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Physics Astrophysics

astro-ph Watch Astrophysics

Thursday 3 September

Astrophysics of Galaxies

Star Formation Evolution in Galaxy Pairs: Constraints from Morphological Disturbances and Recent Star Formation Histories

Shaoze Geng, Shuai Feng, Shuhao Chen et al. (+8 more)

Galaxy interactions can enhance star formation, but how star formation evolves during galaxy interactions remains poorly constrained by observations. We combine pair separation, morphological disturbance, and recent star formation history to study this evolution. We measure morphological disturbance with the shape asymmetry parameter ($A_{\rm shape}$) using deep images from the DESI Legacy Surveys, and use Galaxy Zoo DESI classifications as an independent test. We infer recent star formation histories by comparing SFR and $\mathrm{EW}(\mathrm{H}\alpha)$, which trace current star formation, with $\mathrm{EW}(\mathrm{H}\delta_A)$ and $D_n4000$, which are sensitive to stellar populations formed over longer timescales. At small projected separations, strongly disturbed galaxies show the strongest enhancements in SFR and $\mathrm{EW}(\mathrm{H}\alpha)$, indicating that close encounters trigger strong star formation. At intermediate separations ($d_{\rm p}\sim100\,\mathrm{kpc}$), their current star formation is only moderately enhanced, but their $\mathrm{EW}(\mathrm{H}\delta_A)$ enhancement is the strongest. This indicates a larger contribution from intermediate-age stars formed during stronger star formation in the past $\sim0.1$–$1\,\mathrm{Gyr}$. The TNG100 analysis shows that this pattern results from rapid changes in SFR around close passage. SFR rises sharply during the encounter and declines as the galaxies move apart, while tidal disturbances remain visible. As short-lived massive stars disappear and intermediate-age A-type stars begin to dominate the spectrum, the $\mathrm{EW}(\mathrm{H}\delta_A)$ enhancement peaks later than the SFR enhancement. Our results provide important observational evidence for the evolution of SFR along the merger sequence.
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All authors Shaoze Geng, Shuai Feng, Shuhao Chen, Yaotian Duan, Shiyin Shen, Cailu Shi, Linlin Li, Yijin Niu, Bingxi Huo, Wenyuan Cui, Guozhen Hu

Cosmology and Nongalactic Astrophysics

Implementation of frequency-correlated noise in CMB component separation: Method, Validation, and Early Applications

L. Zapelli, M. Bersanelli, L. P. L. Colombo et al. (+24 more)

Parametric component separation methods used in cosmic microwave background (CMB) analyses commonly assume instrumental noise to be uncorrelated between frequency channels. This approximation may become insufficient for experiments whose design naturally introduces cross-channel correlations, such as interferometric or multi-band bolometric systems. This work aims to provide a consistent framework to include frequency-correlated noise in Commander2 and to quantify its impact on component separation in controlled and instrument-motivated simulations. We generalized the amplitude sampling of the Commander2 framework to consistently handle dense frequency-frequency noise covariance matrices, modifying the likelihood evaluation and parallel architecture. The implementation is validated on low-resolution simulations of a simplified CMB-S4-like configuration. We applied the generalized framework to instrument-motivated simulations of the QUBIC bolometric interferometer, using representative noise models derived from end-to-end simulations. Validation tests show excellent convergence and agreement between sampled parameters and analytical maximum-likelihood estimates. Accounting for frequency correlations reduces the width of the maximum-likelihood residual distributions by up to 8% on average, and up to 11% for individual parameters, relative to the diagonal-noise approximation. In QUBIC-based simulations, accounting for an anti-correlated noise produces posterior widths reduced by about 60%, while a positive-correlation test increases them by about 40%. This shows that neglecting cross-channel correlations can lead to incorrect posterior estimates in either direction. The generalized implementation presented here enables the Commander2 software to consistently propagate such correlations into parameter estimation, providing a framework for assessing their impact in future CMB analyses.
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All authors L. Zapelli, M. Bersanelli, L. P. L. Colombo, A. Mennella, L. G. Bachar, E. Battistelli, I. Bekkaoui, L. A. Bianchi, A. Coppolecchia, B. Costanza, P. De Bernardis, G. De Gasperis, S. Ferazzoli, M. Galloway, B. García, M. Gervasi, N. Mirón-Granese, J-Ch. Hamilton, T. Laclavère, J. G. S. Lunde, S. Masi, Y. Moulane, S. Paradiso, I. D. Queirolo, M. Regnier, G. E. Romero, C. G. Scóccola

Solar and Stellar Astrophysics · Cross-listed from nucl-th

Breakdown of the Plane-Wave Trojan Horse Analysis of the $^{12}\mathrm{C}+{}^{12}\mathrm{C}$ Fusion Reaction: Critical Role of Coulomb Distortions

Akram Mukhamedzhanov

Recently, a new Trojan Horse Method (THM) measurement of carbon-carbon fusion was reported by Li et al. [Phys. Lett. B (2026) 140675]. The purpose of the present work is to demonstrate the breakdown of the plane-wave approximation used in the analysis of these data and the critical role of Coulomb distortions in the initial and final states. The reaction mechanism underlying the THM analysis of the $^{12}\mathrm{C}+{}^{12}\mathrm{C}$ fusion reaction using the $^{16}\mathrm{O}+{}^{12}\mathrm{C}\to \alpha_s+\alpha+{}^{20}\mathrm{Ne}$ reaction is investigated. Particular attention is paid to the spectator momentum distribution and to the dependence of the THM reaction amplitude on the relative carbon-carbon energy $E$. It is demonstrated that agreement with the measured spectator momentum distribution does not by itself validate the plane-wave approximation. Although the experimental momentum distribution can be reproduced, inclusion of Coulomb distortions in both the initial and final channels leads to an energy dependence of the THM amplitude that is completely different from the plane-wave result. Consequently, the energy dependence of the $^{12}\mathrm{C}+{}^{12}\mathrm{C}$ fusion cross section extracted from the THM data can be strongly distorted by the plane-wave treatment. It is concluded that the astrophysical factor extracted in the plane-wave analysis cannot be regarded as reliable and may lead to misleading conclusions concerning the low-energy $^{12}\mathrm{C}+{}^{12}\mathrm{C}$ fusion reaction.
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High Energy Astrophysical Phenomena

Preferential accretion onto eccentric and unequal binary black holes

Stanislav DeLaurentiis, Zoltán Haiman and Magdalena Siwek

Supermassive binary black holes (SMBBHs) are expected to be surrounded by circumbinary disks (CBDs) which affect the binary through gravitational forces and accretion. It has been reported that the binary can experience “preferential accretion” where one black hole (BH) out-accretes the other for hundreds of orbits, but this asymmetry has yet to be fully described or understood. In this work, we utilize a suite of 80 SMBBH hydrodynamical simulations with varying mass ratios ($q_b$) and eccentricity ($e_b$) in order to robustly delineate the behavior of preferential accretion, determine its relationship to the structure of the CBD, and study its observational consequences. We characterize the accretion-rate ratio $\lambda(t) \equiv \dot{M}_2(t)/\dot{M}_1(t)$ and the mass-ratio rate of change $\dot{q}_b \equiv d/dt(M_2/M_1)$ across the suite. We confirm that the secondary tends to out-accrete the primary ($\lambda \geq 1$), and find this preference to be strongest for low-$e_b$, low-$q_b$ binaries and increasingly time-variable toward high $e_b$. We also find that (i) the time-variability of $\lambda$ tracks the precession of the CBD, (ii) there can be sub- and super-Eddington accretion in a single binary, and (iii) the gas-driven approach toward equal mass becomes particularly slow for highly eccentric, high $q_b$ binaries, suggesting that some binaries may not reach $q_b=1$ within the $30\,\mathrm{Myr}$ lifetime of a quasar and therefore allowing LISA to constrain the accretion history of SMBBHs. Our findings also suggest that periodically flickering jets are a potential observable signature of many binaries.
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Cosmology and Nongalactic Astrophysics

The Super-Sample Covariance of Line-Intensity Mapping Power Spectrum

Sefa Pamuk, José Luis Bernal and Azadeh Moradinezhad Dizgah

In this work, we provide the first derivation of the line-intensity mapping (LIM) power spectrum super-sample covariance (SSC) from first principles, and also derive as a by-product the non-Gaussian in-box contributions to the covariance for the first time. Previous studies have typically modelled the LIM power spectrum covariance using either the Gaussian approximation or estimates obtained from mocks or the data itself, neglecting uncertainties related to whether the limited volume surveyed sits in a cosmological overdensity. This contribution, known as the SSC or, depending on the context, the field-to-field variance, cannot be estimated from the data, but it is crucial for a correct inference of global quantities, i.e., for ensemble-averaged parameters rather than the actual values just within the patch of the Universe observed. For our derivation, we employ a combination of the halo model and standard perturbation theory that allows us to capture the nonlinearity and non-Gaussianity of the covariance. After a successful validation of our predictions against painted N-body simulations, we explore different scenarios related to current and future LIM experiments, quantifying the relative importance of the non-Gaussian in-box and SSC. We find that the newly derived contributions to the LIM power spectrum covariance are crucial at intermediate and small scales, especially for cases in which the covariance is not dominated by instrumental noise. We find that the relative relevance of the SSC with respect to the other covariance contributions is roughly independent of the survey volume, but does depend on the specific response of the power spectrum to large-scale modes for each line and redshift. Therefore, the impact of the SSC will be increasingly significant for parameter inference from the current and the next generation high signal-to-noise LIM surveys.
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Instrumentation and Methods for Astrophysics

Identifying Casual SETI Transmissions and Ultra-Faint RFI with Cumulant Imaging

Miguel F. Morales

Techniques for identifying radio beacons transmitted by extra-terrestrial civilizations are well advanced. However, the casual broadband emission from standard radio communication is much harder to detect, and counter-intuitively casual Earth radio transmissions are becoming more difficult to identify as we more efficiently utilize the radio spectrum. In this paper we examine the electric-field statistics behind radio communication and re-conceptualize standard radio imaging as the first non-zero cumulant. This leads us to images of the higher cumulants where the natural stochastic emission from astrophysical sources disappears, leaving images of only modulated sources of radio communication. Faint SETI and RFI sources stand out in these cumulant images, enabling identification of faint communication that is undetectable with current techniques.
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Earth and Planetary Astrophysics

Circumbinary planets in coplanar triple-star systems: I. Minimum eccentricity variation region

Emmanuel Gianuzzi, Mario Sucerquia, Nicolás Cuello et al. (+1 more)

We aim to determine the conditions under which Lidov-Kozai oscillations can arise for circumbinary planets in hierarchical triple-star systems, and to identify the orbital regions where competing secular perturbations minimize eccentricity excitation. We analyzed the statistical properties of hierarchical triples from the Multiple Star Catalog to construct representative synthetic configurations. We then performed N-body simulations of circumbinary planets embedded in these systems, systematically exploring their orbital evolution and long-term stability across a range of semimajor axes and inclinations. For representative compact hierarchical triple-star systems with masses $m_0 \sim m_1 \approx 0.75\,{\rm M}_\odot$ and $m_2 \approx 0.6\,{\rm M}_\odot$ and eccentricities $e_1 \sim 0.1$ and $e_2 \sim 0.4$, dynamically significant stable circumbinary regions exist only in sufficiently hierarchical configurations, with period ratios $P_2 /P_1 \gtrsim 10^2$. In this regime, the secular competition between the tertiary perturbations and the apsidal precession induced by the compact inner binary determines both the onset of Lidov-Kozai oscillations beyond a critical distance ($a_{\rm LK}$) and the location of a region where eccentricity variations are minimized, i.e., the minimum eccentricity variation region (MER). We derived analytical estimates for these dynamical features, showing that the MER is well described by the analytical quantity $a_{\rm short}$ on short and intermediate timescales, while on secular timescales it converges toward the equilibrium prediction $a_{\rm ME}$. These analytical estimates agree well with N-body simulations. Application to the observed triple system WDS 08403+1921 confirms that $a_{\rm LK}$ and $a_{\rm ME}$ accurately identify the main dynamical features of the stability map.
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All authors Emmanuel Gianuzzi, Mario Sucerquia, Nicolás Cuello, Cristian Giuppone

Solar and Stellar Astrophysics · Cross-listed from hep-ph

Stability of Collective Neutrino Oscillations – A Distributional Approach

Rupak Majumder, Dwaipayan Mukherjee, Shamik Gupta et al. (+1 more)

We study the stability of collective neutrino oscillations using a distributional approach motivated by the statistical mechanics of Kuramoto synchronization. Treating the ensemble of neutrino flavor polarization vectors in the thermodynamic limit $N\to\infty$, we derive an exact nonlinear Fokker–Planck (continuity) equation for the one-body distribution $F(\vec{\mathbf{S}},\omega,t)$ on the flavor sphere. This equation admits a two-parameter family of azimuthally symmetric stationary solutions, whose stability we analyze by linearizing around them. The resulting eigenvalue condition determines the growth or decay rate of small perturbations from any initial distribution – not merely from a state close to full flavor coherence – thereby going significantly beyond the conventional linear stability analysis of collective modes. In special limits the condition reproduces known synchronization thresholds in the two-beam model, providing a non-trivial check of the framework. We present analytical results for the eigenvalue equation and explore stability phase diagrams for physically relevant frequency distributions.
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All authors Rupak Majumder, Dwaipayan Mukherjee, Shamik Gupta, Basudeb Dasgupta

Astrophysics of Galaxies

KKR 18: A Late Arrival Galaxy?

R. Brent Tully, Valentina E. Karachentseva, Igor D. Karachentsev et al. (+8 more)

KKR 18 is a dwarf irregular galaxy in the Local Void at a distance of 9.46 Mpc. It is gas rich and was experiencing vigorous star formation 20 - 100 Myr ago. Its metallicity is 4% of Solar from an emission spectrum, qualifying is as extremely metal poor (XMP). Its most remarkable characteristic is an extremely deficient Red Giant Branch. This feature is shared with a small number of other dwarf galaxies and it is inferred that they lack ancient stellar components. It is suggested that these are late arrival galaxies (LAG).
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All authors R. Brent Tully, Valentina E. Karachentseva, Igor D. Karachentsev, Gagandeep S. Anand, Maksim I. Chazov, Serafim S. Kaisan, Ehsan Kourkchi, Lidia N. Makarova, Simon A. Pustilnik, Edward J Shaya, Arina L. Tepliakova

Astrophysics of Galaxies

Linking orbital history to the quenching of isolated dwarf galaxies

Sophia Um, Devontae C. Baxter and Ethan O. Nadler

Recent discoveries of isolated dwarf galaxies (${M}_{\star}\sim 10^{7-9}~{\rm M}_{\odot}$) with no signs of ongoing star formation have challenged the prevailing notion that these solitary systems are exclusively star-forming. Investigating the origins of isolated quenched dwarfs provides important clues into the dominant processes driving galaxy quenching as a function of environment and stellar mass. In this study, we identify central dwarf galaxies in the Illustris-TNG50 cosmological simulation with ${M}_{\star} \sim 10^{7-9}~{\rm M}_{\odot}$, evaluate their star formation and orbital histories, and investigate how their dark matter halo properties correlate with quenching and interactions with massive neighbors. We find that $R_{\rm{peri}}$, defined as the closest separation ever attained between a central dwarf and a galaxy more massive than ${M}_{\star}> 10^{10}~{\rm M}_{\odot}$, is a reliable metric for inferring the star formation history of central dwarfs in TNG50. We also show that isolated quenched dwarf galaxies separate into backsplash and non-backsplash subpopulations as a function of $R_{\rm{peri}}$, and that non-backsplash galaxies are consistent with being quenched by cosmic web stripping or internal feedback mechanisms. Furthermore, we find that $R_{\rm{peri}}$ correlates strongly with dark matter halo mass and star formation proxies based on halo maximum circular velocity, which are commonly used in empirical galaxy-halo connection models. These predictions can be tested with data from upcoming deep and wide surveys (e.g., Rubin LSST and Roman) that are anticipated to significantly increase the cosmic census of dwarf galaxies.
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Astrophysics of Galaxies

Hint of bimodal Mg-Al anticorrelation in the metal-poor Globular Cluster NGC 4372

Camila Beltrand, Macarena Uribe, Sandro Villanova et al. (+1 more)

We present a detailed chemical abundance analysis of seven red giant branch stars in the very metal-poor globular cluster NGC~4372, based on high-resolution UVES spectra. Our study aims to characterize the chemical evolution of NGC~4372 and investigate the presence of multiple populations. We derived abundances for 17 elements, including light, iron-peak, $\alpha$, and heavy elements, using both equivalent width and spectral synthesis methods. We find a mean cluster metallicity of [Fe/H]=$-$2.36 $\pm$ 0.03 dex, with no evidence of an intrinsic iron spread. The cluster exhibits a typical $\alpha$-enhancement of [$\alpha$/Fe]= 0.33 $\pm$ 0.05 dex and a well defined Na-O anticorrelation, confirming that NGC 4372 hosts at least two distinct stellar populations. Furthermore, the measured ratio of [Ba/Eu] =$-0.47 \pm 0.04$ indicates that the synthesis of heavy elements was dominated by $r$-process, consistent with other very metal-poor environments. We also identify a potential bimodal Mg-Al anticorrelation, which aligns with the patterns observed in GCs of similar mass and metallicity. These results reinforce the status of NGC 4372 as a cornerstone for understanding the early chemical enrichment of the Galactic Halo.
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All authors Camila Beltrand, Macarena Uribe, Sandro Villanova, César Muñoz

Astrophysics of Galaxies

Extending the Stellar-to-Halo Mass Relation to Dwarf Galaxies with DESI DR1

Z. Shao, Y. Zu, A. Salcedo et al. (+51 more)

Constraining the dark matter halos of the smallest galaxies offers fundamental insights into the nature of dark matter and stellar feedback. Using the Dark Energy Spectroscopic Instrument (DESI) Data Release 1, we infer the stellar-to-halo mass relation (SHMR) down to the dwarf scale ($M_\star < 10^9\,M_\odot$), without extrapolation from the higher mass range. Leveraging the unprecedented depth of the DESI Bright Galaxy Survey at $0.01 < z < 0.2$, we construct 12 samples spanning nearly four orders of magnitude in stellar mass, and measure their projected clustering $w_p$, galaxy-galaxy lensing $\Delta\Sigma$, as well as a novel observable: satellite occupation number $N_{\rm sat}$. The addition of $N_{\rm sat}$ enables robust subtraction of satellite contributions to both $w_p$ and $\Delta\Sigma$ across the 12 individual halo occupation distribution analyses, yielding an average halo-to-stellar mass relation (HSMR) of $\log \langle M_h(M_\star) \rangle = 12.06 + 0.58\log(M_\star/10^{11}) + (M_\star/10^{11})^{0.73}$. Combining this HSMR with an observed stellar mass function, we constrain the SHMR across five orders of magnitude in halo mass, with the power-law slope steepening from $0.32 \pm 0.06$ above the Milky Way mass to $2.08 \pm 0.21$ in the dwarf regime. Interestingly, the scatter about the SHMR grows from $0.17 \pm 0.02$ dex at Milky Way-like scales to $0.68_{-0.33}^{+0.21}$ dex for systems comparable to the Large Magellanic Cloud, suggesting that smaller galaxies follow increasingly diverse evolutionary paths. Our work highlights the power of DESI in probing the galaxy-halo connection within the dwarf regime, offering an exciting avenue to bridge the gap between large-scale and near-field cosmologies in the future.
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All authors Z. Shao, Y. Zu, A. Salcedo, Y. Lin, Z. Chen, X. Xu, J. Hua, Z. Zhai, J. Aguilar, S. Ahlen, F. Beutler, D. Bianchi, D. Brooks, A. Carnero Rosell, F. J. Castander, T. Claybaugh, A. de la Macorra, Biprateep Dey, Z. Ding, J. E. Forero-Romero, E. Gaztañaga, Satya Gontcho A Gontcho, G. Gutierrez, C. Hahn, S. Juneau, R. Kehoe, A. Kremin, O. Lahav, A. Lambert, M. Landriau, L. Le Guillou, M. Manera, P. Martini, A. Meisner, R. Miquel, J. Moustakas, S. Nadathur, E. Paillas, W. J. Percival, F. Prada, I. Pérez-Ràfols, C. Ravoux, G. Rossi, R. Ruggeri, M. Saraf, L. Samushia, E. Sanchez, C. Saulder, D. Schlegel, J. Silber, M. Siudek, G. Tarlé, B. A. Weaver, H. Zou

Astrophysics of Galaxies

H I Absorbers as Beacons of Hidden Structure at $z \sim 3$: Multi-Component, Metal-Rich Absorption System near a Protocluster

Kentaro Koretomo, Nobunari Kashikawa, Toru Misawa et al. (+12 more)

H I gas traces the large-scale structure and provides the primary fuel for star formation. High-$z$ protoclusters are ideal laboratories to study how H I gas is accreted and consumed during the formation of the most massive structures in the Universe. However, much remains unknown about the distribution and physical state of their H I gas. We examine a rare configuration in which a protocluster candidate is located in front of a quasar at $z=3.09$. Our spectroscopic campaign confirms a protocluster at $z=3.079$: however, no corresponding strong H I absorption is found in the background quasar spectrum. Instead, we serendipitously discover a prominent H I absorption feature at $z\sim 3.01$, offset by $\sim 60$ cMpc from the centre of the protocluster. Spanning an exceptionally broad velocity range of $\sim 2000$ km s$^{-1}$ ($\sim 40$ cMpc), this absorption is decoupled from the confirmed member galaxies. Detailed kinematic modelling reveals this absorption comprises five distinct components rather than a single cloud. Moreover, one of these components exhibits a super-solar metallicity ($[\mathrm{O/H}] = +1.19^{+0.91}_{-0.78}$). We propose two physical scenarios for this unique system: (1) an additional, hidden massive protocluster along the line of sight, and/or (2) metal-rich outflows and metal-poor inflows driven by a single massive galaxy. The discovery highlights that while protoclusters are not universally associated with strong H I absorption, targeting the strong H I absorbers may serve as a beacon for uncovering massive, metal-rich protoclusters or complex gas kinematics in the early Universe.
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All authors Kentaro Koretomo, Nobunari Kashikawa, Toru Misawa, Jun Toshikawa, Yoshihiro Takeda, Hisakazu Uchiyama, Junya Arita, Shunta Shimizu, Ryo Emori, Kei Ito, Satoshi Kikuta, Mariko Kubo, Yoshiaki Ono, Marcin Sawicki, Rhythm Shimakawa

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Waveform models for the gravitational-wave memory effect: III. Phenomenological frequency-domain model for nonspinning binaries

Arwa Elhashash and David A. Nichols

We present a phenomenological frequency-domain model for the gravitational-wave (GW) memory signal from nonspinning binary-black-hole mergers on quasicircular orbits. We develop separate amplitude and phase models for the dominant $(l,m)=(2,0)$ spherical-harmonic mode of the GW memory signal. The amplitude and phase models are built from superpositions of elementary and transcendental functions, which can be evaluated efficiently. Both portions of the model are calibrated against a numerical-relativity surrogate model over mass ratios from one to eight. Their accuracy is assessed by computing their mismatch with the numerical-relativity models using the Advanced LIGO sensitivity curve from the fourth observing run. The mismatches are of the order $10^{-4}\unicode{x2013}10^{-3}$ over the parameter space of total mass covered by LIGO. The resulting frequency-domain model is a more computationally efficient waveform model for the GW memory signal than a related time-domain model earlier produced by the authors. An open-access implementation of both the time-domain and frequency-domain models is provided in the Python package GWMemoryModel, which can be used for relevant analyses of nonspinning binary black holes.
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Cosmology and Nongalactic Astrophysics

Model Predictive Scoring Shows Specific BAO Observations (not SNIa) Drives $w_0w_a$ Tension

Tanveer Karim, Joshua S. Speagle and Renée Hložek

The recent analyses of DESI DR2 BAO, Planck CMB and various Supernovae datasets have shown preferences for evolving dark energy at various levels of significance, under frequentist model comparison tests. However, the same analysis done with a pure Bayesian model comparison test can lead to the opposite conclusion due to the impact of $w_0w_a$ priors. In contrast to these in-sample model comparison route, we approach the problem along a third axis – which model better predicts unseen data. We use the Expected Log Predictive Density (ELPD) metric to score the predictiveness of $\Lambda$CDM and $w_0w_a$CDM models, using the leave-one-redshift-block-out cross-validation estimator. The comparison metric $\Delta$ELPD is out-of-sample, unlike $\Delta \chi^2_{\rm MAP}$ and Bayes Factor, and insensitive to prior width, unlike the Bayes factor. Aggregated, we find modest preferences for $w_0 w_a$CDM, primarily driven by the BAO. Decomposing the $\Delta$ELPD score by redshift we find that a single BAO block, LRG2 ($z = 0.706$), supplies the entire BAO preference. Interestingly, the biggest outlier point, LRG1, contributes little to the model predictive scoring because both $\Lambda$CDM and $w_0w_a$CDM fail to predict the observation by equal amount. On the other hand, all SNIa datasets' $\Delta$ELPD scores are consistent with $0$, indicating that at an out-of-distribution predictive level, the $w_0w_a$CDM tension is entirely driven by one BAO point, not SNIa.
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Astrophysics of Galaxies

Widespread Inflows Reveal Baryonic Cycling in Star-forming and Quiescent Galaxies

Hassen M. Yesuf, Ravi Joshi, Yuxuan Zou et al. (+8 more)

Cool-gas inflows, required to sustain star formation, have been fundamental in simulations yet remained observationally elusive. Using DESI spectroscopy of ~30,000 galaxies, we identify coherent inflowing gas (~100 km/s) in 20-50% of the sample, yielding a population-level census of gas flows. We uncover a striking inversion: inflows are detected in quiescent galaxies, whereas star-forming systems are dominated by gravitationally bound outflows. At fixed age, galaxies with inflows, outflows, or no/weak flows share similar masses, environments, and structures, indicating that these properties do not differentiate flow states. Instead, gas-flow state is linked to stellar population age and recent evolutionary history, consistent with age-dependent gas flows in two regimes. In some star-forming galaxies, elevated star formation surface densities drive outflows that recycle on ~0.5 Gyr timescales, consistent with a galactic fountain. In quiescent systems, low-level “drizzling” inflows persist, consistent with slowly cooling enriched halo gas and weak radio-mode nuclear activity. Broad gas-phase metallicity distributions—and absence of a pristine dilution signature—indicate that detected inflows are predominantly recycled or enriched. Detectability is modulated by dust, ionization, and geometry: in star-forming disks, inflowing gas lies near the disk plane and is obscured or ionized, while outflow hosts exhibit higher dust and metal content. As star formation declines, cold-outflow signatures weaken, and recycled or slowly cooling gas is more readily detected as inflow. Post-starburst galaxies provide snapshots of this transition. Our results resolve the scarcity of observed inflows, provide evidence for widespread gas accretion and recycling in present day galaxies, and establish an observational framework linking gas flows to star formation, chemical evolution, and galaxy structure.
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All authors Hassen M. Yesuf, Ravi Joshi, Yuxuan Zou, Feng Yuan, Luis C. Ho, Lin Lin, Lei Hao, Shiyin Shen, Connor Bottrell, Fulai Guo, John D. Silverman

Astrophysics of Galaxies

Recovering Ionizing Photon Escape and Galaxy Scaling Relations in the LzLCS via Si II and C II Absorption Lines and Mock Spectra from a Radiation-Hydrodynamic Simulation

John Trevino, Simon Gazagnes, Danielle A. Berg et al. (+7 more)

In this work, we use a radiation-hydrodynamic simulation of a single $\sim10^9M_{\odot}$ virtual galaxy to study Si II and C II line profiles seen in stacked HST/COS spectra of 58 galaxies from the LzLCS+ sample. We compare stacks across three mass bins ($M_{\star} \leq 10^8M_{\odot}$, $10^8$-$10^9M_{\odot}$, and $M_{\star} \geq 10^9M_{\odot}$) and three stacking methods (mean, median, and weighted average) to a library of 22,500 mock spectra. We investigate whether the simulation can accurately mimic real gas features, reveal clear trends with galaxy properties, and provide indirect estimates of the ionizing escape fraction ($f_{\rm esc}$). We find reasonable agreement between simulated and observed profiles ($\chi^2 < 1$) across all mass regimes. Notably, extracting line properties such as EW and $R_f$ from best-fit mock profiles provides a robust alternative to direct empirical trends, particularly in the low-S/N regime where noise frequently biases results. The simulation-based LIS features, although derived from a single virtual object, exhibit clear correlations with $M_{\star}$, SFR, and $f_{\rm esc}$, mirroring established empirical scaling relations. We find that the best-matching mock spectra predominantly originate from simulation time steps corresponding to peak UV luminosity and intense starburst phases, suggesting that these active periods generate the ISM diversity observed in star-forming galaxies. Finally, simulation-based estimates ($f_{\rm esc}^{\rm virtual}$) reproduce the observed mass-dependent trends in $f_{\rm esc}$ and are in close agreement with the average $f_{\rm esc}$ of the generated stacks. This simulation-based framework establishes a relevant methodology for interpreting spectroscopic observations, including inferring $f_{\rm esc}$ and characterizing physical scaling relations, in high-redshift galaxies from the Epoch of Reionization.
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All authors John Trevino, Simon Gazagnes, Danielle A. Berg, Kaelee S. Parker, Valentin Mauerhofer, Jeremy Blaizot, Anne Verhamme, Sophia R. Flury, Anne E. Jaskot, Alberto Saldana-Lopez

Solar and Stellar Astrophysics

Improvements to Asteroseismic Fitting of White Dwarfs in the Gaia Era

Andrew H. Dublin, Keaton J. Bell and Agnès Bischoff-Kim

White dwarf asteroseismology aims to constrain the interior structures of pulsating white dwarf stars by fitting observed pulsation periods to those computed for stellar models. However, there remain several obstacles for achieving reliable results with the model grid-fitting approach. We simulate data for a parameter recovery experiment in one and two dimensions (mass and effective temperature) to demonstrate improved methodologies that address challenges for characterizing degenerate asteroseismic solutions. We show that interpolating model periods onto a finer grid can adequately resolve asteroseismic solutions that would be missed with sparse model grids. Incorporating absolute magnitude from Gaia astrometry into the statistical fitting is shown to reduce solution degeneracy. We define a seismic solution as a solution to the mode identification problem, and we show that fitting to consistent model pulsation modes can isolate each candidate solution in degenerate solution space. A criterion based on $\chi^2$ for what should be considered a reasonable fit is adopted, and we identify all combinations of model periods that meet this criterion, not only those nearest to the measured periods. Finally, we demonstrate how fitting Gaussians to probability distributions allows for the robust characterization of each candidate solution, including uncertainties. Our accurate characterization of the degenerate solution landscape is supported by the comparison of our solutions to a direct marginalization of the likelihood function. These fitting approaches can be generalized to higher dimensions, where there are more than two free parameters.
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Astrophysics of Galaxies

AGN-DB: A Unified Multi-Wavelength Database of Active Galactic Nuclei

Alessandro Peca, Nico Cappelluti, C. Megan Urry et al. (+29 more)

We present the Active Galactic Nuclei Database (AGN-DB), a comprehensive, multi-wavelength catalog compiled from more than 100 publicly available AGN catalogs and samples released by the end of 2025, spanning radio to $\gamma$-ray wavelengths. The database contains approximately 8.1 million unique sources, approximately 7.8 million of which remain after flagging stellar contaminants, and approximately 6.8 million of these are classified as AGN. Source cross-matching across catalogs is performed using Lyra, a Bayesian likelihood-ratio framework that jointly considers positional uncertainties, source densities, and photometric information to compute posterior match probabilities. The resulting catalog provides astrometric coordinates, redshifts, photometry, and classifications for each unique source. All multi-catalog provenance is preserved. For every property, we store the full array of values and originating catalog identifiers, enabling multi-epoch and multi-survey analyses. In this paper, we describe the AGN-DB pipeline, including the cross-matching methodology, and present the statistical properties of the v1.0 catalog. AGN-DB is designed to enable population studies, spectral energy distribution modeling, AGN classification, and variability analyses at an unprecedented scale. Its pipeline is designed to facilitate the integration of new catalogs, allowing AGN-DB to be updated regularly, with releases planned at least annually.
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All authors Alessandro Peca, Nico Cappelluti, C. Megan Urry, Zhongtian Hu, Jerry R. Bonnell, Jack McKeown, Giulia Cerini, Xulei Sun, Fabio Pacucci, Tracey Jane Turner, Peter G. Boorman, Aritra Ghosh, Connor Auge, Rebeka L. Böttger, Adi Foord, Massimiliano Galeazzi, Jeyhan S. Kartaltepe, Iver Warburton Kilmarrin, Allison Kirkpatrick, Michael J. Koss, Stephanie LaMassa, Md Mahmudunnobe, Stefano Marchesi, Lea Marcotulli, Isaac Moskowitz, Priyamvada Natarajan, Mitsunori Ogihara, Meredith Powell, David Sanders, Dominic Sicilian, Chuan Tian, Ezequiel Treister

Astrophysics of Galaxies

Resolved Dust-Gas-Metallicity relations in nearby spiral galaxies

Vidhi Tailor, Viviana Casasola, Francesco Calura et al. (+17 more)

Context: Understanding the interstellar medium (ISM) requires high-resolution, multi-component mapping to capture its complex physical structure. Nearby spiral galaxies, with their abundant and diverse ISM, provide an ideal laboratory for such a comprehensive analysis at sub-galactic scales. Aims: We investigate dust-to-gas (DGR) and dust-to-metal (DMR) ratios as a functions of gas-phase metallicity (Z), on spatial scales ranging from 0.6 to 2.3 kpc, in a sample of 10 nearby spiral galaxies, spanning more than an order of magnitude in stellar mass (9.7 \le \log(M_*/M_\odot) \leq 11.0), star formation rate (SFR, \sim 0.3–3 \, M_\odot \, \rm yr^{-1}) and metallicity ranging from 8.3 \lesssim 12 + \log( O/H) \lesssim 8.8. We explore how the DGR-Z and DMR-Z relations are shaped by the assumptions behind the CO-to-H_2 conversion factor (\alpha_{CO}). Methods: We homogeneously combine maps of dust, atomic gas, molecular gas, and metallicity. Motivated by the diversity in L_{CO(1-0)}/SFR ratios and metallicity across our sample, we introduce a hybrid \alpha_{CO} prescription to distinguish between CO-bright and CO-dark regimes. The derived DGR-Z and DMR-Z relations are compared with other global and resolved observational results, and with the predictions of dust and chemical evolution models. Results: Both DGR-Z and DMR-Z relations are dependent on the adopted \alpha_{CO} prescription, and no single \alpha_{CO} can reproduce the properties of the entire sample, motivating the use of a hybrid approach. The DGR increases with metallicity, spanning \sim 1 dex across the sampled range; while the DMR remains approximately constant at \log(\mathrm{DMR}) = -0.53 \pm 0.13, implying that \sim 30 % of metals are locked into dust grains. This flat behavior indicates an evolved dust phase where efficient ISM grain growth drives a saturation regime balancing dust formation and destruction.
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All authors Vidhi Tailor, Viviana Casasola, Francesco Calura, Francesca Pozzi, Jacopo Fritz, Maritza Lara-López, Marco Palla, Simone Bianchi, Santiago Álvarez-Córdoba, Matteo Bonato, María Emilia De Rossi, Sami Dib, Luis E. Garduño, Andrea Giannetti, Omar López Cruz, Marina M. Puebla, Evangelos D. Paspaliaris, Leonid S. Pilyugin, Guillermo Valé, Mabel Valerdi

Earth and Planetary Astrophysics

Composition gradients in sub-Neptunes: K2-18 b and TOI-270 d as case studies

Luca Morf and Ravit Helled

Structure models of sub-Neptunes commonly assume purely adiabatic interiors with distinct layers of homogeneous composition. We assess how allowing for more complex interiors with composition gradients affects the inferred internal structure and bulk compositions of the sub-Neptunes K2-18 b and TOI-270 d. We compare purely adiabatic models with distinct layers against models that include composition gradients and stable non-convective regions. We present solutions that are consistent with the observed masses, radii, and atmospheric boundary conditions. We find that composition gradients significantly increase the range of viable interior structures: For example, the interior degeneracy remains substantial even for fixed mass and radius and the maximum hydrogen-helium (H-He) mass fraction can increase by up to a factor of five for K2-18 b. We further show that correlations, such as those between the H-He abundance and the ice-to-rock or rock-to-iron ratios, can weaken when composition gradients are introduced. For example, the Spearman rank correlation coefficient between the H-He and iron abundances decreases from $\sim0.7$ to $\sim0.4$ for TOI-270 d in our models. Purely adiabatic models underestimate the range of plausible compositions and overestimate the impact of more precise measurements, atmosphere models, and host star constraints on a more accurate characterization. We suggest that interior models of sub-Neptunes should by default include more complex interiors, such as composition gradients and non-convective regions, when using data for interpreting the planetary structure, formation, and evolution.
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Astrophysics of Galaxies

Super-Eddington Accretion and Early-Stage Feedback in Ton S180

Pierpaolo Condò, Giacomo Venturi, Eleonora Parlanti et al. (+15 more)

Narrow-line Seyfert 1 (NLSy1) galaxies are key laboratories for studying rapid supermassive black hole (SMBH) growth and active galactic nucleus (AGN) feedback at high accretion rates. We investigate the nearby NLSy1 Ton S180 with VLT-MUSE optical integral field spectroscopy to connect its nuclear accretion properties with the spatially resolved ionized gas and host-galaxy kinematics. We modeled the unresolved nuclear spectrum and applied a custom point spread function subtraction to recover the host-galaxy emission on kiloparsec scales. The nuclear spectrum requires a complex permitted-line decomposition and a blueshifted [O III] outflow component. Single-epoch estimators and the stellar velocity dispersion imply black hole masses in the range $\log(M_{\rm BH}/M_\odot) = 6.5 - 7.7$. Combined with the observed luminosity, this implies a dimensionless mass accretion rate of $\dot{M} / \dot{M}_{\rm Edd} = 4.1 - 980$, confirming the extreme accretion regime. The host galaxy shows a circumnuclear ring, an inner elongated structure consistent with a bar, and rotation-dominated gas and stellar kinematics. Simple inflow models do not significantly better reproduce the observed velocity field. We detect a resolved ionized outflow extending about 2 kpc west of the nucleus, with mildly blueshifted velocities (with a maximum of $v_{\rm max} \sim 340$ km s$^{-1}$). Its mass outflow rate is only $\sim 4.2 \times 10^{-4}\,M_\odot\,\mathrm{yr}^{-1}$, whereas the unresolved nuclear outflow reaches $v_{\rm max} \sim 1140$ km s$^{-1}$ and $\dot{M}_{\rm out} > 1.5\,M_\odot\,\mathrm{yr}^{-1}$. This contrast may reflect either weak ionized coupling from nuclear to galactic scales or different episodes of AGN activity over time. These results show that Ton S180 is undergoing rapid SMBH growth, while the observed ionized outflow remains confined to the inner few kiloparsecs and is weak on host-galaxy scales.
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All authors Pierpaolo Condò, Giacomo Venturi, Eleonora Parlanti, Marco Berton, Enrico Congiu, Alessia Tortosa, Stefano Carniani, Francesco Tombesi, Tommaso Zana, Claudio Ricci, Ezequiel Treister, Luis C. Ho, Enrico Piconcelli, Miguel Coloma Puga, Emilia Järvelä, Luca Crepaldi, Amelia Vietri, Benedetta Dalla Barba

High Energy Astrophysical Phenomena

A Kinematic Measurement of the Effective Viscosity of the Intracluster Medium: The Cold Front of A3667 Seen by XRISM

Yutaka Fujita and Yuki Omiya

Constraints on the effective viscosity of the intracluster medium (ICM) come almost exclusively from imaging: the power spectrum of X-ray surface brightness fluctuations, and the morphology of Kelvin-Helmholtz rolls at cold fronts. Both indicate a viscosity below the isotropic Spitzer value. XRISM/Resolve opens a complementary, purely kinematic route, in which the viscosity is inferred from the thickness of the viscous shear layer that develops at a sliding contact discontinuity. We apply it to the prototypical cold front of A3667. The interface is the classical Rayleigh problem, in which momentum diffuses to a depth d in a time T, giving a kinematic viscosity \nu ~ d^2/(4T). The XRISM velocity map shows a line-of-sight velocity jump of 535 km/s across the front, completed within the 100 kpc-wide region immediately inside it, the only region with an anomalously broad line. Hence d ~< 100 kpc. Adopting interaction times set by the sizes of the interacting regions divided by this velocity, we obtain dynamic viscosities of 5.2 x 10^3 and 3.3 x 10^3 g/cm/s for the cool and the hot side of the front, or 6.4 and 0.72 times the Spitzer value. Because d is limited by the angular resolution of XRISM, and the viscosity scales as its square, these are upper limits. The kinematic constraint is consistent with, and independent of, the imaging results.
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Astrophysics of Galaxies

JWST/NIRSpec Reveals Diverse Nuclear Environments in Dwarf Galaxies Hosting AGN

Thomas Bohn, Archana Aravindan, Gabriela Canalizo et al. (+18 more)

Dwarf galaxies, in the $\Lambda$CDM framework, are expected to dominate the galaxy number density at all redshifts. As such, studying AGN in these systems, including characterizing their local environments and emission properties, is essential in obtaining a comprehensive view of the AGN population and their influence on their host galaxy. To this end, we present JWST/NIRSpec IFU observations of four dwarf galaxies (M$_\star<$10$^{9.5}\;$M$_\odot$) with evidence of AGN activity. Utilizing the improvements in resolution and sensitivity offered by JWST, we investigate the emission features of the central kiloparsec of these dwarfs. Our findings include the detection of over 100 emission lines across our sample, including coronal lines with ionization potentials greater than 300 eV. The nuclear spectra show diverse emission features. In two galaxies, we measure strong contributions from hot dust to the infrared continuum. We also detect both PAH and coronal line emission within 100 parsecs of the nuclei in three galaxies. We estimate the hot H$_2$ gas mass to be between 1–20 M$_\odot$ within 300 pc across our sample, where both thermal and non-thermal excitation are involved. Lastly, spatial flux maps reveal varied emission structures across all observed gas phases, ranging from radial symmetry around the nucleus to elongated plumes. Kinematic maps also show each galaxy has unique velocity structures despite all being isolated, affirming the diversity of rotation curves problem, a long standing tension between simulations and observations. These results showcase the unique and varied nuclear environments that can be found in dwarf galaxies hosting AGN.
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All authors Thomas Bohn, Archana Aravindan, Gabriela Canalizo, Aditya Togi, Shobita Satyapal, Tohru Nagao, Matthew Malkan, Thomas S.Y. Lai, Hanae Inami, Weizhe Liu, Marina Bianchin, Tanio Diaz-Santos, Aaron Evans, Sean T. Linden, Vivian U, Lee Armus, Loreto Barcos-Munoz, Kirsten Larson, Yiqing Song, Sabrina Stierwalt, Jason Surace

Solar and Stellar Astrophysics

The DESI Data Release 1 white dwarf catalogue

Andrew Swan, Boris T. Gänsicke, Paula Izquierdo et al. (+49 more)

The Dark Energy Spectroscopic Instrument is conducting a redshift survey, mapping the universe in three dimensions to measure the history of cosmic expansion. As well as extragalactic objects, it is targeting millions of Milky Way stars, including white dwarfs. Using Data Release 1 we assemble the largest catalogue of spectroscopically-confirmed white dwarfs to date, whose straightforward selection function enables statistically-robust population studies. We visually inspect and fit models to spectra of 63968 objects, finding 44409 white dwarfs. We present their spectral classifications, atmospheric parameters and radial velocities. We assess survey completeness and uniformity, identify potential spectral contamination caused by flux from nearby sources entering the fibre, and assign confidence scores to our classifications to facilitate selection of statistical and observational samples. We present spectra representing most white dwarf classes, common and exotic. We conclude with recommendations and warnings regarding the use of the catalogue.
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All authors Andrew Swan, Boris T. Gänsicke, Paula Izquierdo, Detlev Koester, Christopher J. Manser, Laura K. Rogers, Siyi Xu, J. Aguilar, S. Ahlen, C. Allende Prieto, L. Beraldo e Silva, D. Bianchi, D. Brooks, F. J. Castander, T. Claybaugh, A. de la Macorra, A. Dey, A. Font-Ribera, J. E. Forero-Romero, E. Gaztañaga, N. Gentile Fusillo, S. Gontcho A Gontcho, G. Gutierrez, J. Guy, K. Honscheid, K. Inight, M. Ishak, R. Joyce, S. E. Koposov, M. Landriau, L. Le Guillou, T. S. Li, M. Manera, A. Meisner, R. Miquel, J. Moustakas, S. Nadathur, J. Najita, I. Pérez-Ràfols, W. J. Percival, F. Prada, G. Rossi, E. Sanchez, D. Schlegel, M. Schubnell, H. Seo, J. Silber, D. Sprayberry, G. Tarlé, B. A. Weaver, R. Zhou, H. Zou

Cosmology and Nongalactic Astrophysics

It's All About the Environment: Local $f_{\rm NL}$ from a Dark Matter Conditioned Multitracer Analysis

Julius Adolff and Uroš Seljak

Primordial non-Gaussianity (PNG) offers a powerful test of inflationary physics beyond the simplest single-field scenarios. In large-scale structure, biased tracers respond to local-type PNG with a distinctive scale-dependent signature that is strongest on large scales, but single-tracer measurements are fundamentally limited by cosmic variance. Multitracer methods can mitigate this limitation; however, many existing proposals require splitting tracers using a wide range of halo masses which are often not available, or using secondary halo properties that are not directly observable. Here we develop and validate an alternative strategy based on splitting a tracer sample by its large-scale dark matter environment. We derive a theoretical framework for the $f_{\rm NL}$ response of environmentally selected tracers and test it in $N$-body simulations, confirming consistency between separate-universe predictions and direct power-spectrum inference. To enable observational implementation, we show that a simple linear-theory reconstruction of the dark matter environment from halos yields unbiased $f_{\rm NL}$ constraints in $\mathtt{Quijote}$ simulations. Forecasts for the DESI LRG sample indicate that environmental multitracing can improve constraints on local PNG by a factor of 2-3 relative to conventional single-tracer analyses for high density tracers, comparable to gains achieved when halo formation time is assumed to be perfectly known. We develop an analytic model explaining why the gains are smaller for a halo environment split and why separate-universe predictions fail in this case. Unlike approaches that require modeling assembly bias or inferring secondary halo properties, our method relies only on linear theory. These results establish environmental multitracer techniques as a promising route toward $\sigma(f_{\rm NL})\sim 1$ with upcoming galaxy surveys.
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Instrumentation and Methods for Astrophysics

ALPACA I: Controlling source and PSF systematics in JWST time-delay cosmography with differentiable lens modeling

Hrvoje Krizic, Martin Millon, Aymeric Galan et al. (+2 more)

Time-delay cosmography provides an independent probe of the Hubble constant ($H_0$), but exploiting the high-resolution imaging of the James Webb Space Telescope (JWST) requires strong-lens models that capture complex source-galaxy morphologies and the point spread function (PSF) with high fidelity. Flexible source and joint PSF reconstruction are computationally expensive, motivating more rigid parameterizations that can bias the inferred time-delay distance $D_{\Delta t}$. We present ALPACA, a semi-automatic, GPU-accelerated, differentiable strong-lens modeling pipeline built on Herculens, Starred, and JAX. ALPACA jointly reconstructs a pixelated correlated-field source, the lens mass, and the PSF within a single likelihood, reducing per-system runtimes from weeks to less than 15 hours. We validate the pipeline on realistic mock JWST/NIRCam observations built from morphologically complex COSMOS galaxy sources. Holding an imperfect PSF (RMSE = 12% from truth) fixed biases $D_{\Delta t}$ by up to 14%, whereas joint PSF reconstruction reduces this bias to the percent level. We further show that the reconstructed PSF core can be marginalized over jointly with the lens parameters during posterior sampling. Propagating the per-lens posteriors of a ten-lens mock sample through hierarchical inference, we recover the input cosmology without significant bias. ALPACA shows that rigorous control of source and PSF systematics is computationally affordable, supporting reliable percent-level precision in the JWST era.
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All authors Hrvoje Krizic, Martin Millon, Aymeric Galan, Sydney Erickson, Phil Marshall

Instrumentation and Methods for Astrophysics

Development of quantum technologies for optical/infrared interferometry

John D. Monnier

Quantum technologies may revolutionize optical interferometry through new means to distribute and preserve electric-field amplitude and phase correlations between widely separated telescopes. After reviewing existing techniques, I survey proposed quantum-sensing and quantum-networking applications and highlight recent laboratory demonstrations of key building blocks. By easing field-transport demands for baselines beyond $\sim$1 km, quantum-enhanced interferometry could enable sub-milliarcsecond imaging and microarcsecond-class differential astrometry. That said, "going quantum" is not a magic shortcut to sensitivity because many of the most compelling science cases remain photon- and turbulence-limited. I therefore emphasize the practical constraints – loss, bandwidth, coherence time, synchronization, and wavelength limits of quantum interfaces – that must also be overcome to make these capabilities useful for astronomy, whether deployed on the ground or from space.
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High Energy Astrophysical Phenomena

A Swift X-ray view of the SMS4 sample - III: Deeper insight into previously undetected sources

Alessandro Maselli, William R. Forman, Christine Jones et al. (+2 more)

We update the X-ray information given in Maselli et al. (2024) for five bright radio sources in the SMS4 catalog, thanks to additional observations with the X-Ray Telescope (XRT) on board the Neil Gehrels Swift Observatory (hereafter Swift) carried out through February 2026. X-ray emission from MRC B1754-597, previously based only on data from the eROSITA-DE DR1 catalogs, is now detected also by Swift, which yields a more precise positional uncertainty. Thanks to ~7 ks of additional exposure with Swift we are now able to detect MRC B1817-391, a source for which no X-ray counterpart is found in eROSITA-DE DR1. Another source that is not detected in the eROSITA-DE DR1 catalogs, and that was not observed by Swift earlier than 2025, is MRC B1827-360: with a ~6 ks X-ray observation, the source is detected. Finally, based on ~8 ks of additional exposure, we detect X-ray emission for MRC B2032-350, a source that lies out of the DR1 footprint. In contrast, additional exposure (~2 ks) just gives an upper limit on the X-ray emission of MRC B1814-519. The analysis of the extent and the hardness ratio of the four detected X-ray sources suggests the presence of soft, diffuse X-ray emission as expected from galaxy group cores or hot galaxy coronae. Using the positional uncertainty of the X-ray detections to constrain the search for counterparts at lower energies, we provide a new infrared/optical counterpart for MRC B1817-391 and confirm the counterparts previously reported in the literature for the three remaining sources.
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All authors Alessandro Maselli, William R. Forman, Christine Jones, Ralph P. Kraft, Matteo Perri

Cosmology and Nongalactic Astrophysics

Supernova microlensing as a probe of ultracompact minihalos and primordial cosmology

Djuna Croon, Sergio Sevillano Muñoz and Miguel Zumalacarregui

We propose using supernova microlensing to search for ultracompact minihalos and other extended dark structures seeded by enhanced primordial small-scale power. Unlike conventional microlensing searches, which are often optimized for primordial black holes, cosmological supernovae are sensitive to lenses with physical sizes comparable to their Einstein radii (up to $\sim {\rm pc}\left(M/10^4M_\odot\right)^{1/2}$ scale), opening a qualitatively different region of dark object parameter space. We compute the extended object detection efficiency relative to point lenses. We then show how projected limits on the abundance of ultracompact minihalos can be mapped, in benchmark formation scenarios, onto constraints on the primordial power spectrum. With the Vera C. Rubin Observatory expected to deliver an unprecedented LSST supernova sample, supernova microlensing is poised to become a timely and complementary probe of small-scale structure and the physics of the early Universe.
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