The galaxy size–mass relation (SMR) is a key scaling relation used to constrain the physical processes that build galaxy structure, yet it is almost always measured in a single rest-frame optical band, where the light traces the bulk of the old stellar mass. Tracing younger populations with flux-weighted ages of ∼100–500 Myr and low-metallicity stars, the rest-frame near-ultraviolet opens a new stellar window on this scaling relation. Because each process redistributes the light of young and old stars differently, the same mechanism shifts the slope and zero point of the SMR by different amounts in the two wavelength regimes. Here we review and synthesize the effects of main physical processes on the form of the SMR for star-forming and quiescent galaxies in the rest-UV and optical. For each process, we start from its underlying physics, the galaxy stellar masses it affects, and the light it adds/removes/rearranges, anchoring the predictions to observations and simulations. We validate the predicted imprints with forward Monte Carlo modelling. The two-wavelength view breaks several degeneracies that single-band analyses cannot, most notably between minor mergers, dry major mergers, and adiabatic expansion. These results motivate joint rest-UV and optical SMR measurements with current and upcoming wide-field imaging surveys.
As images of the supermassive black holes Messier 87* (M87*) and Sagittarius A* (Sgr A*) from the Event Horizon Telescope (EHT) grow in number, we gain a better understanding of the typical conditions of the near-horizon region of these objects, and slowly approach a converged time-average of the black hole image. In this article, we briefly review the signatures of black hole spin that manifest most apparently in these time-averaged images. We divide our discussion between coarse spatial features that are accessible with time averages from terrestrial very-long-baseline interferometry (VLBI) at 230 and 345 GHz, and fine spatial features which require either the extension of VLBI at these frequencies to space or the operation of global VLBI at much higher frequencies. We find that, while both coarse spatial features available from the ground and fine spatial features available only from space can both greatly inform spin, the primary difference is the degree of sensitivity to unknown astrophysical conditions, with photon ring-dominated observables benefitting from the exponential suppression of the details of the accretion disk. We conclude that spin measurements from resolved features of strong lensing are likely to provide sharp (∼±10%) spin measurements of both M87* and Sgr A* in the near future.
Narrow-line Seyfert 1 (NLS1) galaxies host active galactic nuclei (AGN) with narrow optical emission lines of the broad-line region. This is often explained with a relatively lower mass of the central supermassive black hole and super-Eddington accretion. We compared the radio properties of large samples of NLS1 and broad-line Seyfert 1 (BLS1) galaxies compiled from the Sloan Digital Sky Survey. We cross-matched the NLS1 and BLS1 samples with the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) sky survey at 1.4 GHz and the first and second epoch data of the Very Large Array Sky Survey (VLASS) at 3 GHz. We calculated the radio spectral indices, the 1.4-GHz radio power, and the radio loudness. We found lower 1.4-GHz radio detection rates for the NLS1 galaxies. The median radio loudness values, the fraction of radio-loud AGN, and the median 1.4-GHz radio power are also lower for the NLS1 sample. The median spectral indices imply a slightly steeper radio spectrum for the NLS1 sample than for the BLS1 sample. Comparison of the star formation rates estimated from the radio data and the infrared measurements of the Wide-field Infrared Survey Explorer satellite indicated that more than half of the FIRST- and VLASS-detected NLS1 and BLS1 galaxies contain radio-emitting AGN.
Radio frequency interference (RFI) segmentation in Ku-band satellite communications remains challenging because of weak, non-stationary interference characteristics and the scarcity of pixel-level annotated empirical data. To address this limitation, this study proposes a synthetic-to-real deep learning framework in which four parameterized RFI morphologies—narrowband, broadband, impulsive, and frequency-varying—are superimposed onto empirical Ku-band spectrogram backgrounds acquired from a 12-m ground-station platform. A conditional Generative Adversarial Network (cGAN) is then employed for domain adaptation to reduce the synthetic-to-real gap by harmonizing the hybrid spectrograms with empirical thermal noise characteristics. The refined spectrograms and their exact binary masks are subsequently used to train a U-Net model for pixel-level segmentation. Quantitative evaluation on held-out empirical-background hybrid test data shows that the proposed framework achieves an Intersection over Union (IoU) of 0.849 and an F1-score of 0.918, outperforming traditional threshold-based methods and unrefined learning baselines. Additional qualitative validation on naturally observed empirical Ku-band RFI recordings further supports the practical applicability of the proposed framework beyond controlled hybrid test data. These results indicate that generative domain adaptation provides a practical and scalable alternative to manual labeling for automated RFI monitoring in operational Ku-band environments.
The well-established anti-correlation between disk winds and relativistic jets in X-ray binaries is often interpreted in a scale-invariant black hole accretion context. If so, active galactic nuclei (AGN) should exhibit a direct mass-scaled analog. We test this prediction across FRII radio quasars, radio-quiet quasars, and jetted and non-jetted Narrow Line Seyfert 1 galaxies (NLS1) in spirals, among others. They exclude simple scale invariance. The highest-velocity winds occur exclusively in radio-quiet quasars, while powerful FRII quasars host systematically weaker winds despite equally large black hole masses. Jetted NLS1s show strong wind suppression consistent with X-ray binary behavior, whereas FRII quasars occupy a distinct regime in which jets and winds coexist. Black hole mass and spin magnitude alone cannot account for this dichotomy. We argue that the angular momentum direction of the disk relative to that of the black hole (aligned versus anti-aligned or co-rotation versus counter-rotation) is the critical parameter: secularly fueled spiral systems and most post-merger systems favor co-rotation, which is associated with compact ISCO radii, high radiative efficiency, strong winds, and jet suppression, while the counter-rotating subset of merger-influenced ellipticals can sustain powerful jets alongside moderate winds. Moreover, while spiral AGN and merger-driven radio-quiet quasars experience similar strong jet/wind anti-correlation, they cannot be treated as strict scaled analogs of X-ray binaries, which undergo rapid state transitions involving magnetic flux redistribution absent in AGN. At least two distinct wind–jet regimes therefore operate across the mass scale. We identify the details of this behavior across AGN subclasses.
X-ray reflection spectroscopy provides one of the most powerful electromagnetic methods for measuring the dimensionless spin of accreting black holes. It has yielded spin constraints for stellar-mass black holes in X-ray binaries and supermassive black holes in active galactic nuclei, and is central to the science goals of current and future X-ray observatories. However, the technique is subject to observational and modeling systematics, including continuum-reflection degeneracy, limited spectral coverage, unresolved distant reflection or absorption, detector effects, source variability, accretion-state dependence, and assumptions inherent to reflection models. Motivated by discussions at the 2025 Wake Forest workshop *Recent Progress on Black Hole Spin Measurements Across the Electromagnetic and Gravitational Spectra*, we propose a practical framework for evaluating whether published reflection-based spin measurements should be considered robust, provisional, or not assessable from the available information. The framework is built on three principles: **detectability**, requiring an unambiguous relativistic reflection signal; **uniqueness**, requiring that the relativistic component be distinguishable from the continuum, distant reflection, absorption, and instrumental effects; and **robustness**, requiring that the inferred spin remain stable against reasonable changes in model assumptions, data selection, and accretion-state treatment. We translate these principles into assessment criteria, a quality-classification scheme, and a reporting checklist for future studies. Calibration of these criteria through dedicated simulations is outlined here and deferred to a companion paper. Our goal is to establish a reproducible path toward a community-maintained compilation of reliable black hole spin measurements for the high-throughput, high-resolution era of X-ray astronomy.
In this paper, we study the distribution of main-sequence stars over rotational velocities as a function of effective temperature. Using spectroscopic surveys, and after selecting main-sequence stars and retaining only high-quality data, we obtain a sample of 73,340 GALAH objects, 21,654 APOGEE objects, and 2262 Glebocki objects. For stars in the broad temperature range of 3500–8000 K, we analyse the vsini distributions in narrow 500 K bins, and find that in each bin the distribution follows a power law with the exponent varying systematically with temperature. For solar-type stars, the obtained magnetic braking index q is consistent with the Skumanich law.
We present a statistical study of low-surface-brightness (LSB) tidal structures in two large samples of edge-on disk galaxies. Our primary sample comprises 5606 galaxies from the Edge-on Galaxies In SDSS (EGIS) catalog, analyzed using imaging from the DESI Legacy Imaging Surveys, supplemented by Hyper Suprime-Cam Subaru Strategic Program (HSCSSP) data and deep Apache Point Observatory (APO) follow-up observations for selected objects. To assess the robustness of our results, we also examine an independent sample of 14,237 galaxies from the Edge-on Galaxies in the Pan-STARRS survey (EGIPS) catalog. All images were processed using a homogeneous procedure optimized for the detection of faint diffuse emission. Tidal structures were identified through visual inspection and classified into established morphological categories, with careful treatment of imaging artifacts and galactic cirrus contamination. We detected tidal features in 324 EGIS galaxies and 690 EGIPS galaxies, corresponding to incidence rates of 5.8% and 4.8%, respectively. Restricting the analysis to completeness-limited subsamples yields consistent fractions of 6.4% and 6.2%. At a typical DESI r-band surface-brightness depth of 28.6 mag arcsec−2, these values are consistent with previous observational studies but lower than predictions from many cosmological simulations. Recent high-resolution simulations, however, produce incidence rates much closer to those measured here, suggesting that numerical resolution, realistic modeling of observational and instrumental effects, and galaxy formation physics are all critical for accurately predicting the abundance of LSB tidal structures.
Active surface shape control is a key engineering technology enabling high-frequency operation and high-performance observations in modern large-aperture radio telescopes. By determining the achievable controllable accuracy of the primary reflector, its performance further constrains the aperture efficiency and long-term stability of telescope sensitivity. As millimeter- and submillimeter-wave astronomy advances toward higher operating frequencies and larger survey scales, key astrophysical questions increasingly demand the simultaneous achievement of high angular resolution, high surface-brightness sensitivity, and high imaging efficiency over wide fields of view. Limited by field-of-view coverage, sensitivity, or spatial-scale uniformity, traditional single-dish or interferometric array systems struggle to simultaneously satisfy these observational requirements. Consequently, large-aperture, wide-field millimeter/submillimeter single-dish telescopes are regarded as an important technological pathway for achieving multi-scale, high-fidelity observational capability. Their performance critically depends on effective control of primary reflector accuracy and system stability under multiple disturbance sources, such as gravity and thermal effects. From a system-level perspective, this paper provides an overview of the overall architecture of active surface control technologies for large-aperture millimeter- and submillimeter-wave single-dish radio telescopes. Focusing on three core components—surface measurement, actuator execution, and surface control strategies—it systematically reviews the underlying technical principles, representative engineering practices, technological evolution, and recent research progress. The characteristics of different technical approaches are summarized and analyzed, providing a reference for the design and further study of active surface control systems for large-aperture radio telescopes.
The optical counterpart of the gravitational wave event GW170817, known as kilonova, has provided strong evidence that binary neutron star mergers are favourable sites to host the r-process nucleosynthesis. Kilonova is a quasi-thermal electromagnetic emission powered by the radioactive decay of heavy neutron-rich nuclei produced by the r-process. Considering the variety of elements contributing to kilonova ejecta, essential information about its composition can be achieved through spectral characterisation, radiative transfer simulations, and opacities. The latter represents one of the most challenging aspects of the modelling, as it relies on accurate atomic structure calculations of energy levels and transitions. Since light r-process elements are major opacity contributors in early (<2 days) scenario, this work focuses on atomic calculations for Zr I–IV. Energy levels and bound-bound transitions are determined using the GRASP2018 code, assuming two different datasets for each ionisation stage: one including, and one excluding core-core and core-valence correlations. Results demonstrate that the inclusion of f shell and core correlations impacts on both energy levels and transitions. A systematic assessment of the accuracy is performed through detailed comparisons with the NIST ASD and literature references. Finally, these Zr data are integrated on the open access MARTINI platform.
Only recently, observational studies have started providing measurements for the barium isotopic ratio in metal-poor stars with unprecedented detail. This new approach can be extremely useful in tracing back the origin of neutron-capture elements, since the r- and s-process produce different amounts of barium isotopes, and their astrophysical sites of production are still largely unconstrained. We employ here a stochastic chemical evolution model of the Galactic halo to compare observations to theoretical predictions. We find that in the earliest phases of evolution, both r- and s-process sites are required, with the model and observations agreeing well for Sr, Ba and Eu, possibly requiring a slightly larger s-process production for Sr. The model can actually explain the mixture of r- and s-process material often observed in halo stars. This work shows how is it possible now to use isotopic ratios in addition to elemental ratios to obtain additional constraints useful for the Galactic Archaeology investigation.
Weak-lensing observations of the Perseus Cluster now indicate a massive sub-halo associated with NGC 1264 and a connecting mass bridge in a system long treated as a benchmark relaxed cool-core cluster. Perseus is also known from X-ray observations to host large-scale gas sloshing and an ancient cold front extending to several hundred kiloparsecs. This paper uses Perseus as a motivation for a narrower population question: do nominally relaxed clusters retain merger history information in residual mass–gas offsets after the obvious signatures of an active merger have faded? A candidate remnant stress–energy interpretation is introduced as one possible covariant language for such a long-lived structure, but the empirical test does not require acceptance of that interpretation. The work then carries out a literature-based pilot test using the cold front outer radius as an independent merger history proxy, published mass–gas or gas tracer offsets for relaxed/cool-core systems, and a separate control cohort of actively dissociative mergers. The resulting three-regime comparison separates young active mergers, relaxed low-offset systems, and relaxed systems with sourced offsets above 5 kpc. For all seven Regime 3 (relaxed, offset >5 kpc) systems with vetted cold front/history proxies and sourced mass–gas offset measurements, the directional rank-order association has the predicted sign, ρs=0.68, with pone-sided≈0.047 (ptwo-sided≈0.094, N=7). The one-sided statistic crosses the conventional 5% threshold. The sample mixes lensing–X-ray centroid offsets, BCG/X-ray peak offsets, and weak-lensing sub-halo separations, and the result is not a decisive population detection: it is a suggestive directional signal in a small heterogeneous archival pilot. Its significance is that a framework-derived directional diagnostic, specified before the sample was assembled, is non-zero in the predicted sense and can now be tested with a homogeneous weak-lensing/X-ray/SZ survey.
Neutron capture reactions provide essential nuclear physics input for modeling the synthesis of heavy elements in stars. The growing precision of stellar spectroscopy and isotopic measurements in presolar SiC grains now demands cross sections with improved accuracy over the full energy range, and access to unstable nuclei relevant to slow (s-) process branchings and the intermediate (i-) process. This article reviews recent progress in direct neutron capture measurements, focusing on time-of-flight (TOF) experiments at CERN n_TOF and complementary activation techniques. Substantial advances have been achieved for stable s-only and bottleneck isotopes, significantly improving constraints on s-process models. In parallel, the combination of high instantaneous neutron fluxes and advanced detector systems has facilitated first-time neutron capture measurements on several radioactive branching-point nuclei. Feasibility studies, however, reveal current limitations related to sample availability, background conditions, and restricted energy coverage. In this context, the complementarity between TOF and activation emerges as a central strategy. Future developments, including high-flux facilities and novel inverse kinematics experiments in ion storage rings, are expected to extend the boundaries of neutron capture measurements, overcoming current limitations and helping unlock new frontiers in our understanding of stellar nucleosynthesis.
Neutron capture reactions are the main contributors to the synthesis of heavy elements through the s-process. 22Ne(α,n)25Mg is the main neutron source in stars, together with 13C(α,n)16O. At energies Ecm < 700 keV, limited data are available, i.e., reaction cross-section upper limits from direct experiments and highly uncertain estimates from indirect sources exist. The ERC project SHADES is currently performing direct cross-section measurements at these energies. We will present details on the ongoing experiment and discuss target characteristics, experimental backgrounds, and preliminary analyses on the detector efficiency and the 832 keV resonance.
Space energy supply is critical for human space exploration, serving as the foundation to support long-term space missions and future permanent settlement beyond Earth. To date, humanity has developed a variety of technologies for space energy supply. However, due to the constraints of the space environment and the diversity of energy sources, the energy supply technologies adopted by space exploration missions mainly depend on the feasibility of energy acquisition. This review presents a systematic review of the technical principles, power supply devices, and practical applications of space energy supply systems. First, this review summarizes the technologies for space-based solar power generation and energy storage, as well as strategies for improving the efficiency of solar power generation in space. Next, an overview of dynamic power generation technologies and static power systems for space thermal energy is investigated, along with a performance evaluation comparing these two types of systems. Subsequently, the work reviews space nuclear power systems based on thermoelectric generation technology, discusses recent advancements in nuclear fusion research, and analyzes the feasibility of utilizing helium-3 (3He) fusion technology on the Moon. Finally, to address the challenges associated with the storage and transportation of space energy, the review also introduces the applications of battery and fuel cell technologies in space. This review also discusses the technical challenges faced by space energy supply systems and explores future development prospects, aiming to provide a reference for the comprehensive development and utilization of space energy in the future.
We investigate nucleosynthesis during very strong, non-dynamical recurrent He-flashes that are expected to occur in close binary systems hosting a carbon–oxygen white dwarf and a type-B subdwarf companion. In these systems, due to gravitational wave emissions, the subdwarf star is expected to fill its Roche lobe on a short timescale, resulting in mass transfer onto the companion. As accreted matter also deposits angular momentum, the external layers of the accretor begin to rotate very fast. So, dynamical He burning is avoided, and the WD instead experiences recurrent strong He flashes, which secularly reduce its mass. We consider the PTF J2238+743015.1 system as representative of the whole class of similar objects and compute its evolution by coupling our evolutionary code with a full nuclear network, including isotopes with a lifetime longer than 0.8 s. We find that during He-flash episodes, the delivered neutron flux is typical for the i-process nucleosynthesis, even if it is available for a very short time (1–10 h). As a consequence, only weak s-process nucleosynthesis takes place. The nucleosynthetic path in the ejected matter is quite similar to that of supernovae descending from massive stars. However, due to the rarity of these systems, as well as to the small amount of matter ejected during the He-flashes phase, their contribution to the evolution of the interstellar medium is negligible.
Filamentary structures are ubiquitous in the interstellar medium and play a key role in the evolution of molecular clouds and star formation. Their morphology and relative orientation with respect to magnetic fields have been widely used as a diagnostic of magnetohydrodynamic processes, turbulence, and gravitational accretion. In recent years, the growing availability of large continuum, spectroscopic, and polarization data stimulated the development of various filament detection techniques. In this review, we present a systematic overview of filament detection methods applied to observations of the interstellar medium. We classify the existing approaches into methodological categories, discuss underlying principles, illustrate their application on a same observational field, discuss limitations and advantages, in particular with respect to the studies of the relative alignment between magnetic fields and filaments. We conclude with presenting a point of view on the perspectives for filament studies in the era of ever-growing astronomical data volume.
Neutron-capture products, such as molybdenum (Mo) isotopes, are an important tool that cosmochemists use to constrain the stellar precursors of the Solar System and, potentially, the origin of life on Earth. Using high-precision Mo isotope data from meteorites and terrestrial samples, studies have attempted to reconstruct Earth’s formation by linking its composition to material sourced from various heliocentric distances. Debate, however, persists about the nature of Earth’s late-stage building blocks that accreted around the time the Moon formed and whether they delivered life-essential elements (i.e., carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur; CHNOPS), which are presumed to be more prevalent in the outer Solar System. Initially, it was proposed that the Moon-forming event involved the addition of material from both the inner and outer Solar System, thereby providing a mechanism for the delivery of a significant portion of life-bearing elements late in Earth’s formation. Recent advancements in analytical chemistry and their application to a wider range of samples than previously studied, however, led to a revised constraint: the Moon-forming event was dominated by inner Solar System material that was less enriched in CHNOPS, thereby relaxing the requirement for the delivery of a consequential amount of life-bearing elements late in Earth’s formation. A review of analytical approaches and findings is presented here to highlight the utility of neutron-capture products in constraining the origin of life on Earth.
The chemical composition of stellar atmospheres provides a valuable window into the complex processes of stellar nucleosynthesis. Among chemically peculiar cool stars, many objects are the products of mass transfer in binary systems, including most carbon stars, CH stars, and CEMP-s and CEMP-r/s stars. Accurate and precise determinations of heavy-element abundances in these systems serve as powerful tracers of neutron-capture nucleosynthesis operating in the slow (s) and intermediate (i) regimes. Such measurements also place important constraints on binary evolution, mass-transfer mechanisms, the onset of early s-process enrichment, and the astrophysical sites and production pathways associated with the i-process. In this work, we investigate the origin of the extremely metal-poor star HE 1005-1439, which has previously been suggested to exhibit a surface composition enriched by a combination of s- and i-process nucleosynthesis. Using new multi-zone, detailed AGB models for both the s- and i-processes, we find that a mixed i+s scenario provides a plausible explanation for the observed abundance pattern of HE 1005-1439, although a pure i-process AGB model yields an almost equally satisfactory fit.
Carbon–oxygen (C–O) shell mergers in the final evolutionary stages of massive stars play a critical role in shaping the pre-supernova structure and the resulting nucleosynthesis. In this work, we investigate the impact of such a merger on the production of elements beyond the Iron peak, focusing on an extremely metal-poor ([Fe/H]=−5) rotating 15 M⊙ stellar model. The results show that the merger favors the synthesis of weak s-process seeds and light p-nuclei, such as 88Sr, 94Mo, and 98Ru, via photodisintegration of heavier nuclei previously produced by rotational-induced nucleosynthesis. By simulating the subsequent core-collapse supernova explosion with a thermal bomb approach, we demonstrate that these chemical signatures are largely preserved, as the expanded structure of the merged shells significantly modifies the impact of the shock wave. These findings suggest that C–O shell mergers in early-generation stars could provide a primary-like source for intermediate and heavy elements, with important implications for the chemical evolution of the early Universe.
