Galaxies doi: 10.3390/galaxies14050082

Authors: Isaac Shlosman

Globally self-gravitating accretion disks in active galactic nuclei (AGN) have been frequently discussed in the literature, but never observed. A few dozen megamasering accretion disks in AGN have been detected, which display a clear Keplerian rotation on scales of 0.1–1 pc, allowing us to estimate their masses within the sphere of influence (SoI) of the central supermassive black holes (SMBHs) to be smaller by more than a factor of 10, compared with the parent SMBH masses. Furthermore, the stellar components, deep inside the SoI, are dwarfed by the SMBH masses of M•∼few×106–few×107M⊙. Theoretically, no limit exists on sizes and masses of gaseous disks in AGN, which in principle, can exceed masses of their central compact objects. We analyze instabilities which can operate in gaseous disks, i.e., fragmentation for a locally dominant self-gravity and spontaneous breaking of axial symmetry for the globally self-gravitating disks. We invoke the gas response to the latter instability which leads to gravitational collapse, leaving a negligible mass behind and dynamically stable remnants. Consequently, the characteristic timescale for globally self-gravitating disks to exist in AGN should not exceed few rotations, tϕ∼103–4 yrs for M•∼106–8M⊙. Disk rebuilding is expected to be ≳107 yrs, meaning that probability of finding is ≲10−3, which explains their lack of detection. We conclude that observed sub-parsec disks in AGN, at least the Keplerian masering ones, can be remnants of globally self-gravitating accretion disks, and the instability timescale can be related to the duty cycle of AGN, tduty~10tϕ~104–5 yr.

Galaxies doi: 10.3390/galaxies14040081

Authors: Angelo George Marcin Sawicki Ivana Damjanov

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.

Galaxies doi: 10.3390/galaxies14040080

Authors: Daniel C. M. Palumbo

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.

Galaxies doi: 10.3390/galaxies14040079

Authors: Rui Wang Lei Ding

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.

Galaxies doi: 10.3390/galaxies14040078

Authors: Krisztina É. Gabányi S. Komossa Attila Mezősi Emese Forgács-Dajka Sándor Frey

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.

Galaxies doi: 10.3390/galaxies14040077

Authors: Sylvia Biscoveanu

A decade after the first direct detection of gravitational waves, the growing catalog of hundreds of confirmed events is revealing new insights into the spins of stellar-mass black holes. Spin measurements have long been heralded as a promising tracer of compact-object binary formation and evolution, as different formation channels predict distinct spin signatures on a population level. In this review, we summarize the astrophysics, phenomenology, and current measurements of black hole spins. We begin with an overview of the predictions for black hole spin magnitudes and orientations from leading formation channels—isolated binary evolution, dynamical formation in clusters, formation in AGN disks, and hierarchical triples. We then describe the imprint of spin effects on the gravitational waveform and the measurability of spin in individual events. Finally, we review current population-level constraints on spin magnitudes, orientations, and effective spin parameters, including correlations with mass and redshift, and discuss their astrophysical implications. We conclude by highlighting open questions and future prospects, emphasizing how improved detector sensitivity will enable increasingly precise spin measurements for both individual events and the binary black hole population as a whole.

Galaxies doi: 10.3390/galaxies14040076

Authors: Haifan Zhu Wei Wang Wen Yang Mariano Méndez Chenxu Gao Ziyi Xu Pengfu Tian

We report a timing and spectral study of the 2024 outburst of the Be/X-ray binary pulsar 2S 1553-542 using NuSTAR and NICER observations. From the NuSTAR light curve, we measure a pulse period of 9.285022±0.000001 s. The energy-resolved pulse profiles are dominated by a single peak and show a wing-like structure most clearly in the 12–22 keV band. The pulsed fraction remains above 60% and increases with energy. The phase-averaged NuSTAR spectrum is described by an absorbed blackbody plus cutoff power-law continuum, together with an iron emission line and a cyclotron absorption feature. Using the cyclabs model, we obtain a cyclotron energy of Ecyc≃24.1 keV, corresponding to a magnetic field strength of B∼3×1012 G. Phase-resolved spectroscopy shows that the continuum and cyclotron-line parameters vary with pulse phase, and that the line becomes poorly constrained around the pulse-wing phase. We also searched the short NICER GTIs for transient mHz variability using wavelet analysis and a CEEMDAN-based Hilbert–Huang transform. Localized excesses near ∼10 mHz and ∼20 mHz are found, but the short exposures, COI effects, red-noise fluctuations, and the lack of a well-constrained Fourier peak limit their significance. We therefore treat them as candidate mHz variability rather than firm mHz QPO detections.

Galaxies doi: 10.3390/galaxies14040075

Authors: Sebastiano Ettore Spoto

MARS (mineral–organic–aqueous reactor systems) theory is presented as a formal theory for planetary astrobiology, with Martian environments represented as coupled reactor–filter systems. Its central proposition holds that prebiotic synthesis, metabolic plausibility, and biosignature preservation are physically coupled, although their maxima may occur in different places, times, or mineral assemblages. Partial overlap is both allowed and expected; complete co-location is regarded as a restrictive scenario. Admissible states satisfy elemental and charge conservation, non-ideal activity relations, mineral-saturation constraints, reaction-affinity conditions, and cross-domain transport compatibility. Brines, reactive minerals, redox gradients, irradiation, burial, diagenetic overprint, impacts, volcanism, and hydrothermal alteration can therefore enhance one function while suppressing another. Time-dependent atmospheric and redox boundary conditions, cryo-thermal cycling, exogenous catalytic minerals, shock mineralogy, and post-impact hydrothermal circulation are incorporated as sign-variable controls. An illustrative reduced-state ensemble shows the internal logic of window displacement; it does not constitute a calibrated uncertainty analysis or a planet-wide simulation. The theory yields operational thresholds, observable tests, and falsifying outcomes for rover and returned-sample investigations without constituting evidence that life existed on Mars.

Galaxies doi: 10.3390/galaxies14040074

Authors: Dimitris M. Christodoulou Demosthenes Kazanas Silas G. T. Laycock

We introduce a new method of dimensional analysis based on complete systems of units, such as the metric and Planck systems, in which fundamental dimensionless constants arise naturally. In fact, it is the reformulated Planck system that communicates its dimensionless constants to the metric or any other system. The method reveals additional complex dynamical scales and physical effects beyond those amenable to conventional dimensional analysis. We formulate our strategy in simple settings involving pairs of seemingly unrelated constants, and then we extend the analysis to more complicated cases involving combinations of three to five well-known universal constants. In constructions involving several unrelated constants, the method captures increasingly complex effects and places two or more disparate physics areas into a single framework connecting them by never-before-seen combinations of fundamental dimensionless constants, such as the fine-structure constant and the gravitational coupling constant. Thus, this method provides a pathway to blending descriptions of two or more fundamental interactions that have so far eluded a consistent theoretical formulation.

Galaxies doi: 10.3390/galaxies14040073

Authors: Francesco Calura

Despite the small mass fraction typically observed for the interstellar medium, dust plays a significant role as a key component of galaxies, affecting a wide range of properties. This review focuses specifically on how dust grains influence interstellar chemical abundances and on the processes that regulate the evolution of the galactic dust budget. I describe the main physical processes regulating dust evolution, including production by stars and other sources, destruction in supernova shocks and interstellar growth, and the ways in which they are included in galactic chemical evolution models. I discuss the main effects of interstellar dust on the abundances measured in various high-redshift systems that include Damped Lyman α absorbers, detected along the lines of sight of distant quasars and in the absorption spectra of Gamma Ray Burst afterglows. I discuss the measure of dust masses in galaxies and review its global budget, evaluated through the study of the evolution of the comoving dust mass density, for which I present an up-to-date compilation of data chosen from the literature. Interstellar dust growth plays a critical role in regulating the dust budget, for which I present a list of evidence both in favour of it and against. The dust budget at high redshift is one aspect that requires attention to drive significant progress in the future, along with the investigation of the properties of dust in local, low-metallicity systems. Our poor theoretical knowledge of basic aspects related to dust evolution evidences the need for a new high-sensitivity space telescope operating in the far-infrared regime, still awaited by the community since the demise of Herschel.

Galaxies doi: 10.3390/galaxies14040072

Authors: David Garofalo Chandra B. Singh Atticus Magerko Marco Botello Sophia Soto Max North

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.

Galaxies doi: 10.3390/galaxies14040071

Authors: Javier A. García Riley Connors Laura W. Brenneman James F. Steiner

X-ray reflection spectroscopy provides one of the most effective electromagnetic routes to measuring the dimensionless spin parameter of accreting black holes. The method has produced spin constraints for both stellar-mass black holes in X-ray binaries and supermassive black holes in active galactic nuclei, and it is central to the science objectives of present and future X-ray telescopes. At the same time, this method is vulnerable to a set of coupled observational and modeling systematics: continuum-reflection degeneracy, insufficient passband, unresolved distant reflection or absorption, detector effects, source variability, accretion-state dependence, and assumptions built into the reflection model itself. This article synthesizes the talks and discussions held at the 2025 Wake Forest workshop Recent Progress on Black Hole Spin Measurements Across the Electromagnetic and Gravitational Spectra; motivated by them, we propose a practical quality-control framework for assessing whether a published reflection-based spin measurement should be treated as robust, provisional, or not assessable from the published information alone. We organize the problem around three pillars: detectability, meaning that the relativistic reflection signal is unambiguously present in the data; uniqueness, meaning that the relativistic component can be separated from the continuum, from distant reflection, absorption, and instrumental effects; and robustness, meaning that the inferred spin is stable against plausible changes in model assumptions, data selection, and accretion-state treatment. We then translate these principles into applicable criteria, a tiered quality-classification scheme, and a reporting checklist for future analyses. The quantitative calibration of each criterion requires a dedicated campaign of simulations over realistic scenarios, which we outline here and defer to a future publication. We aim to define a reproducible path toward a curated, community-maintained compilation of reliable spin constraints and to guide the implementation of reflection spectroscopy in the high-throughput, high-resolution era.

Galaxies doi: 10.3390/galaxies14040070

Authors: Kyle R. Adams Aleksandr Mosenkov Jonah Seguine Lydia Stacey Thea Spigarelli Jonah George

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.

Galaxies doi: 10.3390/galaxies14040069

Authors: Nikolai Kondratev Ekaterina Malik Arseniy Sachkov Oleg Malkov

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.

Galaxies doi: 10.3390/galaxies14040068

Authors: Peter D. Morley

The author wishes to make the following correction to his paper [...]

Galaxies doi: 10.3390/galaxies14040067

Authors: Sergey S. Savchenko Ilia V. Chugunov Alexander A. Marchuk Vladimir P. Reshetnikov Matvey D. Kozlov Dmitry I. Makarov Aleksandra V. Antipova Anastasia M. Sypkova

Radial brightness profiles of disk galaxies often exhibit so-called breaks—locations where their exponential-scale length abruptly changes. Some galaxies have downbending (Type II) breaks, where their brightness decays faster in outer regions, while other have upbending (Type III) breaks, resulting in more extended outer disks or envelopes. Disk radial profiles without any breaks (Type I) appear to constitute a minority. The exact fractions of different break types depend on many galactic parameters—such as Hubble type, stellar mass, spatial environment, and bar presence—and vary significantly across different studies. Another source of discrepancy is the orientation of galaxies: projection effects may play an important role in break detectability. In this work, we utilize DESI Legacy DR10 imaging to perform photometric decomposition of a sample of 375 edge-on galaxies and investigate their radial breaks. We find that the vast majority (≈90%) of disks in our sample have Type II breaks, which is a considerably higher fraction than in many previous works (∼50%). We carefully tested our results to check if observed breaks can be a result of flaring or two-disk composition. We showed that a high fraction of Type II breaks can be attributed to projection effects, which enhance the observed surface brightness of breaks in edge-on galaxies.

Galaxies doi: 10.3390/galaxies14040066

Authors: Emanuele Spitoni Gabriele Cescutti Ivan Minchev Francesca Matteucci

Understanding how spiral structures influence the chemical evolution of the Galactic disc remains a key issue in Galactic archaeology. Recent advances in two-dimensional chemical evolution modeling allow us to account for the impact of multiple spiral arm patterns, each characterized by different pattern speeds, on the redistribution of elements throughout the Galaxy. In this work, we explore the influence of multi-pattern spiral arms on the radial abundance gradients of heavy elements in the Galactic disc. We focus on a scenario in which, during the most recent stage of evolution, corotation spans the entire disc. Our results indicate that the observed dispersion in the abundance gradients of O, Fe, Eu, and Ba, as traced by Cepheids, can be successfully reproduced if all galactocentric radii have effectively acted as corotation regions over the past 1–3 Gyr. We also note that such an extended phase has previously been identified as necessary to explain the azimuthal abundance variations reported in Gaia DR3 and Gaia-ESO survey data along local and inner spiral arms.

Galaxies doi: 10.3390/galaxies14040065

Authors: Diana Ryder Joel Kastner Paula Moraga Baez

Morpho-kinematic modeling of planetary nebulae (PNe) is important in reconstructing the three-dimensional structure and dynamics of PNe in an effort to understand their formation histories. Here, we present a flexible, modular method for 3D morpho-kinematic modeling of spatial–spectral mapping observations of PN molecular line emission. We show how a combination of basic geometric elements (an ellipsoid for the main nebula, an ellipsoidal mask for a lack of emission or cavity, and an elliptical ring for extended emission) can effectively reproduce the basic geometries and kinematics of the molecular emission regions of PNe, thereby providing constraints on key PNe parameters, including expansion velocity, physical size, and (hence) dynamical age. We apply PyPVNe to SMA and ALMA CO data cubes obtained for the PNe NGC 6720, NGC 3132, and Hubble 5. The results demonstrate the potential of our simple morpho-kinematic modeling methodology to investigate the origins and structural evolution of these and other molecule-rich PNe.

Galaxies doi: 10.3390/galaxies14040064

Authors: Siwagorn Pavitpok Montree Kumngern Pattarapong Phasukkit

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.

Galaxies doi: 10.3390/galaxies14040063

Authors: Stuart Marongwe Stuart Allan Kauffman

We present a novel method for deriving radially resolved dynamical chronometers from galaxy rotation curves, allowing galaxy assembly histories to be reconstructed directly from kinematic data. In the Nexus Paradigm, the baryonic Tully–Fisher relation is used to estimate the dynamical mass profile. We compare this profile with independently derived intrinsic baryonic mass distributions obtained from stellar Sérsic fits and gas surface-density measurement yields. This yields a radial ratio that maps to formation redshift with radial resolution. Inverting this ratio within a standard cosmological framework produces a radial lookback-time profile, representing the time since each radial shell last experienced dynamical reconfiguration. Applying the method to a pilot sample of seven SPARC galaxies, including both high- and low-surface-brightness systems as well as the Milky Way, reveals diverse age structures: stratified profiles associated with inside-out growth and flatter profiles consistent with coherent disk assembly. The method requires no dark-matter halo fitting and offers a kinematic chronometer that complements stellar population and chemical evolution approaches. The NP rotation-curve parameters were determined by minimizing the chi-squared statistic between the observed and predicted velocities using a two-stage optimization consisting of a global differential-evolution search followed by nonlinear least-squares refinement. Observational uncertainties were taken from the published rotation-curve data, supplemented by a 5 km s−1 systematic error floor added in quadrature to account for non-circular motions and other unresolved systematics. We also show that the governing dynamical equation admits a gravitoelectromagnetic interpretation, in which a velocity-dependent term generates disk-wide torques that regulate angular momentum transport. This leads to a unified stability framework in which galaxy morphology emerges from a single parameter regime: balanced conditions favor a coherent spiral structure, whereas dynamically hot regimes naturally produce diffuse and ultra-faint systems. The cosmological scaling of the effective gravitomagnetic field further suggests that the spiral structure is partly regulated by cosmic time. Although the inferred ages depend on the accuracy of the baryonic mass reconstruction and on the local validity of the evolving baryonic Tully–Fisher relation, our results show that rotation curves encode time-resolved dynamical information. This establishes the radial dynamical chronometer as a new observable for studying galaxy evolution and testing gravitational frameworks.

Galaxies doi: 10.3390/galaxies14040062

Authors: Matteo Bezmalinovich

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.

Galaxies doi: 10.3390/galaxies14030061

Authors: Alexander A. Marchuk Sergey S. Savchenko Dmitry I. Makarov Vladimir P. Reshetnikov Ilia V. Chugunov Matvey D. Kozlov Aleksandra V. Antipova Anastasia M. Sypkova Evgenii V. Rubtsov Dmitry V. Bizyaev

We present the EGIDE (Edge-on Galaxies in the DESI survey) project—a catalog of 149,215 edge-on galaxy candidates created using the data of the DESI Legacy Imaging Survey DR10 images. The catalog size is ten times greater than its predecessor and covers more than half of the sky. It is constructed in an automatic way, utilizing the full power of manual annotations from the GalaxyZoo volunteers, implemented in the Zoobot neural model, which was fine-tuned to search for edge-on galaxies specifically. To ensure the credibility of the dataset, subsequent manual supervision was performed. The EGIDE catalog provides homogeneous SExtractor photometry in the griz bands, total stellar mass estimates, redshifts for 98% of the sample, star formation rates, and other information. All of this is publicly available at The Edge-on Galaxy Database site. The preliminary analysis focused on differences between edge-on galaxies in the so-called blue sequence and red cloud populations. These galaxies demonstrate distinct properties: the number of redder galaxies decreases with increasing a/b ratio faster than that of the bluer galaxies; galaxy thickness varies with galaxy color: red sequence galaxies are thicker than blue cloud galaxies; the flattening ratio q=b/a increases significantly with total stellar mass M★ only among redder cloud galaxies. It is an intriguing result that the same trend of q increasing at the high-mass end is detected by both the statistical models of figures of revolution and direct observations of edge-on galaxies in EGIDE independently. The full extent of this relationship’s validity can only be determined after properly accounting for the contributions of the bulge and the PSF.

Galaxies doi: 10.3390/galaxies14030060

Authors: Zahra Al Federico Soto-Badilla Yüksel Karataş Gerardo Ramos-Larios Roberto Vázquez

We present a morphokinematic analysis based on high-resolution long-slit echelle spectroscopy of the [N ii]λ6583 line and narrowband imaging. Position–velocity diagrams reveal asymmetric expansion and localized kinematic features. We derive a systemic velocity of VsysLSR=−25±1 km s−1 (VsysHEL=−34±1 km s−1) and a main shell expansion velocity of Vexp=22±1 km s−1. Three-dimensional modeling indicates an ellipsoidal main body surrounded by a thin shell, two ear-like protrusions, and additional small-scale structures. The corresponding kinematic ages are 3600±700 yr for the ellipsoid and ring, and 7500±1000 yr and 8800±1500 yr for the two opposite ear-like protrusions, respectively, indicating that these outer structures predate the main nebular envelope. The kinematic asymmetry and enhanced emission regions suggest evolution within a non-uniform ambient medium. At the same time, the presence of collimated ear-like structures is consistent with shaping influenced by binary interaction, where earlier outflows preceded the ejection of the dense shell. NGC 6563 therefore appears to be a dynamically evolved system shaped by the combined effects of episodic mass ejection and environmental interaction.

Galaxies doi: 10.3390/galaxies14030059

Authors: Jorge Lerendegui-Marco Javier Balibrea-Correa Victor Babiano-Suarez César Domingo-Pardo Gabriel de la Fuente-Rosales Bernardo Gameiro Ion Ladarescu Ariel Tarifeño-Saldivia Pablo Torres-Sánchez Oliver Aberle Victor Alcayne Simone Amaducci Michael Bacak Jesús Bartolomé Aparna Basavaraja-Allannavar Ana-Paula Bernardes Eric Berthoumieux Roland Beyer Matthew Birch Selin Birincioglu Marian Boromiza Damir Bosnar Benedetta Brusasco Manuel Caamaño Aline Cahuzac Francisco Calviño Marco Calviani Daniel Cano-Ott Adrià Casanovas Donato Castelluccio Francesco Cerutti Gabriele Cescutti Enrico Chiaveri Gerardo Claps Paolo Colombetti Nicola Colonna Patrizio Console Camprini Guillem Cortés Miguel Cortés-Giraldo Luigi Cosentino Sergio Cristallo Angelica D’Ottavi Maria Diakaki Mario Di Castro Augusto Di Chicco Mirco Dietz Emmeric Dupont Ignacio Durán Zinovia Eleme Sylvain Fargier Martin Farkas Beatriz Fernández-Domínguez Paolo Finocchiaro Will Flanagan Varvara Foteinou Valter Furman Aman Gandhi Francisco García-Infantes Aleksandra Gawlik-Ramięga Gianpiero Gervino Simone Gilardoni Enrique González-Romero Styliani Goula Erich Griesmayer Carlos Guerrero Frank Gunsing Carlo Gustavino Jan Heyse William Hillman Elizabeth Jacoby David Jenkins Erwin Jericha Arnd Junghans Ulli Köster Yacine Kadi Nasser Kalantar-Nayestanaki Kalliopi Kaperoni Myroslav Kavatsyuk Michael Kokkoris Sotirios Kopanos Yury Kopatch Milan Krtička Nikolaos Kyritsis Claudia Lederer-Woods Giuseppe Lorusso Alice Manna Trinitario Martínez Marco Martínez-Cañada Alessandro Masi Cristian Massimi Pierfrancesco Mastinu Mario Mastromarco Emilio-Andrea Maugeri Annamaria Mazzone Emilio Mendoza Alberto Mengoni Veatriki Michalopoulou Paolo Milazzo Jacob Moldenhauer Riccardo Mucciola Elizabeth Musacchio González Agatino Musumarra Alexandru Negret Emmanuel Odusina Dimitrios Papanikolaou Carlos Paradela Albert Parmenter Nikolas Patronis José Antonio Pavón Maria Pellegriti Pablo Pérez-Maroto Alberto Pérez de Rada Fiol Giulio Perfetto Jarosław Perkowski Cristina Petrone Nicholas Pieretti Luciano Piersanti Elisa Pirovano Ignacio Porras Javier Praena José-Manuel Quesada René Reifarth Alejandro Reina Dimitri Rochman Yuriy Romanets Annie Rooney Gerard Rovira Carlo Rubbia Adrián Sánchez-Caballero Nicolás Sánchez-Vázquez Rudra N. Sahoo Daniele Scarpa Gavin Smith Nikolay Sosnin Michele Spelta Krzysztof Stasiak Giuseppe Tagliente Antonella Tamburrino Diego Tarrío Giorgios Tsiledakis Stanislav Valenta Pedro Vaz Gianfranco Vecchio Diego Vescovi Vasilis Vlachoudis Rosa Vlastou Anton Wallner Christina Weiss Tobias Wright Renjie Wu Roberto Zarrella Petar Žugec

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.

Galaxies doi: 10.3390/galaxies14030058

Authors: Maurizio Maria Busso

This review traces how our understanding of low- and intermediate-mass stars (hereafter LMS and IMS, respectively) evolved in time, in parallel with our knowledge of slow neutron-capture phenomena (the s-process). I shall focus in particular on the main component of this nucleosynthesis phenomenon, occurring in the above-mentioned stars close to the end of their lifetimes. They start ascending the Asymptotic Giant Branch (AGB), where both H- and He-shells exist, burning alternatively during the phases most relevant to our discussion: the so-called thermal pulses (hence, the name of TP-AGB stages for the final evolutionary period of these stars). I shall outline how such final stages were discovered to be a crucial source for neutron captures. Finally, I will briefly discuss what observational constraints and nuclear measurements have taught us about the status of our theoretical models in this field of nuclear and stellar physics.

Galaxies doi: 10.3390/galaxies14030057

Authors: Bidzina Kapanadze

BL Lacertae objects (BL Lacs) are active galactic nuclei notable for beamed emission generated in the relativistic jets, forming a small angle with respect to our line-of-sight. The broadband spectra of BL Lacs show a two-component spectral energy distribution (SED). The group of high-energy-peaked BL Lacs (HBLs) exhibit their lower-energy SED peak at the UV to X-ray frequencies. Consequently, these objects are generally bright in the 0.3–10 keV band (compared to other blazar subclasses) and allow us to carry out intense timing/spectral studies on the wide range of timescales (from years down to a few minutes). Although X-ray emission of HBLs is widely accepted to have a synchrotron origin (along with the occasional presence of the inverse-Compton component), many problems associated with the jet particle content, their acceleration up to ultra-relativistic energies and unstable mechanisms responsible for the extreme flux/spectral variability still remain to be solved. This review highlights the basic timing and polarimetric and spectral results obtained in the framework of the numerous studies of HBLs in the 0.3–10 keV band, which was covered by the X-ray instruments operating onboard the different space missions. Moreover, the plausible physical processes responsible for the observed HBL features (relativistic shocks, magnetic reconnection, turbulence etc.) are also addressed.

Galaxies doi: 10.3390/galaxies14030056

Authors: Bo Liu Guoqing Zhang Chang Wang Lei Song Le Ouyang

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.

Galaxies doi: 10.3390/galaxies14030055

Authors: Xuan-Dong Jia Xin-Yi Dai Yu-Peng Yang Fa-Yin Wang

The ΛCDM cosmological model has been successful in explaining many astronomical observations. However, recent observations increasingly point to deviations from the standard ΛCDM framework. Among these, one of the most significant discrepancies is the Hubble tension, which refers to the difference in values obtained for the Hubble constant H0 from high-redshift measurement and local observation. To address this issue, numerous cosmological models and methodological approaches have been proposed. This review offers a concise overview of recent progress in resolving the Hubble tension. The combination of Dark Energy Spectroscopic Instrument (DESI) Baryon Acoustic Oscillations (BAO) and uncalibrated Type Ia supernovae data yields a value for H0 that is significantly higher than the ΛCDM predication based on early-universe probes, even without incorporating local distance ladder constraints. This result indicates that the origin of the Hubble tension lies in new physics at low redshifts. Our findings suggest that although many unresolved systematics persist in current observations, they are insufficient to account for the magnitude of the current Hubble tension. This implies the likely existence of new physical mechanisms that have yet to be discovered.

Galaxies doi: 10.3390/galaxies14030054

Authors: Ileana Andruchow Ezequiel J. Marchesini Florencia L. Vieyro

Since their discovery almost 60 years ago, BL Lac objects have been defined by their strong optical variability and their classification in the spectral energy distribution scheme. High-synchrotron-peaked BL Lacs (HBLs) are those whose synchrotron component peaks at frequencies higher than UV/X-rays. Historically, optical variability studies have focused mostly on their counterparts, low-synchrotron-peaked BL Lacs (LBLs), since HBLs have shown weaker optical variability. However, a population-wide study of HBL optical variability is still lacking, and it remains unclear whether HBLs are intrinsically less optically variable as a class or whether this reflects observational biases. Only a handful of HBL sources have been studied extensively due to their strong variability and reported periodicity. These sources have motivated several theoretical models, often conflicting, to explain the optical variability when present. Nevertheless, understanding the connection between the apparent weaker optical variability and the emission processes of HBLs remains a challenge. In this work, we review the current state of knowledge on this topic, with the expectation that upcoming optical monitoring observatories, such as the Vera C. Rubin, will provide new insights into the optical emission (and variability) mechanisms in HBLs.

Galaxies doi: 10.3390/galaxies14030053

Authors: Dana Alina

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.

Galaxies doi: 10.3390/galaxies14030052

Authors: Shawn Hackett

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.

Galaxies doi: 10.3390/galaxies14030051

Authors: Mahiguhappriya Prakash Susmita Das Harinder P. Singh Nitesh Kumar

RR Lyrae stars are pulsating variables crucial for distance determination and galactic structure studies. Metallicities of fundamental-mode (RRab) RR Lyrae stars are commonly derived from photometry using empirical relations involving the Fourier parameter ϕ31 and the pulsation period. We present a new, calibrated G-band relationship between pulsation period P, Fourier parameter ϕ31, and metallicity [Fe/H] for galactic RR Lyrae stars from the Gaia survey. A set of 72 fundamental mode RR Lyrae stars were identified for deriving the relation in the G-band after visual examination of their light curves. Unlike recent large-scale calibrations, our relation prioritizes calibration purity by anchoring exclusively to a homogeneously analyzed sample of high-resolution spectroscopic metallicities from the literature. Our best fit relation is [Fe/H]=(−6.93±0.58)−(6.04±0.37)P+(1.65±0.11)ϕ31. We compare the [Fe/H] predicted by our relation for the stars in our calibration sample with that obtained from previously established relations in the G-band using different approaches. Our calibrated G-band P-ϕ31-[Fe/H] relationship demonstrates high reliability when validated against spectroscopic data, achieving a negligible bias of 0.00 dex and an empirical RMS scatter of 0.26 dex. Furthermore, by applying an Orthogonal Distance Regression (ODR) routine that fully propagates parameter covariance, we establish a mathematically strict empirical baseline whose theoretical uncertainties perfectly align with this observed dispersion. We find that the inclusion of the R21 Fourier parameter offers no significant improvement in metallicity estimation. Comparisons with literature confirm that our linear relation aligns closely with other Gaia DR3-based studies, while offering improved precision over older DR2-based relations.

Galaxies doi: 10.3390/galaxies14030050

Authors: Júlia M. Sisk-Reynés Christopher S. Reynolds James H. Matthews Dominic J. Walton Joanna M. Piotrowska James F. Steiner Javier A. García Angelo Ricarte

Understanding the growth of supermassive black holes (SMBHs) requires observational constraints on how their angular momentum—or spin—varies with mass, since the relative importance of coherent accretion, chaotic accretion, and mergers will be reflected in SMBH spin populations. Here we present an updated compilation of reflection-based SMBH spin measurements from the literature and assemble a set of ancillary quantities of interest for each SMBH (including redshift, Eddington ratio, and X-ray luminosity). No obvious apparent correlation between the Eddington-scaled accretion rate and the black hole spin is seen, noting that formal statistical tests are beyond the scope of this review. We discuss the limitations of using this heterogeneous mass–spin sample to test predictions of SMBH growth from semi-analytic models and cosmological simulations, emphasizing the need for a more uniform sample. We then highlight the encouraging prospects enabled by the next-generation NewAthena X-ray flagship observatory. Finally, we summarize how hierarchical Bayesian population inference applied to observed SMBH mass–spin populations will constitute a powerful framework for confirming tentative mass–spin trends in future samples.

Galaxies doi: 10.3390/galaxies14030049

Authors: Federico Rizzuti Gabriele Cescutti Linda Lombardo Lorenzo Roberti Tatyana Sitnova

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.

Galaxies doi: 10.3390/galaxies14030048

Authors: Aritrya Paul Shreya Banerjee

In this work, we examine viable models of f(Q,T) gravity theories against observational data with the aim to constrain the parameter space of these models. We have analyzed four different models of f(Q,T) gravity and tested them against against late-time background probes: Cosmic Chronometer (CC), Baryon Acoustic Oscillations (DESI BAO), Pantheon+ and Gravitational wave(GWTC-3) data. We put stringent constraints on the f(Q,T) gravity models, f(Q,T)=αQ+βT, f(Q,T)=αQn+βT, f(Q,T)=−αQ−βT2 and f(Q,T)=αQ−2T2 along with other late-time cosmological parameters such as deceleration parameter (q0), equation of state parameter (w0), sound horizon distance (rd) and demonstrate their alignment with the ΛCDM model and the observational data. We show that these models have the capability to alleviate the Hubble tension in late time universe, by predicting the present value of the Hubble parameter close to 74 km/s/Mpc. f(Q,T) gravity theory introduces alterations in the background evolution and imposes a friction term in the propagation of gravitational waves, this phenomenon has also been examined. We have shown their agreement with the Gravitational Wave (GW) luminosity distance with the Electromagnetic (EM) counter part GWTC-3 data from Advanced LIGO and Advanced VIRGO across different observing runs capturing coalescence of Binary Neutron Stars (BNS), mergers of Binary Black Holes (BBHs), and Neutron Star-Black Hole (NSBH) binaries with EM counterparts.

Galaxies doi: 10.3390/galaxies14030047

Authors: Lorenzo Roberti Agnese Falla Luca Boccioli

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.

Galaxies doi: 10.3390/galaxies14030046

Authors: Nurzat Kenzhebayev Manas Khassanov Ruslan Spassyuk Daulet Anarbek Yerlan Aimuratov Medeu Abishev

We examine cyclic nuclear reactions in the lead–bismuth (Pb–Bi) system near the s-process termination point. We present a numerical investigation of the isotopic evolution and decay heat generation in an extended 60-isotope nuclear reaction network under continuous 30 keV neutron irradiation (1014–1028 n cm−2 s−1) using the Chebyshev Rational Approximation Method (CRAM). The network accounts for 88 transitions, utilising a hybrid data approach that combines neutron capture cross-sections from EAF-2010 and TALYS with fundamental decay properties from the ENDF/B-VIII.0. Our simulations reveal two distinct evolutionary regimes. At moderate fluxes (1014–1020 n cm−2 s−1), the system establishes a steady cyclic loop driven by the α-decay of Po210, successfully reproducing the s-process termination isotopic distribution (Pb208≫209Bi>207Pb>206Pb), characteristic of low-metallicity AGB stars. As the flux exceeds 1022 n cm−2 s−1, the classical balance breaks down, propelling mass flow toward heavier trace isotopes and suggesting a potential transition into the intermediate neutron capture (i-process) regime. Heat density calculations demonstrate that while the energy release of the core cycle plateaus near 105 W cm−3, the extended chain drives an energy surge to over 108 W cm−3 at 1024 n cm−2 s−1 before the system enters an unstable transient state at extreme fluxes.

Galaxies doi: 10.3390/galaxies14030045

Authors: Bidzina Kapanadze Stefano Vercellone

Nearby (z<0.1) TeV-detected, high-energy-peaked BL Lacertae objects (HBLs) are among the most prominent extragalactic sources of the highest-energy photons, sometimes detected at energies of ∼10 TeV or beyond. These objects show a strong and complex flux variability, with strong flares and exceptional outbursts, as well as very rapid and large-amplitude TeV-band variations on timescales down to a few minutes during such instances. The higher-energy component of broadband spectral energy distribution (SED) is stretched over the MeV–TeV domain and, generally peaking beyond 100 GeV, has a controversial origin, and different emission scenarios (one- or multi-zone synchrotron self-Compton, hadronic cascades, etc.) are proposed. This paper presents a review of the TeV-band timing and spectral results obtained in the framework of different observational campaigns for nearby HBLs, their implications for different emission scenarios, and basic results from the corresponding SED modelings. Finally, the prospect of filling the observational gaps above some threshold energy by means of the planned projects for the dedicated γ-ray observations and, consequently, solving the different persisting problems related to the innermost structure, particle acceleration, and emission mechanisms are also presented.

Galaxies doi: 10.3390/galaxies14030044

Authors: Katherine R. Bermingham Bradley S. Meyer

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.

Galaxies doi: 10.3390/galaxies14030043

Authors: Olga A. Tsiopa Alexander F. Kholtygin Petr K. Tsiopa

The history of observations of gamma Cassiopeiae (γ Cas) is presented, including references to Soviet-era papers that have not been translated into English. The current state of knowledge is discussed. Particular attention is paid to the period of significant changes in the system’s characteristics during the 1930s and 1940s.

Galaxies doi: 10.3390/galaxies14030042

Authors: Tatyana Sitnova Lyudmila Mashonkina

We present a spectroscopic analysis of three carbon-enhanced metal-poor (CEMP) stars of type CEMP-s and CEMP-rs and determine their non-local thermodynamic equilibrium (NLTE) abundances of Ba and the fractions of the odd Ba isotopes (Fodd). We found Fodd = 0.65−0.34+0.35 in SDSS J1349-0229, which is known in the literature as a CEMP-rs star, while the other two stars, BPS CS 29512-073 and SDSS J1036+1212, exhibit lower Fodd = 0.23−0.10+0.19 and 0.23−0.11+0.22, respectively, and they are known in the literature as CEMP-s stars. The present result supports our earlier finding about distinct Fodd in CEMP-s and CEMP-rs stars. For obtaining observational constraints on i-process nucleosynthesis, further NLTE abundance determinations for many chemical elements are required.

Galaxies doi: 10.3390/galaxies14030041

Authors: Lidiia Zadorozhna Olexandr Gugnin Bohdan Hnatyk Olena Prykhodko Valentyna Babur Vadym Voitsekhovskyi Pavlo Panasiuk

Identifying the sources of Ultra-High Energy Cosmic Rays (UHECRs, E>1018 eV) remains a fundamental challenge in astrophysics due to the significant deflections of charged particles by Galactic and extragalactic magnetic fields. Until now, dozens of events with energies over 1020 eV—Extreme Energy Cosmic Rays (EECRs)—were detected by the Pierre Auger Observatory and Telescope Array, but none of them showed a statistically significant association with potential sources. In this study, we investigate potential sources of EECRs with arrival directions from Local Void region. Since the energy loss lengths of such EECRs are of order of 20–40 Mpc, i.e., smaller than the Local Void extension (∼60 Mpc), potential sources should be predominantly Galactic ones. Since the most promising UHECR accelerators are mildly relativistic shocks, we consider Galactic microquasars, magnetars, and pulsar wind nebulae as potential sources of EECRs in the Local Void sky region. Using event-by-event reconstruction of trajectories of detected EECRs via CRPropa backtracking in the Galactic magnetic field, we find the potential Galactic sources and corresponding charges Z for some of the detected EECRs. The most promising coincidence is found between the EECR event triplet detected by PAO and TA and SGR 1900+14, a Galactic magnetar exhibiting high-energy flaring activity, with the inferred propagation time delay being consistent with the characteristic age of the magnetar.

Galaxies doi: 10.3390/galaxies14030040

Authors: Luiz Augusto Stuani Pereira Rita C. Anjos

High-synchrotron-peaked (HSP) BL Lac objects are extreme particle accelerators whose synchrotron emission peaks at high frequencies, typically in the UV-to-X-ray band (νpeak>1015 Hz; νpeak≥1017 for EHSPs), implying electron Lorentz factors of order 105–106. Their relative proximity (z≲0.5), clean radiation environments, and favorable Hillas parameters make them prime candidates for ultra-high-energy cosmic ray (UHECR) acceleration beyond 1019 eV and for neutrino production above 100 TeV. The 2017 association of IceCube-170922A with the flaring blazar TXS 0506+056 provided compelling evidence for blazars as neutrino sources, while an archival neutrino flare from 2014–2015 with no clear electromagnetic counterpart (13 events) revealed additional complexity in the emission mechanism. This review examines HSP physical properties, identifies them through WISE-based infrared selection (the 2WHSP and 3HSP catalogs, ∼2000 sources), and contrasts leptonic synchrotron self-Compton models with hadronic alternatives. We assess the observational evidence linking HSPs to high-energy neutrinos and UHECRs, finding that extreme baryonic loading (Lp/Le∼103–105) strains energetic budgets, Auger composition measurements favor heavy nuclei over proton-dominated scenarios, and the near-isotropy of UHECR arrival directions is difficult to reconcile with rare beamed sources. Potential resolutions involving magnetic reconnection, structured jets, and duty cycle effects are discussed. Next-generation facilities, including IceCube-Gen2, KM3NeT, CTAO, IXPE, and AugerPrime/TA × 4, will probe key observables to either establish HSP BL Lacs as sources of the highest-energy cosmic particles or redirect the search toward alternative accelerator classes.

Galaxies doi: 10.3390/galaxies14030039

Authors: David Rapagnani Andreas Best Daniela Mercogliano Thomas William Chillery

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.

Galaxies doi: 10.3390/galaxies14030038

Authors: Luciano Piersanti Diego Vescovi Sergio Cristallo Lev R. Yungelson Eduardo Bravo Inmaculada Dominguez Alexandre G. Kuranov

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.

Galaxies doi: 10.3390/galaxies14030037

Authors: Aruna Goswami Arthur Choplin Partha Pratim Goswami Lionel Siess Stephane Goriely

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.

Galaxies doi: 10.3390/galaxies14020036

Authors: Svetlana G. Jorstad Alan P. Marscher José L. Gómez

We review the jet kinematics of HBL blazars based on results of the MOJAVE survey, which obtained images of active galactic nuclei with the Very Long Baseline Array (VLBA) at 15 GHz, and the VLBA-BU-BLAZAR program as well as its successor BEAM-ME program, which have observed γ-ray blazars at 43 GHz. We present and discuss recent kinematic behavior and polarization properties of the parsec-scale jets of three typical HBL sources over the 2020–2025 period. We outline current physical implications for reconciling the high-energy characteristics of HBL sources with their parsec-scale jet properties.

Galaxies doi: 10.3390/galaxies14020035

Authors: Jorge Nisperuza Sebastian Valencia

This technical note evaluates the observational performance limits of unguided smartphone-based astrophotography using a large-aperture Newtonian telescope under low-latitude sky conditions. Observations were conducted with a consumer-grade 10-inch Newtonian reflector coupled to an iPhone 15 Pro Max mounted on a manual altazimuth system, without motorized tracking, under semi-urban skies in Planeta Rica, Colombia (8.4° N). Image acquisition employed 5 s exposures in night mode combined with real-time manual drift correction. Under these conditions, resolved stellar and nebular structures were obtained for the Orion Nebula (M42) and the open clusters Messier 44 and Messier 41, reaching a limiting magnitude of approximately 9.5 while maintaining stellar elongation below ~1–1.3 arcminutes, consistent with the expected sidereal drift during a 5 s exposure. Lunar imaging achieved high spatial fidelity, resolving terminator features such as Tycho and Mare Imbrium with negligible motion artifacts. Imaging of Sirius (–1.46 mag) revealed pronounced sensor saturation and blooming, highlighting dynamic range limitations inherent to smartphone detectors. Quantitative analysis indicates that active manual correction reduced positional drift by approximately 52% relative to theoretical unguided motion models. The results demonstrate that optimized acquisition protocols enable reproducible and methodologically interpretable imaging of bright astronomical targets at equatorial latitudes, providing a practical framework for characterizing the constraints of unguided smartphone astrophotography.

Galaxies doi: 10.3390/galaxies14020034

Authors: Kohji Takahashi

There are some 300 naturally occurring nuclides. In addition, over 3000 radioactive isotopes have become known. The s(low) and r(apid) processes of neutron capture synthesize the nuclides heavier than iron. The synthesis, namely the increase in the atomic numbers Z, is actually governed by β decays. A “flow” of successive neutron captures in the chart of the nuclides is intercepted by a nucleus whose β decay half-life is short enough. In this review, I discuss the s-process exclusively. The neutron capture rate to be compared with the β decay rate is represented by λ=nnvT<σ>, where nn is the neutron number density, vT is the neutron thermal velocity at the temperature T, and <σ> is the Maxwellian averaged (around vT) radiative neutron capture cross-section, which depends on the nucleus of interest. The classical analysis of the solar system abundances of nuclides leads to canonical combinations like nn∼108/cm3 and T∼3×108 K for the s-process. The s-process flow becomes intricate when the neutron capture and β decay timescales are comparable, causing a branch of the flow. Subsequently, an evaluation of β decay rates is required, which is difficult to do straightforwardly. In this review, I will discuss the historical developments and the current status of predicting β decay rates under s-process environments (specified basically by temperature, density, and composition). Those conditions are inaccessible in the laboratory. Embedded in high-temperature environments, even a very massive atomic species could be highly ionized, and its atomic and nuclear excited states could be thermally populated. I will exemplify the consequent difficulties of β decay rate evaluations for s-process studies.

Galaxies doi: 10.3390/galaxies14020033

Authors: Yue Hu

Galactic cosmic rays (CRs) are a fundamental non-thermal component of the interstellar medium (ISM). Understanding the transport of super-high-energy particles is essential for interpreting observations of Galactic PeVatrons. Classical diffusion models assuming a homogeneous and isothermal medium oversimplify the multiphase ISM. We utilize high-resolution three-dimensional magnetohydrodynamic simulations to self-consistently generate a multiphase ISM—comprising the warm (WNM), unstable (UNM), and cold neutral medium (CNM)—and investigate 1.5–15 PeV particle transport using a test-particle approach. We find that thermal phase transitions induce steep magnetic field strength gradients at phase boundaries, creating localized magnetic fluctuations that act as efficient sites for adiabatic mirror reflections and non-adiabatic pitch-angle scattering, strongly enhancing cross-field transport at these interfaces. However, because phase boundaries occupy only a small volume fraction and particles spend most of their trajectory in the weakly scattering WNM and UNM, the global pitch-angle scattering coefficient in the multiphase ISM is smaller than in an equivalent isothermal medium. This locally strong scattering nevertheless drives both parallel and perpendicular spatial diffusion coefficients to ∼1030 cm2 s−1 at 1.5 PeV, with the perpendicular component exceeding its isothermal counterpart (∼1028 cm2 s−1) by two orders of magnitude. Using a phase–phase diffusion matrix decomposition, we show that global CR transport is governed by the volume-filling, trans-Alfvénic WNM and UNM, where particles stream along stochastically wandering field lines. Cross-phase displacement correlations are universally positive, indicating cooperative transport between thermal phases. In contrast, the super-Alfvénic CNM acts as an efficient confinement that substantially suppresses local diffusion.

Galaxies doi: 10.3390/galaxies14020032

Authors: Shakhida T. Nurmakhametova Aziza B. Umirova Nadezhda L. Vaidman Anatoly S. Miroshnichenko Serik A. Khokhlov Azamat A. Khokhlov Damir T. Agishev Dina A. Alimbetova

Supergiants are luminous post-main-sequence massive stars whose effective temperatures (Teff) are key inputs for stellar evolution and feedback studies. We present a photometry-based procedure to derive Teff for a sample of galactic supergiants of spectral types B and A by fitting the spectral energy distributions (SEDs) in the UV-to-mid-IR range to ATLAS9 model spectra converted into synthetic photometry using the corresponding passband transmission profiles while simultaneously solving for the line-of-sight extinction. The SEDs were constructed from published data taken in different photometric systems (Johnson or Kron–Cousins UBVRI, Strömgren uvby, JHK magnitudes from various sources, and AllWISE) and supplemented with UV TD-1 fluxes for brighter stars. The interstellar extinction law is based on Cardelli, Clayton & Mathis approximation assuming a total-to-selective ratio RV=AV/E(B−V)=3.1. The best-fitting parameters are obtained by minimizing a covariance-weighted χ2 statistic in logarithmic flux space over a grid of AV values and a discrete model grid. We test the method on 20 targets and find generally good agreement with published literature temperature estimates. The main limitations are non-simultaneous photometry for possibly variable objects and the residual coupling between temperature and reddening in broadband SED fitting. This study is intended as a methodological demonstration on a pilot sample rather than a definitive parameter catalog.

Galaxies doi: 10.3390/galaxies14020031

Authors: Francesca Lucertini Linda Lombardo

Osmium is a third-peak neutron-capture element predominantly produced by the rapid (r-) process, and it is a valuable tracer of early Galactic chemical enrichment. However, osmium abundance measurements in Galactic stars remain limited due to observational challenges. We present new osmium abundances for 23 stars at intermediate metallicities (−2.5≤ [Fe/H] ≤−1.0) within the framework of the MINCE (Measuring at Intermediate Metallicity Neutron-Capture Elements) project. A standard abundance analysis was carried out using one-dimensional LTE model atmospheres and the optical Os I line at 479 nm observed in high-quality UVES spectra. The derived [Os/Fe] ratio exhibits an anticorrelation with [Fe/H], supporting efficient r-process enrichment during the early phases of the Milky Way’s evolution. We also investigated Os abundances across different Galactic components, finding that halo and Gaia–Sausage–Enceladus stars are more Os-rich than thick-disk stars. A comparison between Os and europium abundances supports a common r-process origin for these elements at intermediate metallicities.

Galaxies doi: 10.3390/galaxies14020030

Authors: Sun Kwok Bruce Balick You-Hua Chu Bruce J. Hrivnak Alberto López Quentin Parker Raghvendra Sahai Albert Zijlstra

While there has been significant progress in our understanding of the origin and evolution of planetary nebulae in the last 50 years, there remain several unsolved problems. These include the true 3D morphological structure of the nebulae, origin of multipolar nebulae, the dust and molecular distribution relative to the optical nebulosity, large-scale structures outside of the main nebulae, the relevance of binarity to planetary nebulae evolution, and a precise definition of the planetary nebula phenomenon. The long-standing problem of elemental abundance discrepancy still remains unsolved. In this paper, we summarize current observations related to these problems and present possible future directions to tackle them.

Galaxies doi: 10.3390/galaxies14020029

Authors: Michele Spelta Gabriele Cescutti Sergio Cristallo Francisco García-Infantes Alice Manna Alberto Mengoni Paolo Maria Milazzo Riccardo Mucciola Giuseppe Tagliente Diego Vescovi Oliver Aberle Victor Alcayne Simone Amaducci Józef Andrzejewski Victor Babiano Michael Bacak Javier Balibrea-Correa Ana-Paula Bernardes Eric Berthoumieux Roland Beyer Marian Boromiza Damir Bosnar Manuel Caamaño Francisco Calviño Marco Calviani Daniel Cano-Ott Adrià Casanovas Donato Castelluccio Francesco Cerutti Sotirios Chasapoglou Enrico Chiaveri Gerardo Claps Paolo Colombetti Nicola Colonna Patrizio Console Camprini Guillem Cortés Miguel Cortés-Giraldo Luigi Cosentino Sophia Florence Dellmann Maria Diakaki Mario Di Castro Mirco Dietz César Domingo-Pardo Rugard Dressler Emmeric Dupont Ignacio Durán Zinovia Eleme Mamad Eslami Sylvain Fargier Beatriz Fernández-Domínguez Paolo Finocchiaro Valter Furman Aman Gandhi Aleksandra Gawlik-Ramięga Gianpiero Gervino Simone Gilardoni Enrique González-Romero Styliani Goula Erich Griesmayer Carlos Guerrero Frank Gunsing Carlo Gustavino Tanja Heftrich Jan Heyse William Hillman David Jenkins Erwin Jericha Arnd Junghans Yacine Kadi Kalliopi Kaperoni Michael Kokkoris Dominik Koll Yury Kopatch Milan Krtička Nikolaos Kyritsis Ion Ladarescu Claudia Lederer-Woods Jorge Lerendegui-Marco Giuseppe Lerner Trinitario Martínez Alessandro Masi Cristian Massimi Pierfrancesco Mastinu Mario Mastromarco Emilio-Andrea Maugeri Annamaria Mazzone Emilio Mendoza Veatriki Michalopoulou Elizabeth Musacchio González Agatino Musumarra Alexandru Negret Nikolas Patronis José Antonio Pavón Maria Pellegriti Pablo Pérez-Maroto Alberto Pérez de Rada Fiol Jarosław Perkowski Cristina Petrone Luciano Piersanti Elisa Pirovano Julio Plaza del Olmo Dominik Plonka Stephan Pomp Ignacio Porras Javier Praena José-Manuel Quesada René Reifarth Dimitri Rochman Yuriy Romanets Annie Rooney Carlo Rubbia Adrián Sánchez-Caballero Marta Sabaté-Gilarte Daniele Scarpa Peter Schillebeeckx Dorothea Schumann Gavin Smith Nikolay Sosnin Maria-Elisso Stamati Antonella Tamburrino Ariel Tarifeño-Saldivia Diego Tarrío Pablo Torres-Sánchez Silvia Tosi Giorgios Tsiledakis Stanislav Valenta Pedro Vaz Gianfranco Vecchio Vasilis Vlachoudis Rosa Vlastou Anton Wallner Christina Weiss Philip John Woods Tobias Wright Petar Žugec

The neutron capture cross section of 64Ni is an important parameter in nuclear astrophysics that is needed to accurately simulate stellar nucleosynthesis and validate stellar models. 64Ni is among the seeds of the s-process and its capture cross section has been found to have an important effect on the predicted abundances of many nuclei synthesized in Asymptotic Giant Branch (AGB) and massive stars. Despite its relevance, the measurements of the 64Ni(n,γ) available in the literature are scarce and discrepant. For this reason, a new accurate time-of-flight measurement has been performed at the n_TOF facility at CERN, taking advantage of its high instantaneous neutron flux, and using a highly enriched 64Ni sample. The first preliminary results show important discrepancies with respect to the cross sections recommended in the most recent releases of the evaluated nuclear data libraries. In particular, a large resonance reported at 9.52 keV is not observed. As a consequence, a significant reduction in the Maxwellian-Averaged Cross Section (MACS) obtained from evaluated data libraries in the 5–25 keV thermal energy region is expected.

Galaxies doi: 10.3390/galaxies14020028

Authors: Terese T. Hansen Mila Racca Timothy C. Beers Rana Ezzeddine Anna Frebel Erika M. Holmbeck Vinicius M. Placco Ian U. Roederer Charli M. Sakari

About half the elements heavier than iron in the universe, like silver and gold, are created in the rapid neutron-capture (r-)process. However, today, almost 70 years after the theoretical prediction of this process, it is still highly debated in what type of stellar explosions it can take place. One of the best places to search for answers is in ancient, metal-poor stars formed from the enriched gas. Their chemical makeup is like a time capsule, a direct fingerprint of the elements produced by the stellar generations that came before them. Since the first highly r-process-enhanced star, CS 22892-052 was discovered more than 30 years ago, multiple projects like the Hamburg/ESO r-Process Enhanced Star (HERES) survey, the Chemical Evolution of r-process Elements in Stars (CERES) project, and the r-Process Alliance (RPA) have searched for more r-process-enriched stars in the Milky Way. At the same time, numerous r-process-enriched stars have been discovered in stellar streams and dwarf galaxies. Here we present an overview of recent advances in finding r-process-enriched metal-poor stars and what the detailed chemo-dynamical analysis of these stars can tell us about heavy element nucleosynthesis and the astrophysical site(s) of the r-process.

Galaxies doi: 10.3390/galaxies14020027

Authors: Mikhail Yu. Kovalev Alexey Yu. Kniazev Oleg Yu. Malkov

We confirmed four spectroscopic binary candidates using new observations obtained with SALT. Three SB2 systems (HD 20784, HD 43519A, HD 62153A) exhibit circular orbits with periods shorter than 10 days, whereas one hierarchical triple system (HD 56024) contains a close binary with an inner eccentric orbit with a period of approximately 14 days, composed of nearly identical stellar components, and a rapidly rotating star on an outer eccentric orbit with a period of approximately 400 days. For two additional SB2 candidates (HD 198174 and HD 208433), our new observations do not allow us to derive reliable orbital solutions.

Galaxies doi: 10.3390/galaxies14020026

Authors: Akiharu Nakagawa Tomoharu Kurayama Hiroshi Sudou Gabor Orosz

Annual parallaxes of Galactic long period variable stars (LPVs) are essential for determining their distances and intrinsic properties, but their measurement remains challenging because of their large stellar sizes, circumstellar matter, and time-variable surface brightness asymmetry. In this study, we compare astrometric measurements obtained from very long baseline interferometry (VLBI) and Gaia Data Release 3 (DR3) for 43 Galactic LPVs. The parallaxes from the two methods are generally consistent within uncertainties for about half of the sample, although Gaia DR3 parallaxes tend to be slightly smaller than the VLBI values. This is consistent with previously reported systematic offsets. The behavior of parallax uncertainties differs between the two techniques: VLBI parallax errors increase with increasing parallax, whereas Gaia DR3 errors remain nearly constant. Consequently, VLBI measurements are more effective for LPVs with parallaxes smaller than approximately 2 mas, corresponding to distances beyond 500 pc. Proper motions are also compared, showing general agreement with a 2-sigma dispersion of approximately 13 km s−1, consistent with typical AGB outflow velocities. These results demonstrate the complementarity between VLBI and Gaia astrometry. We also find that the dispersion of parallax residuals becomes slightly larger for sources with pulsation periods around one year, suggesting a coupling of timescales between the stellar pulsation and the annual parallax.

Galaxies doi: 10.3390/galaxies14020025

Authors: Dimitris M. Christodoulou Demosthenes Kazanas Silas G. T. Laycock

In the original publication [...]

Galaxies doi: 10.3390/galaxies14020024

Authors: James R. Webb Claudia Garcia Jade Irizarry Dennis Moreno Alan P. Marscher

We present the results of the analysis of nine polarization and micro-variability observations of BL Lacertae using a turbulent cell model. We perform a similar analysis of a simulated TEMZ light curve generated with the Turbulent Extreme Multi-Zone (TEMZ) model and compare the results. Observations of short-timescale variability of flux and polarization are important to understanding the physical conditions in the blazar jet. We find that the micro-variations exhibited by the BL Lac data analyzed here are well fit by a turbulent cell model consisting of multiple pulses, with an average correlation coefficient of r~0.94. We compare these results with a similar analysis of light and polarization curves from a TEMZ simulation, which employs many more cells with physical properties related across cells following the Kolmogorov spectrum. We find that groups of turbulent cells identified in the TEMZ model by our analysis are similar to the input cell structure of the simulation. We find that the results from the actual BL Lac light curve and polarization curves match very well with the results from analyzing the TEMZ simulated light curves. We find no apparent trend or direct correlation between the cells determined from the flux curves and polarization degree, or polarization angle in either the BL Lac or the TEMZ data sets.

Galaxies doi: 10.3390/galaxies14020023

Authors: Jonathan H. Jiang Prithwis Das

This study presents a quantitative, scenario-based framework for analyzing humanity’s potential progression along the Kardashev scale, with emphasis on the transition to Type I (planetary-scale) and Type II (stellar-scale) civilization status. Using humanity as an empirical reference case, we integrate four coupled dimensions of civilizational development: energy utilization, information processing capacity, large-scale construction mass, and population dynamics, modeled through historical data, empirical trends, and physically motivated growth constraints. Energy availability is characterized using global energy production records and insolation statistics for potentially habitable exoplanets, explicitly acknowledging observational biases toward cooler host stars. Information processing growth is constrained by thermodynamic limits and observed trends in global data generation, while construction mass and population evolution are described using exponential and logistic growth models, respectively. These components are combined into a composite Civilization Development Index (CDI), a weighted logarithmic metric designed to track multi-scale civilizational advancement and tested through sensitivity analyses. Under optimistic assumptions of uninterrupted technological growth and absence of civilization-scale catastrophes, the framework suggests that humanity could reach Type I civilization status on the order of the 23rd century, while Type II status represents a substantially longer-term outcome extending into the third millennium or beyond. These timescales should be interpreted as lower bounds, as catastrophic events, sociopolitical constraints, or resource bottlenecks could significantly delay or prevent such transitions. By explicitly delineating assumptions, uncertainties, and physical constraints, this work provides a structured baseline for studies of long-term civilizational trajectories and the factors governing the emergence or absence of advanced technological civilizations.

Galaxies doi: 10.3390/galaxies14020022

Authors: Robin Eappen Pavel Kroupa

Mass discrepancies in galaxies are empirically known to appear only below a characteristic acceleration scale a0. Here we show that this behaviour is not limited to galaxies: it extends continuously across the full hierarchy of self-gravitating stellar systems, from gas-rich dwarfs and spirals to massive early-type galaxies, and further down to compact stellar clusters. We introduce the— Milgromian dynamics (MOND) depth index DM, together with dynamical maturity index T=tcross/tH, dynamical collisionality index T1=tcross/trelax, with tcross being the crossing time, tH the Hubble time and trelax the median two-body relaxation time, and the MOND acceleration index A=a¯/a0. We uncover a well-defined two-dimensional dividing surface in dynamical space. The ‘dark matter phenomenon’ is found only in systems that are both in the deep-MOND regime (a¯<a0) and collisionless (trelax>tH), while high-acceleration, collisional systems (a¯>a0, trelax≪tH), including globular clusters and UCDs, show no evidence for a mass discrepancy. This clean dynamical separation defines a new, physically motivated classification scheme for stellar systems, unifying galaxies and clusters under one framework. The observed division emerges naturally within the MOND framework and provides a useful diagnostic for examining how different gravitational paradigms account for the origin of the mass discrepancy.

Galaxies doi: 10.3390/galaxies14020021

Authors: Mohsen Fathi

In this work, we investigate the shadow properties of the Kerr–Newman–Anti-de Sitter black hole coupled to nonlinear electrodynamics. The shadow is constructed by employing the celestial coordinate approach for an observer located at a finite distance, which is required due to the non-asymptotically flat structure of the spacetime. The size, distortion, area, and oblateness of the shadow are analyzed in terms of the black hole parameters, namely, the spin, the effective charge, and the nonlinearity parameter. We show that the nonlinear electrodynamics significantly modifies the photon region and therefore changes the shadow observables, while the rotation mainly controls the deformation of the silhouette. We further confront the theoretical results with the Event Horizon Telescope observations of M87* and Sgr A* in order to constrain the parameter space of the model. The allowed ranges of the effective charge depend sensitively on the nonlinearity parameter, and the combination of both sources leads to tighter and physically more consistent bounds. In addition, we study the energy emission rate derived from the shadow radius and the Hawking temperature and discuss how it is affected by the rotation and the nonlinear electromagnetic field. Our analysis shows that the considered black hole solution provides a consistent extension of the Kerr geometry in a non-asymptotically flat background and that the shadow observables can be used as an efficient tool to test the effects of nonlinear electrodynamics in strong gravity.

Galaxies doi: 10.3390/galaxies14020020

Authors: Paul L. Schechter

We anticipate that hundreds of thousands of distant, strongly gravitationally lensed sources will be detectable with European Space Agency’s (ESA) Euclid mission and the Rubin Observatory Legacy Survey of Space and Time. We consider the virtues and shortcomings of the Singular Isothermal Elliptical Potential (SIEP) with Parallel External Shear (XS‖) for these systems. Its principal virtue is that it admits an analytic forward model that gives image positions and magnifications as functions of the source position (and shape for extended sources). Preliminary experiments suggest a speed-up of a factor in excess of 10,000 compared with conventional models that instead map from the image plane to the source plane and require iteration to converge upon a unique source. A second virtue is that the Witt–Wynne geometric representation of SIEP+XS‖ permits the quick visual verification of the model’s adequacy for a particular lensed system. Unfortunately, the model’s strictly elliptical lens equipotential is inconsistent with strictly elliptical surface mass density contours.The Witt–Wynne construction might nonetheless yield a sufficiently good first approximation to accelerate convergence to one’s preferred lens model.

Galaxies doi: 10.3390/galaxies14020019

Authors: José Antonio Nájera Indranil Banik Harry Desmond Vasileios Kalaitzidis

We test whether f(Q) symmetric teleparallel gravity theories can solve the Hubble tension consistently with DESI DR2 BAO. We consider three f(Q) functional forms: logarithmic, exponential, and hyperbolic tangent. We extend these models by allowing a cosmological constant, and compare to phenomenological models with a flexible exponential, hyperbolic secant, and polynomial decay addition to the standard ΛCDM H(z). We test these models against DESI DR2 BAO, CMB (Planck 2018 + SPT-3G + ACT DR6), local H0, and Cosmic Chronometer data. The logarithmic and hyperbolic tangent f(Q) models do not provide an adequate solution, but the exponential model does. Furthermore, it slightly reduces the (Ωm,H0rd) parameter space tension between CMB and BAO datasets to 2.56σ, down from 2.65σ for ΛCDM. Although ΛCDM faces only 1.66σ tension in DESI data space, the 1σ higher tension in parameter space suggests a real anomaly. The models assisted by the cosmological constant perform slightly better still, at the cost of undermined theoretical motivation. They also perform poorly once local H0 measurements are included. The phenomenological models fit all data reasonably well, yet the best-fitting models predict isotropically averaged BAO distances exceeding the DESI DR2 measurements at all redshifts. This highlights the difficulties of finding a theoretically motivated solution to the Hubble tension while remaining consistent with BAO data.

Galaxies doi: 10.3390/galaxies14020018

Authors: Juan Jordi Ancona-Flores Alberto Hernández-Almada Verónica Motta

Strong gravitational lensing provides valuable insights into the mass distribution of galaxies and the nature of dark matter. However, its modeling is computationally demanding due to the large volume of strong lensing observations. In this work, we explore the application of Convolutional Neural Networks to infer physical parameters from simulated galaxy–galaxy lens systems, described by the Singular Isothermal Ellipsoid (SIE) profile for the galaxy lens. We construct a dataset of 76,396 synthetic lensing images derived from the China Space Station Telescope catalog and employ it to train a modified CNN model, based on the AlexNet architecture, to predict four key SIE parameters, the Einstein radius, the axis ratio and ellipticity components. We analyze the network performance under three distinct dropout configurations to quantify their influence on generalization and parameter inference accuracy. The results indicate that the incorporation of dropout is critical for enhancing the precision and robustness of the estimated parameters as demonstrated using a 4-fold cross-validation procedure. When dropout tools are included, we obtain coefficients of determination up to R2∼0.96 for most SIE parameters and mean peak signal-to-noise ratios of up to ∼37 dB. Relative to the configuration without dropout, the use of dropout reduces the relative errors in the inferred SIE parameters by approximately 60–76%, resulting in errors of at most ∼9% at the 90% confidence level for the majority of parameters. These findings highlight the potential of deep learning approaches to enable scalable, computationally efficient, and high-precision modeling of strong gravitational lensing systems.

Galaxies doi: 10.3390/galaxies14020017

Authors: Linda Lombardo Francesca Lucertini

Molybdenum (Mo, Z = 42) is a neutron-capture element with seven stable isotopes that can be produced by different processes. Previous studies have shown a large scatter in molybdenum abundances for metal-poor ([Fe/H] < −1) stars, indicating that multiple nucleosynthetic channels are responsible for molybdenum production even at very low metallicity. To understand which different nucleosynthesis processes are involved in the chemical enrichment of this element in the Galaxy, a large sample of precise molybdenum abundance is required. In this study, we present molybdenum abundances of 27 metal-poor stars from the Measuring at Intermediate Metallicity Neutron-Capture Elements project sample. We derived molybdenum abundances using three Mo i lines at 550.6 nm, 557.0 nm, and 603.0 nm, which proved to be reliable for measuring Mo abundances in giant stars with [Fe/H] >−2. Our derived [Mo/Fe] abundance ratios show on average slightly higher values (∼0.2 dex) compared to the literature samples. This may be due to an observational bias or to non-local thermodynamic equilibrium effects. We also found that Gaia-Sausage-Enceladus candidate stars have lower [Mo/Fe] than the sample average, while the only Sequoia candidate star has a higher [Mo/Fe] than most sample stars.

Galaxies doi: 10.3390/galaxies14020016

Authors: Dimitris M. Christodoulou Demosthenes Kazanas Silas G. T. Laycock

The two most severe cosmological tensions in the Hubble constant H0 and the matter clustering amplitude S8 have the same relative discrepancy of 8.3%, which suggests that they may have a common origin. Modifications of gravity and exotic dark fields with numerous free parameters introduced in the Einstein field equations often struggle to simultaneously alleviate both tensions; thus, we need to look for a common cause within the standard ΛCDM framework. At the same time, linear perturbation analyses of matter in the expanding ΛCDM universe have always neglected the impact of comoving peculiar velocities v (generally thought to be a second-order effect), the same velocities that, in physical space, cannot be fully accounted for in the observed late-time universe when the cosmic distance ladder is used to determine the local value of H0. We have reworked the linear density perturbation equations in the conformal Newtonian gauge (sub-horizon limit) by introducing an additional drag force per unit mass −Γ(t)v in the Euler equation with Γ≡γ(2H), where γ≪1 is a positive dimensionless constant and 2H(t) is the time-dependent Hubble friction. We find that a damping parameter of γ=0.083 is sufficient to resolve the S8 tension by suppressing the growth of structure at low redshifts, starting at z★≃3.5–6.5 to achieve S8≃0.78–0.76, respectively. Furthermore, we argue that the physical source causing this additional friction (a tidal field generated by nonlinear structures in the late-time universe) is also responsible for a systematic error in the local determinations of H0—the inability to subtract peculiar tidal velocities along the lines of sight when determining the Hubble flow via the cosmic distance ladder. Finally, the dual action of the tidal field on the expanding background—reducing both the matter and the dark energy sources of the squared Hubble rate H2, thereby holding back the cosmic acceleration a¨—is of fundamental importance in resolving cosmological tensions and can also substantially alleviate the density coincidence problem.

Galaxies doi: 10.3390/galaxies14020015

Authors: Roberto Vázquez Jesús A. Toalá Luis F. Miranda Sandra Ayala María E. Contreras Marco A. Gómez-Muñoz Pedro F. Guillen Lorenzo Olguín Gerardo Ramos-Larios Laurence Sabin Federico Soto-Badilla

We present new high-dispersion optical spectra of the planetary nebula NGC 2371 obtained with the Manchester Echelle Spectrometer at the OAN-SPM 2.1 m telescope, complemented with 3D morpho-kinematic modelling using ShapeX. The data reveal that the present-day morphology of NGC 2371 is the outcome of multiple episodic mass-loss events rather than a single outflow. Our best-fitting model simultaneously reproduces the direct images and the Position–Velocity (PV) diagrams, and consists of a barrel-shaped shell with younger polar caps, extended bipolar lobes, and a pair of misaligned low-excitation [N ii] knots interpreted as jet-like ejections. The derived kinematical ages of the main structures, spanning ≃1600 to ≃4400 yr, indicate successive episodes of mass loss with different geometries and timescales. The nearly perpendicular bipolar lobes, the absence of a pronounced waist, and the surface distortions of the large-scale structures cannot be explained solely by standard axisymmetric wind interactions. Instead, our results point to a combination of shaping agents, including a late thermal pulse (born-again scenario) possibly related to the H-deficient [WR]-type nature of the central star, binary-driven interactions, and episodic jet activity. NGC 2371 thus provides a particularly instructive case where multiple shaping agents may operate, and where some of the relevant physical processes remain only marginally explored in current models of PN formation and evolution.

Galaxies doi: 10.3390/galaxies14020014

Authors: Pablo Granizo Yuri Oku Kentaro Nagamine

Numerical galaxy formation simulations are sensitive to numerical methods and sub-grid physics models, making code comparison projects essential for quantifying uncertainties. Here, we evaluate gadget4-osaka within the AGORA project framework by conducting a systematic comparison with its predecessor. We perform an isolated disk galaxy and a cosmological zoom-in run of a Milky Way-mass halo, following the multi-step AGORA calibration procedure. By systematically deconstructing the updated stellar feedback model, we demonstrate that mechanical momentum injection is necessary to suppress unphysical gas fragmentation and regulate star formation, yielding agreement with the Kennicutt–Schmidt relation. Meanwhile, stochastic thermal heating is essential for driving a hot metal-enriched gaseous halo, thereby creating a multiphase circumgalactic medium that is absent in the predecessor code. In the cosmological context, we calibrate the simulation to match the stellar mass growth history targeted by the AGORA collaboration. The validated gadget4-osaka simulation has been contributed to the AGORA CosmoRun suite, providing a new data point for understanding the impact of numerical and physical modeling choices on galaxy evolution.

Galaxies doi: 10.3390/galaxies14010013

Authors: Xiaolan Hou Heng Yu Tong Pan Hu Zou Haoran Dou Emily Moravec Chengkui Li

We present a comprehensive study of host galaxies of radio sources within the 1.35R200 of the Coma cluster by combining deep 144MHz observations from the LOFAR Two-Metre Sky Survey (LoTSS-DR2) with optical spectroscopy and photometry from DESI and SDSS. We identify 79 spectroscopically confirmed cluster members with reliable radio emission and classify them into compact, extended, and tailed subsamples according to their radio morphologies. By combining their radio and optical properties, we find compact radio sources are predominantly associated with massive, quiescent galaxies driven by AGN activity, while tailed sources are largely hosted by star-forming galaxies, tracing ongoing ram pressure stripping (RPS). Using phase-space analysis and a projected infall time proxy (dR), we find that extended sources are preferentially located in the cluster outskirts (dR>1), while tailed sources are concentrated in the intermediate infall region (0.4<dR<1.0), highlighting the influence of the dense intracluster medium.

Galaxies doi: 10.3390/galaxies14010012

Authors: Sophia N. Cisneros Rich Ott Meagan Crowley Amy Roberts Marcus Paz

One key piece of evidence for dark matter is the rotation-curve problem: the disagreement between measured galactic rotation curves and their luminous mass. A novel solution to this problem is presented here, in a model that predicts observed Doppler-shifted spectra based only on the luminous matter estimates and one free model parameter α. This model is applied to fit the rotation curves of the SPARC sample of 175 galaxies, yielding mass-to-light ratios, goodness of fit measurements, and α. The measured average χr2=2.24 compares favorably with the Navarro-Frenk-White dark matter model’s average of χr2=4.19 for the same data, and more galaxies are successfully fit by this model. The model provides a useful formulation linking luminous matter to the observed rotation curves, with the dark matter contribution to galaxies encoded in two transformation terms of the luminous mass. It also offers a lower-parameter characterization of the rotation curve problem, and a power law relationship between α and galactic photometric quantities is observed, potentially removing the need for the free parameter.

Galaxies doi: 10.3390/galaxies14010011

Authors: Kam Ling Chan Andreas Ritter Quentin Andrew Parker Katrina Exter

This work presents integrated flux and velocity channel maps of the planetary nebula Abell 30 (A30) inner knot system. The observations were taken with the INTEGRAL spectrograph at the William Herschel Telescope (WHT), La Palma, Spain. Our IFU data cube has a field of view (FoV) of 12.3″× 16″ that partially covers knots J1 and J2, and completely covers knots J3 and J4 in the system. Optical Recombination Lines (ORLs) of C II, He I, He II, N III, O II and Collisionally Excited Lines (CELs) of [Ar IV], [Ar V], [N II], [Ne III], [Ne IV], and [O III] were detected. Our integrated flux maps visualise the ionisation structure and the chemical inhomogeneity in the system previously reported by other groups. We find that ORLs are concentrated in the polar region (J1, J3), whereas the equatorial knots (J2, J4) are dominated by CELs. The flux ratio map of the diagnostic [O III λ 5007/4363 Å] lines reveals the electron temperature distribution, which shows cold cores of 15,000 K in knots J3 and J4 surrounded by a hot outer layer of above 20,000 K. Our channel maps show positive and negative velocity excursions from the systemic value among the ions. Several ions show variation in their velocity structures from their lower-energy-level counterparts, including [Ar IV] and [Ar V], [Ne III] and [Ne IV], and He I and He II. New recurrent velocity structures are identified in the low-density regions where the ions move much faster compared to their surrounding environments. The velocity dispersion measurements highlight extreme turbulence in some of the ions (σvrad≈140 km/s), consistent with supersonic/hypersonic motion driven by shocks. The forbidden line species [N II] exhibits lower turbulence (σvrad≈ 50–60 km/s), tracing denser, less-turbulent gases. Based on our data, we conclude that both the ionisation and kinematic studies hint at shock heating and multiple ejection history in the evolutionary pathway of A30.

Galaxies doi: 10.3390/galaxies14010010

Authors: Joelson Sartori Cristian G. Bernal Carlos Frajuca

Neutral atomic hydrogen (H I) regulates galaxy growth and quenching, but direct 21 cm measurements remain observationally expensive and affected by selection biases. We develop Bayesian neural networks (BNNs)—a type of neural model that returns both a prediction and an associated uncertainty—to infer the H I mass, log10(MHI), from widely available optical properties (e.g., stellar mass, apparent magnitudes, and diagnostic colors) and simple structural parameters. For continuity with the photometric gas fraction (PGF) literature, we also report the gas-to-stellar-mass ratio, log10(G/S), where explicitly noted. Our dataset is a reproducible cross-match of SDSS DR12, the MPA–JHU value-added catalogs, and the 100% ALFALFA release, resulting in 31,501 galaxies after quality controls. To ensure fair evaluation, we adopt fixed train/validation/test partitions and an additional sky-holdout region to probe domain shift, i.e., how well the model extrapolates to sky regions that were not used for training. We also audit features to avoid information leakage and benchmark the BNNs against deterministic models, including a feed-forward neural network baseline and gradient-boosted trees (GBTs, a standard tree-based ensemble method in machine learning). Performance is assessed using mean absolute error (MAE), root-mean-square error (RMSE), and probabilistic diagnostics such as the negative log-likelihood (NLL, a loss that rewards models that assign high probability to the observed H I masses), reliability diagrams (plots comparing predicted probabilities to observed frequencies), and empirical 68%/95% coverage. The Bayesian models achieve point accuracy comparable to the deterministic baselines while additionally providing calibrated prediction intervals that adapt to stellar mass, surface density, and color. This enables galaxy-by-galaxy uncertainty estimation and prioritization for 21 cm follow-up that explicitly accounts for predicted uncertainties (“risk-aware” target selection). Overall, the results demonstrate that uncertainty-aware machine-learning methods offer a scalable and reproducible route to inferring galactic H I content from widely available optical data.

Galaxies doi: 10.3390/galaxies14010009

Authors: Atila Čeki Olivera Latković

Using twenty sectors of TESS observations and the hitherto unutilized radial velocities from the David Dunlap Observatory survey, we fully characterize the close binary TV UMi. Its nearly sinusoidal light curves are well explained by a low-inclination, shallowly-eclipsing model in marginal contact, with a dark spot whose longitudinal migration is strongly correlated with the eclipse time variations. We derive the orbital parameters of the binary and determine the masses and radii of the components with a precision of a few percent. The estimated age and the position of TV UMi on the theoretical HR diagram indicate it’s a relatively young late-type contact binary of the W subtype.

Galaxies doi: 10.3390/galaxies14010008

Authors: Emilio Elizalde

What does “Big Bang” mean? What was the actual origin of these two words? There are many aspects hidden under this name, which are seldom explained. They are discussed here. To frame the analysis, help will be sought from the highly authoritative voices of two exceptional writers: William Shakespeare and Umberto Eco. Both have explored the tension existing between words and the realities they name. And this includes names given to outstanding theorems and spectacular discoveries, too. Stigler’s law of eponymy is recalled in this context. These points will be at the heart of the quest here, concerning the concept of “Big Bang”, which only a few people know what it means, actually. Fred Hoyle was the first to pronounce these words, in a BBC radio program, with a meaning that was later called inflation. But listeners were left with the image he was trying to destroy: the explosion of Lemaître’s primeval atom (an absolutely wrong concept). Hoyle’s Steady State will be carefully compared with inflation cosmology. They are quite different, and yet, in both cases, the possibility of creating matter/energy out of expanding space is rooted in the same fundamental principles: those of General Relativity. As is also, the possibility of having a universe with zero total energy, anticipated by R.C. Tolman, in 1934 already. It will be shown, how to obtain accelerated expansion from negative pressure; how to reconcile energy conservation with matter creation in an expanding universe; and a curious relation between de Sitter spacetime and Steady State cosmology. Concerning the naming issue, it will be remarked that, today, the same label “Big Bang” is used in very different contexts: (a) the Big Bang Singularity; (b) as the equivalent of cosmic inflation; (c) speaking of the Big Bang cosmological model; (d) to name a very popular TV program; and more.

Galaxies doi: 10.3390/galaxies14010007

Authors: Elie Almurr Jean Claude Assaf

Objective: We examine whether a finite-range scalar–tensor modification of gravity can be simultaneously compatible with cosmological background data, galaxy rotation curves, and local/astrophysical consistency tests, while satisfying the luminal gravitational-wave propagation constraint (cT=1) implied by GW170817 at low redshifts. Methods: We formulate the model at the level of an explicit covariant action and derive the corresponding field equations; for cosmological inferences, we adopt an effective background closure in which the late-time dark-energy density is modulated by a smooth activation function characterized by a length scale λ and amplitude ϵ. We constrain this background model using Pantheon+, DESI Gaussian Baryon Acoustic Oscillations (BAOs), and a Planck acoustic-scale prior, including an explicit ΛCDM comparison. We then propagate the inferred characteristic length by fixing λ in the weak-field Yukawa kernel used to model 175 SPARC galaxy rotation curves with standard baryonic components and a controlled spherical approximation for the scalar response. Results: The joint background fit yields Ωm=0.293±0.007, λ=7.69−1.71+1.85Mpc, and H0=72.33±0.50kms−1Mpc−1. With λ fixed, the baryons + scalar model describes the SPARC sample with a median reduced chi-square of χν2=1.07; for a 14-galaxy subset, this model is moderately preferred over the standard baryons + NFW halo description in the finite-sample information criteria, with a mean ΔAICc outcome in favor of the baryons + scalar model (≈2.8). A Vainshtein-type screening completion with Λ=1.3×10−8 eV satisfies Cassini, Lunar Laser Ranging, and binary pulsar bounds while keeping the kpc scales effectively unscreened. For linear growth observables, we adopt a conservative General Relativity-like baseline (μ0=0) and show that current fσ8 data are consistent with μ0≃0 for our best-fit background; the model predicts S8=0.791, consistent with representative cosmic-shear constraints. Conclusions: Within the present scope (action-level weak-field dynamics for galaxy modeling plus an explicitly stated effective closure for background inference), the results support a mutually compatible characteristic length at the Mpc scale; however, a full perturbation-level implementation of the covariant theory remains an issue for future work, and the role of cold dark matter beyond galaxy scales is not ruled out.

Galaxies doi: 10.3390/galaxies14010006

Authors: Ana Jeakel Gabriel Vieira dos Santos Valerio Marra Rodrigo von Marttens Siddhartha Gurung-López Raul Abramo Jailson Alcaniz Narciso Benitez Silvia Bonoli Javier Cenarro David Cristóbal-Hornillos Simone Daflon Renato Dupke Alessandro Ederoclite Rosa González Delgado Antonio Hernán-Caballero Carlos Hernández-Monteagudo Jifeng Liu Carlos López-Sanjuan Antonio Marín-Franch Claudia Mendes de Oliveira Mariano Moles Fernando Roig Laerte Sodré Keith Taylor Jesús Varela Héctor Vázquez Ramió José Vilchez Christopher Willmer Javier Zaragoza-Cardiel

We present a supervised machine learning classification of sources from the Javalambre Physics of the Accelerating Universe Astrophysical Survey (J-PAS) Pathfinder datasets: miniJPAS and J-NEP. Leveraging crossmatches with spectroscopic and photometric catalogs, we construct a robust labeled dataset comprising 14,594 sources classified into extended (galaxies) and point-like (stars and quasars) objects. We assess dataset representativeness using UMAP analysis, confirming broad and consistent coverage of feature space. An XGBoost classifier, with hyperparameters tuned using automated optimization, is trained using purely photometric data (60-band J-PAS magnitudes) and combined photometric and morphological features, with performance thoroughly evaluated via ROC and purity–completeness metrics. Incorporating morphology significantly improves classification, outperforming the baseline classifications available in the catalogs. Permutation importance analysis reveals morphological parameters, particularly concentration, normalized peak surface brightness, and PSF, alongside photometric features around 4000 and 6900 Å, as crucial for accurate classifications. We release a value-added catalog with our models for star-galaxy classification, enhancing the utility of miniJPAS and J-NEP for subsequent cosmological and astrophysical analyses.

Galaxies doi: 10.3390/galaxies14010005

Authors: Eleonora Polini Antonino Chiummo

The low-frequency sensitivity of gravitational-wave detectors can be degraded by noise arising from the re-coupling of stray light with the main interferometer beam. This review describes the re-coupling mechanism and shows how the experience gained with current detectors can be used to anticipate and mitigate stray-light issues in third-generation instruments. We summarize the work carried out on numerical simulations and on the extensive characterization of stray light originating from both core and auxiliary optics. We also discuss possible improvements to the interferometric readout system aimed at reducing stray-light-induced noise, as well as diagnostic approaches for identifying potentially harmful scattering elements. Overall, this review summarizes best practices for the effective control of stray light in future gravitational-wave detectors, supporting design approaches aimed at preventing unforeseen noise issues.

Galaxies doi: 10.3390/galaxies14010004

Authors: Anton Smirnov Alexander Marchuk Viktor Zozulia Natalia Sotnikova Sergey Savchenko

We investigated the properties of boxy/peanut-shaped (B/PS) bulges in a sample of 71 galaxies from the Edge-on Galaxies in the Pan-STARRS Survey (EGIPS) and 20 simulated galaxies from Illustris TNG50 using multicomponent photometric decomposition. For each real and simulated galaxy, we obtained a suitable photometric model in which the B/PS bulge was represented by a dedicated 2D photometric function. For real galaxies, we found that more flattened X-structures are generally residing in larger B/PS bulges. When tested against the galaxy masses, we verified that both larger bulges and more flattened X-structures are typically found in more massive galaxies. Since large bars are also known to reside in more massive galaxies, we conclude that the flatness of X-structures in larger B/PS bulges has a physical origin, rather than being solely a result of projection effects due to differences in observed bar viewing angles. When comparing the properties of B/PS bulges between EGIPS galaxies and TNG50 galaxies, with bars rotated for different viewing angles, we found that B/PS bulges in TNG50 are considerably smaller and less luminous in terms of total intensity. This is consistent with previous studies of bar properties in TNG50, indicating the B/PS bulges in TNG50 differ from those in real galaxies, as do their parent bars.

Galaxies doi: 10.3390/galaxies14010003

Authors: Arya Sudhakaran Debbijoy Bhattacharya Puthiyaveettil Shalima Gulab Chand Dewangan Parameshwaran Sreekumar

Despite several efforts to investigate the accretion disk and torus, near-simultaneous broadband studies of the nuclear regions of radio-quiet AGNs remain lacking. NGC 4151, one of the closest and brightest Seyfert galaxies, provides an excellent laboratory for probing the circum-nuclear regions of AGNs. A detailed, near-simultaneous broadband spectral study of NGC 4151 is carried out during one of its historic minimum activity states, using archival data from the Ultraviolet (UV) to the Infrared (IR) regions. We used the radiative transfer code SKIRT to model the source and to constrain the properties of the torus. We found that the observed broadband spectral energy distribution is best explained by a two-torus geometry with a polar conical shell structure.

Galaxies doi: 10.3390/galaxies14010002

Authors: David Garofalo Zhiyuan Liu Atticus V. Magerko

Double-double radio galaxies (DDRGs) display inner and outer jets or lobes thought to result from intermittent accretion. Due to randomly triggered accretion events, the lifetime of the retriggered jet is not expected to have any connection to the time of quiescence between jets, yet we show that a correlation between the two quantities may exist, which we interpret as resulting from continued accretion through the quiescent jet phase. Despite continuous accretion, a jet is absent because its presence depends on a non-zero value of black hole spin, but accretion transitions the system from counter-rotation to corotation, and therefore through zero black hole spin where a jet cannot form. The time of jet quiescence depends on how long it takes to spin the black hole up again in corotation, which is longer for lower accretion rates. Once the black hole spin is large enough for a renewed jet, this inner jet will last longer the lower the accretion rate is. Hence, in a continuous accretion scenario, longer quiescent times tend to associate to longer inner jet times. In addition, DDRG jets are of FRII morphology which we show to result from the absence of a tilt in the accretion disk in the transition through zero black hole spin, ensuring the absence of an FRI jet in a way that connects with our understanding of X-shaped radio galaxies. Both correlated timescales as well as sameness in jet morphology offers evidence in favor of our picture.

Galaxies doi: 10.3390/galaxies14010001

Authors: Vladislavs Bezrukovs Oleg Ulyanov Artem Sukharev Vyacheslav Zakharenko Mikhail Ryabov Viktor Ozhinskyi Volodymyr Vlasenko Anatolyi Poikhalo Oleksandr Konovalenko Eugene Alekseev Mykhailo Palamar Viktor Voityuk Vladyslav Chmil Dmytro Bakun Daniil Zabora Ivar Shmeld Marina Konuhova

Perseus A (3C 84), a powerful radio source located at the centre of the giant elliptical galaxy NGC 1275—classified as a Seyfert type II AGN and the dominant member of the X-ray bright Abell 426 cluster–exhibits radio emission variability over a wide range of timescales, from decades to hours. This study investigates intraday variability (IDV) in the 6.5 GHz radio emission of 3C 84 using the RT-32 radio telescope in Zolochiv, Ukraine. A novel low-amplitude azimuthal scanning method enabled quasi-simultaneous measurements of antenna and system temperatures, allowing for separation of intrinsic source variations from propagation effects. During an observation session in August 2021, a burst with a peak intensity of 13.5 Jy above the background was detected, likely corresponding to a Fast Radio Burst (FRB). Additionally, quasi-periodic low-amplitude variations with timescales from 0.3 to 6 h were observed. These fluctuations correlate strongly with local atmospheric changes, such as dew formation on the telescope structure, and, to a lesser extent, with ionospheric acoustic–gravity waves. The findings highlight the importance of accounting for propagation conditions when interpreting short-timescale radio variability in AGNs and suggest the need for multi-station, multi-frequency monitoring campaigns to distinguish between intrinsic and environmental modulation of AGN flux densities.

Galaxies doi: 10.3390/galaxies13060137

Authors: Sarut Puangragsa Tanawit Sahavisit Popphon Laon Utumporn Puangragsa Pattarapong Phasukkit

The proliferation of terrestrial and space-based communication systems introduces significant radio frequency interference (RFI), which severely compromises data acquisition for radio telescopes, necessitating robust and dynamic scheduling solutions. This study addresses this challenge by implementing a Deep Recurrent Reinforcement Learning (DRL) framework for the control and dynamic scheduling of the X-Y pedestal-mounted KMITL radio telescope, explicitly trained for RFI avoidance. The methodology involved developing a custom simulation environment with a domain-specific Convolutional Neural Network (CNN) feature extractor and a Long Short-Term Memory (LSTM) network to model temporal dynamics and long-horizon planning. Comparative evaluation demonstrated that the recurrent DRL agent achieved a mean effective survey coverage of 475 deg2/h, representing a 72.7% superiority over the non-recurrent baseline, and maintained exceptional stability with only 1.0% degradation in median coverage during real-world deployment. The DRL framework offers a highly reliable and adaptive solution for telescope scheduling that is capable of maintaining survey efficiency while proactively managing dynamic RFI sources.

Galaxies doi: 10.3390/galaxies13060136

Authors: Carlos Viscasillas Vázquez Gražina Tautvaišienė Erika Pakštienė Arnas Drazdauskas Yuriy Chorniy Vilius Bagdonas Šarūnas Mikolaitis Renata Minkevičiūtė Edita Stonkutė

The determination of stellar ages remains one of the greatest challenges in astrophysics, as age cannot be directly measured. Advances over the last decade highlight a great potential of chemical clocks, particularly abundance ratios involving s-process and α-elements to estimate stellar ages with improved precision. For a sample of 205 stars observed with the high-resolution spectrograph and 1.65 m telescope at the Molėtai Astronomical Observatory in Lithuania, we determined Y and Mg abundances and derived new asteroseismic ages from TESS observations. Our results reveal the dependence of the [Y/Mg]–age relationship on the Galactic birthplaces of thin-disc stars, while confirming previous results on negligible correlations for thick-disc stars. This study highlights the importance of integrating chemical compositions, asteroseismic data, and precise astrometric measurements from Gaia to refine the applicability of chemical clocks and enhance our understanding of Galactic chemical evolution.

Galaxies doi: 10.3390/galaxies13060135

Authors: Fen Liu Difu Guo Xu Chen Kai Li Changming Zhang Jiaming Ai

This study presents multi-band photometric observations and detailed period analysis of a totally eclipsing binary system exhibiting low photometric amplitude. The system exhibits characteristic W Ursae Majoris (EW)-type light curves with complete eclipses. In our light curve modeling, we tested two setups: one excluding third light and the other including it as a free parameter (accounting for a potential tertiary component). Photometric analysis reveals that ASASSN-V J171815.10+450432.9 (hereafter J171815) represents a marginal contact binary system with an extreme mass ratio (the more massive component is designated as the primary star), approaching the theoretical lower limit for stable contact configurations. Furthermore, our investigation of orbital period variations uncovers a long-term period increase at a rate of dPdt=(1.08±0.05)×10−6dayyr−1, which is likely attributable to ongoing mass transfer between components. This interpretation aligns with the system’s geometric configuration and observed light curve asymmetries. The unique characteristics presented by this binary system serve as a rare opportunity for in-depth research on the mass ratio theory, and also provide an important opportunity for testing the Thermal Relaxation Oscillation (TRO) theory.

Galaxies doi: 10.3390/galaxies13060134

Authors: Sander K. Sijtsma Pooya Saffarieh Nathan A. Holland Sil T. Spanjer Wouter B. J. Hakvoort Conor M. Mow-Lowry

This paper proposes a non-smooth controller optimization method and shows the results of ongoing research on the implementation of this method for gravitational-wave applications. Typical performance requirements concerning these type of suspensions are defined in terms of both H2- and H∞-type constraints. A non-smooth optimization approach is investigated, which allows the use of non-convex cost functions that are often a result of mixed H2/H∞ optimization problems. Besides the controller, the distribution of the actuation is integrated with the optimization to investigate the feasibility of simultaneous controller and actuator optimization. The results demonstrate that the proposed non-smooth optimization method is able to find suitable solutions for the control and actuator distribution that satisfy all required performance and design constraints.

Galaxies doi: 10.3390/galaxies13060133

Authors: Eoin Ó Colgáin Saeed Pourojaghi M. M. Sheikh-Jabbari

We continue scientific scrutiny of the DESI dynamical dark energy (DE) claim by explicitly demonstrating that the result depends on the analysis pipeline. Concretely, we define a likelihood that converts the w0waCDM model back into the (flat) ΛCDM model, which we fit to DESI constraints on the ΛCDM model from DR1 Full-Shape (FS) modeling and BAO. We further incorporate CMB constraints. Throughout, we find that w0 and wa are within 1σ of the ΛCDM model. Our work makes it explicit that, in contrast to DR1 and DR2 BAO, there is no dynamical DE signal in FS modeling, even when combined with BAO and CMB. Moreover, one confirms late-time accelerated expansion today (q0<0) at ≳3.4σ in FS modeling + BAO. On the contrary, DR1 and DR2 BAO fail to confirm q0<0 under similar assumptions. Our analysis highlights the fact that trustable scientific results should be independent of the analysis pipeline.

Galaxies doi: 10.3390/galaxies13060132

Authors: P. A. Patsis P. Okalidis

Grand-design spiral structures typically emerge in N-body simulations of disk galaxies as barred-spiral configurations forming during the early evolutionary stages of the system. In this study, we explore the dynamical conditions that allow for the formation and sustained presence of a non-barred, bisymmetric grand-design spiral pattern in fully self-consistent N-body models over considerable time periods. We present a model in which such non-barred morphologies persist for approximately 2.5 Gyr. The simulation is carried out using a standard implementation of the GADGET-3 code, incorporating both stellar and gaseous components in the disk and embedding them within a live dark matter halo. A characteristic feature of the simulation is that during its normal spiral grand-design phase the disk remains submaximal. Star formation is active throughout the model’s evolution. Analysis of the resulting morphology indicates that dominant inner, symmetric spiral arms extend between the inner Lindblad resonance (ILR) and the radial inner 4:1 resonance. This structure is evident in both the stellar and gaseous components, exhibiting extensions and bifurcations consistent with predictions from orbital theory.

Galaxies doi: 10.3390/galaxies13060131

Authors: Emil Lenc Philip G. Edwards Susmita Sett Manisha Caleb

A radio source with a period of 75.88 s, suspected of being an ultra-long period pulsar, was discovered in 2020 with the MeerKAT radio telescope. Here, we report the detection of radio pulses from this object in multi-epoch ASKAP image data at frequencies between 744 MHz and 1800 MHz and a search for pulses made in Murchison Widefield Array data at 154 MHz. The ASKAP detections pre-date and extend other published observations and so support the belief the pulsar emission has been persistent. The non-detection of the pulsar in MWA data is consistent with a recent report that the spectrum turns over at low frequencies. An ASKAP image of the field centred at 943 MHz confirms the MeerKAT detection of diffuse emission surrounding the pulsar.

Galaxies doi: 10.3390/galaxies13060130

Authors: Dmitry A. Ladeyschikov Elena A. Filonova Anton I. Vasyunin

We develop predictive models for OH maser occurrence in Galactic star-forming regions by integrating dense-clump physical properties from the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) and Herschel Infrared Galactic Plane Survey (Hi-GAL) 360° catalogs with maser detections and non-detections compiled in the MaserDB.net database. We compare two predictive modeling approaches for Galactic OH maser incidence: a Generalized Linear Model (GLM; logistic regression) and a compact Keras-based binary neural network (BNN). For the 1665/1667 MHz lines, both models achieve recall of 90% with a precision of approximately 50%, while for the excited-state 6031/6035 MHz lines, precision reaches roughly 20% at the same recall. We found no statistically significant difference between the BNN and GLM in out-of-sample performance. This implies that maser occurrence may be expressed as a monotonic trend without requiring nonlinear interactions. Across different catalogs and transition lines, luminosity, luminosity-to-mass ratio (L/M), dust temperature, and H2 column, surface, and volume densities are the most influential features for maser prediction. These variables support a physical picture in which radiative pumping favors warm, luminous, and compact clump environments. We provide an accessible online tool that allows users to predict the likelihood of OH maser emission toward ATLASGAL or Hi-GAL sources based on coordinate lists.

Galaxies doi: 10.3390/galaxies13060129

Authors: Oleg Malkov Alexey Sytov Gang Zhao Zehao Zhong

Type Ia supernovae are used as fundamental probes of the cosmological parameters, based on a tight empirical relation between their peak luminosity and the width of their light curve. However, it has been recognized that SNe Ia are not “standard” candles, since important variations in their peak luminosities are observed, as a function of the metallicity, age, environment, and morphological type of the supernova hosts. The largest correction in the standardization scheme is related to extinction. While extinction in the Milky Way (MW) Galaxy is usually known and extinction between galaxies can be assumed to be zero, the value of extinction in the SN Ia host galaxy (Ahost) is determined with much more uncertainty. In this paper, we provide an estimate of the Ahost value based on statistical modeling. To do this, we generate, based on MaNGA data, a set of galaxies in the vicinity of the MW, and distribute the parameters of the galaxies and the positions of SNe Ia in them. As a result, using a simplified model for the distribution of interstellar matter, which is the same for all the sampled galaxies, we can estimate the probability that Ahost exceeds a certain value. Our estimates show, in particular, that in almost all cases, Ahost > 0.10 mag V, and in 25% of cases, Ahost > 0.25 mag V.

Galaxies doi: 10.3390/galaxies13060128

Authors: Tapan K. Sasmal Soumen Kumar Bera Xuelei Chen Yougang Wang Soumen Mondal Taotao Fang

STRange and Odd Morphology Extragalactic Radio Sources (STROMERSs) is a new category of radio galaxies that shows extremely peculiar anatomy. A purely manual visual search is carried out for the identification of such interesting sources. We reported a total of 108 STROMERS sources from the LOFAR Two-meter Sky Survey second data release (LoTSS DR2) at 144 MHz. The host galaxies are found ∼94% of the sources. We studied the radio and optical properties of the sources. Redshifts were found in 76% of sources with known host galaxies. The redshifts of STROMERS range from 0.0015 to 1.6599 and peak at 0.15. Among the reported STROMERS sources, there are 17 giant radio galaxies (GRG) with a linear size of greater than 700 kpc. Among them, only five GRGs are new, which is a small fraction of the population of GRGs from LoTSS DR2 data. The source ILTJ164117.44 +380208.4 has the highest linear size, approximately 1.8 Mpc. To study the reasons behind these interesting morphologies, we studied the galaxy cluster environment of each candidate within a 1 Mpc search radius. We found that 53% of STROMERS candidates are associated with cluster environments with known redshifts. The source ILTJ150956.65+332642.9 is associated with a high mass galaxy cluster Abell 2034 with mass a 7.57 ×1014M⊙. We also propose that the merger scenario is one of the reasons for the formation of STROMERS in the paper.

Galaxies doi: 10.3390/galaxies13060127

Authors: Nissim Fraija C. G. Bernal A. Galván B. Betancourt Kamenetskaia M. G. Dainotti

Recent centimeter-to-millimeter monitoring of nearby gamma-ray bursts (GRBs) has revealed late-time (≳102–104 days) radio rebrightenings and spectral turnovers not explained by standard forward-shock scenarios with steady microphysics. We attribute these features to a buried millisecond magnetar whose surface dipole, initially submerged by early fallback (hours after birth), re-emerges via Hall–Ohmic diffusion on year–to–decade timescales, partially re-energizing the external shock. We combine a minimally parametric analytic framework with axisymmetric magnetohydrodynamic simulations of the hypercritical fallback phase to characterize burial depths and the initial conditions for reemergence. The growth of the external dipole is modeled as E˙(t)∝E˙0fG(t)σ and calibrated against physically plausible diffusion timescales τm∼years–decades. Spin-down power couples to the afterglow through the surrounding ejecta via a single effective coupling factor and a causal delay kernel, encapsulating mediation by supernova ejecta/pulsar-wind nebulae in collapsars and by merger ejecta/winds in compact-object mergers. Applied to a representative set of events with late-time radio detections and upper limits, our scheme reproduces the observed rebrightenings and turnovers with modest coupling efficiencies. Within this picture, late-time centimeter–millimeter afterglows provide a practical diagnostic of magnetic-burial depth and crustal conductivity in newborn magnetars powering GRB afterglows, and motivate systematic radio follow-up hundreds to thousands of days after the trigger.

Galaxies doi: 10.3390/galaxies13060126

Authors: Ivar Shmeld Vladislavs Bezrukovs Jānis Šteinbergs Karina Šķirmante Artis Aberfelds Sergey A. Belov Ross A. Burns Dmitrii Y. Kolotkov Valery M. Nakariakov Dmitrijs Bezrukovs Matīss Purviņš Aija Kalniņa Arturs Orbidans Marcis Bleiders Marina Konuhova

The Irbene single-baseline radio interferometer (ISBI), operated by the Ventspils International Radio Astronomy Centre (VIRAC), offers a rare and versatile configuration in modern radio astronomy. Combining the 32-m and 16-m fully steerable parabolic radio telescopes separated by an 800-m baseline, this system possesses a unique capability for high-sensitivity, time-domain interferometric observations. Unlike large interferometric arrays optimized for sub-arcsecond resolution imaging, the Irbene system is tailored for studies that require high temporal resolution and a strong signal-to-noise ratio. This paper reviews key scientific applications of the Irbene interferometer, including simultaneous methanol maser and radio continuum variability studies, high-cadence monitoring of quasi-periodic pulsations (QPPs) in stellar flares, ionospheric diagnostics using GNSS signals, orbit determination of navigation satellites and forward scatter radar techniques for space object detection. These diverse applications demonstrate the scientific potential of compact interferometric systems in an era dominated by large-scale observatories.

Galaxies doi: 10.3390/galaxies13060125

Authors: Shinjirou Kouzuma

We propose a simple method for estimating the fill-out factor of overcontact binary systems using the derivatives of light curves. We synthesized 74,431 sample light curves, covering the typical parameter space of overcontact binaries. On the basis of a recent study that proposed a new classification scheme using light curve derivatives up to the fourth order, the sample light curves were classified. Among the classified types, for systems exhibiting high mass ratios and high inclinations (i.e., SPf type), we found that the fill-out factor has a strong correlation with the time interval between two local extrema in the third derivatives of their light curves. An empirical formula to estimate the fill-out factor was derived using regression analysis for the identified correlation. Application to real overcontact binary data demonstrated that the proposed method is practical for obtaining reliable estimates of the fill-out factor and its associated uncertainties.

Galaxies doi: 10.3390/galaxies13060124

Authors: Tanawit Sahavisit Popphon Laon Supavee Pourbunthidkul Pattharin Wichittrakarn Pattarapong Phasukkit Nongluck Houngkamhang

Radio astronomy requires precise target localization and tracking to ensure accurate observations. Conventional regulation methodologies, encompassing PID controllers, frequently encounter difficulties due to orientation inaccuracies precipitated by mechanical limitations, environmental fluctuations, and electromagnetic interferences. To tackle these obstacles, this investigation presents a reinforcement learning (RL)-oriented framework for high-accuracy monitoring in radio telescopes. The suggested system amalgamates a localization control module, a receiver, and an RL tracking agent that functions in scanning and tracking stages. The agent optimizes its policy by maximizing the signal-to-noise ratio (SNR), a critical factor in astronomical measurements. The framework employs a reconditioned 12-m radio telescope at King Mongkut’s Institute of Technology Ladkrabang (KMITL), originally constructed as a satellite earth station antenna for telecommunications and was subsequently refurbished and adapted for radio astronomy research. It incorporates dual-axis servo regulation and high-definition encoders. Real-time SNR data and streaming are supported by a HamGeek ZedBoard with an AD9361 software-defined radio (SDR). The RL agent leverages the Proximal Policy Optimization (PPO) algorithm with a self-attention actor–critic model, while hyperparameters are tuned via Optuna. Experimental results indicate strong performance, successfully maintaining stable tracking of randomly moving, non-patterned targets for over 4 continuous hours without any external tracking assistance, while achieving an SNR improvement of up to 23.5% compared with programmed TLE-based tracking during live satellite experiments with Thaicom-4. The simplicity of the framework, combined with its adaptability and ability to learn directly from environmental feedback, highlights its suitability for next-generation astronomical techniques in radio telescope surveys, radio line observations, and time-domain astronomy. These findings underscore RL’s potential to enhance telescope tracking accuracy and scalability while reducing control system complexity for dynamic astronomical applications.

Galaxies doi: 10.3390/galaxies13060123

Authors: T. Joseph W. Lazio Stephen M. Lichten

The Deep Space Network (DSN) is the spacecraft tracking and communication infrastructure for NASA’s deep space missions. At three sites, approximately equally separated in (terrestrial) longitude, there are multiple radio antennas outfitted with cryogenic microwave receiving systems both for receiving transmissions from deep space spacecraft and for conducting radio astronomical observations, particularly in the L band (1350 MHz–1800 MHz), X band (8200 MHz–8600 MHz), and K band (18 GHz–27 GHz). In particular, the 70 m antennas at the Canberra and Madrid DSN Complexes are well-equipped to participate in international very long baseline interferometry (VLBI) observations. Over the past five years, there has been an effort to refurbish and modernize equipment such as receiving and signal transport systems for radio astronomical observations. We summarize current capabilities, on-going refurbishment activities, and possible future opportunities.

Galaxies doi: 10.3390/galaxies13060122

Authors: Holly Buroughs Anatoly S. Miroshnichenko Steve Danford Alicia N. Aarnio Sergei V. Zharikov Hans Van Winckel Nadine Manset Ashish Raj Stephen Drew Chojnowski Gregor Rauw Azamat A. Khokhlov

HD 50138 is a 6.6 mag emission-line B–type star, whose nature is still controversial. It has been thought to be a pre-main-sequence Herbig Be star and an evolved object with the B[e] phenomenon, possibly a mass-transferring binary system. However, it has mostly been studied on short timescales. We collected ∼1000 medium- and high-resolution spectra and available optical photometric data, which cover a time frame from 1981 to 2025, and extended the study from emission lines to a range of absorption lines. A few episodes of dramatic emission-line strength variations were uncovered as well as fast variations of the absorption line widths on timescales of several days. We also found a few previously unreported fadings of the star’s optical brightness seemingly associated with the Hα line profile changes. At the same time, it is still unclear whether the object is a single star or a binary system, as no regular variations of its observed parameters have been detected.

Galaxies doi: 10.3390/galaxies13060121

Authors: Nadezhda L. Vaidman Almansur T. Agishev Serik A. Khokhlov Aldiyar T. Agishev

We model the short-period cataclysmic variable EZ Lyn with MESA binary evolution and infer its present-day parameters through a staged statistical search. First, we compute a coarse grid of tracks in (M1,0,P0) at fixed M2,0 and rank snapshots by a profile likelihood. We then resample the neighbourhood of the minimum to build a refined Δχ2 surface. Finally, we sample this surface with an affine-invariant MCMC to obtain posteriors, using a likelihood that treats the one-sided constraint on the donor temperature and the ambiguity of component roles in the binary output. The best-fit snapshot reproduces the observables and identifies EZ Lyn as a period bouncer with a substellar donor. We infer MWD=0.850±0.019M⊙, M2=0.0483±0.0137M⊙, RWD=0.0092±0.0001R⊙, R2=0.099±0.005R⊙, TWD=11,500±20K, and T2=1600±50K. The instantaneous mass-transfer rate at the best-fit snapshot is M˙=3.66×10−11M⊙yr−1, consistent with the secular range implied by the white-dwarf temperature. Independent checks from the Roche mean-density relation, surface gravities, and the semi-empirical donor sequence support the solution. In population context, EZ Lyn lies in the period-minimum spike and on the low-mass tail of the donor mass–period plane. The classification is robust to modest displacements along the shallow Δχ2 valley. We release inlists, tracks, and analysis scripts for reproducibility.

Galaxies doi: 10.3390/galaxies13060120

Authors: Mareki Honma Tomoya Hirota Tomoaki Oyama Akiharu Nakagawa

We review the past 20 yr evolution of VERA (VLBI Exploration of Radio Astrometry) in both science and techinology. VERA is a VLBI array in Japan which consists of four 20 m-diameter telescopes, originally dedicated to phase-referencing VLBI astrometry. Its main observing bands are K (22 GHz) and Q (43 GHz) for conducting astrometry observations of H2O and SiO maser sources. In its 20 yr history, VERA has conducted astrometry observations of ∼100 maser sources, revealing the three-dimensional structure of the Milky Way Galaxy. Its long-term observations of Sgr A* resulted in the first parallax detection of the super-massive black hole at the Galaxy center. Observations of maser sources also revealed physical properties of star-forming regions and provided calibration of AGB stars’ distances and their Period–Luminosity relation. In parallel, several upgrades have been carried out in receivers as well as digital back-ends and correlator to extend the frequency bands and the data rate.