Papers for Tuesday, Jan 27 2026

We investigate the thermodynamics of a relativistic Fermi gas governed by a modified dispersion relation in the Magueijo Smolin (MS) formulation of Doubly Special Relativity (DSR), characterized by the presence of an invariant ultraviolet energy (deformation) scale. We study the system in two physically distinct regimes: the near degenerate low temperature limit, and the high temperature regime. In the low temperature regime, we derive the thermodynamic quantities using the standard Sommerfeld expansion. In the high temperature regime, we evaluate all thermodynamic quantities numerically from the exact grand canonical potential and demonstrate that the thermodynamics of the Fermi gas reduces to the standard relativistic ideal gas behavior. We apply the resulting low temperature equation of state to study compact astrophysical objects, namely, non rotating white dwarfs and neutron stars. Helium white dwarfs exhibit a strong dependence on the deformation scale, while white dwarfs composed of heavier elements are less affected. For neutron stars, the modified equation of state leads to configurations that are smaller in radius and lower in mass than is by nucleonic equations of state. Our results highlight how modified relativity theories can be probed by studying astrophysical objects.

Comet C/2025 N1 or 3I/ATLAS is the third confirmed interstellar object. It has passed perihelion on 2025 October 29, and is currently on a path to leave the solar system. During its outbound journey, it will pass close to Jupiter at a distance of 0.358 au. NASA JPL \textsc{Horizons} has updated the non-gravitational parameters of the comet based on the CO$_2$ sublimation model, where $g(r)= 1/r^2$. In this research note, we use the non-gravitational accelerations from \textsc{Horizons} together with symmetric and asymmetric H$_2$O sublimation models derived using \texttt{Find\_Orb} software. We calculate the resulting perijove distances and compare them with our earlier results at epoch JD 2460867.5.

How galaxies formed and evolved in the expanding Universe is the main science goal of Near-Field Cosmology research. Studies of the properties of galaxies' resolved stars open a widow on their ancient galactic components, probing star formation during epochs more than 10 billion years ago. Extragalactic Planetary Nebulae (xPNe) can help decipher the signatures of mergers and interactions persisting over many dynamical times by tracing elemental abundances coupled with their kinematics and spatial distributions. With new facilities, reaching higher angular resolution, area coverage and sensitivity, one can use xPNe to map Oxygen and Argon element abundances, in addition to their kinematics, to extend the Galactic Archeology investigation to the oldest stellar aggregates in our Local Universe.

Aims. We aim to investigate the connection between star formation histories (SFHs) and the inner dark matter density profiles of simulated galaxies. In particular, we test whether the burstiness and temporal distribution of star formation influence the formation of cored versus cuspy dark matter profiles. Methods. We homogeneously analysed simulated galaxies from the NIHAO and FIRE-2 projects. For each galaxy, we derived dark matter density profiles and measured the logarithmic slope in the inner region of the dark matter halo (1-2% of R$_{\rm vir}$). To characterise star formation burstiness, we introduced a criterion based on comparing the star formation rate (SFR) averaged over two distinct timescales. We further quantified the duration of SFHs by computing $M_{\star, \rm post}$ / $M_{\star, \rm pre}$, the ratio of stellar mass formed after versus before the epoch of reionisation at redshift z $\sim$ 6.5. Results. Homogeneous analysis reveals that inner slope versus stellar-to-halo mass ratio trends for NIHAO and FIRE-2 galaxies are in much better agreement than reported in previous works. The burstiness and duration of the SFH explain the scatter in the inner slope versus stellar-to-halo mass ratio relation, revealing that galaxies with above average burstiness and more extended SFHs are more efficient at developing cored dark matter profiles. In contrast, galaxies with smoother SFHs and earlier stellar mass assembly tend to maintain cuspier dark matter profiles. We present an analytic expression that improves predictions for the inner slope using the parameter $M_{\star \rm,post}$ / $M_{\star \rm,pre}$, which reduces the mean squared error in both simulation suites relative to previous formulations based solely on the stellar-to-halo mass ratio.

The Transiting Exoplanet Survey Satellite (TESS) has observed nearly the entire sky, producing full-frame images (FFIs) every 30 min (Cycles 1$-$2), 10 min (Cycles 3$-$4), and now 200 s (Cycle 5+), over 27-day sectors. Light curves extracted from FFIs can be used to measure stellar rotation periods ($P_{\rm rot}$) in nearby open clusters, and are well-suited for studying low-mass stars ($\lesssim$1.2 M$_\odot$) younger than $\approx$1 Gyr, whose $P_{\rm rot}$ are generally still $\leq$15 days. A challenge to exploiting TESS data fully is its 21$''$ pixel size, which can cause strong signals from a source to contaminate the signals of nearby sources in the crowded environments found, e.g., in the more distant and/or richest clusters. We conducted a test with the young ($\approx$350 Myr old), moderately distant (470 pc), and rich open cluster NGC 3532 ($N_\star$ > 3000), which has an extensive $P_{\rm rot}$ catalog from ground-based photometry, to examine the reliability of $P_{\rm rot}$ obtained from TESS data. We recovered 69% of the literature periods from at least one of the three TESS cycles in which NGC 3532 was observed before any quality analysis. We then used all available TESS data for low-mass members of NGC 3532 and, applying a set of quality cuts that combined information from TESS and from Gaia, measured $P_{\rm rot}$ for 885 cluster stars, adding 706 new $P_{\rm rot}$ to the existing catalog. We conclude that, when considered with appropriate caution, TESS data for stars in crowded fields can yield reliable $P_{\rm rot}$ measurements.

Recent observations of supermassive black holes (SMBHs) at high redshifts pose challenges to standard seeding mechanisms. Among competing models, the collapse of self-interacting dark matter (SIDM) halos provide a plausible explanation for early SMBH formation. While previous studies on modeling the gravothermal collapse of SIDM halos have primarily focused on non-relativistic evolution under the assumption of hydrostatic equilibrium, We advance this framework by relaxing the equilibrium assumption and additionally incorporating general-relativistic effects. To this end, we introduce the Misner-Sharp formalism to the SIDM context for the first time. Our model reproduces the standard hydrostatic models in the early long-mean-free-path (LMFP) regime, but displays interesting distinct behavior in the late short-mean-free-path (SMFP) regime, where intense outward heat flux drives a rapid expansion of the outer envelope, removing mass from the core and significantly decelerating the collapse. Our general relativistic treatment enables us to follow halo evolution to the final stage when the apparent horizon forms. Our simulation yields a seed black hole mass of approximately $3\times10^{-8}$ of the halo mass at horizon formation, suggesting that additional mechanisms such as baryonic effects are critical for seeding black holes that are sufficiently massive to account for SMBHs in the early Universe.

We present an improved semi-analytical model to predict density profiles of self-interacting dark matter (SIDM) halos and apply it to constrain the self-scattering cross section using SPARC galaxy rotation curves. Building on the isothermal Jeans approach, our model incorporates (i) velocity-dependent cross sections, (ii) an empirical treatment of core collapse, and (iii) enhanced robustness for identifying solutions. These advances allow us to fit a large sample of galaxies, including systems with baryon-dominated centers often excluded in earlier studies. We find that roughly 1/6 of galaxies admit both a core-growth and a core-collapse solution, while the rest favor a unique evolutionary state. Joint constraints across the sample reveal clear velocity dependence: the allowed parameter space forms an L-shaped degeneracy, where both nearly constant, low cross sections ($\sigma_0\sim2\,{\rm cm}^2$/g, $\omega\gtrsim500\,$km/s) and strongly velocity-dependent models ($\sigma_0\sim100\,{\rm cm}^2$/g, $\omega\sim60\,$km/s) are viable. Adopting the core-growth interpretation yields best-fit values $\sigma_0\simeq5\,{\rm cm}^2$/g and $\omega\simeq250\,$km/s. Our constraints are remarkably consistent with previous results derived from a variety of independent probes. Compared to cold dark matter (CDM) models, SIDM outperforms simple adiabatic-contraction profiles and rivals empirical feedback-based CDM profiles, yet shows no correlation with stellar-to-halo mass ratio, a proxy for feedback strength, offering a distinct explanation for dwarf galaxy diversity. Moreover, SIDM does not affect galaxy-halo scaling relations significantly and makes concentration systematically lower. Our results highlight SIDM as a compelling framework for small-scale structure, while future low-mass kinematic data will be crucial for breaking degeneracies in velocity-dependent cross-section models.

We introduce the \textsc{Tailed-Uniform} proposal distribution for generating training simulations in simulation-based inference. Instead of sampling parameters uniformly within bounded regions, we extend the distribution beyond prior boundaries with smooth Gaussian tails. This eliminates sharp discontinuities that cause neural posterior estimators to fail when the posterior distribution intersects or extends beyond the prior bounds. The method requires minimal hyperparameter tuning, with tail widths of 10--30\% of the prior width proving robust across problems. We demonstrate these benefits on a synthetic Gaussian linear task and cosmological parameter inference from the matter power spectrum. We also find that \tail-trained models outperform \textsc{Uniform} ones near the boundaries across various training set sizes and dimensions of the parameter space. This advantage grows in higher dimensions, where boundaries dominate parameter space volume. All code is publicly available on Github at this https URL.

Our Galaxy, Andromeda and their companion dwarf galaxies form the Local Group. Most of the mass in and around it is believed to be dark matter rather than gas or stars, so its distribution must be inferred from the effect of gravity on the motion of visible objects. Modelling efforts have long struggled to reproduce the quiet Hubble flow around the Local Group, as they require unrealistically little mass beyond the haloes of the two main galaxies. Here we revisit this using $\Lambda$CDM simulations of Local Group analogues with initial conditions constrained to match the observed dynamics of the two main haloes and the surrounding flow. The observations are reconcilable within $\Lambda$CDM, but only if mass is strongly concentrated in a plane out to 10 Mpc, with the surface density rising away from the Local Group and with deep voids above and below. This configuration, dynamically inferred, mirrors known structures in the nearby galaxy distribution. The resulting Hubble flow is quiet yet strongly anisotropic, a fact obscured by the paucity of tracers at high supergalactic latitude. This flattened geometry reconciles the dynamical mass estimates of the Local Group with the surrounding velocity field, thus demonstrating full consistency within the standard cosmological model.

The spatial and kinematic structure of the circumgalactic medium (CGM) remains poorly constrained observationally. In this article we compute the clustering of CIV absorption systems at cosmic noon using quasar pairs. We analyze VLT/UVES and Keck/HIRES high-resolution spectra (R = 45000) of a sample of 8 projected and 4 lensed quasar pairs that probe transverse separations, $\Delta r$, from sub-kpc to a few Mpc, over the redshift range 1.6 < z < 3.3. We detect and fit Voigt profiles to a total of 141 CIV systems, corresponding to 620 velocity components across all quasar lines-of-sight. We compute the two-point correlation function of CIV, $\xi(\Delta v, \Delta r)$, where $\Delta v$ is the velocity difference between components across all available scales. We find a strong dependence of $\xi(\Delta r)$ with $\Delta r$ at all velocities. $\xi(\Delta r)$ reaches a sharp peak at the smallest scales analyzed here, $\Delta r\approx 0.1$ kpc, decreases steadily up to $\Delta r\approx 5$ kpc and remains flat up to $\Delta r\approx 500$ kpc, where it begins to decrease again. By fitting power-laws to the projected transverse correlation function $\Xi(\Delta r)$, we infer two coherence lengths: $r_1 = 654^{+100}_{-87}$ kpc, which we interpret as a representative size for the CIV enriched regions at $z\approx 2$, and $r_2 = 4.70^{+1.60}_{-1.19}$ kpc for the individual CIV-bearing "clouds". Projecting instead in $\Delta r$, we find consistent amplitudes of $\xi(\Delta v)$ with previous work using quasars and extended background sources. Our results suggest that CIV may be a good tracer of not only the small, internal structure of the circumgalactic medium, but also of the way in which galaxies cluster at cosmic noon.

We investigate galaxies in the GARDEN (Galaxies at All Redshifts Deciphered and Explained with the NIRSpec MSA) survey that show auroral emission lines, enabling spatially resolved measurements of electron temperature and direct oxygen abundances. Two galaxies have spectra suitable for this analysis: CANDELS 8005 at z=3.794 and CANDELS 7986 at z=4.702. For both, we measure auroral and key nebular emission-line fluxes across their full extent, allowing direct-method oxygen abundance determinations in individual spaxels. These observations demonstrate the viability of deep JWST/NIRSpec MSA spectroscopy for spatially resolved chemical analyses at high redshift, aided by weak nebular continua and low interstellar extinction. We derive global direct abundances of 12 + log(O/H) = 8.008 (+0.025, -0.027) for CANDELS 8005 and 7.89 (+0.027, -0.028) for CANDELS 7986. Emission-line diagnostics indicate neither galaxy hosts an active galactic nucleus. A first-order kinematic analysis suggests a potential merger in CANDELS 8005. The direct abundances agree with strong-line estimates from our data and recent high-redshift calibrations. We build emission line, radial velocity, strong-line abundance, electron temperature, and direct abundance maps for both galaxies. From these maps, we measure linear radial metallicity gradients of -0.111 (+0.026, -0.025) dex/kpc for CANDELS 8005 (statistically significant) and -0.093 +/- 0.088 dex/kpc for CANDELS 7986, where the large uncertainties limit significance. These results represent the first detection of a radial metallicity gradient from direct-method abundances with measurements taken in galaxies at z>0, supporting inside-out galaxy growth with feedback-regulated chemical enrichment.

We discuss the suite of STIS calibration programs executed during HST Cycle 30, covering the period 2022 Nov 07 through 2023 Nov 05. For each of the 19 current regular calibration programs, we provide brief descriptions of the objectives, observations, analysis procedures, and results - with comparisons to the results from previous cycles and to desired accuracies, as well as references to more detailed analyses of the calibration data. Many of these calibration programs produce routine reference file deliveries or demonstrate the continuing applicability of existing reference files for processing STIS observations. This ISR provides a brief snapshot of the current instrument performance, similar to those given in annual reports for Cycles 7-10 and 17-21. Two Appendices briefly discuss the state of the onboard calibration lamps and the ongoing major effort to revise the flux calibration for the many STIS spectroscopic and imaging modes.

Detached eclipsing binary stars (DEBS) are currently the best source of accurate and precise fundamental stellar parameters. This makes DEBS crucial targets for constraining the impact of various physical processes on stellar structure and evolution. Long-period binaries are particularly interesting because their separation minimises interactions between the components. This makes long-period binaries more comparable to single stars. However, the current sample of DEBS with high precision stellar parameters are dominated by short-period systems (e.g. ~90% of the Gaia DR3 eclipsing binaries have periods < 5 days). Facilities capable of performing detailed studies of long-period DEBS will be essential to further improve our understanding of stellar structure and evolution. Such facilities would need to be able to obtain spectroscopic observations of more distant objects at high resolution and cadence. 2-8m class telescopes with echelle spectrographs and an ability to monitor a large sample of stars would be required.

Accurate redshift estimates are a vital component in understanding galaxy evolution and precision cosmology. In this paper, we explore approaches to increase the applicability of machine learning models for photometric redshift estimation on a broader range of galaxy types. Typical models are trained with ground-truth redshifts from spectroscopy. We test the utility and effectiveness of two approaches for combining spectroscopic redshifts and redshifts derived from multiband ($\sim$35 filters) photometry, which sample different types of galaxies compared to spectroscopic surveys. The two approaches are (1) training on a composite dataset and (2) transfer learning from one dataset to another. We compile photometric redshifts from the COSMOS2020 catalog (TransferZ) to complement an established spectroscopic redshift dataset (GalaxiesML). We used two architectures, deterministic neural networks (NN) and Bayesian neural networks (BNN), to examine and evaluate their performance with respect to the Legacy Survey of Space and Time (LSST) photo-$z$ science requirements. We also use split conformal prediction for calibrating uncertainty estimates and producing prediction intervals for the BNN and NN, respectively. We find that a NN trained on a composite dataset predicts photo-$z$'s that are 4.5 times less biased within the redshift range $0.3<z<1.5$, 1.1 times less scattered, and has a 1.4 times lower outlier rate than a model trained on only spectroscopic ground truths. We also find that BNNs produce reliable uncertainty estimates, but are sensitive to the different ground truths. This investigation leverages different sources of ground truths to develop models that can accurately predict photo-$z$'s for a broader population of galaxies crucial for surveys such as Euclid and LSST.

Ordinary matter-including particles such as protons and neutrons-accounts for only about one sixth of all matter in the Universe. The rest is dark matter, which does not emit or absorb light but plays a fundamental role in galaxy and structure evolution. Because it interacts only through gravity, one of the most direct probes is weak gravitational lensing: the deflection of light from distant galaxies by intervening mass. Here we present an extremely detailed, wide-area weak-lensing mass map, covering 0.77 deg x 0.70 deg, using high-resolution imaging from the James Webb Space Telescope (JWST) as part of the COSMOS-Web survey. By measuring the shapes of 129 galaxies per square arcminute-many independently in the F115W and F150W bands-we achieve an angular resolution of 1.00 +/- 0.01 arcmin. Our map has more than twice the resolution of earlier Hubble Space Telescope maps, revealing how dark and luminous matter co-evolve across filaments, clusters, and under-densities. It traces mass features out to z ~ 2, including the most distant structure at z ~ 1.1. The sensitivity to high-redshift lensing constrains galaxy environments at the peak of cosmic star formation and sets a high-resolution benchmark for testing theories about the nature of dark matter and the formation of large-scale cosmic structure

This review of the rapid-neutron-capture (i.e. r-) process starts with determining the Solar System r-abundance pattern via first obtaining (and subtracting) the contribution from the slow-neutron capture (s-) process. We emphasize the extensive work in this area by our late colleague Roberto Gallino and continue in an overview, concentrating on attempts to reproduce the solar r-process pattern with historical site-independent approaches, based on nuclear physics far from stability. In a second step we address the existing proposals for astrophysical sites. Among stellar observations we start with available observations of individual events before analyzing low-metallicity stars, which witness r-process contributions in the early this http URL conclude with a comparison of observations and model predictions, focusing on our present ability to identify the responsible individual astrophysical sites by their imprint in Galactic evolution.

Polarized thermal emission from Galactic dust is the dominant foreground for CMB polarization measurements at high frequencies, with its statistical properties set by the interplay between turbulence and magnetic fields in the multiphase interstellar medium (ISM). Variations in turbulence regime and density-magnetic-field alignment across the warm (WNM), unstable (UNM), and cold (CNM) neutral media should imprint distinct signatures on the power spectra and $EE/BB$ power ratio, yet the relative phase contributions remain poorly constrained. Using high-resolution 3D magnetohydrodynamic simulations of a turbulent multiphase ISM coupled with synthetic dust polarization maps, we quantify phase-dependent turbulence, anisotropy, and alignment properties. We find that the trans-Alfvénic and transonic WNM and UNM are strongly anisotropic, exhibiting tight alignment of density and velocity structures with the local magnetic field. In contrast, the super-Alfvénic and supersonic CNM displays reduced anisotropy and weak alignment. These dynamical differences are reflected in the statistical scaling of fluctuations: the square root of the second-order velocity structure function exhibits a slope near $1/3$ in the WNM, near $1/2$ in the CNM, and intermediate in the UNM. Our synthetic observations reproduce the polarization power spectra measured by Planck. We find that polarization from UNM dust yields spectral indices most consistent with Planck, whereas WNM and CNM dust produce steeper and shallower spectra, respectively. The WNM yields $EE/BB>2$, the UNM gives $EE/BB\sim2$, and the CNM yields $EE/BB\approx1$. These results indicate that UNM dust could be the dominant contributor to the polarized foreground. We present predictions at 150 GHz to improve foreground separation.

Stellar flybys are a common dynamical process in young stellar clusters and can significantly reshape protoplanetary discs. However, their impact on dust dynamics remains poorly understood, particularly in the weakly coupled regime (St$\gg$1). We present three-dimensional hydrodynamical simulations of parabolic stellar flybys-both coplanar and inclined-interacting with a gaseous and dusty protoplanetary disc. Dust species with Stokes numbers ranging from 15 to 100, corresponding to four grain sizes under a uniform initial gas surface density, are included. Perturber masses of 0.1 and 1$\mathrm{M}_{\odot}$ are considered. The induced spiral structures exhibit distinct dynamical behaviours in gas and dust: dust spirals retain a nearly constant pattern speed, while gas spirals gradually decelerate. The pitch angles of both components decrease over time, with dust evolving more rapidly. In the weakly coupled regime, gas and dust spirals are spatially offset, facilitating dust accumulation around both structures. Equal-mass flybys truncate the disc at approximately $\sim$0.55$r_{\mathrm{Hill}}$, producing tightly wound, ring-like spirals that promote dust concentration. By mapping the streaming instability growth rates in the solid abundance-Stokes number space across three evolutionary phases, we find that a low-mass flyby suppresses dust concentration below the critical clumping threshold after periastron and maintains this suppression over time, indicating long-lasting inhibition of dust clumping. An equal-mass flyby raises local solid abundance well above the threshold, suggesting that such encounters may foster conditions favourable for dust clumping. Flyby-induced spirals play a central role in shaping dust evolution, leading to distinct spatial and temporal behaviours in weakly coupled discs.

We present constraints on quintessence dark energy models using the observational detection of the Integrated Sachs-Wolfe (ISW)--thermal Sunyaev-Zeldovich (tSZ) cross-correlation dataset. Our analysis compares three classes of quintessence dynamics: thawing, tracker, and scaling-freezing with the standard $\Lambda$CDM cosmology. Through a comprehensive likelihood analysis, we derive best-fit values and 68\% confidence intervals for key cosmological parameters, finding $\Omega_{\rm m} = 0.322^{+0.027}_{-0.030}$ and $\sigma_8 = 0.735^{+0.045}_{-0.035}$ for $\Lambda$CDM, with deviations in alternative models consistent within $1\sigma$. For the thawing model, we consider an exponential potential with slope $\lambda = 0.736^{+0.270}_{-0.227}$, while for the tracker and scaling-freezing models, we use inverse axion-like and double exponential potentials, respectively. Observationally, the tracker model yields $n = 5.651^{+1.625}_{-1.604}$ and $f = 0.258^{+0.149}_{-0.096}$, and the scaling-freezing model gives $\lambda_1 = 0.405^{+0.293}_{-0.322}$ and $\lambda_2 = 23.226^{+7.975}_{-7.258}$. The dimensionless tSZ amplitude ($\widetilde{W}^{\rm SZ}$) and cosmic infrared background (CIB) parameters are tightly constrained across all models, providing additional insights into astrophysical foregrounds. Our results demonstrate the effectiveness of ISW--tSZ cross-correlations as a probe of dark energy dynamics, with the Thawing quintessence model yielding the lowest $\chi^2_{\rm min}$ among the tested scenarios, and highlight the need for future high-precision measurements to distinguish between quintessence models and $\Lambda$CDM.

Individual radio pulses from a pulsar are directly linked to the underlying emission processes and the associated magnetic field geometry within its magnetosphere. Thus, single-pulse studies across frequencies can provide crucial insights into the physics of radio emission. Multiple studies have investigated single-pulse correlations in PSR B0329+54 with widely separated discrete frequencies, reporting the broadband nature of pulsar emission. However, understanding the frequency evolution of these correlations has been limited by poor frequency sampling, and the physical origin of these correlations remains unexplored. We present a detailed study of single-pulse correlations in PSR B0329+54 at low radio frequencies using the upgraded Giant Meterwave Radio Telescope (uGMRT), with well-sampled time series spanning 300-1460 MHz. We derived an inverted flux spectrum for this pulsar, with a turnover near 470 MHz. We used flux-calibrated and scintillation-corrected single pulses to study correlations across frequencies. Our results show that maximum correlations consistently occur near the longitude of the central component, with correlation strength exceeding 69\% for all frequency combinations, while outer components exhibit correlations above 46\%. These findings indicate very strong inter-frequency correlations, with no anticorrelations detected. No cross-component correlations were observed; only corresponding components correlate across frequencies. The longitudes of maximum correlation do not coincide with the intensity peaks of the average profile. We also examine how correlations vary with frequency at selected fiducial longitudes. The observations reported in this work favor curvature radiation from relativistic charge bunches in the pulsar plasma; however, reproducing the correlation curves along with spectra remains an open challenge.

The Westerlund 1 (Wd 1) is the most massive known young star cluster in the Galaxy, and an extended $\gamma$-ray source HESS J1646-458 surrounding it has been detected up to 80 TeV in the very high energy, implying that cosmic rays (CRs) are accelerated effectively in the region. However, the dominant radiation process contributing to the $\gamma$-ray emission is not well constrained. In the present work, we develop a model of CR acceleration at the termination shock in the superbubble inflated by the interaction of the cluster wind from the Wd 1 with the surrounding interstellar medium. We then calculate the flux and radial profile of $\gamma$ rays produced by the inelastic collisions of the hadronic CRs with the ambient gas. Our results with reasonable parameters can explain well the spectrum and radial profile of the $\gamma$-ray emission of HESS J1646-458, and consequently the $\gamma$-ray emission of HESS J1646-458 is likely to be of hadronic origin.

We present a rest-ultraviolet to infrared spectral energy distribution (SED) analysis of 63 heavily reddened quasars (HRQs) at redshifts z=0.7-2.7 and with dust extinctions E(B-V)=0.4-1.8. Our analysis demonstrates that SEDs with red optical and blue UV continua are very common in HRQs, with more than 82 per cent of the sample showing a UV-excess relative to the reddened quasar continuum. We model the SEDs by combining a reddened quasar and an unobscured scattered light component, though contributions from a star-forming host galaxy cannot be ruled out. The average scattering fraction is small (0.3 per cent). Higher scattering fractions are ruled out by the (i-K)=2.5 colour-cut used to select HRQs which pre-dates the discovery of the JWST "Little Red Dot" (LRD) population. Hence, LRDs generally have bluer UV continua. Nevertheless, four HRQs satisfy the LRD UV/optical continuum slope selections and are therefore massive, cosmic noon analogues of LRDs. Analysis of the near-infrared SEDs of HRQs reveals a deficit of hot dust relative to blue quasars, similar to what is observed in LRDs. This suggests HRQs trace a phase where strong AGN feedback processes eject dust from the inner torus. The UV scattering fraction of HRQs is weakly correlated with the amount of hot dust emission and anti-correlated with the line-of-sight extinction, E(B-V). This is consistent with the hot dust acting as the scattering medium, and the line-of-sight extinction being dominated by dust on interstellar medium scales in the host galaxy.

Despite its proximity, the mass of the supermassive black hole (SMBH) in the spiral galaxy M81 (NGC~3031) has remained uncertain, with previous dynamical measurements being unreliable. We present the first robust stellar-dynamical measurement of its mass using high-resolution, two-dimensional kinematics from JWST/NIRSpec observations of the central $3''\times3''$. By tracing stellar motions in the near-infrared, our data penetrate the obscuring nuclear dust and allow for the separation of stellar light from the non-thermal AGN continuum. We modeled the kinematics using JAM within a Bayesian framework, exploring a comprehensive suite of models that systematically account for uncertainties in the point-spread function, orbital anisotropy, and stellar mass-to-light ratio. This ensemble modeling approach demonstrates that a central dark mass unambiguously drives the central rise in velocity dispersion. The models yield a robust SMBH mass of $M_{\rm BH} = (4.78^{+0.07}_{-0.10})\times10^7$ M$_\odot$. This result resolves a long-standing uncertainty in the mass of M81's black hole and provides a crucial, reliable anchor point for SMBH-galaxy scaling relations.

We report on optical spectroscopic and photometric follow-up observations of the eROSITA discovered transient SRGt 062340.2-265751 and show that it displays the characteristics of a nova-like cataclysmic variable (CV), with possible indications of being a magnetic system. We try to put better constraints on the classification of SRGt 062340.2-265751 using optical time-resolved spectroscopic and photometric observations to find any periodicities in the system. From these periodicities we can classify the CV sub-type that it belongs to. Spectroscopic observations revealed a very low amplitude, K $\sim$ 14 km s$^{-1}$, in the radial velocity of the H$\beta$ and H$\gamma$ emission lines, suggesting that the system is likely observed at a low inclination angle. High-speed photometric observations revealed highly stochastic variability, characteristic of many magnetic cataclysmic variable systems. A probable 3.645 $\pm$ 0.006 hour orbital period was found by applying Lomb-Scargle period analysis to the H$\beta$ and H$\gamma$ emission line radial velocities. A 24.905 $\pm$ 0.065 min period was found from photometric observations, which we associate with the white dwarf spin. However, it was also found that the photometry revealed multiple periodicities from night to night. TESS observations in three sectors did not reveal any of the periodicities found from ground-based observations, but did show a prominent period in only one sector, which might be attributed to a positive superhump period. These multiple periodicities as well as the HeII $\lambda$4686 and Bowen blend emission lines seen in the spectra indicate that SRGt 062340.2-265751 is likely a nova-like CV, and might belong to the VY Scl sub-type.

Scenarios such as the QCD axion with the Peccei-Quinn symmetry broken after inflation predict an enhanced matter power spectrum on sub-parsec scales. These theories lead to the formation of dense dark matter structures known as minihalos, which provide insights into early Universe dynamics and have implications for direct detection experiments. We examine the mass loss of minihalos during stellar encounters, building on previous studies that derived formulas for mass loss and performed N-body simulations. We propose a new formula for the mass loss that accounts for changes in the minihalo profile after disruption by a passing star. We also investigate the mass loss for multiple stellar encounters. We demonstrate that accurately assessing the mass loss in minihalos due to multiple stellar encounters necessitates considering the alterations in the minihalo's binding energy after each encounter, as overlooking this aspect results in a substantial underestimation of the mass loss. We further extend our analysis to the Galactic environment by more accurately incorporating multiple stellar encounters and dynamical relaxation timescales, simulating minihalo orbits in the Galactic potential. Our results show stellar interactions are more destructive than previously estimated, reducing minihalo mass retention at the solar system to ~30%, compared to earlier estimates of ~60%. This enhanced loss arises from cumulative energy injections when relaxation periods between stellar encounters are accounted for. The altered minihalo mass function implies a larger fraction of axion dark matter occupies inter-minihalo space, potentially increasing the local axion density and improving haloscope detection prospects. This thesis highlights the significance of detailed modeling of stellar disruptions in shaping the axion dark matter distribution.

Archived high-resolution X-ray spectra in the 13~Å to 22~Å range from the Flat Crystal Spectrometer (FCS), an instrument on the Solar Maximum Mission operating in the 1980s, are analyzed with reference to nonflaring active regions, and to the \ion{Fe}{17} line emission in light of laboratory and atomic data for nearby \ion{Fe}{16} satellites. The satellites allow temperature to be found for these relatively low-temperature spectra, at which more conventional temperature-dependent line ratios are unavailable. By this means, the spectra can be arranged by temperature, showing that the \ion{Fe}{17} lines are evident at temperatures of $<3$~MK. We confirm that the problem of the underintense Fe XVII 3C and 3D lines is not due to resonant scattering, and instead suggest that, for comparison with CHIANTI spectra, the problem may lie with a needed revision of collisional excitation rates. The line ratio 3G/3H is in theory density-dependent but for \ion{Fe}{17} the ratio is in the low-density limit. However, we suggest that spectra taken during the impulsive stage of flares might reveal a departure from this limit and so allow densities to be derived and hence properties of the flaring plasma. Suggestions for the design of future crystal spectrometers are made in the light of the fluorescence background in FCS spectra.

We report the discovery of an extremely metal-poor galaxy at a redshift of z = 3.654, identified through infrared spectroscopy using the James Webb Space Telescope (JWST). This galaxy, CAPERS-39810, exhibits a metallicity of 12 + log(O/H) = $6.73\pm0.13$, indicative of its primitive chemical composition, resembling the early stages of galaxy formation in the Universe. We use JWST NIRSpec/MSA for spectroscopic analysis, complemented by photometric data from the COSMOS2025 catalog. Our analysis employs the R3 strong-line diagnostic method to estimate metallicity, due to the lack of auroral lines in the spectrum. The galaxy's emission lines, including Hb, [O III], Ha and He I, are clearly detected. The rest-frame equivalent widths of the strong hydrogen recombination lines are EW_0(Hb) = $184\pm48$ Åand EW_0(Ha) = $1144\pm48$ Å. Furthermore, we perform detailed spectral energy distribution modeling to derive a galaxy logarithmic stellar mass of $8.02^{+0.22}_{-0.34}$ $M_\odot$. This discovery adds to the growing body of evidence for the existence of very low-metallicity galaxies existed at cosmic noon of $z\approx3$, which are crucial for understanding the processes of chemical enrichment and star formation in young galaxies at the cosmic noon.

(Abridged) Recent JWST observations of Cassiopeia A (Cas A) reveal unprecedented ejecta substructure, including a web of filaments and the enigmatic "Green Monster" (GM), characterized by nearly circular holes and rings. These features provide new constraints on supernova (SN) explosion physics and ejecta-circumstellar medium (CSM) interactions. We present high-resolution three-dimensional hydrodynamic and magnetohydrodynamic simulations of a neutrino-driven SN explosion tailored to Cas A, following the system from core collapse to an age of $\sim 1000$ yr. The models include key physical processes such as hydrodynamic instabilities, Ni-bubble effects, radiative cooling, non-equilibrium ionization, and electron-ion temperature equilibration. Our results show that the filamentary ejecta network naturally forms during the early explosion due to the interaction of neutrino-driven bubbles and instabilities, retaining a memory of the initial conditions before being progressively modified by the reverse shock. The GM morphology is reproduced by the interaction of dense ejecta clumps with an asymmetric, forward-shocked CSM shell, with radiative cooling enhancing fragmentation and generating the observed holes and rings. Overall, our study demonstrates that Cas A's complex morphology reflects both the imprint of the explosion mechanism and subsequent ejecta-CSM interactions.

Dark matter (DM) halos in $\Lambda$ Cold DM cosmological simulations are triaxial. Most exhibit figure rotation. We study 40 isolated halos with stellar disks from the TNG50 simulation suite across $\sim 4$~Gyr to understand whether and how a triaxial halo's tumbling and orientation relative to the disk can drive warps. We measure a warp angle $\psi$ and find even our isolated disks are all at least slightly warped, with each galaxy's maximum $\psi > 1.8^{\circ}$. We perform a modified cross-correlation analysis between $\psi$ and the figure rotation pattern speed, as well as the misalignment between the disk spin axis and (a) the figure rotation axis, (b) the halo minor axis, and (c) the gas angular momentum axis. We use snapshots spanning a lookback time $t_{lb} ~4$ Gyr with 25 linearly-spaced lags from $ 0 - 2.33$ Gyr. We do not find evidence for a consistent lag between the onset of a warp and any of the aforementioned factors on the population level. However, we find significant correlations between individual time-series at various lags. These maximum correlation coefficients were significantly offset from random chance at the population level, suggesting that several of these factors do correlate with disk warping in specific situations. By examining four case studies whose maximum correlation coefficients were significantly higher than random chance, we establish clear qualitative relationships between these factors and warps. While a non-warped galaxy typically shows minimal halo tilt and figure rotation, warped galaxies can have strong/weak tilts and/or strong/weak figure rotation. Keywords: Disk galaxies(391), Galaxy dynamics(591), Hydrodynamical simulations(767), Galaxy DM halos(1880)

Using a sample of $\sim$126,000 late-type galaxies (LTGs) from SDSS, we analyzed stellar mass as a function of dynamical mass. Stellar masses were estimated using eight SPS models with constant IMFs, while dynamical masses were derived from seven formulations based on Newtonian dynamics and virial equilibrium, incorporating both stellar and gas velocity dispersions. We account for key factors affecting dynamical mass estimation, including inclination, colour, concentration, and Sérsic index. We find that the difference between dynamical and stellar mass ($\Delta \log \mathbf{M}$) ranges from nearly zero to $\sim$95% of the dynamical mass, depending on mass and redshift. $\Delta \log \mathbf{M}$ appears to decreases with increasing redshift, but exhibits a saddle-like shape at low mass and low redshift-especially in disk-dominated LTGs-transitioning into a steep, linear trend at higher masses and redshifts. In the high-mass regime, the behavior resembles that of early-type galaxies. Moreover, our results indicate that this evolution is not discrete but follows a continuous transition between morphological regimes. Dark matter within LTGs is at most equal to $\Delta \log \mathbf{M}$, depending on the impact of the IMF and SPS on stellar mass estimation. Although SPS-based stellar masses do not include the gas component, previous studies have shown that galaxies with log($\mathbf{M_{Stellar}/M_{Solar}}) > 10$ at $z \leq 0.3$ are predominantly stellar-mass dominated. Most galaxies in our sample fall within this regime, minimizing the impact of gas exclusion. Our findings go beyond the scope of single galaxies, providing insight into the nearby Universe and highlighting the influence of dark matter in determining the Universe's structure and evolution.

Accurate modeling of gravitational interactions is fundamental to the analysis, prediction, and control of space systems. While the Newtonian point-mass approximation suffices for many preliminary studies, real celestial bodies exhibit deviations from spherical symmetry, including oblateness, localized mass concentrations, and higher-order shape irregularities. These features can significantly perturb spacecraft trajectories, especially in low-altitude or long-duration missions, leading to cumulative orbit prediction errors and increased control demands. This article presents a tutorial introduction to spherical harmonic gravity models, outlining their theoretical foundations and underlying assumptions. Higher-order gravitational fields are derived as solutions to the Laplace equation, providing a systematic framework to capture the effects of non-uniform mass distributions. The impact of these higher-order terms on orbital dynamics is illustrated through examples involving Low Earth Orbit satellites and spacecraft near irregularly shaped asteroids, highlighting the practical significance of moving beyond the point-mass approximation.

Stellar chromospheric activity serves as a valuable proxy for estimating stellar ages, though its applicable range and accurate functional form are still debated. In this study, utilizing the LAMOST spectra we compiled a catalog of open cluster members and field stars to investigate $R_{\rm{HK}}^{'}$--age relations across various spectral types. We find that a linear model, specifically a Skumanich-type relation, can best describe the overall decline of chromospheric activity with age, with the slope varying across different spectral types. However, we also identify variations in the decay rate along the main sequence, which call for more accurate follow-up investigation. Finally, we find that lower-metallicity stars exhibit enhanced activity for F-, G-, and K-type stars, whereas no clear metallicity dependence is observed for M dwarfs.

We report the detection of Lyman continuum (LyC) photons from three massive ($\text{M}_{*}>10^{10}\:\text{M}_{\odot}$) spiral galaxies at a redshift of nearly 1 in the AstroSat UV Deep Field South. Notably, all three systems are viewed at low inclination (i.e., nearly face-on), prompting an investigation into the role of galaxy orientation in the detectability of LyC emission from disk systems. Two of the three galaxies, however, host active galactic nuclei (AGNs), adding complexity to the interpretation of the LyC signal. We present a detailed analysis of the likely star-forming case, and report tentative evidence that a face-on viewing angle may enhance the likelihood of LyC detection in disk galaxies. This represents the first detection of LyC emission from well-characterized spiral galaxies at high redshift, offering a new window into LyC escape mechanisms in such systems. Our findings highlight the need to consider geometric factors and anisotropic escape pathways facilitated by feedback processes alongside more traditional density-bounded scenarios that imply isotropic escape.

We have studied a B-class solar flare and an associated filament eruption through multi-wavelength observations. The flare triggers at 16:24~UT on June 7$^{th}$, 2017 from an active region (AR) 12661, and it maximizes at 16:54~UT. The magnetic flux cancellation occurs near the polarity inversion line (PIL) preceding the flare, and ultraviolet (UV) brightenings occur in the pre-flare phase at the flux cancellation sites, suggesting the reconnection occurs in the lower atmosphere, initially. The S-shaped sigmoid forms through successive steps in corona, i.e., small-scale brightenings, helical/twisted field lines, bright patches, and finally, a developed sigmoid. It justifies that runaway reconnection within the coronal arcades forms the sigmoid within the filament. The differential emission-measure (DEM) analysis reveals the existence of the plasma at a temperature of more than 10 MK within the sigmoid. The initial magnetic reconnection reorganizes the field overlying the filament as per the tether-cutting model. Therefore, it enables the filament to rise slowly, and around~16:41~UT, the eruption phase of the filament begins. The filament eruption removes the overlying coronal field, including the sigmoid. During the eruption phase, we have found intersecting/crossing of coronal loops and jet-like structures far away from the sigmoid-filament system. In conclusion, all the observational findings (e.g., magnetic flux convergence, cancellation, UV brightenings, and spatial and temporal correlation between formation/evolution of the sigmoid and rise/eruption of the filament) suggest that the formation of a solar flare and the eruption of the filament are consistent with the tether-cutting model of solar eruption.

The Fe K$\alpha$ fluorescence line at 6.4 keV is a powerful probe of cold matter surrounding X-ray sources and has been widely used in various astrophysical contexts. The X-ray microcalorimeter spectrometer onboard XRISM can measure line shifts with unprecedented precision of $\sim$0.2 eV, equivalent to a line-of-sight velocity of $\sim$10 km s$^{-1}$. At this level of accuracy, however, several factors that influence the line energy must be carefully considered prior to astrophysical interpretation. One such important factor is the ionization degree, Fe$^{q+}$. The K$\alpha$ line shifts redward by $\sim$4 eV as $q$ increases from 0 (neutral) to 8 (Ar-like). Additionally, the accompanying Fe K$\beta$ line at 7.06 keV shifts blueward by $\sim$30 eV from $q=0$ to 8. We demonstrate that this effect is actually observable in the XRISM data of the high-mass X-ray binary Centaurus X-3 (Cen X-3). We advocate that the differential energy shift between the K$\alpha$ and K$\beta$ line provides a robust estimate of $q$ by decoupling from other effects that shift the two lines in the same direction. We derived $q \sim 5$ (Sc-like) for the fluorescing matter by comparing the observation with atomic structure calculations of our own and in the literature. By accounting for the derived charge state and the corresponding shift in the rest-frame line energy, we made corrections for this effect and reached a consistent residual shift among the K$\alpha$, K$\beta$, and the optical measurement attributable to the systemic velocity of the system. Consequently, we obtained a new constraint on the location of the cold matter. This ionization effect needs to be assessed in all use cases of the Fe K$\alpha$ line shift beyond Cen X-3, and the proposed metric is generally applicable to all of them.

This study characterizes the physical and kinematic properties within the innermost 500 au region of the L1527 bipolar outflow, a Class 0/I low-mass protostar using JWST MIRI/MRS spectroscopy across 5-28 micron at 0.2-1.0 arcsec resolution. We identify emission lines from molecular and ionized species and analyze their spatial morphology using line integrated intensity maps. We derive gas temperature and column density through excitation diagram analysis of H2 rotational lines and compared results with shock models. The observations reveal extended molecular hydrogen emission tracing the bipolar outflow, with the H2 gas temperatures distributed into warm (~550 K) and hot (~2500 K) components, likely originating from moderate velocity J-type shocks and some UV irradiation. We detect forbidden atomic and ionized emission lines of [Ni ii], [Ar ii], [Ne ii], [Ne iii], [S i], and [Fe ii] showing spatially extended morphology. Double peaked emission profiles were seen in [Ar ii], [Ne iii], and [Fe ii], in the eastern region, suggesting that the high velocity component traces a fast, highly ionized jet. Radial velocity map derived from [Ne ii] emission shows the eastern region to be redshifted and the western region blueshifted, contrary to earlier interpretations. The analysis of the MIRI/MRS observations reveals the presence of molecular, atomic, and ionized emission lines in this low-mass protostar connected with active outflow signatures. The most striking feature discovered is the presence of a poorly collimated high velocity ionized jet, embedded within a broader wide-angle molecular outflow likely driven by a disk wind. The co-existence of these components supports a stratified outflow structure and suggest L1527 exhibits unique jet-launching characteristics atypical for its early evolutionary stage.

We present an automated, DAOFind-based pipeline developed to reprocess J-band Atlas All Sky Release Survey Images from the Two Micron All Sky Survey (2MASS). By optimizing the detection parameters and implementing a screening procedure that jointly evaluates the signal-to-noise ratio and central sharpness, the pipeline effectively identifies faint point sources that were previously undetected. Applying this method to eight representative sky regions improves the 2MASS detection limit from 16.20 to 16.60 mag and increases the number of detected point sources by approximately 21.36% relative to the 2MASS Point Source Catalog, with a false-positive rate of only 4.80%. These results demonstrate that the proposed reprocessing pipeline can substantially enhance the scientific yield of archival 2MASS data, providing valuable faint-source supplements for studies of time-domain variability, Galactic structure, and cold, low-luminosity objects.

The origin mechanism of the cosmic-ray knee region remains an unresolved mystery, with acceleration, interaction, and propagation models drawing significant attention. The latest experimental observations of the PeV total spectrum, composition energy spectrum, and anisotropy-particularly the precise measurements of the proton spectrum by the LHAASO experiment-have provided crucial breakthroughs in uncovering its origin. Based on the latest LHAASO measurements of the proton energy spectrum, combined with cosmic-ray spectral and anisotropy data, this study proposes that the spectral index variation in the knee region arises from changes in the propagation coefficient. By introducing a knee position $\rm \mathcal{R}_{knee}$ and an index variation $\rm \delta_{knee}$, we construct a rigidity-dependent double-power-law diffusion model to reproduce the knee-region spectral structure. Through modifications to the diffusion coefficient, we successfully replicate the observed knee-region spectral structure in the LHAASO proton spectrum and calculate the corresponding anisotropy. Under current data and model dependencies, a joint analysis of the energy spectrum and anisotropy does not support the propagation origin model of the cosmic-ray knee at a 95\% confidence level. We hope that future LHAASO experiments will provide precise measurements of the energy spectra and anisotropies of various nuclei in the knee region, thereby offering a definitive test of the propagation model as the origin mechanism of the knee-region spectral structure.

We present forecasts for the $E_G$ statistic using redshift distributions of realistic mock galaxy samples from the upcoming Chinese Space Station Survey Telescope (CSST). The dominant uncertainty in $E_G$ stems from the redshift space distortion parameter ${\beta}$, whose precision limits the overall constraining power. Our analysis shows that CSST will nevertheless achieve $E_G$ constraints at the few-percent level (3%-9%) over $0 < z < 1.2$, an improvement by a factor of several to an order of magnitude over current observations. Within the $\mu-\Sigma$ modified gravity framework, the parameter $\Sigma_0$, associated with the effective gravitational constant of the Weyl potential, can be constrained to $\sim 5\%$ precision. In a plausible scenario where upcoming spectroscopic surveys determine ${\beta}$ to 1\% accuracy, $E_G$ constraints tighten to the percent level, and $\Sigma_0$ becomes measurable at $\sim 1\%$. These results demonstrate that CSST will serve as a powerful facility for testing gravity and underscore the essential synergy between photometric weak lensing and spectroscopic surveys in probing cosmic acceleration.

With increasing sensitivity of the gravitational wave (GW) detectors, we expect a significant rise in the detectable GW events. To process, analyse and identify such large amounts of GW signals arising from mergers of Binary Black Holes (BBH), we need both speed and accuracy. In the search for (massive) BBH signals, the biggest hurdle is posed by the various non-gaussian noise transients called glitches. Compared to our previous work, which used a simple convolutional neural network to distinguish BBHs from Blip glitches, this work uses transfer learning with InceptionNetV3 to distinguish BBHs from six types of most popular glitches from the third observing run of LIGO. While the glitches are real and identified via GravitySpy, the BBH signals are simulated and then injected into the real detector noise for each of the two LIGO detectors. We generate Sine-Gaussian Projection (SGP) maps by cross-correlating data with Sine-Gaussian functions of varied quality factors ($Q$) and central frequencies ($f_0$) and projected on the $Q$ - $f_0$ plane. We find that SGP maps make it easier to distinguish BBHs from glitches that look very similar to BBHs in the Time-Frequency maps like the Blips, while also maintaining significant morphological differences between BBHs and the more frequent glitches - Scattered Light and Fast Scattering. Our network has an accuracy of $87%$, a TPR of 0.83 for an FPR of 0.1 on our test dataset. It is also robust, retaining its level of accuracy, when tested on real BBH events identified in the first three observing runs of LIGO. Our proposed method shows the viability of using the SGP maps and neural networks for fast identification of GW events improving the efficiency of standard search pipelines.

Third-order statistics provide information beyond two-point measures, but extracting this information requires accurate and consistent modelling. We measure and detect the three-point correlation function and third-order aperture-mass statistics of intrinsic alignments (IA) for galaxies and for haloes with $M_{\rm halo} > 10^{13}\,{\rm M}_\odot$ in the $(2.8\,\mathrm{Gpc})^3$ simulation volume of the FLAMINGO hydrodynamical simulation suite. We model the third-order aperture-mass statistics and show that on large scales both the galaxy and halo samples are well described by the tree-level effective field theory (EFT) of IA across the three dark matter density-shape combinations and a wide range of triangle configurations, with the alignment amplitude consistent with that inferred from two-point statistics. We compare the full EFT to several other models: a version neglecting the velocity-shear term, the non-linear alignment model (NLA), and to a reduced EFT assuming co-evolution relations that follow from the assumption that alignment is linear in Lagrangian space. The first two models yield biased constraints on the alignment amplitude, but the reduced EFT performs remarkably well, achieving a low reduced chi-squared and minimal bias. We examine the redshift and mass dependence of the higher-order bias parameters, finding that the linear Lagrangian bias assumption is approximately satisfied across the explored halo mass and redshift ranges for both galaxies and haloes, suggesting that the galaxies broadly follow the alignment properties of their host haloes. These co-evolution relations can be valuable for photometric shear surveys, where limited constraining power on IA parameters favours models with fewer free parameters.

We propose an infrared mechanism for alleviating the Hubble constant tension, based on a small departure from entanglement equilibrium at the cosmological apparent horizon. If the horizon entanglement entropy falls slightly below the Bekenstein-Hawking value, we parametrize the shortfall by a fractional deficit $\delta(a)$ evolving with the FLRW scale factor $a$. The associated equipartition deficit at the Gibbons-Hawking temperature then sources a smooth, homogeneous component whose density scales as $H^{2}/G$, with a dimensionless coefficient $c_{e}^{2}(a)$ of order unity times $\delta(a)$. Because this component tracks $H^{2}$, it is negligible at early times but can activate at redshifts $z\lesssim 1$, raising the late time expansion rate by a few percent without affecting recombination or the sound horizon. We present a minimal three parameter activation model for $c_{e}^{2}(a)$ and derive its impact on the background expansion, effective equation of state, and linear growth for a smooth entanglement sector. The framework predicts a small boost in $H(z)$, a mild suppression of $f\sigma_{8}(z)$, and a corresponding modification of the low-$z$ distance-redshift relation. We test these predictions against current low-redshift data sets, including SN~Ia distance moduli, baryon acoustic oscillation distance measurements, cosmic chronometer $H(z)$ data, and redshift space distortion constraints, and discuss whether the $H_0$ tension can be consistently interpreted as a late-time, horizon-scale information deficit rather than an early universe modification.

The energy released by active galactic nuclei (AGNs) is considered to have a profound impact on the cold gas properties of their host galaxies, potentially heating or removing the gas and further suppressing star formation. To understand the feedback from AGN radio activity, we investigate its impacts on the cold gas reservoirs in AGNs with different radio activity levels. We construct a quasar sample with a mean $z\sim1.5$ and a mean $L_{\rm bol}\sim10^{45.8}\ \rm erg\ s^{-1}$, all with Herschel detections to enable estimates of the total gas mass through the galactic dust continuum emission. The sample is then cross-matched with radio catalogs and divided into radio loud (RL) quasars, radio-detected radio quiet (RQ) quasars and radio-undetected quasars based on their radio loudness. Through spectral energy distribution (SED) fitting, we find the radio-detected RQ quasars exhibit evidence of gas deficiency with host galaxies possessing $\sim 0.3$ dex lower dust and gas masses compared to the other two groups, despite being matched in $M_{\rm BH}$, $L_{\rm bol}$, $M_{*}$ and SFR. Furthermore, evidence from optical spectra shows that both the fraction and velocity of outflows are higher in the radio-detected RQ group, suggesting a connection between the ionized gas outflows and the moderate radio activity. These results suggest that the AGN feedback could be more efficient in AGNs with weak/moderate radio emission than in those without radio detection or those with strong radio emission. Further high-resolution observations are needed to understand the interaction between the interstellar medium and the weak/moderate AGN radio activity.

The decay of magnetically dominated turbulence exhibits robust inverse transfer of magnetic energy even in the absence of net magnetic helicity, challenging traditional cascade-based phenomenology. While recent studies suggest that magnetic reconnection governs the evolution of such systems, a comprehensive understanding has been lacking. Here we test a reconnection-mediated model for decaying magnetic turbulence in two-dimensional (strict-2D), 2.5D, and three-dimensional (3D) systems with both helical and nonhelical initial conditions. We show that the magnetic-energy decay timescale scales with the Lundquist number in a manner consistent with Sweet-Parker-type reconnection rather than Alfvenic or purely resistive timescales. We develop a broken power-law model for the magnetic energy spectra and provide analytic predictions for the temporal evolution of energy across both sub-inertial and inertial ranges, which are confirmed by high-resolution simulations. In nonhelical turbulence, these results favor anastrophy as the dominant constraint over helicity fluctuations. Using Minkowski functionals to analyze reconnecting current sheets in real space, we find that the structures controlling the decay are substantially smaller than the global magnetic correlation scale, implying local Lundquist numbers well below the system-scale value. This explains the weak sensitivity of global decay laws to current-sheet resolution and that the current-sheet aspect ratios converge toward Sweet-Parker predictions only at sufficiently high resolution. Together, these results establish magnetic reconnection as the organizing principle underlying inverse transfer, spectral evolution, and decay in magnetically dominated turbulence, providing a unified picture applicable across dimensionality and helicity regimes with direct implications for astrophysical plasmas.

The rotational properties of asteroids provide critical information about not only their internal structure but also their collisional and thermal histories. Previous work has revealed a bimodal distribution of asteroid spin rates, dividing populations into fast and slow rotators, but to date this separation remains poorly understood (e.g. its dependency on composition). We investigate whether the valley separating fast and slow rotators in rotational period-diameter space depends on the composition of the asteroid, approximated by asteroids' spectral class. First, we extended the Minor Planet Physical Properties Catalogue (MP3C) to include the available spectral classes of asteroids. Then, for each asteroid we selected the best diameter, rotational period, and spectral class. Building upon a semi-supervised machine-learning method, we quantify the valley between fast and slow rotators for S- and C-complex asteroids, which are linked to ordinary and carbonaceous chondrites respectively. The method iteratively fits a linear boundary between the two populations in rotational period-diameter space to maximise their separation. We find a clear compositional dependence of the valley: for C-complex asteroids the transition occurs at longer periods than for S-complex, with P* = 14.4 D_km^0.739 (C-complex) and P* = 11.6 D_km^0.718 (S-complex), where period and diameter are given in hours and kilometres respectively. This corresponds to mu Q approximately 2 and 13 GPa, respectively, where mu is the rigidity and Q the quality factor. The dependence of the valley on spectral classes likely reflects compositional and structural differences: C-complex asteroids, being more porous and weaker, dissipate angular momentum more efficiently than stronger, more coherent S-complex asteroids. This represents quantitative evidence of class-dependent rotational valleys within asteroid populations.

We present a study of the interstellar medium associated with the two middle-aged supernova remnants (SNRs) W41 and G22.7-0.2, both detected in TeV gamma-rays. Using high-angular-resolution $^{12}$CO($J$ = 1-0) data from the Nobeyama 45-m telescope and HI data from the VLA, we investigated the spatial and kinematic properties of molecular and atomic gas that interact with the SNRs. We identified associated clouds in the velocity ranges of +50-+80 km s$^{-1}$ for W41 and +76-+110 km s$^{-1}$ for G22.7-0.2. Column density analysis indicates that target protons are dominated by molecular hydrogen, while atomic hydrogen contributes less than $\sim$10-15% even after correction for self-absorption. The mean proton densities are $\sim$1.2$\times$10$^{3}$ cm$^{-3}$ for W41 and $\sim$5.3$\times$10$^{2}$ cm$^{-3}$ for G22.7-0.2. From the gamma-ray luminosities, we estimate the total energy of accelerated cosmic-ray protons as $W_\mathrm{p}$ $\sim$3$\times$10$^{47}$~erg for W41 and $\sim$1$\times$10$^{48}$ erg for G22.7-0.2, corresponding to 0.03-0.1% of the canonical supernova explosion energy. hese $W_\mathrm{p}$ values agree with the decreasing trend in $W_\mathrm{p}$ observed in the middle-aged SNRs within the previously reported SNR age-$W_\mathrm{p}$ relation.

Neutrino interactions play a central role in transport and flavor evolution in the ejecta of binary neutron star mergers. Simulations suggest that neutron star mergers may produce magnetic fields as strong as $10^{17}$ G, but computational difficulties have hampered the inclusion of magnetic field effects in neutrino interaction rates. In this paper we give approximate interaction rates for neutrinos in the presence of strong magnetic fields, including the effects of Landau quantization and anomalous magnetic moments with errors of order $\sqrt{T/M}$. We also comment on a neutrino production channel from individual neutrons that can produce low-energy $\nu \bar{\nu}$ pairs even at low density.

The formation of planetesimals via the streaming instability (SI) is a crucial step in planet formation, yet its triggering conditions and efficiency are highly sensitive to both disk properties and specific evolutionary processes. We aim to study the planetesimal formation via the SI, driven by the stellar X-ray photoevaporation during the late stages of disk dispersal, and quantify its dependence on key disk and stellar parameters. We use the DustPy code to simulate the dust dynamics including coagulation, fragmentation, and radial drift in a viscously accreting disk undergoing stellar X-ray photoevaporation. Stellar X-rays drive the disk dispersal, opening a cavity at a few au orbital distance and inducing the formation of an associated local pressure maximum. This pressure maximum acts as a trap for radially drifting dust, therefore enhancing the dust density to the critical level required to initiate the streaming instability and the subsequent collapse into planetesimals. The fiducial model produces 31.4 M_\oplus of planetesimals with an initial dust to final planetesimal conversion efficiency of 20.4%. This pathway is most efficient in larger disks with higher metallicities, lower viscosities, higher dust fragmentation threshold velocities, and/or around stars with higher X-ray luminosities. This work demonstrates that stellar X-ray photoevaporation is a robust and feasible mechanism for triggering planetesimal formation via the SI during the final clearing phase of protoplanetary disk evolution.

We perform the classification of black hole and neutron star X-ray binary systems using deep neural networks applied to archival RXTE X-ray spectral data. We first construct two neural network models: one trained using only spectral flux values and another trained using both fluxes and their associated errors. Both models achieve high classification accuracies of ~90-94 %. To gain physical interpretability of these networks, we fit all spectra with a simple phenomenological model consisting of a thermal disk component and a power-law. From this analysis, we identify the blackbody temperature, power-law index, the ratio of blackbody to power-law flux, the reduced $\chi^2$, and the variance of the data as key parameters that likely contribute to the classification. We validate this inference by designing an additional neural network trained exclusively on this reduced parameter set, without using the spectral data directly. This parameter-based model achieves a classification accuracy comparable to that of the spectral models. Our results show that deep neural networks can not only classify compact objects in X-ray binaries with high accuracy but can also be interpreted in terms of physically meaningful spectral parameters derived from conventional X-ray spectral analysis. This framework offers a promising, mission-agnostic approach for compact object classification in current and future X-ray surveys.

We present a JWST/NIRSpec rest-frame optical spectroscopic census of ALMA 1-mm continuum sources in the Hubble Ultra Deep Field (UDF) identified by the deep ALMA UDF and ASPECS programs. Our sample is composed of the ALMA flux-limited ($S_{1\,\mathrm{mm}}\gtrsim 0.1\,\mathrm{mJy}$) sources observed with medium-resolution NIRSpec spectroscopy from JADES and SMILES, 16 faint submillimeter galaxies (SMGs) at spectroscopic redshifts of $z\sim 1$-$4$. These SMGs show bright longer-wavelength optical lines (H$\alpha$, [N II]$\lambda\lambda6548,6583$, and [S II]$\lambda\lambda6717,6731$) and faint shorter-wavelength optical lines (H$\beta$ and [O III]$\lambda\lambda4959,5007$) with a large nebular attenuation, $E(B-V)\sim0.3$-$1.8$. We test the SMGs using BPT diagnostics and Chandra X-ray fluxes, and find that most SMGs are classified as AGNs; the AGN fraction is $\sim80\%$ for the SMGs at $M_*>10^{10.5} M_\odot$. We find only one SMG ($<10\%$) with a broad Balmer line, indicating that the SMGs are predominantly obscured AGNs. With the optical lines, we estimate the metallicities of the SMGs to be moderately high, $\sim0.4$-$2 Z_\odot$, exceeding the model-predicted dust-growth critical metallicity ($\sim0.1$-$0.2Z_\odot$), which naturally explains the dusty nature of the SMGs. Interestingly, the SMGs fall in the mass-metallicity relation and the star-formation main sequence, showing no significant differences from other high-$z$ galaxies. Similarly, we find electron densities of $n_e\sim10^2$-$10^3\,\mathrm{cm}^{-3}$ for the SMGs that are comparable with other high-$z$ galaxies. Together with the high SMG fraction ($\sim 100\%$) at the massive end ($M_*>10^{10.5} M_\odot$), these results indicate that the SMGs are mostly not special, but typical massive star-forming galaxies at high redshift.

We use $N$-body simulations to investigate the distinct bar formation processes in disks residing in halos of various concentrations. In a highly concentrated halo, the bar development is limited by the dominant multi-arm modes as a result of the swing amplification in the early stage. Only after the multi-arm modes decay, the bar growth proceeds mechanically owing to the particle trapping in continuation of that bar seed. In this scheme, the corotation resonance of the bar modes does not come into play at all, justified by a low amount of disk-halo angular momentum transfer and a modestly decreasing bar pattern speed. On the other hand, although reducing the halo concentration suggests the reduction of the preferred swing-amplified modes to be bi-symmetric, the bar formation in a lowly concentrated halo does not involve the swing amplification at all. Rather, the fast-growing linearly unstable bar modes of a single uniform frequency is solely the governing factor, attributed to a mild shearing. The bar modes trigger the corotation resonance since the beginning and such resonance is maintained until the end, which leads to a high amount of angular momentum transfer and a fast slowdown. For the intermediate halo concentration, the kinematical analyses of multiple non-axisymmetric modes suggests that the linear modes, the swing amplification, and the particle trapping are all present in the evolution chronology. To specify bars formed in the different halo concentrations, full analyses of the isophotal shape, the radial Fourier amplitude, and the resonance diagram can be of use.

Photospheric horizontal velocity fields play essential roles in the formation and evolution of numerous solar activities. Various methods for estimating the horizontal velocity field have been proposed in the past. Aiming at the highest available (and future) spatial resolution (10 km/pixel) observations, a new method the Shallow U-net models (SUVEL) based on realistic numerical simulation and machine learning techniques was recently developed to track the photospheric horizontal velocity fields. Although SUVEL has been tested on numerical simulation data, its performance on solar observational data remained unclear. In this work, we apply SUVEL to the photospheric intensity observations from four ground-based solar telescopes (DKIST, GST, NVST, and SST) with the largest available apertures, and compare the results obtained from SUVEL with the Fourier local correlation tracking method (FLCT). Average correlation indices between granular regions and velocity fields inferred by SUVEL (FLCT) are 0.63, 0.81, 0.80, and 0.87 (0.00, 0.11, 0.16, and 0.10) for DKIST, GST, NVST, and SST observations. Higher correlation indices between the velocity fields tracked by SUVEL and granular patterns than FLCT reveal the superior performance of SUVEL, validating its reliability with respect to solar observational data.

The thermally pulsating asymptotic giant branch (TP-AGB) phase plays a key role in the evolution of low- to intermediate-mass stars, driving mass loss that influences their final stages and contributes to galactic chemical enrichment. However, the mechanisms behind mass loss, particularly at the end of AGB, are still not well understood. We aim to investigate the relationship between stellar parameters and envelope dynamics during the TP-AGB phase, evaluating whether dynamical instabilities in the envelope can act as a possible mass-loss mechanism. We use hydrodynamics method in MESA to simulate the dynamical pulsations and resulting mass loss during the TP-AGB phase of a star evolved from a 1.5 Msun zero-age main sequence. Our simulations reproduce the dynamical pulsation behavior of stars during the TP-AGB phase, demonstrating that the envelope mass is a key factor governing pulsational properties. As the envelope mass decreases, both the pulsation period and radial amplitude increase, consistent with observational trends. For 1.5 Msun model, once the envelope mass declines to approximately 0.25 Msun, the model enters a regime of violent pulsations, potentially ejecting the remaining envelope within a few hundred years. We suggest that the instability can act as the dominant mass-loss mechanism in the end of the TP-AGB phase, marking a rapid transitional stage toward the post-AGB phase.

The Sun has been observed through a telescope for four centuries. However, its study made a prodigious leap at the end of the nineteenth century with the appearance of photography and spectroscopy, then at the beginning of the following century with the invention of the coronagraph and monochromatic filters, and finally in the second half of the twentieth century with the advent of large ground-based telescopes and space exploration. This article retraces the main stages of solar instrumental developments in Meudon, from its foundation by Jules Janssen in 1876 to the present day, limited to ground-based or balloon instrumentation, designed in Meudon and installed there or in other places (Nan{\c c}ay, Pic du Midi, Canary Islands). The Meudon astronomers played a pioneering role in the history of solar physics through the experimentation of innovative techniques. After the golden age of inventions, came the time of large instruments, studied in Meudon but often installed in more favourable sites, and that of space, in a framework of international collaboration, but this is not discussed here.

The chemical evolution of pre-stellar cores during their transition to a protostellar stage is not yet fully understood. Detailed chemical characterizations of these sources are needed to better define their chemistry during star formation. Our goal is to characterize the chemistry of the starless cores C2 and C16 in the B213/L1495 filament of the Taurus Molecular Cloud, and to understand how it relates to the environmental conditions and the evolutionary state of the cores. We made use of two complete spectral surveys at 7 mm of these sources, carried out using the Yebes 40-m telescope. Derived molecular abundances were compared with those of other sources in different evolutionary stages and with values computed by chemical models. Including isotopologs, 22 molecules were detected in B213-C2, and 25 in B213-C16. The derived rotational temperatures have values of between $\sim$ 5 K and $\sim$ 9 K. A comparison of the two sources shows lower abundances in C2, except for l-C$_{3}$H and HOCO$^{+}$, which have similar values in both cores. Model results indicate that both cores are best fit assuming early-time chemistry, and point to C2 being in a more advanced evolutionary stage, as it presents a higher molecular hydrogen density and sulfur depletion, and a lower cosmic-ray ionization rate. Our chemical modeling successfully accounts for the abundances of most molecules, including complex organic molecules and long cyanopolynes (HC$_{5}$N, HC$_{7}$N), but fails to reproduce those of the carbon chains CCS and C$_{3}$O. Chemical differences between C2 and C16 could stem from the evolutionary stage of the cores, with C2 being closer to the pre-stellar phase. Both cores are better fit assuming early-time chemistry of t $\sim$ 0.1 Myr. The more intense UV radiation in the northern region of B213 could account for the high abundances of l-C$_{3}$H and HOCO$^{+}$ in C2.

The gravitational wave event GW190521 seems to be the only BH merger event possibly correlated with an electromagnetic counterpart, which appeared about 34 days after the GW event. This work aims to confirm that the electromagnetic bump towards the Active Galactic Nucleus (AGN) J1249+3449 can be explained within the framework of the gravitational microlensing phenomenon. In particular, considering the data of the Zwicky Transient Facility (ZTF), what emerges from a detailed analysis of the observed light curve using three fitting models (Point Source Point Lens, Finite Source Point Lens, Uniform Source Binary Lens) is that the optical bump can be explained as a microlensing event caused by a lens with mass {$\sim\,$0.1 $M_{\odot}$}, lying in the host galaxy of the AGN in question.} %MDPI: Please confirm if the bold formatting is necessary; if not, please remove it.

The radius-luminosity ($R_{\rm BLR}$-$L_{5100}$) relation is fundamental to active galactic nucleus (AGN) studies, enabling supermassive black hole (SMBH) mass estimates and AGN-based cosmology applications. However, its high-luminosity end remains poorly calibrated due to insufficient reliable reverberation mapping (RM) data. We present a four-year RM campaign of the luminous quasar E1821+643 using the Lijiang 2.4-m telescope, supplemented by archival multi-wavelength data. E1821+643 is the most luminous AGN with an \hb\ RM measurement to date. The measured time lag of $83.2_{-18.7}^{+17.5}$ days is a factor of 5.6 shorter than predicted by the canonical $R_{\rm BLR}$-$L_{5100}$ relation. By compiling the full \hb\ RM sample, we find that such deviation defines a lower envelope ($0.2R_{\rm BLR}$) of measured lags across the entire luminosity range, while the upper envelope lies near $2R_{\rm BLR}$, implying that the scatter for individual AGNs can reach 1 dex. Spectral decomposition reveals two distinct \hb\ components: a core component with a lag of $267.0_{-17.6}^{+16.6}$ days closer to the $R_{\rm BLR}$-$L_{5100}$ relation, and a redshifted tail with a much shorter lag of $-49.0_{-34.5}^{+50.5}$ days. The short-lag component not only accounts for the significantly shortened overall lag, but also leads to an opposite interpretation of the intrinsic BLR kinematics. These effects can introduce systematic uncertainties in black hole mass estimates by factors of up to tens. Our findings demonstrate that shortened lags in high-accretion-rate AGNs arise from multi-component BLR structures, posing substantial challenges to single-epoch mass estimates and impacting SMBH demographics and cosmological applications.

In the past few decades, X-ray astronomy satellites equipped with grating spectrometers and microcalorimeters have enabled high-resolution spectroscopic observations of astrophysical objects. The need for accurate atomic data has arose as we attempt detailed analysis of the high-resolution spectra they provide. This is because current spectral models, which heavily rely on theoretical calculations, entail non-negligible uncertainties. We employ a plasma spectroscopy device called electron beam ion trap (EBIT) to experimentally obtain precise atomic data. An EBIT with a design that allows combined operation with synchrotron radiation facilities was developed based on the Heidelberg Compact EBIT and installed at ISAS/JAXA for this purpose. We conducted a spectroscopic experiment using the JAXA-EBIT at the synchrotron radiation facility SPring-8, and successfully obtained high-resolution spectra of the L$\alpha$ resonance transition of Ne-like Fe$^{16+}$ ions, 3C, as well as the K$\alpha$ resonance transition of He-like O$^{6+}$ ions. We also measured another Ne-like Fe$^{16+}$ L$\alpha$ resonance transition, 3G, and constrained an upper limit of the oscillator strength ratio of 3G to 3C, using our experimental results. The experimental values obtained in this study will be applied to observational studies of astrophysical objects as a part of the plasma spectral modeling.

The Great Oxidation Event (GOE), which marked the transition from an anoxic to an oxygenated atmosphere, occurred 2.4 billion years ago on Earth, several hundreds of millions of years after the emergence of oxygenic photosynthesis. This long delay implies that specific conditions in terms of biomass productivity and burial were necessary to trigger the GOE. It could be a limiting factor for the development of oxygenated atmospheres on inhabited exoplanets. In this study, we explore the specificities of a terrestrial planet in the habitable zone of an M dwarf for a GOE. Using a 1D coupled photochemical-climate model, we simulate the atmospheric evolution of TRAPPIST-1 e, an Earth-like exoplanet, exploring the effect of oxygen sources (biotic or abiotic). Our results show that the stellar energy distribution promotes O3 production at lower O2 concentrations compared to Earth, and the ozone layer on TRAPPIST-1 e forms more efficiently. This lowers the threshold for atmospheric oxidation, suggesting that the GOE on TRAPPIST-1 e would occur quickly after the rise of oxygenic photosynthesis, up to 1Gyrs earlier than on Earth, and would reach O2 enabling oxygenic respiration and thus the development of animals. We may question whether this is a general behavior around several M-stars. Furthermore, we discuss how the overproduction of ozone could make O3 detection possible using the James Webb Space Telescope, providing a potential method to observe oxygenation signatures on exoplanets in the near future. Previous studies predicted that for an Earth-like atmosphere O3 would require over 150 transits for detection, but our results show that significantly fewer transits could be needed.

We investigate the role of resolution and initial magnetic field strength on core-collapse supernovae in simulations of a non-rotating $13 \mathrm{M_\odot}$ progenitor. Specifically, we study the effect on shock revival, explosion dynamics, and the properties of the compact remnant. We run four models with different numerical grid resolutions with an initial central dipole field strength of $\mathord{\approx}10^{12}\, \mathrm{G}$. Two of those resolutions are also run with a weaker central magnetic field of $\mathord{\approx}10^{10}\, \mathrm{G}$ . The shock revival time for all models is largely independent of resolution and initial magnetic field strength, but we find higher explosion energies when the initial magnetism is stronger and at higher resolutions. We find that models with strong magnetic fields have lower neutrino luminosity and energies, due to a proto-neutron star (PNS) that is deformed by the strong magnetic fields. At higher resolutions, magnetic fields are amplified more efficiently in the gain region and in the PNS via the small-scale dynamo. Although the strong magnetic fields do not directly drive the explosion, they have a subsidiary impact on the explosion mechanism and compensate for the reduced neutrino heating. Stronger magnetic energies in the PNS also affect energy and angular momentum redistribution, leading to more extended and vigorous PNS convection zones at higher resolutions.

Recently, the Pierre Auger Observatory has found strong evidence supporting the extragalactic origin of the most energetic cosmic rays. Despite several observed excesses in the distribution of arrival directions for the highest energy cosmic rays, the sources remain unidentified. Accretion shocks in galaxy clusters have been proposed as potential sources in the past. These immense shock waves, which can have radii on the order of megaparsecs, are generated by the infall of material from the intergalactic medium into the gravitational potential wells of galaxy clusters. In this work, we investigate the possibility that ultrahigh-energy cosmic rays are accelerated in these regions. Nearby massive galaxy clusters, including Virgo, are treated as a discrete component of the cluster mass distribution. Less massive galaxy clusters, as well as distant massive ones, are assumed to follow a continuous distribution in agreement with cluster mass statistics. We fit the flux at Earth and the composition profile measured by the Pierre Auger Observatory, assuming the injection of different nuclear species by these sources, to determine the values of the model parameters. Our results indicate that cosmic ray acceleration in cluster accretion shocks may account for at least a fraction of the observed UHECR flux at energies below the suppression scale. At higher energies, direct acceleration from the thermal pool would be feasible only if local fluctuations create favorable conditions, such as magnetic fields about an order of magnitude stronger than those typically expected in cluster accretion shocks, or for particular shock normal-magnetic field configurations.

Velocity fields in the cosmic web are fundamental to structure formation but remain difficult to observe directly beyond the linear regime. Here we present observational evidence that galaxy filaments connecting pairs of galaxy clusters undergo a split infall, with opposite velocity flows toward the two clusters. Using spectroscopic galaxies from the Sloan Digital Sky Survey, we isolate the internal filament velocity field by subtracting its rigid-body background motion and Hubble flow, and detect this effect at greater than $5\sigma$ significance across a wide range of cluster and filament selections. The measured velocity profile exhibits a sign reversal near the filament midpoint and a maximum infall amplitude of $\sim30$ km/s ($\sim20$ km/s projected onto the line-of-sight) for clusters of mass $\sim10^{14.3}M_\odot$, substantially lower than expected for infall from an average cosmic environment. Multiple results on density-velocity correlation, mass-dependency, and validation with simulation indicate that filaments dynamically respond to competing gravitational potentials rather than acting as passive mass transport channels. Our results establish a new observational window on quasi-linear velocity fields in the cosmic web and provide a promising probe of mass measurement, testing gravity and velocity reconstruction with upcoming wide-field spectroscopic surveys.

Large-scale filaments ubiquitously exist in the Galactic interstellar medium, and their radial profiles offer insights into their formation mechanisms. We present a statistical analysis of molecular hydrogen column density ($\rm N(H_2)$) and dust temperature ($\rm T_d$) radial profiles for 35 Galactic large-scale filaments. We divided their spines into 315 segments, extracted the radial profiles of each segment using $\rm N(H_2)$ and $\rm T_d$ maps derived from $Herschel$ Hi-GAL data, and estimated the asymmetry degree within the radial profiles ($\alpha_{\rm asy}$), as well as the length proportion of segments with asymmetric profiles across the entire filament ($f_{\rm asy}$). We found that Galactic large-scale filaments reside in surroundings distinctly asymmetric and varied in $\rm N(H_2)$, and mild asymmetric yet stable in $\rm T_d$. Different filament morphology types do not show significant differences in $\alpha_{\rm asy}$ or $f_{\rm asy}$. A bent filament shape does not necessarily correspond to an asymmetric radial profile, whereas a straight filament shape may be associated with a symmetric profile. Segments with asymmetric surroundings in $\rm N(H_2)$ may not simultaneously appear asymmetric in $\rm T_d$, and vice versa. We found three filaments with 4-44% of their spine show asymmetric $\rm N(H_2)$ and $\rm T_d$ radial profiles in inverse trends, likely caused by nearby HII region. HII regions of similar scale to large filaments can induce asymmetric radial profiles within them, indicating their influence on filament evolution. However, they are unlikely to independently trigger the formation of an entire Galactic large-scale filament, in contrast to their role in small-scale filament formation.

The standard approach to modeling X-ray spectral data relies on local optimization methods, such as the Levenberg-Marquardt algorithm. While effective for simple models and speedy spectral fitting, these local optimizers are prone to becoming trapped in local minima, particularly in high-dimensional or degenerate parameter spaces, and typically require extensive user intervention. In this work, we introduce XFit, a global optimization method for fitting X-ray data, which makes extensive use of the Ferret evolutionary algorithm. XFit enables automated exploration of complex parameter spaces, efficient mapping of confidence intervals, and identification of degenerate solutions that may be overlooked by local methods. We demonstrate the performance of XFit using two representative X-ray sources: the Central Compact Object in Cassiopeia A and the supernova remnant G41.1-0.3. These examples span both low- and high-dimensional models, allowing us to illustrate the advantages of global optimization. In both cases, XFit produces solutions that are consistent with or improve upon those found with traditional methods, while also revealing alternative fits or degenerate solutions within statistically acceptable confidence levels. The automated mapping of parameter space offered by XFit makes it a powerful complement to existing spectral fitting tools, particularly as models and data quality become increasingly complex. Future work will expand the application of XFit to broader datasets and more physically motivated models.

Previous VLBI kinematic studies of the blazar 3C 66A have unveiled complex jet kinematic behaviors. Using follow-up high-resolution VLBI observations and archival data, we investigate the morphology and the variations in orientation and core flux density of the 3C 66A jet to gain a deeper insights into its kinematic behavior and physical origins. We performed KVN and VERA array (KaVA) observations at 22/43 GHz over three epochs in 2014 and collected 109 sets of Very Long Baseline Array (VLBA) archival data at 43 GHz between 1996 - 2025. We imaged the parsec-scale jet and parameterized it using circular Gaussian fittings to the UV visibilities. Finally, we derived the inner jet PA and the core flux densities for the VLBA data. The jet presents a twisted morphology in the KaVA maps. The PA of the fitted Gaussian components is in the range between 170 deg and 195 deg. Our kinematic analysis using the VLBA data indicates that the PA oscillates with an amplitude of 7.77 pm 0.79 deg and a period of 10.94 pm 0.22 years, presented for the first time in this work. This oscillation is topped by a continuous clockwise shift of the PA by -0.83 pm 0.07 deg/year. We also identified a strong core flux variability with possible periodicity and a 2 sigma correlation between the core flux density and the inner jet PA change. We discuss possible physical models that could explain the observed features for this object; in particular, a supermassive black hole binary (SMBHB) system, Lense Thirring (LT) effect, and jet or disk instabilities. The oscillation and continuous shift of the PA and the possible radio flux periodicity, together with the optical flux periodicity of approximately 2 years that had previously been confirmed in several independent studies, favor a jet precession scenario driven by orbital motion and disk-orbit misalignment in a SMBHB system.

Past kinetic simulations and spacecraft observations have shown that traveling foreshocks (TFs) are bounded by either foreshock compressional boundaries (FCBs) or foreshock bubbles (FBs). Here we present four TFs with a different kind of structure appearing at one of their edges. Two of them, observed by the Cluster mission, are bounded by a hot flow anomaly (HFA). In one case, the HFA was observed only by the spacecraft closest to the bow shock, while the other three probes observed an FCB. In addition, two other TFs were observed by the MMS spacecraft to be delimited by a structure that we call HFA-like FCB. In the spacecraft data, these structures present signatures similar to those of HFAs: dips in magnetic field magnitude and solar wind density, decelerated and deflected plasma flow and increased temperature. However, a detailed inspection of these events reveals the absence of heating of the SW beam. Instead, the beam almost disappears inside these events and the plasma moments are strongly influenced by the suprathermal particles. We suggest that HFA-like FCBs are related to the evolution and structure of the directional discontinuities of the interplanetary magnetic field whose thickness is larger than the gyroradious of suprathermal ions. We also show that individual TFs may appear together with several different types of transient upstream mesoscale structures, which brings up a question about their combined effect on regions downstream of the bow shock.

The assembly history of the Galactic bulge is intimately tied to the formation of the proto-Milky Way, yet reconstructing this early phase is difficult because mergers and secular evolution have erased most of its original structure. Among present-day stellar systems, only globular clusters retain the ancient signatures needed to trace these primordial building blocks. Here we present the most detailed characterization to date of Tonantzintla 2, a prime candidate for a relic of the Milky Way's primordial bulge. It is a moderately metal-rich globular cluster projected onto the bulge that has remained largely unexplored despite its potential to constrain the early formation of the inner Milky Way. We derive its fundamental parameters using proper motion-corrected Hubble Space Telescope WFC3 and ACS photometry. By applying an isochrone fitting to very clean data, we obtain an age of 13.58 Gyr, a reddening E(B-V) = 1.44, a metallicity [M/H]=-0.68, and a heliocentric distance of d = 7.38 kpc. A complementary chemical-abundance analysis of seven member stars from APOGEE high-resolution spectroscopy reveals an enrichment pattern consistent with an in-situ origin. Tonantzintla 2 is among the oldest globular clusters studied in the literature, and the oldest so far analyzed in the Galactic bulge. Its age places a stringent constraint on the onset of the bulge formation, implying that star formation in the inner Galaxy began within ~0.2 Gyr of the Big Bang and that Tonantzintla 2 represents an exceptional relic of the Milky Way's earliest chemical enrichment.

The nature of Dark Matter (DM) is one of the most outstanding mysteries of modern astrophysics. While the standard Cold DM (CDM) model successfully explains observations on most astrophysical scales, DM particles have not yet been detected, leaving room for a plethora of different models. In order to identify their observable signatures, we use the AIDA-TNG cosmological simulation suite to predict the distributions of gas and neutral hydrogen (HI) in the CDM, Self-Interacting DM (SIDM), velocity-dependent SIDM (vSIDM), and Warm DM (WDM) models. We find that the DM models investigated have very limited impact on the median gas and HI profile of haloes. In particular, for the most massive haloes ($M_{\rm vir}\sim10^{14}\,\mathrm{M}_\odot$), we find that DM self-interactions can shallow the central potential and thereby enhance gas cooling. We find that, in all models, the halo-to-halo variation in the HI profiles is explained by AGN feedback, and that the specific characteristics of DM model is largely subdominant. Nevertheless, we detect some systematic difference in the case of SIDM, with more HI surviving close to the centre with respect to other models. We provide fitting functions for the gas and HI profiles. We investigate the galaxy-Ly$\alpha$ cross-correlation function (\galacc) for different halo masses, redshift and observation strategies. We find that at $z=0$ vSIDM can be distinguished from CDM in haloes with $10^{12}\lesssim M_{\rm vir}\lesssim10^{13}\,{\rm M}_\odot$, while SIDM1 can be distinguished from CDM in haloes with $M_{\rm vir}\gtrsim10^{13}\,{\rm M}_\odot$. We estimate that statistically-robust detection requires sampling $\sim160$ haloes with $\sim20$ sightlines each, a task that can be achieved with current and future facilities like WEAVE, 4MOST, PFS, ELT and WST.

Bow-shock pulsar wind nebulae are valuable sources to investigate the dynamics of relativistic pulsar winds and the mechanisms by which they are converted into cosmic-ray leptons at the highest energies. The Lighthouse Nebula is one such object, famous for the high velocity of its pulsar and a long misaligned X-ray jet that is understood as a specific escape channel for the most energetic particles. We aim to get a better understanding of how the bulk of non-thermal particles are released into the interstellar medium. We focus on GHz radio observations, which probe lower-energy particles that are dominant in number and long-lived, thus offering a picture of how escape proceeds in the long run. We analyze 10.5h of MeerKAT observations in the 0.9-1.7GHz band. MeerKAT observations reveal a highly structured synchrotron nebula downstream of pulsar PSR J1101-6101. A cometary tail is detected up to beyond 5pc from the pulsar, while a system of multiple transverse two-sided emission streaks is observed for the first time. No radio counterpart of the misaligned X-ray jet is seen. The radio streaks are interpreted as the occasional charge-independent release of energetic leptons from the tail into the surrounding medium, as a result of dynamical instabilities and reconfiguration in the downstream flow. The intensity layout suggests that most of the particle content of the nebula is discharged into the ambient medium within several parsec. Once escaped, particles light up the ambient magnetic field, which appears to have a coherence length of at least a few parsec. The length and persistence of the streaks indicate a low level of magnetic turbulence, possibly slightly enhanced with respect to average cosmic-ray transport conditions in the Galaxy. Such a confinement may result from self-generated turbulence by resonant streaming instability, or be due to past activity of the progenitor star.

With the operation of JWST, atmospheric characterization has now extended to low-mass exoplanets. In compact multiplanetary systems, secular spin-orbital resonance may preserve high obliquities and asynchronous rotation even for tidally-despinning, low-mass planets, potentially leading to unique atmospheric circulation patterns. To understand the impact on the atmospheric circulation and to identify the potential atmospheric observational signatures of such high-obliquity planets, we simulate the three dimensional circulation of a representative mini-Neptune K2-290 b, whose obliquity may reach about 67 degrees. Whether synchronously rotating or not, the planet's slow rotation, moderate temperature and radius result in a global Weak-Temperature-Gradient (WTG) behavior with moderate horizontal temperature contrasts. Under synchronous rotation, broad eastward superrotating jets efficiently redistribute heat. Circulation in an asynchronous rotation exhibits a seasonal cycle driven by high obliquity, along with quasi-periodic oscillations in winds and temperatures with a period of about 70 orbital periods. These oscillations, driven by wave-mean flow interactions, extend from low to mid-latitudes due to the slow planetary rotation. Higher atmospheric metallicity strengthens radiative forcing, increasing temperature contrasts and jet speeds. Clouds have minimal impact under synchronous rotation but weaken jets under nonsynchronous rotation by reducing temperature contrasts. In all cases, both thermal emission and transmission spectra exhibit moderate observational signals at a level of 100 ppm, and high-obliquity effects contribute differences at the 10 ppm level. Our results are also applicable to a range of potential high-obliquity exoplanets, which reside in the WTG regime and likely exhibit nearly homogeneous horizontal temperature patterns.

Black holes are the simplest possible objects, characterised by only mass and spin. We see them via accretion, so there is one more fundamental parameter which is the mass accretion rate. Here I will review how the data from both stellar and supermassive black holes can be fit into a framework where there is a major spectral transition at $\dot{m}=L/L_{\rm Edd}\sim 0.01$ where the optically thick disc is replaced by a hot flow. This dramatic spectral change also affects the expected properties of thermal and radiatively powered winds, matching the overall properties of winds seen in new XRISM data from the stellar mass binaries, though there can also be additional UV and dust driven winds in supermassive black holes. The radio data in stellar and supermassive black holes are clear that the hot flow (not the disc) connects to the radio jet, and the radio-X-ray 'fundamental plane' can be qualitatively understood if the radio quiet AGN and stellar mass black holes have low to moderate spins, with the jet power set as a constant fraction of the accretion power. A small fraction of AGN (radio loud) instead have much higher (factor $100-1000\times$) radio-to-X-ray ratio at the same black hole mass and mass accretion rates. I speculate that these have higher jet power due to high black hole spin. I review the multiple issues still remaining in this picture, most of which are connected to the geometry and nature of the X-ray corona, and the conflicting constraints on this which come from reflection spectroscopy and polarimetry.

Cross-correlations between 21cm observations and galaxy surveys provide a powerful probe of reionization by reducing foreground sensitivity while linking ionization morphology to galaxies. We quantify the constraining power of 21cm-Galaxy cross-power spectra for inferring neutral hydrogen fraction $x_\mathrm{HI}(z)$ and mean overdensity $\langle 1+\delta_\mathrm{HI} \rangle(z)$, exploring dependence on field of view, redshift precision $\sigma_z$, and minimum halo mass $M_\mathrm{h,min}$. We employ our simulation-based inference framework EoRFlow for likelihood-free parameter estimation. Mock observations include thermal noise for 100h SKA-Low with foreground avoidance and realistic galaxy survey effects. For a fiducial survey ($\mathrm{FOV}=100\,\mathrm{deg}^2$, $\sigma_z=0.001$, $M_\mathrm{h,min}=10^{11}\mathrm{M}_\odot$), cross-power spectra yield unbiased constraints with posterior volumes (PV) of $\sim$10% relative to priors. Cross-power measurements reduce PV by 20-30% versus 21cm auto-power alone. With foreground avoidance, spectroscopic redshift precision is essential; photometric redshifts render cross-correlations uninformative. Notably, cross-power spectra constrain ionizing source properties, the escape fraction $f_\mathrm{esc}$ and star formation efficiency $f_*$, which remain degenerate in auto-power (PV $>$60%). Tight constraints require either deep surveys detecting faint galaxies ($M_\mathrm{h,min} \sim 10^{10}\mathrm{M}_\odot$) with moderate foregrounds, or conservative mass limits with optimistic foreground removal (PV $<$15%). 21cm-Galaxy cross-correlations enhance morphology constraints beyond auto-power while enabling previously inaccessible source property constraints. Realizing full potential requires precise redshifts and either faint galaxy detection limits or improved 21cm foreground cleaning.

The revision of the fourth Fermi Large Area Telescope (LAT) catalog of gamma-ray point sources (rev4FGL) revealed that the gamma-ray sky is populated by emerging populations of jetted active galactic nuclei (AGN) other than blazars and radio galaxies. Narrow-Line Seyfert 1, Seyfert 1, intermediate, and Seyfert 2 galaxies, changing-look AGN, plus a number of ambiguous or unclassified sources. After a short historical introduction on the gamma-ray observations of Seyfert-type AGN, I explore the main statistical properties of 1477 jetted AGN from the rev4FGL with spectroscopic redshift, and also the cross-match with Very Large Baseline Array (VLBA) radio observations at 15~GHz from the Monitoring Of Jets in Active galactic nuclei with VLBA Experiments (MOJAVE) program. I then discuss the difference between gamma and non-gamma jetted AGN, and the implications on the classification.

Energetic particles interact with the plasma surrounding them, resonating with certain plasma waves to stabilize them while destabilizing others, and changing the character of the background turbulence in ways that have not been fully quantified or understood. Interaction with the turbulent background plasma is key to the acceleration of many types of energetic particles including high-energy cosmic rays, solar energetic particles, and pick-up ions. This is a process that would ideally be described by a kinetic model, a type of model that follows a probability distribution function (PDF) for all particles in 7-dimensional space. Because of the high dimensionality of a kinetic model, such simulations use the largest computational resources available, and are yet unable to simulate a realistic number of particles, reach the large scales necessary for astrophysical problems, or use high-precision numerical methods. Two available alternatives to kinetic plasma models have been explored: a multi-fluid model, and a hybrid fluid/Fokker-Planck model. These methods are hampered by the physical modeling of the coupling. We develop a new model, which follows the PDF for all particles; this can be viewed as a step toward physical realism above a multi-fluid MHD model, while also being more computationally efficient than a kinetic model. The equations we develop model both the background plasma and the energetic particles self-consistently. Over the last decade, similar PDF methods have been developed to a high level of sophistication to model reactive flows and turbulent combustion for engineering applications. For treatment of the feedback of the energetic particles on a background plasma, a PDF closure approach should evaluate the mean characteristics, including the density, with better statistical quality than will particle-sampling procedures.

Galaxy clusters are the largest virialized structures in the Universe and are predominantly dominated by dark matter. The hydrostatic mass and the mass obtained from gravitational lensing measurements generally differ, a discrepancy known as the hydrostatic mass bias. In this work, we derive the hydrostatic mass of galaxy clusters within the framework of Rastall gravity and investigate its implications under two scenarios: (i) the absence of dark matter and (ii) the existence of dark matter. In the first scenario, Rastall gravity effectively reduces the hydrostatic mass, bringing it closer to the observed baryonic mass. The best linear fit yields a slope $\mathbf{M}=1.07\pm0.11$, indicating a near one-to-one correspondence between the two masses. In the second scenario, Rastall gravity helps to alleviate the hydrostatic mass bias. The linear fit between the Rastall hydrostatic mass and the observed lensing mass results in a best-fit slope $\mathbf{M}=1.01\pm0.16$, which is very close to unity. These results suggest that Rastall gravity provides a statistically favorable framework for addressing mass discrepancies in galaxy clusters.

The era of multi-messenger astrophysics requires rapid and efficient follow-up of transient events, many of which, such as gravitational waves (GW), gamma-ray bursts (GRB), and high-energy neutrinos, suffer from poor sky localisation. We present tilepy, a Python-based software designed to optimize observation schedules for these events. We here detail the modular architecture of tilepy, which separates high-level scheduling logic from low-level tiling and pointing tools, enabling full adaptability for ground- and space-based observatories. Furthermore, we describe the integration of tilepy into the Astro-COLIBRI platform, providing the community with a user-friendly interface and API for triggering complex observation campaigns in real time.

We recently used a large set of Monte Carlo simulations of globular clusters (GCs) to define new fully empirical parameters (named A5, P5, and S2.5) able to trace the internal dynamical evolution of dense stellar systems. These parameters are specifically designed to quantify the steepness of the cumulative radial distribution of stars in the innermost region of the host system, which tends to progressively increase with dynamical aging due to core contraction. Following the original definitions, here we measure A5 and P5 in a sample of 40 Galactic GCs homogeneously surveyed through HST photometric observations. In agreement with the predictions of our simulations, the largest values of A5 and P5 are found for the most dynamically evolved GCs, i.e., those previously classified as post-core collapse systems based on the shape of their density profile, and those characterized by the shortest central relaxation times. Moreover, the new dynamical parameters here measured strongly correlate with A+rh, another fully empirical, independent parameter that traces the dynamical age of star clusters through the level of central segregation of blue straggler stars.

We investigate how the orbital evolution and mass distribution of infalling satellite galaxies shape the phase-space and radial distributions of intracluster light (ICL) relative to the underlying cluster dark matter (DM) halo. Using N-body simulations, we follow the tidal stripping and orbital evolution of satellite galaxies as they are accreted into a live cluster halo, systematically varying satellite-to-host mass ratio and orbital circularity. We measure the specific orbital energy and angular momentum of stripped stellar and DM material, finding that the stripped stars consistently occupy lower-energy and lower-angular momentum regions of phase-space than the stripped DM. The magnitude of this difference increases strongly towards more equal satellite--to--host mass ratios, while the dependence on orbital circularity is weak. We construct a predictive model for the phase-space properties of stripped stars and DM from a whole infalling satellite population and find that the resulting phase-space difference between the components are driven primarily by the characteristic mass of the infalling satellite stellar mass function. We find that the ICL is always more centrally concentrated than the DM. The magnitude of this offset depends on the characteristic mass and increases towards higher characteristic masses. Comparisons with four independent cosmological hydrodynamical simulations show that, once the infalling satellite stellar mass function is matched, the model reproduces the radial stellar-to-DM density profile offsets to better than the inter-simulation scatter. This demonstrates that the radial relationship between the ICL and the DM distribution is largely governed by satellite demographics. With adequate constraints on the infalling satellite population, ICL density profiles can therefore be used as informative tracers of the underlying radial DM distribution in clusters.

We show that Schwarzschild primordial black holes (PBHs) formed in the radiation-dominated era can grow extremely rapidly through $\textit{radiative absorption}$ governed by the full Stefan-Boltzmann law. By introducing a principle of isonomy - ensuring identical particle species dependence for Hawking emission and absorption - we find that, whenever the temperature of the PBH environment is larger than the PBH horizon temperature, PBHs generically gain mass. In particular, for PBH masses following the critical collapse mass-scaling law with critical exponent $\gamma_\mathrm{crit}$, with $\gamma_\mathrm{crit} \in (0.33, 0.49)$, the aforementioned radiative absorption mass growth mechanism produces a striking effect: PBHs forming with a mass $10^6M_\odot$ during BBN can reach $\mathcal{O}(10^{10} M_\odot)$ within $\mathcal{O}(10^{6} \mathrm{s})$ ($\sim $ 58 days). Interestingly enough, small deviations from $\gamma_\mathrm{crit}$, depending itself on the number of relativistic species present in the primordial plasma, yield a continuous PBH mass spectrum providing us ultimately with a single, Standard-Model-based explanation for the origin of stellar-mass, intermediate-mass, and supermassive black holes (SMBHs), and naturally accounting for the early appearance of SMBHs. The Schwarzschild treatment presented here can be extended to spherically symmetric cosmological black holes, indicating that radiative absorption is a dominant and previously overlooked PBH growth channel in the early Universe.

The detection of likely thermal ultraviolet emission from a few old neutron stars suggests that at least one internal heating mechanism is present in these stars. One proposed mechanism is rotochemical heating, in which the continuous contraction of the neutron star due to its spin-down produces chemical imbalances that induce Urca reactions, and the latter deposit heat in the neutron star core. If the protons in the star are superconducting, their energy gap suppresses the reactions, except in microscopic magnetized regions (such as quantized flux tubes) in which the protons act as if they were normal. Therefore, the strength of the internal magnetic field controls the rate at which reactions proceed and thus affects the thermal evolution of the neutron star. Here, we present the first comprehensive study of the effect of an internal magnetic field in the superconducting interior on rotochemical heating. We simulate the evolution of neutron stars for different internal magnetic field strengths and neutron energy gaps, comparing the results to Hubble Space Telescope observations of old neutron stars. All the observational data can be accounted for if the proton energy gap is large ($\sim 1.5\,\mathrm{MeV}$) and the neutron energy gap is small ($\lesssim 0.1\,\mathrm{MeV}$) or vanishing, while the millisecond pulsar PSR~J0437$-$4715 needs to have a very weak internal magnetic field. Our results suggest that neutron-star cores are characterized by a large proton pairing gap and a small or vanishing neutron gap, and that millisecond pulsars have very weak internal magnetic fields. Under these conditions, rotochemical heating alone can account for the observed thermal emission of old neutron stars.

It is still not clear which environmental processes operate in filaments. Given the ubiquity of filaments and their importance in feeding clusters, a proper understanding of these mechanisms is crucial to a more complete picture of galaxy evolution. To investigate them, we need large galaxy samples with resolved imaging. For this study, we analyse resolved H$\alpha$ maps of 685 galaxies inside and outside the filaments around the Virgo cluster in addition to extensive measurements of integrated physical properties. We create a pipeline to decompose the H$\alpha$ images into individual clumps. We find that the number and average size of clumps in a galaxy are well-defined functions of distance and angular resolution. In particular, the power-law relation between the number of clumps and the distance of a galaxy is consistent with a fractal structure of star forming regions. We formulate an algorithm to compare filament and non-filament galaxies after removing observational differences. Although we do not have any conclusive evidence for a difference in clump size distributions between filament and non-filament galaxies, we do find that filament galaxies have slightly more peripheral clumps than their non-filament counterparts.

Sub-Neptune planets are often modeled with a dense rocky or metal-rich interior beneath a thick hydrogen/helium (H/He) atmosphere; though their bulk densities could also be explained by a water-rich interior with a thin H/He atmosphere. Atmospheric composition provides a key mechanism to break this degeneracy between competing interior models. However, the overall composition of sub-Neptunes inferred from spectra obtained with the James Webb Space Telescope, remains debated in part due to differences in modeling assumptions. While previous studies explored parameter spaces such as stellar spectra, atmospheric metallicities, and carbon-to-oxygen ratios, they often assumed fixed intrinsic temperatures (Tint) and vertical eddy diffusion coefficients (Kzz) - two critical, yet poorly constrained, drivers of atmospheric chemistry. To address this, we present a self-consistent grid of models that covers the full plausible range of Tint (60 - 450 K) and Kzz (10^{5} - 10^{12} cm^2/s) using the open-source PICASO and VULCAN packages to better characterize sub-Neptune atmospheres. Focusing on K2-18b analogs, we demonstrate that Tint and Kzz significantly impact CH4, CO2, CO, NH3 and HCN abundances, with H2O being largely unaffected. Our work demonstrates that comprehensive parameter space exploration of thermal and mixing parameters is essential for accurate interpretation of sub-Neptune spectra, and that single-parameter assumptions can lead to misclassification of planetary interiors. We provide a diagnostic framework using multi-molecule observations to distinguish between competing atmospheric models and advance robust characterization of sub-Neptunes.

The Colours of the Outer Solar System Origins Survey (Col-OSSOS) measured the optical/NIR colours of a brightness-complete sample of Trans-Neptunian Objects (TNOs). Like previous surveys, this one found a bimodal colour distribution in TNOs, categorised as red and very red. Additionally, this survey proposed an alternative surface classification scheme: FaintIR and BrightIR. Cold classical TNOs mostly have very red or FaintIR surfaces, while dynamically excited TNOs show a mixture of surfaces. This likely indicates that formation locations and proximity to the Sun influenced surface characteristics and color changes. Our study combines the data from Col-OSSOS with two dynamical models describing the formation of the Kuiper belt during Neptune's migration. We investigate the proposed surface-colour changing line and explore the distribution of different surfaces within the primordial disk. By comparing radial colour transitions across various scenarios, we explore the origins of surface characteristics and their implications within the context of BrightIR and FaintIR classifications. Moreover, we extend our analysis to examine the distribution of these surface classes within the present-day Kuiper Belt, providing insights into the configuration of the early solar system's planetesimal disk prior to giant planet migration. We find that the most likely primordial disk compositions are inner neutral / outer red (with transition $30.0^{+1.1}_{-1.2}$ au), or inner BrightIR / outer FaintIR (with transition $31.5^{+1.1}_{-1.2}$ au).

We develop a fully analytical framework for predicting the one-point probability distribution function (PDF) of dispersion measures (DM) for fast radio bursts (FRBs) using the baryonification (BFC) model. BFC provides a computationally efficient alternative to expensive hydrodynamical simulations for modelling baryonic effects on cosmological scales. By applying the halo mass function and halo bias, we convolve contributions from individual halos across a range of masses and redshifts to derive the large-scale structure contribution to the DM PDF. We validate our analytical predictions against consistency-check simulations and compare them with the IllustrisTNG hydrodynamical simulation across a range of redshifts up to $z = 5$, demonstrating excellent agreement. We demonstrate that our model produces consistent results when fitting gas profiles and predicting the PDF, and vice versa. We show that the BFC parameters controlling the gas profile, particularly the halo mass scale ($M_\mathrm{c}$), mass-dependent slope ($\mu$), and outer truncation ($\delta$), are the primary drivers of the PDF shape. Additionally, we investigate the validity of the log-normal approximation commonly used for DM distributions, finding that it provides a sufficient description for a few hundred FRBs. Our work provides a self-consistent model that links gas density profiles to integrated DM statistics, enabling future constraints on baryonic feedback processes from FRB observations.

We introduce a novel modeling pipeline for strongly lensed point sources, using the GIGA-Lens framework, running on four A100 GPUs via the JAX platform. Using simulations, we demonstrate accurate and precise recovery of image positions, fluxes, and time delays, together with inference of complex lens mass distributions -- including the mass density slope, $\gamma$ -- from images of lensed point sources alone. We further show that we can achieve statistical uncertainty of $\sim 3.6\%$ ($\sim 2.5\, \mathrm{km\, s^{-1}/Mpc}$) on $H_0$ from a single system, with full forward modeling, i.e., simultaneous inference of all lens model parameters together with $H_0$. We apply our pipeline to two well-studied lensed SNe Ia, Zwicky and iPTF16geu. For SN iPTF16geu, unlike previous modeling efforts, we model only the images of the lensed point source (the SN) and do not use the lensed images of the extended host-galaxy. Nevertheless, we are able to infer all of the mass parameters modeled in earlier studies, and our best-fit values, including $\gamma$, are fully consistent with published results. In the case of SN Zwicky, taking the same approach, however, we obtain an alternative best-fit model compared to published results, underscoring the importance of fully exploring the model parameter space.

The spherical harmonics $Y_{\ell m}(\theta,\varphi)$ are complex-valued functions on the surface of a sphere, and have found widespread application in physics and astronomy. Every physics students knows them from quantum mechanics and electromagnetic theory, where they form the basis of hydrogen orbitals and of the multipole expansion, respectively. More advanced applications include the physics of the cosmic microwave background, gravitational lensing, and gravitational waves. In this paper I aim to contrast their usual $3d$ visualisation with Peirce's quincuncial projection, a conformal projection of the sphere onto a $2d$ unfolded square dihedron, where the projection respects the fundamental rotational symmetries and preserves angles. With this mapping, I guide the reader through the properties of the spherical harmonics in a pedagogical way and show that many of their mathematical relations have an intuitive visualisation on Peirce's $2d$ map, which might be useful for people challenged by processing $3d$ shapes, or which people might appreciate aesthetically.

The search for extraterrestrial life has long been a primary focus of scientific exploration, driven by rapid advancements in technology and our understanding of the universe. The discovery of water on Mars has sparked significant interest, raising the question of whether life could exist on the planet. This study proposes a novel approach to simulate and illustrate the detection of life using a proof-of-life module integrated into a Mars rover. The module is an autonomous system capable of traveling to designated regions, excavating soil, collecting samples, and performing biochemical testing onboard the rover itself. The project is inherently multidisciplinary, integrating mechanical systems such as a drill mechanism and a vacuum system, alongside biochemical analysis for soil testing. The module is capable of successfully detecting the presence or absence of living components of life from the collected soil particles. This proof-of-life module serves as a proof-of-concept for autonomous life detection in extraterrestrial environments and lays the foundation for future exploration missions.

Low-Earth Orbit (LEO) constellations expand 5G coverage to remote regions but differ fundamentally from terrestrial networks due to rapidly changing topologies, fluctuating delays, and constrained onboard resources. Existing 3GPP Non-Access Stratum (NAS) timers, inherited from terrestrial and geostationary (GEO) or medium Earth orbit (MEO) systems, fail to accommodate these dynamics, leading to signaling storms and inefficiency. This paper introduces AstroTimer, a lightweight, adaptive framework for sizing NAS timers based on LEO-specific parameters such as link variability, processing delays, and network-function placement. AstroTimer derives a closed-form timer model with low computational cost and optimizes both watchdog and backoff timers for the 5G registration procedure. Simulation results demonstrate that AstroTimer significantly reduces registration time, retry frequency, and user equipment (UE) energy consumption compared to 3GPP defaults, while preventing signaling overloads. The proposed approach provides an operator-ready foundation for reliable, efficient, and scalable non-terrestrial 5G/6G deployments.

3D kinetic particle-in-cell (PIC) simulations are performed using the kinetic Alfvén wave (KAW) eigenvector relations from a two-fluid model as initial conditions, in order to study turbulent fluctuations and intermittent structures at sub-ion and electron scales. Simulations with different ion-to-electron mass ratios are set up to investigate the role of electron scales in the formation of intermittent structures. We analyze the current sheet structures that develop in these simulations. Two algorithms, namely Breadth-First Search (BFS) and Density-Based Spatial Clustering of Applications with Noise (DBSCAN), are employed to determine the thickness, length, and width of the current sheets, and both methods are found to yield consistent results. The average current sheet thickness scales inversely with the square root of the ion-to-electron mass ratio, with values close to the electron skin depth ($d_e$), indicating the presence of electron-scale current sheets in the simulations. The widths and lengths of the current sheets show a weaker scaling with the mass ratio. The scale-dependent kurtosis reveals enhanced intermittency at electron scales, consistent with magnetosheath observations. Distributions of scale-dependent properties of the current sheets also align with the electron skin depth of the different simulations and they lie within ranges observed in kinetic scale solar wind turbulence. This study reveals the nature of sub-ion-scale current sheets in KAW turbulence and their role in dissipation.

Separating turbulent fluctuations from coherent large-scale background flows is a fundamental challenge in the analysis of numerical simulations and astronomical observations. Traditional approaches to this problem commonly rely on decomposition-based techniques, including scale-based filtering methods such as Fourier or wavelet transforms, as well as adaptive methods like the Hilbert-Huang transformation. In realistic flows, however, coherent motions and turbulent fluctuations often overlap across a broad range of scales and interact nonlinearly, rendering any clear and unique separation inherently ambiguous, particularly in astrophysical settings where data are projected or sparsely sampled. In this work, we assess the robustness of AI-based turbulence-background separation using two-dimensional incompressible Navier-Stokes simulations of decaying hydrodynamic turbulence. The simulations are initialized with a coherent background flow and divergence-free turbulent perturbations with a Kolmogorov-like power spectrum, and evolve without external forcing, providing a conservative physical testbed. A neural network trained exclusively on static synthetic images is applied to simulation snapshots at different evolutionary stages. We find that the model successfully recovers turbulent fluctuations during early and intermediate stages, when partial scale separation is preserved. At later stages, despite the substantial decay of turbulent energy and the resulting reduction in fluctuation strength, the model continues to recover visually and spectrally plausible turbulent structures and preserves inertial-range spectral scaling, demonstrating robust separation under increasingly challenging conditions. These results demonstrate the potential of applying AI models trained on static data to time-evolving turbulent flows, with direct implications for astrophysical and cosmological applications.

Detecting the stochastic gravitational wave background (SGWB) from our Universe under the inflationary era is one of the primary scientific objectives of DECIGO, a space-borne gravitational wave detector sensitive in the 0.1 Hz frequency band. This frequency band is dominated by the gravitational waves from inspiraling compact object binaries. Subtracting these signals is necessary to search for the primordial SGWB. In this paper, we assess the feasibility of the subtraction of such binary signals by employing the population model inferred from the latest gravitational wave event catalogue of the LIGO-Virgo-KAGRA Collaboration. We find that the projection scheme, which was originally proposed by Cutler & Harms (2005), is necessary to reduce the binary signals to the level where DECIGO can detect the primordial background.

This chapter introduces the fundamental principles of gravitational wave detectors in a simple and comprehensive manner. Because these instruments aim for extremely high sensitivity, it is essential to understand their various noise sources, how such noise couples to the detector output, and the strategies used to mitigate them. These noises contributions are computed in the frame of the Virgo detector and a sensitivity curve is calculated. Although a simplified layout of a gravitational wave detector is considered, it takes into account the most dominant effects and yields in a sensitivity estimate close to the what is observed in real detectors.

The marginal likelihood, or Bayesian evidence, is a crucial quantity for Bayesian model comparison but its computation can be challenging for complex models, even in parameters space of moderate dimension. The learned harmonic mean estimator has been shown to provide accurate and robust estimates of the marginal likelihood simply using posterior samples. It is agnostic to the sampling strategy, meaning that the samples can be obtained using any method. This enables marginal likelihood calculation and model comparison with whatever sampling is most suitable for the task. However, the internal density estimators considered previously for the learned harmonic mean can struggle with highly multimodal posteriors. In this work we introduce flow matching-based continuous normalizing flows as a powerful architecture for the internal density estimation of the learned harmonic mean. We demonstrate the ability to handle challenging multimodal posteriors, including an example in 20 parameter dimensions, showcasing the method's ability to handle complex posteriors without the need for fine-tuning or heuristic modifications to the base distribution.

The impact of the symmetry energy on the properties of compact stars is analyzed considering constraints from nuclear physics and astrophysics. A compact star can be a neutron star composed only of nuclear matter or a hybrid star with a quark core. Two typical models (soft and stiff) are considered for the nuclear equation of state, and for the hybrid one, a parameterized first-order phase transition approach, completed with a linear quark matter equation of state, is implemented. We show that the phase transition reduces the tension between GW170817 and NICER observations, and we illustrate the impact of the symmetry energy for the understanding of the nature of the binary system in GW170817. We also confirm our previous findings that the GW170817 waveform is best described as a binary HS with a low-density onset of stiff quark matter. This could also be interpreted as a quarkyonic cross-over.