)$, where $\alpha$ is a constant and $H(a)\equiv\dot{a}/a$ is the Hubble parameter. We combine the bounds derived from the positivity of entropy and the second law of thermodynamics with observational constraints on the Chevallier-Polarski-Linder (CPL) and Barboza-Alcaniz (BA) parameterizations of the equation of state (EoS) of the component. We use Type Ia supernovae (SN Ia) data from Pantheon+; baryon acoustic oscillation (BAO) data from DESI DR2; and cosmic microwave background (CMB) measurements from Planck. For $\alpha>0$ (particle creation), the thermodynamic restrictions yield only upper limits for the $\mu_{0}n_{0}$ product, while in the case of $\alpha<0$ (particle destruction) they establish both upper and lower limits, allowing for a range of values to be obtained. In both scenarios, however, we find that the chemical potential of dark energy must be negative, $\mu<0$, which indicates a preference for the phantom regime. In particular, when $\alpha<0$, it is noted that the thermodynamic bounds are simultaneously compatible only for very small absolute values of $\alpha$, with $\alpha=-0.0002$ being the limiting case and resulting in $\mu_{0}n_{0}(\alpha=-0.0002)=-2.2_{-0.7}^{+1.0}\,\,GeV/m^{3}$.

Temperate ($T_{\rm eq}<400$ K) gas giants represent an unexplored frontier in exoplanet atmospheric spectroscopy. Orbiting a G-type star every ~100 days, the Saturn-mass exoplanet TOI-199 b ($T_{\rm eq}=350$ K) is one of the most favorable low-temperature gas giants for atmospheric study. Here, we present its transmission spectrum from a single transit observed with JWST's NIRSpec G395M mode. Despite lower-than-nominal precision due to a pointing misalignment, Bayesian retrievals reveal the presence of CH$_4$ (Bayes factor of $\sim$700 in a cloudy atmosphere), corresponding to a metallicity of $\rm{C/H}=13^{+78}_{-12}\times$ solar, although the absence of detectable CO and CO$_2$ disfavors metallicities $\gtrsim50\times$ solar. We also tested several haze prescriptions (Titan-like tholin, soot, and water-rich tholin), but the preference for these models is weak (Bayes factors of $\sim 2$ relative to the clear case). The spectrum also shows an increase in transit depth near 3 $\mu$m, which our self-consistent models attribute to either NH$_3$ or, less likely, HCN. Follow-up observations will distinguish between these species, helping determine the planet's vertical mixing regime. The TOI-199 system exhibits strong transit timing variations (TTVs) due to an outer non-transiting giant planet. For planet c, our TTV analysis reduces its mass uncertainty by 50% and prefers a slightly longer orbital period (still within the conservative habitable zone) and higher eccentricity relative to previous studies. TOI-199 b serves as the first data point for studying clouds and hazes in temperate gas giants. The detection of methane supports the emerging trend that temperate low-molecular-weight atmospheres display spectral features in transmission.

The Dark Energy Spectroscopic Instrument (DESI) second data release shows a moderate preference for dark energy with a time-varying equation of state parameter, suggesting that the standard $\Lambda$CDM model may need to be revised. In particular, DESI favors dark energy whose equation of state parameter can drop below $-1$, violating the null energy condition. Chen and Loeb have recently suggested that this violation may be avoided if a subcomponent of the dark matter possesses a time-dependent equation of state. In this work, we present a renormalizable realization of that idea, which can be regarded as a more natural effective field theory. We show that such a construction not only yields dark matter with a time-varying equation of state parameter, but also naturally produces a self-interacting dark matter candidate with a velocity-dependent cross section as a consequence of gauge invariance. The second feature is relevant for addressing tensions between $\Lambda$CDM and observations of small-scale structure, particularly the diversity of galactic rotation curves. Even if further study ultimately finds our fiducial model to be disfavored, this work is valuable for constraining the space of renormalizable, natural models that have the potential to realize the behavior desired by Chen and Loeb.

We introduce a new, non-parametric method for estimating the mass enclosed within a sphere of arbitrary radius centered on the Sun. The method is based on the divergence theorem as applied to measurements of the line-of-sight accelerations of millisecond pulsars. We describe a procedure for inferring the mean mass density within a sphere of a given radius centered on the Sun and find results that are consistent with previous analyses. When combined with a model for the distribution of baryons, this provides the mean mass density of dark matter as a function of distance from the Sun, rather than a single value as is typically reported by kinematic studies. However, with the present pulsar data, the method cannot unambiguously measure a signal from the local distribution of dark matter at this time; such a measurement is expected to soon become possible as the amount of pulsar acceleration data grows and its precision improves. We derive an extension of the well-known shell theorem to a spherical-harmonics expansion of the density and potential, and use the result to obtain estimates for density asymmetries with respect to the Galactic midplane from the observed acceleration data. The predicted asymmetries do not follow the observed distribution of MW disk stars or gas; this can potentially be explained by a non-uniform distribution of dark matter in the Solar neighborhood.

The Epoch of Reionization (EoR) provides critical insights into the role of early galaxies in shaping the ionization state of the universe. However, because of the opacity of the intergalactic medium, it is often not possible to make direct measurements of the ionizing photon escape fraction ($f_{\mathrm{esc}}^{\: \mathrm{LyC}}$) of high-redshift ($z \gtrsim 4$) galaxies. To explore the agreement and systematics of common indirect approaches, we applied six empirically calibrated diagnostics to predict $f_{\mathrm{esc}}^{\: \mathrm{LyC}}$ for the 45 nearby star-forming galaxies from the COS Legacy Spectroscopic SurveY (CLASSY). These methods- based on ultraviolet (UV) absorption lines, the UV continuum slope, Ly$\alpha$ kinematics, a multivariate model, radiation-hydrodynamic simulations, and nebular emission line ratios- enable us to explore systematic differences between predictions and assess how galactic properties influence inferred LyC escape. Despite significant variations in method predictions, there is broad consistency in the resulting weak and strong LyC leaker classifications, with approximately half exhibiting predicted escape fractions $>$1%. We find evidence for two different pathways of LyC escape in nearby star-forming galaxies: (1) an early escape model driven by very young stellar populations, and (2) a delayed escape model that is consistent with supernova-driven outflows and time-dependent ISM clearing. The early escape model is favored among galaxies with a single, intense burst of recent star formation. In contrast, the delayed escape model is common among galaxies with more extended starburst histories. To interpret ionizing photon escape during the EoR, it will be necessary to recognize and understand this diversity in LyC escape mechanisms.

Short-period sub-Neptunes are common in extrasolar systems. These sub-Neptunes are generally thought to have primary atmospheres of protoplanetary-disk gas origin. However, atmospheric escape followed by degassing from their interiors can lead to the transition to secondary atmospheres depleted in gases less-soluble to magma, such as helium. These primary and secondary atmospheres can potentially be distinguished from observations of escaping hydrogen and helium. This study aims to elucidate the impact of the primary-secondary transition on atmospheric compositions of short-period sub-Neptunes. We simulate their evolution with atmospheric escape driven by stellar X-ray and extreme ultraviolet irradiation and degassing of hydrogen, helium, and water from their rocky interiors, with a one-dimensional structure model. We show that the transition takes place for low-mass, close-in planets which experience extensive atmospheric escape. These planets show the depletion of helium and enrichment of water in their atmospheres, because of their low and high abundances in the planetary interiors, respectively. A compilation of our parameter survey (the orbital period, planetary mass, envelope mass, and mantle FeO content) shows a correlation between the planet radius and the helium escape rate. We suggest that the transition from primary to secondary atmospheres may serve an explanation for helium non-detection for relatively-small ($\lesssim 2.5\ R_\oplus$) exoplanets.

New long range forces acting on ordinary matter are highly constrained. However it is possible such forces act on dark matter, as it is less constrained observationally. In this work, we consider dark matter to be made of light bosons, such as axions. We introduce a mediator that communicates a new force between dark matter particles, in addition to gravity. The mediator is taken to be light, but not massless, so that it can affect small scale galactic behavior, but not current cosmological behavior. As a concrete application of this idea, we analyze the effects on scalar dark matter solitons bound by gravitation, i.e., boson stars, which have been claimed to potentially provide cores of galaxies. We numerically determine the soliton's profiles in the presence of this new force. We also extend the analysis to multiple mediators. We show that this new force alters the relation between core density and core radius in a way that can provide improvement in fitting data to observed galactic cores, but for couplings of order the gravitational strength, the improvement is only modest.

Shock breakout and, in some cases, jet-driven high-energy emission are increasingly recognized as key signatures of the earliest phases of core-collapse supernovae, especially in Type IIn systems due to their dense, interaction-dominated circumstellar environments. We present a comprehensive photometric analysis of SN 2019vxm, a long-duration, luminous Type IIn supernova, $M_V^{}=-21.41\pm0.05\;{\rm mag}$, observed from X-ray to near-infrared. SN 2019vxm is the first superluminous supernovae Type IIn to be caught with well-sampled TESS photometric data on the rise and has a convincing coincident X-ray source at the time of first light. The high-cadence TESS light curve captures the early-time rise, which is well described by a broken power law with an index of $n=1.41\pm0.04$, significantly shallower than the canonical $n=2$ behavior. From this, we constrain the time of first light to within 7.2 hours. We identify a spatial and temporal coincidence between SN 2019vxm and the X-ray transient GRB191117A, corresponding to a $3.3\sigma$ association confidence. Both the short-duration X-ray event and the lightcurve modeling are consistent with shock breakout into a dense, asymmetric circumstellar medium, indicative of a massive, compact progenitor such as a luminous blue variable transitioning to Wolf-Rayet phase embedded in a clumpy, asymmetric environment.

Magnetic field is the key physical quantity in solar physics as it controls all kinds of solar activity, ranging from nanoflares to big flares and coronal mass ejections (CMEs). However, so far only the magnetic field on the solar surface can be more or less precisely measured, and the most important coronal magnetic field remains undetectable accurately. Without the knowledge of the coronal magnetic field, it is even more difficult to obtain secondary quantities related to magnetic field, such as the magnetic helicity and magnetic configuration, including the curvature of field lines. The prevailing approaches to obtain the coronal magnetic field include coronal magnetic extrapolation and coronal seismology. Actually there were scattered efforts to derive secondary magnetic quantities based on imaging observations of solar filaments, without the help of polarization measurements. We call this approach solar filament physiognomy. In this paper, we review these efforts made in the past decades, and point out that this approach will be promising as large telescopes are being built and more fine structures of filament channels will be revealed.

Helium white dwarfs (WDs) with masses less than 0.3 $\rm M_{\sun}$ are known as extremely low-mass WDs (ELM WDs), which cannot be produced by single stellar evolution in theory. Generally, these stars are believed to form through binary interactions. Recently, two ELM WDs in unusually wide orbits were reported, i.e., KIC 8145411 and HE 0430-2457. Their orbital separations are too wide to be produced by the binary evolution scenario. In this work, we study the formation of wide-orbit ELM WD binaries from hierarchical triple systems. In this scenario, an ELM WD is formed from the inner binary and subsequently forms a wide binary system with the third object. We find that the merger of an evolved star with a brown dwarf in the inner binary fails to produce single ELM WDs, but Type Ia supernovae (SNe Ia) explosions can successfully do so. Furthermore, we investigate the impact of the supernova explosion on the orbital distribution of the surviving binary and find that this channel may have a probability of reproducing the orbital parameters of HE 0430-2457, but fails to reproduce the observed features of KIC 8145411. This supports recent observational recalibrations suggesting that KIC 8145411 resides in a triple system rather than a binary.

We present James Webb Space Telescope (JWST) NIRSpec observations of the starless dark cloud Barnard 68 that reveal the spatially-resolved signature of cosmic-ray excited molecular hydrogen (CRXH$_2$) emissions for the first time. Following up on our initial detection of CRXH$_2$ emissions from B68 (Bialy et al. 2025), we now exploit JWST's sensitivity and spatial multiplexing to map CRXH$_2$ rovibrational lines across 16 sight lines through the cloud. By disentangling the CRXH$_2$ and UV-pumped H$_2$ components, we isolate the para-H$_2$-dominated spectrum attributable to cosmic-ray excitation. We find that there are significant spatial variations in the ratio of the CRXH$_2$ line intensity to the line-of-sight H$_2$ column density; these cannot be accounted for by dust extinction alone and demonstrate a clear attenuation of the cosmic-ray flux with increasing shielding column. Modeling B68 as a Bonnor-Ebert sphere, we constrain both the unshielded cosmic-ray ionization rate, $\zeta_{\rm H_2}$, and how it decreases with shielding column. At a reference depth of $N({\rm H}_2) = 3 \times 10^{21}$ cm$^{-2}$, we infer $\zeta_{\rm H_2} \approx 1.4 \times 10^{-16}$ s$^{-1}$, a factor of $\approx 3$ higher than the average value derived from H$_3^+$ absorption studies. These results provide the most direct probe to date of cosmic-ray penetration into cold, dense gas, offering new constraints on both the microphysics of CR-H$_2$ interactions and the attenuation of low-energy cosmic rays in molecular clouds. Our findings establish CRXH$_2$ emission as a powerful new diagnostic of the cosmic-ray environment in interstellar space.

In this work, we constrain the phenomenological interacting dark energy (IDE) model using \emph{Fermi} gamma-ray burst (GRB) dataset and the latest baryon acoustic oscillation (BAO) data from the Dark Energy Spectroscopic Instrument (DESI) Data Release 2 (DR2). Through a joint Bayesian analysis, we perform a cosmological comparative assessment of the $\Lambda$CDM, $w$CDM, and CPL models with the phenomenological IDE model. For the phenomenological IDE model in a flat universe, we obtain: $\xi=2.644^{+1.144}_{-0.933}$, $\xi + 3w_X = -1.001^{+2.827}_{-3.153}$ with the GOLD sample ($z \geq 1.4$) and DESI DR2; and $\xi=2.879^{+0.995}_{-0.990}$, $\xi + 3w_X = 0.086^{+1.365}_{-1.440}$ with the FULL sample ($z \geq 1.4$) and DESI DR2. Our analysis shows that the $\Lambda$CDM model without interaction are consistent with the latest \emph{Fermi} sample and DESI DR2 at $1\sigma$ confidence level.

We present a measurement of the $i$-band galaxy luminosity function from the present-day to $z = 2$, using over 1.1 million galaxies from the Physics of the Accelerating Universe Survey (PAUS). PAUS combines broad-band imaging from the Canada-France-Hawaii Telescope Lensing Survey with narrow-band photometry from PAUCam, enabling high-precision photometric redshifts with an accuracy of $\sigma_{68} (\Delta z) = 0.019$ down to $i_{\textrm{AB}} = 23$. A synthetic lightcone mock catalogue built using the \texttt{GALFORM} semi-analytic model is used to simulate PAUS selection effects and photometric uncertainties, and to derive a machine-learning based estimate of the $k$-correction. We recover rest-frame $i$-band luminosities using a random forest regressor trained on simulated $ugriz$ photometry and redshifts. Luminosity functions are estimated using the $1/V_{\textrm{max}}$ method, accounting for photometric redshift and magnitude errors, and validated against mock data. We find good agreement between observations and models at $z < 1$, with increasing discrepancies at higher redshifts due to photometric redshift outliers. The bright-end of the luminosity function becomes flatter at high redshift, primarily driven by redshift errors. We show that the faint-end of the luminosity function becomes more incomplete with increasing redshift, but is still useful for constraining models. We analyze the red and blue galaxy populations separately, observing distinct evolutionary trends. The model overpredicts the number of both faint red and blue galaxies. Our study highlights the importance of accurate redshift estimation and selection modeling for robust luminosity function recovery, and demonstrates that PAUS can characterise the galaxy population with photometric redshifts across a wide redshift baseline.

Gravitational scattering of small bodies (planetesimals) by a planet remains a fundamental problem in celestial mechanics. It is traditionally modeled within the circular restricted three-body problem (CR3BP), where individual particle trajectories are obtained via numerical integrations. Here, we introduce a patched-conic framework to describe the random walk of the orbital energy $x$ for an ensemble of test particles on planet-crossing orbits. We show that the evolution of each particle's orbital elements $(a, e, i)$ is fully encapsulated by the 3D rotation of the relative velocity vector $\mathbf{U}_\infty$, whose magnitude remains constant. Consequently, the system can be reduced to two degrees of freedom. By averaging over all possible flyby geometries, we derive explicit expressions for the drift and diffusion coefficients of $x$. We then solve the resulting Fokker--Planck equation to obtain a closed-form solution for the time evolution of the particle distribution. A characteristic scattering timescale naturally emerges, scaling as $(P_{p}/M_{p}^{2})/500$, where $P_{p}$ is the planet's orbital period and $M_{p}$ its mass ratio to the central star. The typical ejection speed of small bodies by a planet is estimated to be $3 v_p M_{p}^{1/3}$, where $v_p$ is the planet's orbital speed. Our analytical solution constitutes a universal law applicable to both the Solar System and exoplanetary systems, providing a computationally efficient alternative to costly $N$-body simulations for studying the orbital distributions and ejection of planetesimals and planets (e.g., Kuiper Belt, Oort Cloud, debris disks, interstellar objects, and free-floating planets).

This paper optimizes the design and analysis of the mechanical test platform for the scientific probe module of the Cool Planet Imaging Coronagraph, which is the fifth part of the China Space Station survey Telescope. First, according to the module layout and economic requirements, the preliminary structural design of the module mechanical test platform is carried out, and the stiffness sensitive parameters of the assembly are identified to determine the optimization parameters. The Central Composite Design method is used to design the test platform, and a third-order regression model is constructed for response surface analysis. The third-order response surface model of the fundamental frequency and amplitude of the test platform is obtained by fitting the test data with the least squares method, and the structure of the module mechanical test platform is determined. The modal analysis is carried out to determine the fundamental frequency and vibration modes of the mechanical test platform. The vibration response of the platform is simulated by sine, random and swept frequency vibration simulations. The response surface fitting algorithm is verified by the test platform swept frequency test. The agreement between the response surface fitting algorithm and the experiment is good. The fundamental frequency of the test platform is 436.2Hz (>300Hz), which meets the design index requirements of the test platform and can accurately guide the optimization design work. At the same time, it provides the theoretical basis and design method for the structural design of the Chinese manned space station.

Bar structures are present in about half of local disk galaxies and play pivotal roles in secular galaxy evolution. Bars impose a non-axisymmetric perturbation to the rotating disk and transport gas inward to feed central starburst and, possibly, the activity of the nuclear supermassive black hole. They are believed to be long-lived structures and are now identified at redshift $z>2$. Yet, little is known about the onset and effect of bars in the early cosmic epoch because spectroscopy of distant bars at sufficient resolution is prohibitively expensive. Here, we report a kinematic study of a galactic bar at redshift 2.467, 2.6 billion years after the Big Bang. We observe the carbon monoxide and atomic carbon emission lines of the dusty star-forming galaxy J0107a and find the bar of J0107a has gas distribution and motion in a pattern identical to local bars. At the same time, the bar drives large-scale non-circular motions that dominate over disk rotation, funneling molecular gas into its center at a rate of $\approx600$ solar masses per year. Our results show that bar-driven dynamical processes and secular evolution were already at play 11.1 billion years ago, powering active star formation amid the gas-rich and far-infrared luminous growth phase in a massive disk galaxy.

We forecast the constraint on the Hu-Sawicki $f(R)$ model from the photometric survey operated by the Chinese Space Station Survey Telescope (CSST). The simulated $3\times2$pt data of galaxy clustering, weak lensing, and galaxy-galaxy lensing measurements within 100 deg$^{2}$ are used in the analysis. The mock observational maps are constructed from a light cone, redshift sampling and noise. The angular power spectra are measured with pseudo-$C_\ell$ estimators and compared to theory in the same basis using validated weighting functions and an analytic covariance matrix that includes Gaussian, connected non-Gaussian, and super-sample terms. We model the theoretical spectra using two methods. The first one uses MGCAMB to compute the linear modified-gravity clustering power spectra, and the second one adopts the FREmu emulator with a baseline of nonlinear $\Lambda$CDM prescription. Parameter inference is performed with Cobaya, and the cosmological and modified-gravity parameters are sampled within the emulator training domain, which is jointly fitted with the systematic parameters. We find that the predictions from the two methods are in good agreement at the overlapping large scales, and the emulator method can correctly provide additional high-$\ell$ information. The $1\sigma$ upper bounds of $\log_{10}|f_{R0}|$ are found to be $<-5.42$ for cosmic shear only case and $<-5.29$ for the 100 deg$^2$ CSST $3\times2$pt probe. The full CSST photometric survey with 17,500 deg$^2$ survey area is expected to further improve the constraint precision by about one order of magnitude. Our results demonstrate that the CSST $3\times2$pt survey can deliver strict tests on $f(R)$ gravity.

Type II Cepheids are a class of pulsating variable stars that play a critical role in our understanding of stellar evolution, distance measurement and tracing the structure and kinematics of old stars in nearby galaxies. This review provides a comprehensive summary of the current state of research on Type II Cepheids, including their observed properties, pulsation mechanisms and their distinction from other variable stars. These pulsating variable stars, found primarily in older stellar populations, exhibit well-defined period-luminosity relations but with an added advantage that they exhibit weak or negligible dependence on metallicity. We explore their relevance in the context of their role as distance indicators and potential calibrators of the first rung of the extragalactic distance ladder. Finally, the review highlights recent advancements in theoretical models, observations across different wavelengths and ongoing debates concerning their classification.

JWST/NIRCam observations reveal dense stellar cores in high-redshift galactic bulges, indicative of sustained star formation and potential stellar accretion. We introduce accretion-modified star (AMS) as a new component in the chemical evolution of high-redshift bulges hosting active galactic nuclei (AGNs). The gas-phase chemical evolution of bulge environments containing AMS is modeled within 1 Gyr by combining population evolution and galactic chemical evolution formalisms, and observational signatures are tracked via photoionization modeling on Baldwin-Phillips-Terlevich (BPT) diagrams. Sustained high accretion onto AMSs leads to rapid gas-phase metal enrichment of the bulge, producing abundance peaks up to five times solar metallicity within 0.1 Gyr and significantly modifying elemental ratios in the gas phase. Atypical gas-phase abundance patterns during early, high-accretion phases and gradually diminish as the accretion rate declines. In BPT diagrams, high-AMS-accretion scenarios shift the modeled emission-line sequence toward the local AGN branch and extend into the high-metallicity regime. Super-solar narrow-line regions observed in AGNs at z>15 may reflect such AMS-driven gas-phase enrichment of host bulge under extreme gas densities. While direct detection of AMSs within AGN bulges remains challenging, the model provides testable predictions for future spectroscopic surveys and motivates further exploration of non-canonical stellar populations in AGN host bulges.

We study a cosmological model featuring evolutionary dark energy, according to the idea that the creation of its constituents arises from the gravitational field of the expanding universe, whose non-equilibrium physics is described by a non-zero bulk viscosity coefficient. This physical scenario calls for two additional parameters with respect to the {\Lambda}CDM model, one of which is the equation of state parameter of the created dark energy. The model is constrained by the requirement that its deceleration parameter coincides with the one predicted by the {\Lambda}CDM model. Then, we construct the effective running Hubble constant, a theoretical function that corresponds to the ratio of the Hubble parameter in our model to the {\Lambda}CDM expansion rate. The model's theoretical predictions for the effective running Hubble constant are compared with the binned data of the Supernovae Ia Master Sample. The comparison is performed by a MCMC procedure for each bin, with three parameters left free to vary, while the particle creation rate is taken from a grid of values, each of which is fixed in the given MCMC run. The most important result emerging from this analysis is that the created dark energy constituent corresponds to an equation of state parameter with phantom character. Only if particle creation is removed do the dark energy constituents acquire a quintessence character. No matter the intrinsic nature of the constituents, their effective z-dependent equation of state parameter is, both with and without considering particle creation, entirely of phantom nature across the considered redshift range.

Spectroscopic characterization of rocky exoplanets with the James Webb Space Telescope has brought the origin and evolution of their atmospheres into the focus of exoplanet science. Time-evolved models of the feedback between interior and atmosphere are critical to predict and interpret these observations and link them to the Solar System terrestrial planets. However, models differ in methodologies and input data, which can lead to significant differences in interpretation. In this paper, we present the experimental protocol of the Coupled atmospHere Interior modeL Intercomparison (CHILI) project. CHILI is an (exo-)planet model intercomparison project within the Climates Using Interactive Suites of Intercomparisons Nested for Exoplanet Studies (CUISINES) framework, which aims to support a diverse set of multi-model intercomparison projects in the exoplanet community. The present protocol includes the initial set of participating magma ocean models, divided into evolutionary and static models, and two types of test categories, one focused on Solar System planets (Earth & Venus) and the other on exoplanets orbiting low-mass M-dwarfs. Both test categories aim to quantify the evolution of key markers of the links between planetary atmospheres and interiors over geological timescales. The proposed tests would allow us to quantify and compare the differences between coupled atmosphere-interior models used by the exoplanet and planetary science communities. Results from the proposed tests will be published in dedicated follow-up papers. To encourage the community to join this comparison effort and as an example, we present initial test results for the early Earth and TRAPPIST-1 b, conducted with models differing in the treatment of energy transport in the planetary interior and atmosphere, surface boundary layer, geochemistry, and the in- and outgassing of volatile compounds.

We present one of the first measurements of the mass-metallicity relation (MZR) in multiple massive protoclusters at cosmic noon, using Hubble Space Telescope (HST) G141 slitless spectroscopy from the MAMMOTH-Grism survey. We identify 63 protocluster member galaxies across three overdense structures at $z = 2\text{-}3$ with robust detections of [OIII], H$\beta$, and [OII] emission. The sample spans gas-phase metallicities of $12 + \log(\text{O/H}) = 8.2\text{-}8.6$, dust-corrected H$\beta$-based star formation rates (SFRs) of $10$-$250\,M_\odot\,\text{yr}^{-1}$, and stellar masses of $M_\ast \sim 10^{9.4}$-$10^{10.5}\,M_\odot$, derived via spectral energy distribution fitting using deep HST and ground-based photometry. We stack spectra in five $M_\ast$ bins to obtain average metallicities and SFRs. Relative to field galaxies at similar redshifts, protocluster members show elevated SFRs at $M_\ast < 10^{10.25}\,M_\odot$ and a systematically shallower MZR: $12 + \log(\text{O/H}) = (6.96 \pm 0.13) + (0.143 \pm 0.017) \times \log(M_{\ast}/M_{\odot})$. We detect a mass-dependent environmental offset: massive protocluster galaxies are metal-poor compared to field counterparts of similar mass, whereas lower-mass systems exhibit comparable or mildly enhanced metallicities. This trend is consistent with a scenario where cold-mode accretion dilutes the interstellar medium (ISM) across the full mass range, while efficient recycling of feedback-driven outflows preferentially enriches the ISM in low-mass galaxies. Finally, we assess the dependence of metallicity offsets on local overdensity and find no significant trend, likely reflecting the survey's bias toward protocluster cores.

We present here the results from a second epoch of phase-referenced VLBA observations of 8 Seyfert and LINER galaxies from the KISSR sample. These sources were chosen based on the presence of double peaks or asymmetries in their emission lines as observed in SDSS spectra. Parsec-scale radio emission is detected in 7 of the 8 sources in the second epoch. Jet-like features appear to persist over a $\sim4-9$ year timeline in these `radio-quiet' AGN. A few sources like KISSR1494, however, show significantly different structures after a 9 year interval. KISSR102, which was previously suggested to be a binary black hole candidate based on the presence of two compact cores, shows the tentative signatures of superluminal jet motion ($1.05\pm0.45$c). Tentative superluminal motion in a jet knot has been reported in another source, KISSR872 ($1.65\pm0.57$c). We present 1.5 GHz images from the VLA A-array of 4 sources. These images reveal core-lobe or core-halo structures. The alignment of the VLBI jet direction with the kpc-scale spectral index gradient, as well as the mismatch between the star formation rate derived from the radio and H$\alpha$ line emission, support the suggestion that the kpc-scale emission is AGN-jet-related. The jets in KISSR sources appear to lose collimation over spatial scales between 200 parsec and 1 kpc. Overall, the characteristics of the KISSR jets are reminiscent of similar properties observed in VLBI monitoring studies of `radio-loud' AGN jets even as subtle differences related to the compactness and brightness of jet features remain.

Our previous work identified a class of SDSS quasars exhibiting multiple Gaia detections, classifying them as candidates for various astrophysical systems such as quasar-star pairs, dual quasars, and gravitationally lensed quasars. In this paper, we present a pilot VLBI study targeting a radio-bright subsample and report the first high-resolution imaging results. By leveraging the milliarcsecond-scale resolution of VLBI and its precise astrometric coordination incorporating with Gaia, we aim to refine the classification of these multiple matched sources, search for potential dual AGNs, and assess the efficacy of the combined Gaia-VLBI approach in resolving ambiguous quasar systems. We cross-matched the SQUAB quasar sample with the FIRST and NVSS catalogs, identifying 18 radio-emitting sources. The three brightest were selected for dual-frequency (1.6 and 4.9 GHz) VLBA observations. We performed VLBI imaging at both Gaia positions, constructed spectral index maps, and estimated brightness temperatures to characterize the radio morphology and physical properties. For the three target sources, our VLBI observations reveal compact radio structures consistent with single AGN at the primary Gaia positions. No significant emission is detected at the secondary Gaia locations. These results support the interpretation of the sources as quasar$-$star pairs, in line with earlier studies. This pilot study demonstrates the value of radio-VLBI high-resolution follow-ups on Gaia-selected quasar systems with multiple counterparts, showing how they can unambiguously reveal the true nature of these systems and help remove contaminants from dual AGN candidate samples.

The Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) Balloon with Radio (PBR) is an instrument designed to be borne by a NASA suborbital Super Pressure Balloon (SPB), in a mission planned to last as long as 50 days. The PBR instrument consists of a 1.1 m aperture Schmidt telescope, similar to the POEMMA design, with two cameras in its hybrid focal surface: a Fluorescence Camera (FC) and a Cherenkov Camera (CC), both mounted on a frame that can be tilted to point from nadir up to 13 degrees above the horizon. The FC camera is designed to detect the fluorescence emission of Extensive Air Showers produced by Ultra-High Energy Cosmic Rays from sub-orbital altitudes. This measurement will validate the detection strategy for future space-based missions, such as POEMMA. The FC will be made of 4 Photo Detection Modules (PDMs), each consisting of a 6x6 matrix of 64-channel Multi Anode PhotoMulTipliers (MAPMT), for a grand total of 2304 pixels for each PDM. Custom-designed SPACIROC-3 ASICs perform single photoelectron counting on each pixel as well as charge integration on groups of 8 pixels to measure extremely bright or fast signals, reaching a double pulse resolution in the order of 10 ns for a 1 microsecond acquisition gate. A field flattener lens and a BG3 filter, to match the wavelength range of interest (300-400 nm), are mounted in front of the PDM. The camera will be able to detect showers in a field of view of 24x24 square degrees, with a pixel size on ground corresponding to 115 m. Details on the camera design and implementation will be given, along with the expected performance and the state of the construction.

Amorphous silicate dust is a major component in the interstellar and circumstellar dust formed in the outflow of asymptotic giant branch (AGB) stars. Although iron depletion is observed in the interstellar medium (ISM), the exact form and fraction of iron in solid remains under debate. In particular, it is unclear whether amorphous silicate dust around AGB stars contains metallic iron. We aimed to provide optical constants of amorphous silicate nanoparticles and examine the effects of metallic iron on their spectral features to better constrain the dust properties by producing amorphous silicate nanoparticles with and without metallic cores. We performed condensation experiments using an induction thermal plasma system to produce dust analogues of the CI chondritic composition in the Mg-Ca-Na-Al-Si-Fe-Ni-O and Mg-Ca-Na-Al-Si-O systems. We measured the absorbance and reflectance of the samples, observed the structure of the products, and determined the optical constants. Two types of amorphous silicate nanoparticles (10-200 nm in diameter) with nearly CI chondritic composition were produced: one contained kamacite (Fe: Ni=0.9: 0.1) cores with a diameter ratio ranging 0-0.87 (average ~0.50), and the other was iron-free homogeneous amorphous silicate. The amorphous silicates of the CI chondritic composition with various sized metallic cores may be prevalent in circumstellar and interstellar dust.

We present a novel empirical method for correcting asteroid phase curves for rotational and geometrical effects using precomputed spin-and-shape models. Our approach normalizes sparse photometric data to a pole-on geometry, enabling consistent phase-curve fitting across apparitions. We fit both the H,G1,G2 and H,G12 phase functions to the normalized data. We also numerically derive new constraints on parameter ranges that ensure physically meaningful solutions. These constraints are based on the requirement that the reduced magnitude must monotonically decrease with phase angle and remain within plausible slope bounds. Compared to earlier bounds, our new constraints are more permissive. We also compare derivative-based and derivative-free optimization methods, highlighting convergence issues with the HG12 function and offering mitigation strategies. We applied our method to over 25,000 asteroids observed by the ATLAS survey, demonstrating its usability. The new method enables the selection of the preferred spin-and-shape solution based on either statistical phase-curve model selection criteria and/or physically motivated constraints on the phase-curve shape.

The recent preference for a dynamical dark energy (DE) from the Dark Energy Spectroscopic Instrument seems to call for interactions between DE and dark matter (DM), either from direct DM-DE interaction or indirect interaction induced by modified gravity. Therefore, an independent probe for these kinds of DE-DM interactions would be appealing from observational aspects. In this paper, we propose the black hole superradiance as a novel astrophysical probe for field-theoretic interacting DE-DM models, providing complementary constraints independent of large-scale cosmological observations. The core principle is that the DE-DM interaction can alter the effective mass of the superradiant ultralight boson, thereby modifying its superradiant instability rate around spinning black holes. We explore this connection through two distinct scenarios: a model where the DE field mediates a dark fifth force within the DM sector, affecting the superradiance from DM particles; and a novel mechanism where the DE field itself becomes superradiant due to the effective mass enhancement induced by dense DM spikes around supermassive black holes. By applying a statistical framework to black hole observations in both scenarios, we derive constraints on the fundamental DE-DM coupling strength. Although the current constraints are rather loose due to small samples and inaccurate measurements, our work provides new astrophysical constraints on these interacting DE-DM scenarios and establishes a new synergy between black hole physics and cosmology for probing the fundamental nature of the dark sector.

Cygnus X-1 (Cyg X-1) exhibited a low hard state in 2022, observed by several missions. The IXPE reported that the polarization angle is aligned with the radio jet and gave a polarization degree approximately 4 times higher than the general expectations of $1\%$ through the analysis of the time-integrated data with a simple spectral model, indicating that the disk inclination is higher than a canonical value of about $30^{\circ}$. Many subsequent theoretical studies employed a non-standard model to explain this high PD. Here, we revisit the disk/corona spectrum through a detailed joint analysis using IXPE, NuSTAR, and NICER data. By investigating the time variability of the spectrum, we find that the two-Comptonization components model can better reproduce the data than the one-Comptonization component model originally adopted. We observed a lower disk photon temperature of about 0.15 keV. Detailed simulation suggests that lowering the disk temperature by a factor of 2 increases the PD by roughly 2 percentage points in the IXPE 2--8 keV band for a slab-like corona geometry, helping to reconcile the observed high PD with theoretical predictions. However, The simulated PDs are still significantly lower than the observed ones - even for a rather high $60^{\circ}$ inclination. We also investigated the polarization properties of a simple wedge-shaped corona with a truncated disk and a sandwiching slab corona. We find that the slab corona predicts an apparent energy dependence in PD while PA remains constant in the IXPE band, in agreement with the observed polarization. Therefore, we suggest that Cyg X-1 in 2022 May exhibits a two-Comptonization coronal emission with different optical depths, and the hard one is in a sandwiching slab geometry. We also discuss how the polarization is affected by other parameters of the black hole and the corona.

Comet 3I/ATLAS, also known as C/2025 N1, was discovered on 2025 July 1 UT by NASA Asteroid Terrestrial-impact Last Alert System (ATLAS), with a v$_{\infty}$ $\sim$ 58 kms$^{-1}$. This is the fastest among the three interstellar objects discovered so far. In this work, we study the interaction of the 3I/ATLAS with Mars, pre-perihelion, and Jupiter post-perihelion. We also present the results of the dynamical simulations of the orbital evolution of the comet for a hundred years in the past and future. For our analysis, we have used REBOUND, an N-Body simulation package, to study these situations. We use the adaptive size mathematical integrator \textsc{Ias15}, with a 1-day time step for long-term integration, and a 1-hour time step to study the effect of the planets on this body during the close encounters. We have seen an effect of Jupiter on the orbital parameters of the comet, which affects its post-perijove trajectory significantly. The impact of Mars on this comet is minimal compared to the effect of Jupiter. This is consistent with the point that the comet moves well past Mars's Hill radius but very close to Jupiter's Hill radius at the respective close approaches. However, the effect of non-gravitational forces will alter the results. Since the non-gravitational forces are not yet known, we predict the variation of the orbital parameters considering a range of possible magnitudes of the non-gravitational acceleration.

Constraining the Epoch of Reionization (EoR) with physically motivated simulations is hampered by the high cost of conventional parameter inference. We present an efficient emulator-based framework that dramatically reduces this bottleneck for the photon-conserving semi-numerical code SCRIPT. Our approach combines (i) a reliable coarse-resolution MCMC to locate the high-likelihood region (exploiting the large-scale convergence of SCRIPT) with (ii) an adaptive, targeted sampling strategy to build a compact high-resolution training set for an artificial neural network based emulator of the model likelihood. With only $\approx 10^3$ high-resolution simulations, the trained emulators achieve excellent predictive accuracy ($R^2 \approx 0.97$--$0.99$) and, when embedded within an MCMC framework, reproduce posterior distributions from full high-resolution runs. Compared to conventional MCMC, our pipeline reduces the number of expensive simulations by a factor of $\sim 100$ and lowers total CPU cost by up to a factor of $\sim 70$, while retaining statistical fidelity. This computational speedup makes inference in much higher-dimensional models tractable (e.g., those needed to incorporate JWST and upcoming 21 cm datasets) and provides a general strategy for building efficient emulators for next generation of EoR constraints.

We analyse the formation of troughs in the continuous spectra of sources in redshift range $5-15$ for two reionization histories followed from the distant galaxy spectra and CMB anisotropy. We supposed that neutral hydrogen and helium atoms of homogeneous intergalactic medium are mainly in ground state and absorb the light of distant sources in the lines of Lyman series and continuums of HI, HeI and HeII. The frequency dependence of optical depths in the 40 lines of Lyman series of HI and HeII, and in 10 lines of HeI, as well as in their continuums were computed in order to estimate the spectral flux of radiation from halos virialized during Cosmic Dawn and Reionization epochs. Assuming the thermal continuous spectra with virialized temperature of halos with dwarf galaxy mass $\sim10^9$ M$_\odot$, we compute the spectral fluxes from such halos in the vicinity of our galaxy taking into account the cosmological distances, redshifts and absorptions by each absorber and all together. The obtained spectral transmittance functions of intergalactic medium, $S(\lambda;z)$, are analysed on the subject which absorber systems of HI, HeI and HeII are corresponding for formation of troughs in the continuous spectra of sources at redshift range $5-15$ and how it depends on reionization history. It is shown, that spectral features in the continuous spectra of sources in redshift range $5-7$ are very sensitive to the reionization histories of both elements, hydrogen and helium.

Analogous to the HR diagram for stars, the thermal equilibrium curve encodes the thermodynamics of accretion disks by expressing the local balance between heating -- primarily via viscous dissipation -- and cooling -- typically through radiative transfer. These curves are commonly plotted as surface density versus effective temperature. When an S-shaped locus appears, local annuli become bistable, and limit-cycle oscillations arise when the external mass-transfer rate falls within an unstable band. This behavior underpins the disk instability model for recurring outbursts in cataclysmic variables. This paper reviews first-principles thermal equilibrium curves for accretion disks driven by magnetorotational instability (MRI), with emphasis on dwarf novae. Unlike the parameterized $\alpha$-viscosity approach, the curves are obtained by solving the governing equations with radiation magnetohydrodynamics simulations, thereby reproducing S-shaped loci without prescribing $\alpha$. The disk instability in dwarf-nova systems and the physical origin of angular-momentum transport (shear stresses) are also briefly reviewed. Notes on the stability of radiation-dominated accretion flows are included in the Appendix.

Classical Wolf-Rayet (WR) stars are hot, massive stars with depleted hydrogen. At low metallicities (Z), WN3-type WR stars have relatively thin winds and are major sources of ionizing flux. The detection of high-ionization emission lines in high-redshift ($z$) galaxies as well as nearby low-Z dwarf galaxies raises questions about the origin of He II ionizing radiation and its role in galaxy evolution, as stellar population models fail to reproduce the required fluxes. Low-Z WN3 stars may provide the missing contribution but are easily hidden in integrated light. Using the Local Volume Mapper, we compare resolved optical spectra of SMC WN3 stars with integrated regions, focusing on the broad He II $\lambda4686\,Å$ line. We find stellar emission diluted within nebular regions, becoming undetectable when integrating over areas larger than 24 pc. Nonetheless, these stars emit enough ionizing photons to explain observed He II nebular emission, being strong candidates for the He II ionizing sources in low-Z and high-$z$ galaxies.

The galaxy size-luminosity and size-stellar mass relations are important constraints on the galactic baryon cycle of gas accretion, star formation, and feedback. There are conflicting claims in the literature regarding how environment influences size: both direct transformative effects and `assembly bias' may contribute to observed variations with environment. We construct a large homogeneous sample of size measurements to M*~10^7 Msun. Our sample fills a gap in field galaxy size measurements around 10^7-10^8 Msun; the literature at these masses is biased towards satellites of L* galaxies and members of galaxy clusters. We use sizes from the DESI-LS, together with a published catalog that contains stellar masses and cluster positions derived from DESI-LS photometry. Our sample extends to z<0.3 and comprises 540,228 galaxies with spectroscopic redshifts and 9,513,732 galaxies with photometric redshifts. We explore the environmental dependence of size for a mass-limited subset of our sample at z<0.05, based on distance to the nearest cluster center. We obtain size-luminosity and size-mass relations in good agreement with previous studies. By separating galaxies according to color and morphology, we show that the environmental variation of the overall size-mass relation on Mpc scales can be understood as the consequence of a changing mixture of subpopulations, rather than direct size transformation. For example, at fixed mass, quiescent (red) late-type galaxies within 2Mpc of a cluster have the same size as quiescent late-type galaxies 30Mpc from the nearest cluster. Our results support individual galaxy assembly histories as the primary determinant of galaxy size. The existence of significantly different, environment-insensitive size mass relations for subpopulations separated by color and Sersic index provides a clear target for calibration of the baryon cycle in cosmological simulations.

Recent low-frequency array (LOFAR) radio signal detections bearing from the $\tau$ Boötis system have been cautiously attributed to auroral emissions from the hot Jupiter $\tau$ Boötis Ab. The auroral emissions are believed to be excited by interaction between the exoplanet and the winds of its host star. Since stellar winds respond to stellar surface magnetism, three-dimensional stellar wind modelling, able to account for the star's contemporaneous magnetic field geometry, can aid the interpretation of radio detections. For the first time, we present spectropolarimetric observations of $\tau$ Boötis A from the same epoch as the LOFAR detections. We derive a contemporaneous large-scale magnetic map of $\tau$ Boötis A, which shows a poloidally dominated field with mean strength 1.6 G. From our magnetic map, we create a three-dimensional numerical wind model and characterise the wind properties around $\tau$ Boötis Ab. To compute the wind power dissipated in $\tau$ Boötis Ab's magnetosphere, we apply two approaches: A) the solar system-based empirical relation called Bode's law; and B) a resolved numerical model of the planetary magnetosphere. When consistently applying best-case assumptions, we redict radio flux densities around 50 mJy and 0.68 mJy respectively. Our values are much too small to be consistent with the reported observation of $890_{-500}^{+690}$ mJy; a stellar surface magnetic field scaling $\gtrsim 10$ is required to reproduce the observed signal strength. As $\tau$ Boötis A has a rapid magnetic cycle, we speculate that wind variations cased by variation in stellar magnetism may explain the lack of detections from follow-up observations. Our work emphasises the importance of contemporaneous observations of stellar magnetism and observational signatures of star-planet interaction.

In this report, we examine the behavior of Charge Transfer Efficiency (CTE) on the WFC3/UVIS detector over time as computed by the Extended Pixel Edge Response (EPER) technique, using internal calibration data acquired from 2009 through 2025. We find that the CTE has continued to decline as expected, with a steeper loss rate for lower signal levels. The lowest signal level (160e-) has continued to decline at a rate of 0.0001 per year, with a total overall decline of 0.0015. Analyses from 2016 and 2020 found that the rate of decline was not well fit by a linear function. This report verifies the rate of decline is instead better fit by a quadratic function (which results in the smallest min. and max. residuals, on average) or a cubic function (which has the best "goodness of fit" $\chi^2$ and $R^2$ values). We continue to see periodic oscillations of the residuals around all three fit lines (linear, quadratic, and cubic) on which we perform a Lomb-Scargle periodogram analysis of the residuals. We find a periodicity of about 8 years for the residuals around the linear fit lines and about 9 years for the quadratic and cubic fit lines.

We examine the relative offsets of the linear terms in the geometric distortion between WFC3/IR and the Gaia DR3 catalog using the Mikulski Archive for Space Telescopes (MAST) pipeline WFC3/IR to Gaia DR3 alignment solutions to assess temporal stability over the lifetime of the WFC3 instrument (2009-2024). We find a period of increased uncertainty and offsets in the rotation term between 2018 and 2021, as seen in a previous analysis of WFC3/UVIS linear geometric distortion (O'Connor et al., 2024), corresponding with a period of increased jitter. We find a similar pattern of increased uncertainty between 2018 and 2021 in the skew offsets to Gaia DR3, as well. We find no significant linear temporal evolution in the rotation, skew, or scale offsets between the WFC3/IR IDCTAB distortion solution and Gaia DR3 over the 16-year lifetime of the WFC3 instrument; however, we do see temporal evolution in the shift offsets (the difference -in pixels- between the IDCTAB and Gaia WCS positions), which are dominated by telescope pointing inaccuracy external to the WFC3/IR geometric distortion solution. For observers requiring high-precision astrometry, we continue to recommend that observers verify or improve image alignment using the tweakreg routine.

The measurement of dust size from millimeter-wavelength spectra provides direct constraints on grain growth in protoplanetary disks. The spectral indices between 0.88 mm and 2.9 mm have been measured in multiple young star-forming regions, such as Taurus, Ophiuchus, and Lupus, which have ages of 1-3 Myr. These spectral indices are as low as 2-3, suggesting that grains in disks are much larger than those in the interstellar medium. In this study, we analyze the ALMA archival data of 23 disks in the Upper Scorpius region. The observed wavelength is 2.9 mm in Band 3, the angular resolution is 3.3 arcsec x 2.1 arcsec, which is not high enough to resolve the targets, and the rms noise is below 0.075 mJy beam$^{-1}$ for almost all sources. Together with the literature values of the Band 7 fluxes of the same targets, we find that the average spectral index of the disks in the Upper Scorpius region is $\alpha_\mathrm{mm}=2.09 \pm 0.10$, which is equal to or slightly smaller than those at the other younger regions. To explain the relationship between the fluxes and spectral indices of the disks in the Taurus, Ophiuchus, Lupus, and Upper Scorpius regions, we construct simple disk evolution models. The observations are best reproduced by models in which the inner radius of the disk increases. This suggests that a substantial amount of dust mass must persist in the outer disk regions where the dust temperature is lower than 20 K even at late evolutionary stages. These findings offer key insights into the grain growth and the temporal evolution of protoplanetary disks.

HST is designed to use two guide stars (GSs) in the fine-guidance sensors (FGSs) to maintain its pointing and tracking during exposures. The primary GS holds the boresight fixed and the secondary GS keeps the orientation fixed. However, HST is also able to track using only a single GS by fixing the boresite on one star and maintaining the orientation using the available gyro(s). We evaluate the pointing quality achieved in this latter case, when one GS and one gyro (RGM, a.k.a., reduced gyro mode) are used. We find that in 1GS-RGM, there is indeed more drift during the course of an orbit than when two guide stars are used, but the drift is much smaller than was seen in previous times of sub-optimal gyro performance. We quantify the 1GS-RGM drift seen in recent archival GO data and in images from a test calibration program and find that (a) for exposures < 500 sec, the PSF quality in 1GS is indistinguishable from that of 2GS and (b) over the course of full orbits (~2500 sec), the drift in four of five cases was less than 0.2 pixel and ~0.4 pix in the other case. Such a drift is marginally detectable in observations, but it should have a marginal impact on most science programs, since the variation in the PSF caused by drift is smaller than the PSF variations with focus and with location on the detector. For observers who wish to correct drift effects, we show that the use of a perturbed PSF during post-acquisition data analysis removes essentially all astrometric residuals, even for drift levels up to ~0.5 pix, as well as most of the photometric residuals.

The matter distribution of the Universe can be mapped through the weak gravitational lensing (WL) effect: small distortions of the shapes of distant galaxies, which reflects the inhomogeneity of the cosmic density field. The most dominant contaminant in the WL effect is the shape noise; the signal is diluted due to the finite number of source galaxies. In order to explore the full potential of WL measurements, sharpening the signal by removing the shape noise from the observational data, i.e., WL denoising, is a pressing issue. Machine learning approaches, in particular, deep generative models, have proven effective at the WL denoising task. We implement a denoising model based on the diffusion model (DM) and conduct systematic in-depth comparisons with generative adversarial networks (GANs), which have been applied in previous works for WL denoising. Utilizing the large suite of mock simulations of WL observations, we demonstrate that DM surpasses GAN in the WL denosing task in multiple aspects: (1) the training process is more stable, (2) taking the average of multiple samples from DM can robustly reproduce the true signal, and (3) DM can recover various statistics with higher accuracy.

Observed metal abundances in the intracluster medium (ICM) of galaxy groups and clusters, $Z_{ICM}$, exceed what is expected from present-day stellar populations alone. Galaxy clusters are presumed to be near closed-box systems, allowing constraints to be placed on the origins of metals and stellar populations responsible for $Z_{ICM}$. We present a uniform XMM-Newton survey of 26 galaxy groups and clusters, measuring radial metallicity profiles and relating $Z_{ICM}$ with the stellar fraction $M_*/M_{gas}$. We determine $Z_{ICM}$ via spectral fitting across multiple annuli finding a best fit of $Z_{ICM} = -0.08^{+0.07}_{-0.07}\, log\left(\frac{M_*}{M_{gas}}\right) + 0.30^{+0.06}_{-0.06}$ with intrinsic scatter $\sigma_p = 0.09^{+0.02}_{-0.01}$. We use closed-box chemical evolution models to estimate the metallicity yield from observable stellar populations, incorporating updated supernova yields and corrections for metals locked in remnants, $Z_* = (1.14 \pm 0.52) \, log\left(1 + \frac{M_*}{M_{gas}}\right)$. Our results demonstrate that present-day stellar populations systematically underpredict $Z_{ICM}$, with an inferred excess component increasing in systems with low $M_*/M_{gas}$. This trend supports the need for an early enrichment population (EEP) distinct from visible stars, $Z_{EEP}$. We find this necessity holds when reconsidering the closed-box assumption by removing all galaxy groups, potential leaky systems, deriving $Z_{EEP}$ within $1\sigma$ when including and excluding groups. Three systems (NGC1132, NGC5098, and NGC4325) deviate from the survey trend, exhibiting steep negative radial metallicity gradients and unusually low $Z_{ICM}$. We posit these systems to be late-forming whose ICM enrichment reflects only recent stellar populations. Our analysis quantifies the necessity of an EEP and provides trends for testing cluster chemical evolution models.

In the standard cold dark matter (CDM) model, sub-galactic structures hierarchically collide and merge to build up larger structures. Mergers and collisions between dwarf galaxies and dark matter subhaloes (DMSHs) play an important role in the evolution and formation of structures within a massive galaxy. We investigate the collision frequency between DMSHs associated with a massive host galaxy such as the Milky Way. We analytically estimate the density distribution of DMSH pairs for the relative distance and relative velocity ($r_\mathrm{rel}$-$v_\mathrm{rel}$) and the distance from the centre of the host halo and relative velocity ($r$-$v_\mathrm{rel}$) planes, based on the distribution function of the host halo in the phase space. Then, we evaluate the collision frequencies of DMSHs by integrating the orbital evolution of DMSHs in Milky-Way-like host haloes selected from cosmological $N$-body simulations. The frequency of violent encounters, in which the relative distance of DMSHs is shorter than the sum of scale radii, is averaged as $2.1\times 10^2\,\mathrm{Gyr}^{-1}$. Since the time scale of violent encounters, $4.7\,\mathrm{Myr}$, is shorter than the dynamical time of the host halo, collisions between DMSHs occur frequently within the host halo. Although interactions between DMSHs produce pairs with higher relative velocities, the density distributions of all and colliding pairs between DMSHs provided by numerical results are approximately similar to those of the analytical model neglecting the interactions of DMSHs on $r_\mathrm{rel}$-$v_\mathrm{rel}$ plane for all pairs and $r$-$v_\mathrm{rel}$ plane for colliding pairs. We compare our results with observed colliding dwarf galaxies and provide insight into the abundance of DMSHs.

Dark asteroids with featureless neutral to red spectra are of particular interest due to their ability to potentially harbour primitive, hydrated, and possibly organic-rich material. These asteroids belong to the spectroscopic C-complex, to the X-types with low geometric visible albedo values as well as to the T- and D-type end members of the Bus-DeMeo spectroscopic taxonomy. Here we used Gaia Data Release 3 visible reflectance spectra to study the average spectral profiles of the C- and X-complex asteroid families in the central and outer main belt (orbital semi-major axis between 2.5 - 3.7~au). We found that eight of these families, namely 96 Aegle, 627 Charis, 1484 Postrema and 5438 Lorre, previously classified as C-complex families, and 322 Phaeo, 1303 Luthera, 5567 Durisen and 53546 2000BY6 previously classified as X-complex families, have redder slopes than implied by their previous classification and could be better classified as T-/D-type families. Some of these families may also feed the near-Earth asteroid population, being responsible for the observed T-/D-type excess. However, the analysis of their principal components of Gaia Data Release 3 spectra suggest that further near-infrared observations are needed in order to verify this identification.

Transit Timing Variations (TTVs) are a powerful tool for detecting unseen companions in systems with known transiting exoplanets and for characterizing their masses and orbital properties. Large-scale and homogeneous TTV analyses are a valuable method to complement the demographics of planetary systems and understand the role of dynamical interactions. We present the results of a systematic TTV analysis of 423 systems covering 16000 transits, each with a single transiting planet first discovered by the TESS mission and afterwards confirmed or validated. The primary aim of this survey is to identify the most promising candidates for dynamically active systems that warrant further investigation. In the first stage of our analysis, precise measurements of the transit times are extracted for each system in an homogeneous way. In the second stage, we apply a decision framework to classify candidates by analyzing the resulting variations. Based on excess timing scatter and the difference in Bayesian Information Criterion of periodic models over linear ones, the TTVs are classified as significant, marginal, or non-detections. We find 11 systems with significant TTVs, 5 of which were announced in previous works, and 10 more systems with marginal evidence in our sample. We present 3-panel diagnostic plots for all the candidates, showing phase-folded light curves, the transit variations over time, and the variations folded on the recovered TTV period. A comprehensive summary table detailing the fitted parameters and TTV significance for the entire survey is also provided. This survey constitutes the largest homogeneous TTV analysis of TESS systems to date. We provide the community with updated ephemerides and a catalogue of high-quality TTV candidates, enabling targeted follow-up observations and dynamical modelling to uncover the nature of unseen companions and study system architectures.

In recent years, imaging atmospheric Cherenkov telescopes (IACTs) have emerged as promising platforms for optical interferometry through the use of intensity interferometry. IACTs combine large segmented mirrors, photodetectors with nanosecond-scale time response capable of detecting signals from just a few photo-electrons, and array configurations with baselines of hundreds of meters. As a result, all major IACT facilities have now been upgraded to function also as optical intensity interferometers, achieving sensitivities an order of magnitude better than their predecessor, the Narrabri Stellar Intensity Interferometer. However, further improvements in sensitivity are currently limited by key IACT design constraints, namely the combination of poor optical quality and small focal ratios. Here we present three practical implementations of the "I3T concept", in which segments of the IACT primary mirror are focused onto different pixels of its camera. This approach yields several unexpected but significant advantages. Optics with larger focal ratios allow to integrate narrow-band optical filters, while lower photon fluxes enable to deploy next-generation photodetectors operating in photon-counting mode. We demonstrate that this so-called "Butterfly's Eye" configuration enhances the sensitivity of IACT-based intensity interferometers by a factor between 4 and 6. Moreover, as originally envisioned, the I3T design introduces imaging capabilities on angular scales from 2 to 40 milliarcseconds, unlocking new scientific opportunities such as direct surface imaging of nearby red giants. Besides, realistic simulations show that it can have a transformative impact on at least two key science cases: imaging the earliest stages of nova ejecta, and measuring the oblateness and circumstellar disks of fast-rotating stars.

Neutrino flavor evolution in dense astrophysical environments is inherently nonlinear and sensitive to many-body (MB) quantum effects beyond the mean-field (MF) approximation. Existing MB studies are constrained by small system sizes, closed boundaries, and highly idealized symmetry assumptions. We present a unified tensor-network framework that enables simulations of inhomogeneous and anisotropic flavor evolution under conditions relevant to core-collapse supernovae and neutron-star mergers. Within this framework, we examine the effects of inhomogeneity, boundary conditions, and convergence with resolution for multiple neutrino distributions, allowing direct comparison of these setups under one consistent formulation. In our simulations, many-body systems equilibrate earlier than their mean-field counterparts while approaching similar final flavor states. Enlarging the interaction region allows open boundaries to reproduce closed-system behavior, but only when the beams begin superimposed and interact continuously. By contrast, initially separated configurations develop entanglement more slowly, interact over longer times, and equilibrate to a flavor content that differs from that obtained from initially superimposed calculations.

Passively cooling neutron stars (NSs) should reach undetectably low surface temperatures $T_s<10^4$ K in less than $10^7$ yr. However, HST observations have revealed likely thermal UV emission from the Gyr-old millisecond pulsars PSR~J0437$-$4715 and PSR~J2124$-$3358, and from the $\sim10^{7-8}$ yr-old classical pulsars PSR~B0950$+$08 and PSR~J0108$-$1431, implying $T_s\sim10^5$ K and the need for heating mechanisms. We compute the thermal evolution of these NSs including rotochemical heating (RH) in the core with normal or Cooper-paired matter, vortex creep (VC) in the inner crust, and crustal heating through nuclear reactions, and compare the results with observations and with the upper limit for PSR~2144$-$3933. No single mechanism explains all sources. The high temperature of PSR~J0437$-$4715 can be reproduced by RH with a large Cooper pairing gap $\Delta_i\sim1.5$ MeV for either neutrons or protons, but this requires an unrealistically short initial period $P_0\lesssim1.8$ ms to activate the same mechanism in PSR~B0950$+$08. Conversely, the latter can be explained by RH with modified Urca reactions in normal matter or by VC with an excess angular momentum $J\sim3\times10^{43}$ erg,s, but these models underpredict PSR~J0437$-$4715. A model combining RH with a large pairing gap and VC matches both pulsars and is consistent with the upper limits for the remaining three. It further predicts that their temperatures should lie close to these limits, suggesting that deeper or broader-wavelength observations would provide a strong test of this scenario.

Over the past 25 years, observations have uncovered a large population of free-floating planets (FFPs), whose origins remain debated. Massive FFPs (several Jupiter masses or more) may form via gravitational collapse of molecular clouds, similar to stars. Lower-mass FFPs likely originate in planetary systems and are later ejected through dynamical interactions. We show that disc fragmentation in very young stellar binaries may be an abundant source of Jupiter-like FFPs (JFFPs), with masses above 0.3 Jupiter masses. In our model, disc fragmentation at tens to 100 au from the primary star produces gas giants, while fragmentation further out forms a more massive object that will eventually evolve into the secondary star. We present 3D simulations of massive, self-gravitating discs with embedded Jupiter-mass planets and a secondary seed ($5-50 M_J$). Chaotic migration leads to frequent planet-secondary interactions, imparting velocity kicks via gravitational slingshot that usually end in planet ejection. The ejection fraction increases steeply with the secondary-to-primary mass ratio, $q_s$, reaching 0.6 for $q_s > 0.05$. Compared to Core Accretion JFFPs, disc fragmentation JFFPs: (i) form earlier, and may be more abundant in young clusters; (ii) are ejected at much lower velocities; (iii) may retain compact circum-planetary discs. To reproduce the observed abundance of JFFPs, disc fragmentation planets must be in the post-collapse configuration. They must also either form more frequently in binary systems than around single stars, or be frequently disrupted in inner disc regions, as previously suggested in certain versions of the theory.

The eclipsing binary LL Aqr is a bright V = 9.32, detached system consisting of two solar-type stars in an eccentric orbit (P = 20.2 d). The secondary component, LL Aqr B, was previously found to have physical and atmospheric parameters very similar to the Sun. Using high-precision photometry from TESS along with previously published orbital solutions, we obtain updated model-independent stellar radii and masses: $R_A = 1.3180 \pm 0.0013~R_{\odot}$, $R_B = 0.9927 \pm 0.0008~R_{\odot}$, $M_A = 1.1947 \pm 0.0009~M_{\odot}$, and $M_B = 1.0334 \pm 0.0006~M_{\odot}$. We derive the bolometric flux and fundamental effective temperature for each component using observed magnitudes, flux ratios from light curves in multiple bands and angular diameters derived from the radii and parallax from long baseline interferometry, measuring the following values: $T_{\rm eff,A} = 6242 \pm 50$ K, $T_{\rm eff,B} = 5839 \pm 44$ K, with an additional 9 K systematic error from the flux scale zero-point. We confirm that LL Aqr displays low stellar activity by obtaining $2\sigma$ upper limits on the mean surface magnetic field strengths of 78 G and 96 G. Our results suggest an age of 2.67 - 3.01 Gyr, which is consistent with previous studies. LL Aqr now joins an ever-growing sample of well-characterised benchmark stars that can be used to test and calibrate a wide variety of methods and techniques in stellar astrophysics.

Models in which a subcomponent of dark matter interacts with dark radiation have been proposed as a solution to the Hubble tension. In this framework, the interacting subcomponent of dark matter is in thermal equilibrium with the dark radiation in the early universe, but decouples from it around the time of matter-radiation equality. We study this general class of models and evaluate the quality of fit to recent cosmological data on the cosmic microwave background (from Planck 2018 and ACT DR6), baryon acoustic oscillations, large-scale structure, supernovae type Ia, and Cepheid variables. We focus on three benchmark scenarios that differ in the rate at which the dark matter decouples from the dark radiation, resulting in different patterns of dark acoustic oscillations. Fitting without ACT DR6 data, we find that all three scenarios significantly reduce the Hubble tension relative to $\Lambda$CDM, with an exponentially fast decoupling being the most preferred. The tension is reduced to less than $2 \, \sigma$ in fits that don't include the SH0ES collaboration results as part of the data and to less than $1 \, \sigma$ when these are included. When ACT DR6 data is included, the fit is significantly worsened. We find that the largest $H_0$ value at the $95 \%$ confidence region is $70.1$ km/s/Mpc without the SH0ES data, leading to only a mild reduction in the tension. This increases to $72.5$ km/s/Mpc, corresponding to a reduction in the tension to less than $3 \, \sigma$, if the SH0ES results are included in the fit.

Extracting polarimetric information from very long baseline interferometry (VLBI) data is demanding but vital for understanding the synchrotron radiation process and the magnetic fields of celestial objects, such as active galactic nuclei (AGNs). However, conventional CLEAN-based calibration and imaging methods provide suboptimal resolution without uncertainty estimation of calibration solutions, while requiring manual steering from an experienced user. We present a Bayesian polarization calibration and imaging method using Bayesian imaging software resolve for VLBI data sets, that explores the posterior distribution of antenna-based gains, polarization leakages, and polarimetric images jointly from pre-calibrated data. We demonstrate our calibration and imaging method with observations of the quasar 3C273 with the VLBA at 15 GHz and the blazar OJ287 with the GMVA+ALMA at 86 GHz. Compared to the CLEAN method, our approach provides physically realistic images that satisfy positivity of flux and polarization constraints and can reconstruct complex source structures composed of various spatial scales. Our method systematically accounts for calibration uncertainties in the final images and provides uncertainties of Stokes images and calibration solutions. The automated Bayesian approach for calibration and imaging will be able to obtain high-fidelity polarimetric images using high-quality data from next-generation radio arrays. The pipeline developed for this work is publicly available.

FQ Cir was an ordinary fast He/N classical nova, peaking at $V$=10.9. The pre-eruption and post-eruption counterpart was at $V$=14.0, making the smallest known classical nova amplitude of 3.1 mag. The nova light and the counterpart coincide to 0.034 arc-seconds, and the counterpart is a rare hot/blue emission-line star with flickering, so the identification of the quiescent nova is certain. The counterpart is a weak Be main sequence star, B1 V(n)(e). A coherent photometric period appears in all four {\it TESS} Sectors and in the AAVSO post-eruption light curve, as ellipsoidal modulation with orbital period 2.041738 days. The companion must have been spun-up to a fast rotation, and like all Be stars, a decretion disk is exuded. With the constraints of the blackbody radius and the main sequence, the companion mass is 13.0$^{+0.2}_{-0.5}$ $M_{\odot}$, with radius 6.2$\pm$0.2 $R_{\odot}$. This is the discovery of a cataclysmic variable with a high-mass companion, a new class that we call `High Mass Cataclysmic Variables'. The white dwarf mass is 1.25$\pm$0.10 $M_{\odot}$ and must have an accretion disk that supplies fuel for the nova eruption. FQ Cir represents a new mode of accretion in interacting binaries, with Roche lobe overflow from the decretion disk feeding mass into the usual accretion disk around the white dwarf, for disk-to-disk accretion. From the mass budget of the binary, the primary star must have its initial mass $>$7.6 $M_{\odot}$, forming an ONe white dwarf, so FQ Cir can never become a Type Ia supernova.

It has been noted that with the pre-recombination early dark energy (EDE) resolution of Hubble tension, the preference of recent datasets for the evolving dark energy (DE) can be suppressed significantly. In this work, we clarify and reconfirm this result with DESI DR2 and the latest ACT DR6 and SPT-3G D1, the tightest small-scale CMB constraints up to date. In the $w_0w_a$CDM model with EDE, a quintessence-like component ($w_0+w_a\geq-1$) can be 1$\sigma$ consistent with Planck+ACT+SPT+DESI+Pantheon+SH0ES datasets, and $\Delta\chi^2\lesssim -14$ compared with $w_0w_a$CDM model without EDE. This reveals the possibility that when the potential resolutions of Hubble tension are considered, current accelerated expansion can attribute to a canonical evolving scalar field or cosmological constant, and again highlights the importance of re-examining the nature of DE within the broader context of cosmological tensions.

We outline in this paper observations of the young pre-main-sequence low-mass star TWA 7, hosting a debris disk and a distant planet. Using data collected with the near-infrared SPIRou spectropolarimeter / precision velocimeter at the Canada-France-Hawaii Telescope from early 2019 to mid 2021, we detected the magnetic field of TWA 7 from the circularly polarized Zeeman signatures and Zeeman broadening of atomic spectral lines, and the rotational modulation of its longitudinal component at the known stellar rotation period (of 5.012+-0.007 d). We then modeled the large-scale and small-scale magnetic properties of TWA 7 using Zeeman-Doppler imaging. We found that TWA 7 hosted a mainly poloidal field that significantly evolved from 2019 to 2021, the dipole component getting stronger (increasing from 0.5 kG in 2019 to 0.7 kG in 2021) and less inclined to the stellar rotation axis (from 22° in 2019 to 15° in 2021). We also analyzed the radial velocities of TWA 7 derived from the SPIRou data, and found a tentative planet signature at a period of 15.2 d (with aliases at 20.8 and 30.4 d), very close to the detection limit of our data and that would correspond to a 0.17 Mjup planet at a distance of 0.09 au if confirmed. We finally report modulation of the 1083 nm He I and 1282 nm Pa-beta lines of TWA 7 with a period of 6.6 d, different from the rotation period and potentially hinting at the presence of a close-in planet triggering star-planet interactions.

Variability is a striking features of quasars, observed at all timescales wavelengths. Studying its properties and the correlations with the physical parameters (e.g. black hole mass and accretion rate) provides significant insights into accretion physics. However, the detailed picture and the exact interplay between different emitting regions are not yet clear. We combine data from Sloan Digital Sky Survey (SDSS), the Panoramic Survey Telescope and Rapid Response System 1 (Pan-STARRS1, PS1), the Zwicky Transient Facility (ZTF), and the Gaia space telescope to constrain the power spectrum of quasars in the Stripe-82 region over a broad frequency range, 10^{-1} to 10^{-3} day^{-1}(rest frame). Light curves are matched and cross-calibrated to reach \sim 20 years in the r-band for 4037 quasars. We split the sample into bins of the same black hole mass, accretion rate, and redshift, and measure the ensemble power spectral density (PSD) in each bin. The power spectra of SDSS, ZTF, and Gaia are measured independently. We do not measure it on PS1 data due to more erratic cadence, but we discuss the use of interpolation techniques, eventually allowing us to use the data together. We find significant evidence that the long-term UV/optical variability of quasars is stationary, as the ensemble PSD estimates from SDSS, Gaia and ZTF are consistent within the errors despite coming from different surveys and years. The PSD shape is consistent with a bending power law with spectral indices of -2.7 and -1 at high and low frequencies. A fit with the PSD associated with a damped random walk is significantly worse. The PSD amplitude below the break does not depend on black hole mass, but there is some evidence for anti-correlation with the accretion rate. The bending frequency, instead, scales with the black hole mass as $\nu_b$ \propto M_{\mathrm{BH}}^{-0.6\pm0.1} and does not depend on the accretion rate.

Thermal convection in rotating stars and planets drives anisotropic turbulence and strong differential rotation, both capable of feeding energy into global oscillations. Using 3D simulations of rotating convection in spherical shells, we show that inertial modes--oscillations restored by the Coriolis force--emerge naturally in rotationally constrained turbulence, without imposing any external forcing. By varying the rotation rate at fixed thermal forcing, we find that coherent modes appear only when the convective Rossby number, the ratio of the rotation period to the convective turnover time, falls below about one-half, where rotation dominates the dynamics. These modes are mostly retrograde in the rotating frame, equatorially symmetric, and confined to mid and high latitudes, with discrete frequencies well below twice the rotation rate. At lower viscosities, or smaller Prandtl number, mode excitation becomes more efficient and a broader spectrum of inertial modes emerges. While the precise excitation mechanism remains uncertain, our results suggest that the modes are driven by shear instabilities rather than stochastic forcing by convection. We conclude that similar inertial modes are likely to exist in the interiors of giant planets and stars, though their low frequencies will make them difficult to detect.

We introduce a novel parameterization of supernova neutrino energy spectra with a clear physical motivation. Its central parameter, $\tau(t)$, quantifies the characteristic thermal-diffusion area during the explosion. When applied to the historic SN1987A data, this parameterization yields statistically significant fits and provides robust constraints on the unobserved low-energy portion of the spectrum. Beyond this specific application, we demonstrate the model's power on a suite of 3D core-collapse supernova simulations, finding that the temporal evolution of $\tau(t)$ distinctly separates successful from failed explosions. Furthermore, we constrain the progenitor mass of SN 1987A to approximately 19 solar masses by applying Smoothed Isotonic Regression, while noting the sensitivity of this estimate to observational uncertainties. Moreover, in these simulations, $\tau(t)$ and the gravitational-wave strain amplitude display a strong, synergistic co-evolution, directly linking the engine's energetic evolution to its geometric asymmetry. This implies that the thermodynamic state of the explosion is imprinted not only on the escaping neutrino flux, but also recorded in the shape of the energy spectrum. Our framework therefore offers a valuable tool for decoding the detailed core dynamics and multi-messenger processes of future galactic supernovae.

The asymmetric nature of GW190814, particularly its mass ratio ($q \approx 1/10$), has made its astrophysical origin elusive. We explore isolated binary evolution as a potential explanation for GW190814's formation. Using the binary population synthesis code COSMIC, and the backpop sampling technique to map the observed parameters of GW190814 to the initial conditions of Zero Age Main Sequence binary stars while simultaneously inferring the astrophysical prescriptions for common envelope evolution, stable mass transfer and natal kick kinematics that are needed for its formation and eventual merger. We find that the initial conditions for the binary stellar population that forms GW190814 do not stand out significantly from massive star populations observed in the Local Group. Our backpop simulations recover a dominant formation pathway where the first Roche overflow phase includes a common envelope evolution and the second Roche overflow phase remains stable. Our findings suggest that natal kicks imparted during compact object formation play the strongest role in forming GW190814-like systems. Specifically, our models require a low magnitude first natal kick (independent of direction) that prevents the binary from unbinding and a large second natal kick with its direction in the plane of the orbit and toward the binary's center of mass. The second natal kick strength and direction crucially increases the orbital eccentricity, leading to shorter delay times, and thus enabling mergers within a Hubble time. We estimate the chance probability for GW190814-like events that experience such a lucky kick and find that it occurs in $\sim20\%$ of systems if natal kicks are randomly oriented. We discuss the astrophysical implications for the formation of asymmetric GW190814-like systems under the context of binary stellar evolution.

Operational forecasting of the ionosphere remains a critical space weather challenge due to sparse observations, complex coupling across geospatial layers, and a growing need for timely, accurate predictions that support Global Navigation Satellite System (GNSS), communications, aviation safety, as well as satellite operations. As part of the 2025 NASA Heliolab, we present a curated, open-access dataset that integrates diverse ionospheric and heliospheric measurements into a coherent, machine learning-ready structure, designed specifically to support next-generation forecasting models and address gaps in current operational frameworks. Our workflow integrates a large selection of data sources comprising Solar Dynamic Observatory data, solar irradiance indices (F10.7), solar wind parameters (velocity and interplanetary magnetic field), geomagnetic activity indices (Kp, AE, SYM-H), and NASA JPL's Global Ionospheric Maps of Total Electron Content (GIM-TEC). We also implement geospatially sparse data such as the TEC derived from the World-Wide GNSS Receiver Network and crowdsourced Android smartphone measurements. This novel heterogeneous dataset is temporally and spatially aligned into a single, modular data structure that supports both physical and data-driven modeling. Leveraging this dataset, we train and benchmark several spatiotemporal machine learning architectures for forecasting vertical TEC under both quiet and geomagnetically active conditions. This work presents an extensive dataset and modeling pipeline that enables exploration of not only ionospheric dynamics but also broader Sun-Earth interactions, supporting both scientific inquiry and operational forecasting efforts.

We assume axion-like particles (ALPs) to provide the full dark matter abundance and derive various lower bounds on the ALP mass. We contrast the post- and pre-inflationary symmetry breaking cases and present allowed regions in the plane of ALP mass and energy scale of inflation. For the post-inflationary case, we revisit bounds from isocurvature perturbations taking into account that, as suggested by simulations, axion radiation by cosmic strings during the scaling regime provides the dominant production mechanism of dark matter, obtaining significantly weaker limits than previously. Combining isocurvature, with constraints from black hole superradiance and free streaming, we find that the bound $m_a \gtrsim 10^{-17}$ eV applies for most cases considered here. It can be potentially relaxed to $\sim 6\times 10^{-19}$ eV only in the post-inflationary case with a strongly temperature-dependent axion mass, subject to uncertainties on the axion emission spectrum. Significantly stronger bounds are obtained in the post-inflationary scenario from the non-observation of CMB tensor modes, which can be as strong as $m_a > 5\times 10^{-7}$ eV for small reheating efficiencies, $\epsilon \lesssim 5\times 10^{-4}$.

We introduce SpectralPINN, a hybrid pseudo-spectral/physics-informed neural network (PINN) solver for Kerr quasinormal modes that targets the Teukolsky equation in both the separated (radial/angular) and joint two-dimensional formulations. The solver replaces standard neural activation functions with Chebyshev polynomials of the first kind and supports both soft -- via loss penalties -- and hard -- enforced by analytic masks -- implementations of Leaver's normalization. Benchmarking against Leaver's continued-fraction method shows cumulative (real+imaginary part) relative frequency errors of $\sim 0.001\%$ for the separated formulation with hard normalization, $\sim 0.1\%$ for both the soft separated and soft joint formulations, and $\sim 0.01\%$ for the hard joint case. Exploiting our ability to solve the joint equation, we add a small quadrupolar perturbation to the Teukolsky operator, effectively rendering the problem non-separable. The resulting perturbed quasinormal modes are compared against the expected precision of the Einstein Telescope, allowing us to constrain the magnitude of the perturbation. These proof-of-concept results demonstrate that hybrid spectral-PINN solvers can provide a flexible pathway to quasinormal spectra in settings where separability, asymptotics, or field content become more intricate and high accuracy is required.

Gravitational waves propagating across gravitational potentials undergo lensing effects that, in the wave-optics regime, manifest as frequency-dependent amplitude and phase modulations. In this work, we revisit the diffraction integral formalism of gravitational lensing and demonstrate that it admits a natural and transparent interpretation within the framework of scattering theory. We establish a direct correspondence between the lensing amplification factor and the scattering amplitude of waves propagating in curved spacetime, clarifying how familiar lensing limits map onto distinct scattering regimes. In particular, we show that the diffraction integral matches exactly the eikonal limit of the scattering amplitude at lowest post-Minkowskian order, after a change in coordinates and the inclusion of finite-distance effects. We further extend the standard formalism by including subleading corrections to the post-Minkowskian and eikonal approximations. Our results provide a unified theoretical framework for the interpretation of lensed gravitational-wave signals and open the way to more accurate waveform modeling for future lensed observations.

The textbook N=1 supergravity has an F-term potential depending on a superpotential $W(z_i)$ and a Kahler potential $K(z^i, \bar z^{\bar i})$, with the scalar potential $V(z^i, \bar z^{\bar i})=e^K (|DW|^2 - 3 |W|^2)$. In this approach, it is not always easy to find the potential $V(z^i, \bar z^{\bar i})$ with the required properties. We show that in supergravity with a nilpotent superfield and with any Kahler potential $K(z^i, \bar z^{\bar i} )$ one can obtain any desired potential $V(z^i, \bar z^{\bar i})$ by a proper choice of the Kahler metric of the nilpotent superfield. This construction is particularly suitable for cosmological and particle physics applications, which may require maximal freedom in the choice of kinetic terms and scalar potentials.

Imminent radio telescope observatories provide massive data rates making deep learning based processing appealing while simultaneously demanding real-time performance at low-energy; prohibiting the use of many artificial neural network based approaches. We begin tackling the scientifically existential challenge of Radio Frequency Interference (RFI) detection by deploying deep Spiking Neural Networks (SNNs) on resource-constrained neuromorphic hardware. Our approach partitions large, pre-trained networks onto SynSense Xylo hardware using maximal splitting, a novel greedy algorithm. We validate this pipeline with on-chip power measurements, achieving instrument-scaled inference at 100mW. While our full-scale SNN achieves state-of-the-art accuracy among SNN baselines, our experiments reveal a more important insight that a smaller un-partitioned model significantly outperforms larger, split models. This finding highlights that hardware co-design is paramount for optimal performance. Our work thus provides a practical deployment blueprint, a key insight into the challenges of model scaling, and reinforces radio astronomy as a demanding yet ideal domain for advancing applied neuromorphic computing.

We explore and compare two distinct temperature definitions for scalar field inflation in the context of small- and large-field potentials. The first is based on a real gas, fluid-like temperature, $T_{RG}$, while the second corresponds to a relativistic species-like temperature, $T_{RS}$. We derive the fundamental thermodynamic relations for both and analyze their implications for the most viable inflationary potentials, consistent with Planck constraints. We also investigate non-minimally coupled scenarios, finding that $T_{RS}$ is the most self-consistent choice, as it decreases during inflation, satisfies standard thermodynamic laws, and exhibits frame-independent behavior in both the Jordan and Einstein frames. Remarkably, the $T_{RS}$ approach shows that the inflaton's dynamics is well-described by Van der Waals-like isotherms, linking inflationary evolution to thermodynamic phase transitions. We find that the onset of inflation is associated with a phase transition acting as the ``trigger'' of the inflationary epoch. Our analysis highlights inconsistencies in the hilltop potential and, more generally, in small-field potentials unless a non-minimal coupling is introduced. Conversely, the Starobinsky and $\alpha$-attractor models emerge as the most suitable paradigms. We further show that \emph{frame independence} is achieved only for coupling values $\zeta \leq 1/6$, supporting very small values. Finally, our study of natural inflation with non-minimal coupling reveals a strong dependence on the coupling parameter, where bounds associated with thermodynamic phase transitions coincide with observationally viable ranges, suggesting that thermodynamic considerations may provide an additional criterion to discriminate among inflationary scenarios.

Cosmic-ray muons, owing to their high penetration power and abundance, have been widely employed as a natural probe in experimental particle physics. We developed a meter-scale cosmic-ray muon telescope, consisting of two parallel super-layers (1 m $\times$ 1 m) separated vertically by one meter. A super-layer is composed of two orthogonal detection layers, of which each consists of eighteen modules arranged in parallel and packed closely together. A module consists of a plastic scintillating bar precisely aligned and stacked on top of an underlying scintillating fiber mat. The telescope employs a detection scheme combining scintillating bars and fibers to meet the requirement of spatial resolution and to reduce the number of readout electronic channels. This article presents the comprehensive development of the telescope, encompassing its geometric design, data acquisition system, and performance evaluation. Experimental results show that the telescope achieves a position resolution better than 2 mm and an overall detection efficiency of $\sim$85%. The innovative design keeps the manufacturing cost low while maintaining high spatial resolution and detection efficiency.

The non-conservation of the energy-momentum tensor in $f(R,T)$ gravity can be interpreted as an effective manifestation of dissipation. Motivated by this, we propose a new formulation of $f(R,T)$ gravity based on the Herglotz variational principle, which extends the usual {Hamilton} variational principle to dissipative systems by allowing the Lagrangian to depend explicitly on the action. The resulting gravitational field equations extend those of $f(R,T)$ gravity by including Herglotz contributions. In the Newtonian limit, these contributions modify the gravitational potential, allowing us to constrain the Herglotz vector through Mercury's perihelion precession and the relativistic light deflection. Remarkably, the Herglotz corrections lead to a scaling law consistent with observations from the Cassini spacecraft. Examining two representative cosmological models, the Herglotz vector effectively reduces to a single function that, under suitable conditions, can play the role of a cosmological constant, providing an alternative mechanism for the Universe's accelerated expansion. Within the Herglotz variational approach, the linear $f(R,T)=R+\alpha T$ model, previously ruled out in the standard formulation due to its fixed deceleration parameter, becomes consistent with observations.

When moduli roll in the early universe, all physical scales - including string tensions - simultaneously evolve. The dynamics of cosmic string loops with time-varying tension can produce cosmic string loop trackers in which most of the energy density of the universe lies in the form of string loops. This solution can exist as an attractor until the rolling modulus reaches its minimum, when the loops ultimately decay through gravitational wave emission. We explore the spectrum of gravitational waves produced by such string loop trackers. The resulting spectrum is high-frequency and peaks in the GHz regime today. The amplitude of the signal is diluted by any subsequent matter-dominated epochs, and thus the potential observability of the signal crucially depends on the duration of the moduli-dominated epoch that follows once the moduli settle down and oscillate about their minimum.

Dual-phase liquid xenon time projection chambers are the core detector elements of many experiments that conduct searches for Dark Matter and rare events, as well as in neutrino and high-energy physics. As part of this detector technology, high-voltage electrodes are instrumental for the generation of observable signals and their physical interpretation. Thus, electrode design and manufacturing has to fulfill stringent requirements, and their production is associated with significant engineering challenges. In this work we describe the successful development of electrodes on the 1.5 m-scale, from their design and simulation to subsequent assembly and high-voltage testing in a gaseous argon environment. The produced electrodes were recently installed as an anode and a cathode during an upgrade to the XENONnT experiment.

We generalize thermal WIMP (Weakly Interacting Massive Particle) freeze-out within Tsallis nonextensive statistics. Using Curado-Tsallis $q$-distributions $f_q(E;\mu,T)$ we compute $q$-deformed number and energy densities, pressure, entropy density and Hubble rate, $\{n_q,\rho_q,P_q,s_q,H_q\}$. The Boltzmann equation is generalized accordingly to obtain the comoving abundance $Y_{\chi,q}(x)$ and relic density $\Omega_{\chi,q}h^2$ for a dark-matter candidate $\chi$ in a model-independent setup. The thermally averaged cross section is expanded as $\langle\sigma v\rangle_q \approx a + b\,\langle v_{\rm rel}^2\rangle_q$ up to $p$-wave. The freeze-out parameter $x_f(q)$ is determined from $\Gamma_{{\rm ann},q}(T_f)\simeq H_q(T_f)$ using a $q$-logarithmic inversion, with the expansion rate modified through ultra-relativistic rescalings $R_\rho(q)$ of the effective relativistic degrees of freedom $g_*$ and $g_{*s}$. We show that $x_f$ increases with $q$ and that QCD-threshold features propagate into $Y_{\chi,q}(x)$ and $\Omega_{\chi,q}h^2$. We then perform two $q$-grid scans: fixing $\langle\sigma v\rangle_q$ while varying the dark-matter mass $m_\chi$, and fixing $m_\chi$ while varying the $s$-wave coefficient $a$. For an $s$-wave dominated scenario we construct $\chi^2$ profiles in these planes by comparing $\Omega_{\chi,q}h^2$ with the Planck benchmark $\Omega_c h^2 = 0.120\pm 0.001$. In both cases we find a clear degeneracy in the preferred nonextensive parameter $q_{\rm best}$ along valleys in parameter space. However, fixed-mass scans (varying $\langle\sigma v\rangle_q$) are significantly more constraining than fixed-cross-section scans, reflecting that $\Omega_{\chi,q}h^2$ is mainly controlled by $\langle\sigma v\rangle_q$, so that for realistic cross sections the best-fit $q_{\rm best}$ remains close to the extensive limit $q\to 1$.

We present the $N$-fit algorithm designed to improve the reconstruction of neutrino events detected by a single line of the ANTARES underwater telescope, usually associated with low energy neutrino events ($\sim$ 100 GeV). $N$-Fit is a neural network model that relies on deep learning and combines several advanced techniques in machine learning --deep convolutional layers, mixture density output layers, and transfer learning. This framework divides the reconstruction process into two dedicated branches for each neutrino event topology --tracks and showers-- composed of sub-models for spatial estimation --direction and position-- and energy inference, which later on are combined for event classification. Regarding the direction of single-line events, the $N$-Fit algorithm significantly refines the estimation of the zenithal angle, and delivers reliable azimuthal angle predictions that were previously unattainable with traditional $\chi^2$-fit methods. Improving on energy estimation of single-line events is a tall order; $N$-Fit benefits from transfer learning to efficiently integrate key characteristics, such as the estimation of the closest distance from the event to the detector. $N$-Fit also takes advantage from transfer learning in event topology classification by freezing convolutional layers of the pretrained branches. Tests on Monte Carlo simulations and data demonstrate a significant reduction in mean and median absolute errors across all reconstructed parameters. The improvements achieved by $N$-Fit highlight its potential for advancing multimessenger astrophysics and enhancing our ability to probe fundamental physics beyond the Standard Model using single-line events from ANTARES data.

We investigate a non-separable subset of $k$-essence in which the kinetic and potential sectors interact through an $X^{\rho}V(\phi)$ coupling, implemented via a potential-dependent prefactor $f(\phi)=1+2\mathcal{K}V$. In slow roll, this structure preserves a constant sound speed $c_s^2=1/(2\rho-1)$ while modifying the Hubble flow in a controlled way, thereby shifting the inflationary observables relative to the separable template. For monomial potentials $V=A\phi^n$ (with $n=2$ and $n=2/3$ as representative cases) we derive closed analytic expressions for $n_s(N_\ast)$ and $r(N_\ast)$ to $\mathcal{O}(\epsilon_{\rm mix}^2)$, where $\epsilon_{\rm mix}\propto\mathcal{K}$ encodes the non-separable $X^\rho V$ mixing, and we validate them against exact background integrations. The analytic and numerical predictions agree at the sub-per-mille level for $n_s$ and at the percent level for $r$, confirming the accuracy of the small-mixing expansion. For $\mathcal{K}<0$ the mixing systematically lowers both $n_s$ and $r$ at fixed $N_\ast$, allowing otherwise marginal monomials to fall within the region favored by recent ACT+{\it Planck}+BAO constraints (P--ACT--LB). All solutions shown satisfy the health conditions $f(\phi)>0$, $\rho>\tfrac12$, and the positivity bound $V<1/(2|\mathcal K|)$ (from $f>0$). We also discuss parameter dependence and the expected equilateral-type non-Gaussianity, which remains comfortably within current bounds for the benchmarks considered.

Domain walls are topological defects that may have formed in the early Universe through the spontaneous breakdown of discrete symmetries, and can be a strong source of gravitational waves (GWs). We perform 3D lattice field theory simulations with CosmoLattice, considering grid sizes $N = 1250$, $2048$ and $4096$, to study the dynamics of the domain wall network and its GW signatures. We first analyze how the network approaches the scaling regime with a constant $\mathcal{O}(1)$ number of domain walls per Hubble volume, including setups with a large initial number of domains as expected in realistic scenarios, and find that scaling is always reached in a few Hubble times after the network formation. To better understand the properties of the scaling regime, we then numerically extract the Equal Time Correlator (ETC) of the energy-momentum tensor of the network, thus determining its characteristic shape for the case of domain walls, and verifying explicitly its functional dependence as predicted by scaling arguments. The ETC can be further extended to the Unequal Time Correlator (UTC) controlling the GW emission by making assumptions on the coherence of the source. By comparison with the actual GW spectrum evaluated by CosmoLattice, we are then able to infer the degree of coherence of the domain wall network. Finally, by performing numerical simulations in different background cosmologies, e.g. radiation domination and kination, we find evidence for a universal ETC at subhorizon scales and hence a universal shape of the GW spectrum in the UV, while the expansion history of the Universe may instead be determined by the IR features of the GW spectrum.

Over the next decade, $\mathcal{O}(100)$ diffuse supernova neutrino background (DSNB) events are expected in Hyper-Kamiokande. Another neutrino source that has received far less attention is binary neutron star mergers. Including the data from recent simulations, we find that detection in current and near-future neutrino experiments is not feasible, and a megaton-scale detector with $\mathcal{O}(10)$ MeV threshold, such as the proposed Deep-TITAND, MEMPHYS, or MICA, will be required. This is due to the updated binary neutron star merger rate and the time-of-flight delay caused by the nonzero neutrino mass. Regarding the former, recent results from LIGO, Virgo, and KAGRA has significantly lowered the upper limit on the neutron star merger rate. As for the latter, neutrino events from neutron star mergers are expected to be recorded shortly after the gravitational wave signal. Limiting the analysis to such short time windows can significantly reduce background rates. While this approach has been qualitatively discussed in the literature, the effect of the time delay caused by neutrino mass, which can substantially extend the observation windows, has been disregarded. We present a refined analysis employing energy-dependent time windows and luminosity distance cuts for the mergers and provide realistic estimates of the detector runtime required to record neutrinos from binary neutron star mergers with small background contamination. The relative timing between the neutrino and gravitational wave signals can also be employed to probe the scale of neutrino mass. We find that the sensitivity to the lightest neutrino mass exceeds both the most stringent terrestrial bounds from KATRIN and the projections based on galactic supernovae. This level of sensitivity may become particularly relevant in the future if terrestrial and supernova constraints are not significantly improved.