Does a galaxy’s gas content tell us anything about its future growth once its dark-matter halo history is already known? We test this question in the CAMELS CV suite using 27 fixed-parameter realizations of the IllustrisTNG and SIMBA galaxy-formation models. For each galaxy, we compare three predictor families — internal galaxy properties, halo/assembly-history properties, and environment — as predictors of future stellar growth, quenching, and halo growth from z≃0.77 to z=0. We measure how much predictive power each family adds beyond increasingly strict halo controls, ending with a 13-feature assembly-history baseline.In TNG, gas reservoir information predicts future stellar growth beyond the full assembly-history control at low-to-intermediate stellar mass, up to logM∗/M⊙≃10.55. This is not simply a current-star-formation effect: the gas signal survives controls for stellar mass, SFR, and sSFR. It is also not a gas-use-efficiency effect: gas amount remains informative, while depletion time adds no comparable information once gas amount is included. Halo assembly history strongly predicts the gas reservoir itself (R2≃0.8), but the residual gas component still predicts future growth. Thus the gas reservoir is shaped by halo history but not exhausted by it.Near logM∗/M⊙≃10.55, the predictive structure changes. Black-hole/quenching state, traced by catalog-level black-hole proxies rather than direct feedback-energy measurements, becomes more informative, and the high-mass population is largely quenched. The full assembly-history (L3) control is available only for TNG; because SubLink-equivalent merger trees are unavailable for SIMBA, we compare the two models at a matched static-halo (L1) control, where they express residual baryonic information in different channels — stellar growth in TNG and quenching in SIMBA — with no SIMBA L3-controlled claim. We caution that the low-mass edge is resolution/floor-sensitive rather than a sharp physical threshold, and that the environment result is limited to the CAMELS CV volume and features. Overall, the results are consistent with a fuel-limited to quenching-limited picture of future galaxy growth and motivate an observational test: gas-rich galaxies should grow preferentially at fixed stellar mass and assembly proxies in surveys such as xGASS/xCOLDGASS.
The accretion-induced collapse (AIC) of carbon-oxygen (CO) white dwarfs (WDs) accreting from helium-star (He-star) donors in ultracompact binaries represents a previously unexplored gravitational-wave (GW) source channel that differs fundamentally from the well-studied oxygen–neon (ONe) WD AIC pathway. We perform Monte Carlo population-synthesis calculations for 5×104 post-AIC CO-WD + He-star binaries spanning three He-donor sub-classes: Class A (low-mass He donors, MHe=0.35–0.70M⊙, AM CVn progenitors), Class B (medium He donors, MHe=0.70−1.20M⊙, ultracompact X-ray binary progenitors) and Class C (massive He donors, MHe=1.20–2.50M⊙, double-detonation survivors). CO WD masses span MWD=1.05–1.35,M⊙ and initial separations ai=0.01−0.50R⊙, placing these systems directly in the LISA millihertz band at birth. Natal kicks are drawn from a Maxwellian with σkick=5kms, reflecting the smaller mass loss (ΔM≲0.01,M⊙) of CO WD AIC relative to the ONe WD channel. We find that approximately 97% of binaries remain bound following collapse, with more than half born directly within the 1–20 mHz LISA sensitivity band and most of the remainder evolving through it during their inspiral. This behaviour contrasts sharply with the ONe-WD AIC channel, where only a small fraction of systems become observable by LISA. The three donor subclasses produce distinct chirp-mass distributions that are well separated from both the Galactic DWD foreground and stellar-mass black-hole binaries, providing a unique observational signature. We estimate subclass merger-rate densities of RAMC≈0.04–0.35, RUCXB≈0.09–0.72 and RHe≈0.18–1.40Gpc−3yr−1, corresponding to a total rate of Rtot≈0.31–2.47Gpc−3yr−1. At a Galactic-centre distance of DL=8kpc, we predict approximately 5–20 individually resolvable LISA sources from this channel. These results identify ultracompact CO-WD + He-star AIC binaries as a promising and previously unrecognized population of millihertz GW sources whose detection would constrain CO WD ignition physics, common-envelope evolution, stable mass transfer, and He-star binary evolution.
The ΛCDM paradigm provides a successful framework for the formation of cosmic structures on large scales, yet persistent tensions might remain on galactic and sub-galactic scales. The Milky Way and the Local Universe offer a uniquely accessible laboratory to probe these discrepancies through detailed chemo-dynamical studies of resolved stellar populations. In the era of large photometric and spectroscopic surveys, understanding disk assembly, dynamical heating, and galactoseismology requires not only wide-field coverage but also high-angular-resolution, near-infrared spectroscopy capable of penetrating dust-obscured regions and resolving crowded stellar environments. We propose a set of science cases that exploits the advanced capabilities of SHARP, a multi-mode near-infrared spectrograph designed for Extremely Large Telescopes and future space facilities such as the Habitable World Observatory. Operating over 0.95–2.45μm in a single exposure, SHARP enables efficient access to key stellar and gas tracers across the Galactic bulge, disk, halo, and nearby galaxies. The NEXUS mode provides adaptive-optics-assisted multi-object spectroscopy over a 1.2′×1.2′ field with spectral resolutions up to R∼17,000 for point sources, enabling gas and stellar kinematics. Complementarily, the VESPER multi-IFU mode delivers spatially resolved spectroscopy in crowded and complex regions, allowing the reconstruction of internal kinematics and stellar population gradients on sub-arcsecond scales. By combining SHARP observations with ongoing and upcoming surveys such as Gaia, APOGEE, LAMOST, LSST, 4MOST, and ELT–MOSAIC, this project will map six-dimensional phase-space structures of disk and bulge stars, stellar streams, and nearby disk galaxies (e.g. LMC, SMC). The resulting data will enable detailed investigations of bars, spiral arms, warps, flares, and satellite interactions, providing critical constraints on disk evolution, merger history, and dark matter substructure. These efforts will significantly advance our understanding of the dynamical assembly of the Milky Way and the Local Universe, and provide stringent tests of ΛCDM predictions on the smallest accessible scales.
In the light of the renewed interest in the exploration of the Moon, techniques of stably computing trajectories near the Moon in the multi-body gravitational environment would be in high demand. Conquering the gravitational singularity in the Sun–Earth–Moon-particle system is a challenging task due to the non-autonomous nature of the restricted four-body problem. This paper derives the regularized equations of motion for the bicircular restricted four-body problem with the aid of an energy differential equation. The Levi-Civita and Kustaanheimo–Stiefel transformations are applied to planar and spatial problems, respectively. An application example of the regularized framework using singular collision orbits is presented and further potential applications are discussed.
Within the Hauser–Feshbach framework in the TALYS 1.96 code, the Maxwellian-averaged cross sections (MACS) and thermonuclear reaction rates are analyzed for the 70Ge(n,γ)71Ge, 72Ge(n,γ)73Ge, 74Ge(n,γ)75Ge, and 76Ge(n,γ)77Ge radiative capture processes. The impact of nuclear level densities (NLD) and γ-strength functions on capture cross-sections relevant to the s-process is investigated. The constant temperature model (CTM), combined with the Kopecky–Uhl γ-strength function, offers the best consistency with experimental data, while microscopic models require scaling adjustments. Our results highlight significant nuclear structure effects, with the 76Ge(n,γ)77Ge process operating as a barrier in the weak s-process. The present analysis for MACS at kT=30 keV shows consistency with prior findings, underscoring the importance of precise nuclear inputs for modeling neutron capture and the synthesis of intermediate mass elements in stars.
Ultra-Diffuse Galaxies (UDGs) challenge current galaxy formation models within the ΛCDM framework, particularly regarding their dark matter content and formation histories. Globular Clusters (GCs) serve as excellent tracers for probing the halos of these faint systems; however, current spectroscopic facilities struggle to reach the depth required to fully characterize GC populations beyond the local neighborhood. In this work, we present the scientific potential of NEXUS@SHARP, a near-infrared multi-slit spectrograph proposed on the upcoming Extremely Large Telescope (ELT). We demonstrate that NEXUS is uniquely positioned to overcome current observational limitations by combining high spatial resolution with efficient multiplexing. We show that NEXUS can efficiently help to characterize the GC population in UDGs across diverse environments – out to 60 to 70 Mpc – with a few hours of ELT time. These capabilities will allow for precise measurements of radial velocities and stellar populations, enabling robust dynamical mass estimates and distinguishing between competing UDG formation scenario.
Solar magnetic flux evolution fundamentally drives solar variability, whose atmospheric effects are traditionally assessed through various solar activity proxies. Building upon our previous findings on strong flux density relationships, we present a comprehensive analysis of daily weak flux densities (WFDs) derived from Solar Dynamic Observatory/Helioseismic Magnetic Imager data, categorized into five magnetic threshold ranges. We examine their relationships with two key solar activity proxies: MgII index and f10.7 cm. Our statistical analysis, employing Pearson correlations complemented by correlograms, wavelet analysis, and MSSA analysis reveal distinctive patterns in WFD-proxy relationships. Notably, WFDs of 1 to 3 demonstrate robust positive strong correlations and WFD4 shows moderate correlations with the MgII index with 0 lag, suggesting that the variables WFDs 1-4 and the MgII index appear to exhibit synchronous effects. Most WFDs show moderate correlations with the activity proxies, except for WFD5 , which displays weak correlations. Wavelet analysis reveals that WFD2 and the MgII index maintain a consistent phase relationship, characterized by coherent rightward-pointing arrows within confidence intervals, while WFD3 shows similar but less consistent phase patterns. Moreover, the MSSA analysis confirms that the WFDs and solar activity proxies have a strong relationship. These findings establish WFD2, which defined in the ranges 60-100 G (active network), is the stronger contributor to MgII index variability on solar rotational timescales during the minimum phase This advances our understanding of solar magnetic flux-proxy relationships.
We present a detailed investigation of the spectral properties of X-ray point-like sources in the nearby spiral galaxy NGC 4631, located at a distance of ∼7.6 Mpc. Our analysis is based on 12 Chandra observations obtained during 2000 and 2023, complemented by XMM-Newton data from 2021. From this dataset, we identify 10 X-ray point-like sources with source counts ≥100, enabling detailed spectral modeling and variability analysis in some sources. Among these, X-4 and X-5 exhibit pronounced long-term variability, with X-5 emerging as the brightest source in NGC 4631, reaching a peak luminosity of ∼6.8−0.3+0.4×1039ergs−1. Both sources also show significant short-term variability on kilosecond timescales. The hardness-ratio evolution shows that X-5 and X-6 remain in a hard spectral state across all observed luminosity levels. The source X-2 is identified as a highly absorbed Ultraluminous X-ray source exhibiting a stable accretion regime, except for a temporary dip in luminosity during one observational epoch. In contrast, X-7 undergoes clear spectral state transitions, characterized by repeated episodes of spectral hardening and softening, along with detectable short-term variability. The remaining sources, X-3, X-9, X-10, X-11, & X-12, exhibit luminosities typical of X-ray binaries. Overall, NGC 4631 hosts a diverse population of transients, ULXs and persistent X-ray binaries.
Nuclear star clusters and supermassive black holes are the dominant compact components in galaxy nuclei. They can coexist within the same system, and their relative prominence traces the history of gas inflow, star formation, and dynamical evolution on parsec scales. Key questions remain open concerning the physical channels that assemble nuclear star clusters, the mass regimes in which supermassive black holes become dynamically dominant, and the conditions under which compact stellar nuclei are suppressed, destroyed, or replaced by cusp-like structures.We describe how near-infrared integral-field spectroscopy with SHARP on the Extremely Large Telescope, combined with high-resolution imaging from MICADO, enables quantitative tests of nuclear formation and evolution scenarios within a unified framework. The joint analysis of stellar dynamics, stellar populations, and nuclear structure allows black-hole masses, internal kinematics of nuclear star clusters, and signatures of gas inflow to be measured consistently within the same systems, and defines the mass and distance ranges where robust constraints can be obtained.Recent discoveries of compact active nuclei at high redshift indicate that efficient black-hole growth can occur in systems with weak or compact stellar components. Although nearby galaxies are not evolutionary analogues of early systems, the diversity of nuclear configurations accessible with SHARP and MICADO provides a local laboratory for isolating the physical mechanisms that regulate the coupled evolution of central black holes and nuclear stellar structures.
We present our results on the cataclysmic variable binary, the nova-like system V592 Cassiopeia. We use our own observational data obtained with the 2.0 m telescope at the National Astronomical Observatory (NAO) Rozhen, Bulgaria and data from TESS (The Transiting Exoplanet Survey Satellite). By photometric analysis on the data from the 2.0 m telescope, we estimate the periodicity in the brightness variations seen in the light curves of this object with amplitudes in the range 0.2-0.4 mag. We report an appearance of superhumps with periodicity: p(s & planckh;) = 0.1221 +/- 0.0003 d (2.930 +/- 0.03 h) and p(s & planckh;) = 0.1223 +/- 0.0003 d (2.935 +/- 0.03 h), in the U band during two nights. Flickering activity in the U and B bands are detected in all nights. The average dereddened color index is estimated as (U-B)(0) = -1.18 +/- 0.002 and it is lower than expected. We found variations with various amplitudes of the flux rate in the data from TESS for two time-intervals of observations: October 7-November 2, 2019 and April 16-May 12, 2020. A superhumps activity with periodicity of p(s & planckh;) = 0.1223 +/- 0.0003 d (2.935 +/- 0.03 h) over the first observational time-interval and p(s & planckh;) = 0.1225 +/- 0.0003 days (2.940 +/- 0.02 h) over the second observational time-interval are identified. Manifestation of flickering with amplitudes of approximate to 270-460 e-/s are also observed in the light curves during both intervals. Using the observational data, empirical curves of the effective temperature are constructed. We apply our model to build temperature distribution in the accretion disc of V592 Cas. Based on comparison of the effective temperature's radial profiles, we make a proven assumption for the presence of superhumps during the two observational intervals.
We present a new regular exact solution to the Einstein field equations describing compact stellar objects with anisotropic matter in the absence of electric field. The spacetime geometry is assumed to be static and spherically symmetric. A novel, singularity-free anisotropy ansatz is introduced, yielding a physically viable compact star model with mass and radius with close matching to compact objects GW190814 and GW200210. Hydrostatic equilibrium is investigated through the Tolman-Oppenheimer-Volkoff (TOV) equation. The model generates stellar masses and radii consistent with previously reported observational data. All stability and energy conditions are satisfied, and the gravitational metric potentials and matter variables exhibit regular and well-behaved profiles throughout the stellar interior.
In this article, we investigates the motion of three bodies in a rotating reference frame by incorporating additional perturbative forces arising from radiation pressure, albedo effects, and Stokes-type dissipative forces together with their corresponding components and directional axes. The locations of the equilibrium (Lagrange) points are determined for several real astronomical systems and their stability properties are examined in detail. The results indicate that the positions of the equilibrium points are significantly influenced by variations in the physical parameters associated with radiation pressure and albedo effects. To further explore the nonlinear dynamics of the system, Lyapunov characteristic exponents (LCEs) are computed for several representative trajectories in order to analyze the chaotic behavior of the orbits. Lyapunov exponents provide a quantitative measure of the sensitivity of the system to small variations in initial conditions, enabling the classification of orbital motion as regular, moderately chaotic or strongly chaotic. Numerical simulations are performed using a variational method combined with the modified Gram-Schmidt orthonormalization technique. The findings reveal that even trajectories traditionally considered regular can display substantial sensitivity to initial conditions, emphasizing the intrinsically chaotic nature of the three-body problem and its important implications for orbital predictability and space mission design.
This paper investigates two different dark energy stellar models within the context of teleparallel gravity theory. We formulate the modified field equations by considering a static and spherically symmetric interior spacetime. By applying suitable linear equations of state that relate dark energy components with the ordinary matter, we obtain solutions of the corresponding field equations. As the system of equations still remains under-determined, two different models, namely the polytropic equation of state and Karmarkar condition are also assumed to close it, which lead us to two different solutions. In this scenario, appropriate junction conditions are imposed to determine the unknown constants at the boundary of sphere. Furthermore, several physical requirements are examined to ensure that the obtained models are well-behaved and physically acceptable throughout the interior region. We also use the calculated data of a compact star for the case study together with different choices of the parameter values to graphically assess our models. The analysis finally indicates that both stellar solutions meet the conditions required for physical viability under certain parametric values.
The VRIC light curves were regularly measured for two eclipsing binaries, NSVS 01031772 and 2MASS J04100497+2931023 as part of our long-term observational project to study low-mass eclipsing binaries with a short orbital period and surface activity. The solution of the Tess light curves in Phoebe results in a detached configuration. Absolute parameters of all components were improved: for N103: M1=0.5475±0.0035 M⊙, R1=0.5297±0.0035 R⊙, M2=0.5038±0.0040 M⊙, R2=0.5217±0.0035 R⊙, for 2M0410: M1=0.639±0.045 M⊙, R1=0.655±0.035 R⊙, M2=0.609±0.045 M⊙, R2=0.631±0.035 R⊙, where the temperatures of the primary components were adopted according to previous studies. The spectral type of the primary components was confirmed to be M4 and K5, and the mass ratio was derived as q=0.920±0.003 or 0.952±0.010, respectively. We propose the presence of a third body in these systems: in the case of N103, a companion with a minimal mass of 50 MJup, orbiting the eclipsing pair with a period of about 19 years, and in 2M0410 a third body with a minimal mass of about 0.1 M⊙ and a short orbital period of about 2.1 years. For N103, the hierarchical structure (2+1)+1 of a possible quadruple system was tested, but its stability was not proven. The characteristics and statistics of the flare events and dark regions on the surface of the components were estimated on the basis of the Tess and our own data. For N103, a mean frequency of flares of one per 40 h was determined. In the case of 2M0410, practically no flares were detected.
Supermassive black holes (SMBHs) are ubiquitous in massive galaxies, and their cosmic growth is commonly modeled with continuity equations describing the evolution of the black hole mass function (BHMF). We investigate the inverse problem associated with an accretion-driven cosmological continuity equation, focusing on the stability and identifiability of reconstructing earlier mass distributions from present-day observational information. We formulate and implement a numerical inversion framework to estimate the ancient SMBH population using synthetic present-day BHMFs contaminated with different levels of observational noise. Our analysis considers an idealized scenario in which black hole growth occurs exclusively through smooth mass accretion, without mergers or stochastic variability.The inverse framework consistently reproduces the present-day BHMF with good accuracy across all tested noise levels, while the reconstruction of the initial condition is significantly more sensitive to observational perturbations. Although the recovered initial distributions generally preserve the global structure of the reference solution, the associated errors exhibit substantial dispersion and non-monotonic behavior driven by nonlinearities, moderate parameter degeneracies, and local minima in the optimization landscape. Monte Carlo analyses further indicate that the inverse reconstruction remains numerically stable under different stochastic noise realizations, despite occasional outlier solutions.These results highlight the intrinsic ill-posedness of inverse mass-transport problems subject to single-redshift constraints. Although restricted to an accretion-only framework, the proposed methodology provides a controlled computational basis for studying inverse cosmological mass transport and establishes a benchmark case for future extensions that incorporate merger-driven growth and multi-redshift observational constraints.
Primordial binary open clusters (PBOCs), formed through the co-collapse of gas within the same molecular cloud, provide useful constraints on clustered star formation and early dynamical evolution in the Galactic disc. Although Gaia has substantially expanded the sample of PBOC candidates, observationally constrained studies of their dynamical evolution remain limited. As part of the Dali Binary Cluster Project (DL-BCP), we investigate the early dynamical evolution of four PBOC candidates using initial conditions based on Gaia Data Release 3 (Gaia DR3) and N-body simulations in a Galactic potential. We derived astrometric and structural parameters using Bayesian distance estimates and radial density profile fitting, and evolved the systems for 50 Myr while including stellar evolution, binary interactions, and Galactic tidal effects. P1 and P4 show continuous separation growth, increasing from 34.13 to 449.46 pc and from 35.96 to 189.47 pc, respectively, whereas P2 and P3 first contract from 52.70 to 12.30 pc and from 41.89 to 31.38 pc before re-separating to 408.48 and 72.93 pc at 50 Myr. The four systems therefore do not follow a single evolutionary pattern, and their dynamical behaviours may be associated with a combination of total mass, mass ratio, age, and density structure. These results provide observationally motivated dynamical constraints on the four PBOC candidates and offer a basis for future studies of similar systems.
The stellar initial mass function (IMF), which describes the distribution of stellar masses at birth, is a fundamental ingredient in shaping galaxy evolution. Recent observations indicate that the IMF varies between galaxies, depending on their mass, morphology, and stellar content. In local early-type galaxies (ETGs), spectroscopy, dynamics, and lensing reveal bottom-heavy IMFs in dense central regions, with radial gradients toward a Milky Way-like distribution in the outskirts. Yet, the chemical enrichment of massive ETGs implies a dominant role of massive stars during their early formation phases. These findings can be reconciled if the IMF evolves over cosmic time – initially more top-heavy to enable rapid enrichment, and later dominated by long-lived, low-mass stars. Directly measuring the IMF at z≳1 is therefore essential to test such time-dependent IMF scenarios, including variations in the dwarf-to-giant and stellar mass-to-light ratios. To date, no direct observational confirmation of these IMF variations – or of their physical origin – has been obtained. The SHARP spectrograph on the E-ELT, with unprecedented spatial resolution and sensitivity compared to facilities such as JWST, and broader spectral coverage than other E-ELT instruments, will enable spatially resolved spectroscopy of IMF-sensitive features in high-redshift ETGs up to z∼3, providing unique insights into the origin of the non-universal IMF in massive galaxies.
The Extremely Large Telescopes (ELTs), with their large apertures and cutting-edge Multi-Conjugate Adaptive Optics (MCAO) systems, promise to deliver data that is both sharper and deeper than even the James Webb Space Telescope (JWST) across large fields. SHARP is a concept study for a near-IR (0.95–2.45μm) spectrograph specifically designed to fully exploit the collecting area and angular resolution capabilities of the upcoming ESO’s ELT. The instrument concept is driven by the goal of tackling the most important questions in astrophysics and cosmology, from exploring primordial galaxies to studying the formation of young stellar object and planetary systems in the nearby dust-enshrouded regions, bridging the gap between the local and the distant Universe. This requires versatility to accommodate diverse observational needs. SHARP is composed of two main units: NEXUS, a Multi-Object Spectrograph (MOS) optimized for detecting the faintest sources, and VESPER, a multi-object Integral Field Unit (multi-IFU) designed for brighter ones. This article provides an overview of the scientific design drivers, the solutions developed to meet them, and the resulting optical design that achieves the required performance.
