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Physics Astrophysics Astrophysics of Galaxies

astro-ph.GA Watch Astrophysics of Galaxies

Thursday 8 October

Astrophysics of Galaxies

Isotopic ratios as probes of star formation and the origin of molecular gas in the Central Molecular Zone

Laura Colzi

The Central Molecular Zone (CMZ) contains most of the dense molecular gas in the Milky Way but forms stars at a surprisingly low rate. Isotopic ratios provide a unique tool to investigate both the local physical conditions and the nucleosynthetic history of this gas. I summarize recent isotopic studies toward the molecular cloud G$+$0.693$-$0.027. Deuterium fractionation (D/H ratios) reveals a cold ($T_{\rm kin}\lesssim30$ K), relatively quiescent gas component embedded within the otherwise warm and turbulent CMZ, indicating that the earliest stages of star formation can survive in this extreme environment. I also present new $^{12}$C/$^{13}$C measurements from HC$_3$N and HC$_5$N, including the first constraints from doubly substituted $^{13}$C isotopologues. After accounting for isotopic fractionation with astrochemical models, the inferred elemental ratio ($\sim37$–48) exceeds the canonical CMZ assumed value ($\sim$20), supporting a scenario in which the Galactic center is replenished by less chemically processed gas flowing inward along the Galactic bar.
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Astrophysics of Galaxies

The Binary Fraction of Milky Way Field Stars in DESI: Dependence on Chemical Abundance

Tian Qiu, Wenting Wang, Sergey E. Koposov et al. (+39 more)

Binary populations encode information about the physical conditions of star formation and the subsequent evolution of stellar populations. Adopting a statistical method based on multi-epoch line-of-sight velocity variations, we constrain the binary fraction, $f_b$, of field main-sequence turn-off stars in the Milky Way using data from the second data release of the DESI Milky Way Survey. $f_b$ is found to primarily increase with lower [Fe/H]. At $[\mathrm{Fe}/\mathrm{H}]\gtrsim -1.3$, $f_b$ shows a modest increase with increasing [Mg/Fe], whereas no clear trend is detected at lower [Fe/H]. The apparent variations of $f_b$ with angular momentum and Galactic height are largely explained by their underlying [Fe/H] distributions, while the remaining variations broadly follow differences in [Mg/Fe]. Within overlapping regions of the [Fe/H]–[Mg/Fe] plane, the thin disk, thick disk, stellar halo and GSE populations exhibit no significant differences in their binary fractions. Thus, our measurements indicate that the variation in $f_b$ is dominated by chemical abundance, which could be explained by the metallicity-dependent gas cooling efficiency and fragmentation. The weaker [Mg/Fe] dependence at fixed [Fe/H] might be associated with the formation conditions of stars, with higher [Mg/Fe] stars generally forming earlier under a more gas-rich and turbulent environment.
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All authors Tian Qiu, Wenting Wang, Sergey E. Koposov, Songting Li, Nathan Sandford, Ting S. Li, Joan Najita, Jessica Nicole Aguilar, Steven Ahlen, Davide Bianchi, David Brooks, Aurelio Carnero Rosell, Todd Claybaugh, Andrei Cuceu, Axel de la Macorra, Arjun Dey, Peter Doel, Jaime E. Forero-Romero, Enrique Gaztañaga, Satya Gontcho A Gontcho, Gaston Gutierrez, Stephanie Juneau, Robert Kehoe, Martin Landriau, Laurent Le Guillou, Aaron Meisner, Ramon Miquel, Enrique Paillas, Will Percival, Francisco Prada, Ignasi Pérez-Ràfols, Corentin Ravoux, Graziano Rossi, Eusebio Sanchez, Christoph Saulder, Edward Schlafly, David Schlegel, Michael Schubnell, Joseph Harry Silber, Małgorzata Siudek, Gregory Tarlé, Benjamin Alan Weaver

Astrophysics of Galaxies · Cross-listed from astro-ph.CO

Galaxy Clustering Can Reveal Host-Galaxy Properties of Binary Black Hole Mergers

Daiki Watarai, Hayato Imafuku and Fumihiro Chuman

Galaxy clustering encodes information about the host galaxies of binary black hole (BBH) mergers even when individual hosts remain unidentified, because the distribution of neighboring galaxies depends statistically on the host-galaxy population. We construct event-level host-type likelihoods from host-conditioned galaxy-count distributions within gravitational-wave localization regions and combine them to infer the fractions of BBH mergers hosted by different galaxy populations. The framework applies to common and rare galaxy populations without prescribing formation efficiencies or merger delay-time distributions. Using measured star-forming and quenched galaxy clustering, idealized one-year forecasts assuming all mergers occur in quenched galaxies yield median one-sided 90% lower credible limits of 0.19, 0.48, and 0.92 on the quenched-host fraction for O5, post-O5, and third-generation networks. These forecasts illustrate the potential for host-galaxy population inference before the third-generation detector era.
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Wednesday 7 October

Astrophysics of Galaxies

NGC 6426: Colour-Magnitude diagram and variable star population as indicators of metallicity, distance, and age

A. Arellano Ferro, R. Michel, D. Deras et al. (+3 more)

We present new VI CCD photometry of the globular cluster NGC 6426. The membership status of all point sources and, in particular, of all the variables in the field of view is discussed, including four recently detected variables. The double mode nature of variables V3 and V9 is confirmed and their periods are calculated. The presence of a cluster member anomalous Cepheid (V17) is reported. Employing only likely members we produce a decontaminated colour-magnitude diagram (CMD) differentially dereddened, which enables us to compare it with theoretical predictions and to study the variable stars distribution. The mean cluster metallicity and distance were calculated via the RR Lyrae V-band light curve Fourier decomposition and an I-band calibration of the Period-Magnitude-Metallicity relation. Further, a comparison using a Bayesian approach between theoretical isochrones of Dartmouth Stellar Evolution Database (DSED), with a deep HST CMD, gave us independent estimates of distance modulus, metallicity, colour excess, and cluster age.
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All authors A. Arellano Ferro, R. Michel, D. Deras, M. Vaca Montejano, S. Muneer, I. Bustos Fierro

Astrophysics of Galaxies

Central stellar depletion in the Draco dwarf from Subaru photometry

Eduardo Vitral, Kyosuke S. Sato, Jorge Peñarrubia et al. (+2 more)

Dark matter subhaloes are a fundamental prediction of the standard cosmological model, but their low-mass population remains difficult to constrain observationally. Recent work has shown that interactions between subhaloes and dwarf spheroidal galaxies can induce large-scale, out-of-equilibrium fluctuations in their stellar surface density fields, identifiable through Fourier-based statistics. We apply this formalism to deep Subaru photometry of the Draco dwarf, extending previous tests to $\gtrsim\mathcal{O}(10^{4})$ resolved stars. We use artificial-star tests to assign completeness weights to individual stars and incorporate them into a discrete likelihood-based framework. Relative to a cored axisymmetric Plummer model, Draco shows radial corrugations that appear in the filtered normalised residuals as a central stellar depletion surrounded by a ring-like excess. The same feature appears in Fourier space as a low-frequency peak with a signal-to-noise ratio ${\rm S/N}=6.0$. Independently, fitting the surface density $\Sigma$ with an $\alpha\beta\gamma$ model yields ${\rm d}\Sigma/{\rm d}R>0$ at $>99.9\%$ confidence – i.e., a profile that decreases towards the centre. Although these signatures cannot yet be regarded as robust evidence for dark subhaloes, they suggest that central stellar depletion in dwarf galaxies may reflect genuine physical structure rather than crowding alone.
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All authors Eduardo Vitral, Kyosuke S. Sato, Jorge Peñarrubia, Sakurako Okamoto, Veronika Dornan

Astrophysics of Galaxies

The conditional colour-magnitude distribution: III. A study of galaxy colour- and luminosity-dependent counts-in-cells statistics

Raymon Isaac and Zheng Zheng

The conditional colour-magnitude distribution (CCMD) model connects the galaxy colour-luminosity distribution with dark matter halo mass, which has been constrained in Xu et al. by jointly modelling the two-point correlation functions of a large galaxy sample of the Sloan Digital Sky Survey (SDSS) in fine bins of galaxy colour and luminosity. We test the CCMD model of the galaxy-halo connection using counts-in-cells (CIC) statistics by comparing CCMD model predictions with SDSS measurements for 16 subsamples of galaxies in various luminosity and colour bins. In addition, we compare SDSS measurements with three analytic models of CIC distribution. The CCMD model provides a good description of the SDSS CIC measurements for most subsamples. The exceptions are the void probability functions and CIC distributions with cell radius 5 Mpc/h for a few subsamples in the luminous bins, which are not well described by the analytic models, either. For these subsamples, in general, removing the Sloan Great Wall from SDSS or introducing velocity bias to the CCMD model does not resolve the disagreement. Finally, with the help of the CCMD mocks, we investigate the cause of the variations of the galaxy counts in cells. For small cells or cells with a low mean galaxy count, the variation reflects effects from fluctuations in both the matter environment and the halo occupation distribution, while for large cells or cells with a high mean galaxy count, the environment effect dominates. We discuss the implications of our work for investigating galaxy assembly bias.
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Astrophysics of Galaxies

Mass Proxy Quality of Halo Properties in IllustrisTNG and FLAMINGO Simulations: II. Galaxies, Stars, and Black Holes

Eddie Aljamal, August E. Evrard, Arya Farahi et al. (+1 more)

We study the stellar, black hole, and satellite galaxy populations of group- and cluster-scale halos in the IllustrisTNG, TNG-Cluster, and FLAMINGO cosmological hydrodynamical simulations. We characterize the mass-conditioned scaling relations, covariance, conditional likelihoods, and mass proxy quality (MPQ) of integral properties within $R_{\rm 500c}$: total stellar mass ($M_{\star,\,\rm tot}$), brightest central galaxy stellar mass ($M_{\star,\,\rm BCG}$), intracluster light mass ($M_{\star,\,\rm ICL}$), total black hole mass ($M_{\rm BH}$), satellite occupation ($N_{\rm sat}$), and satellite velocity dispersion ($\sigma_{\rm sat,\,1D}$), at $z\in \{0,0.5,1,2\}$. While normalization differences of up to a factor of two emerge among simulations, many properties exhibit remarkably similar mass-localized slopes, intrinsic scatters, and MPQs across halo samples and redshifts. Correlations among stellar, satellite, and gas properties are generally consistent in sign and their dependence on halo mass and redshift, whereas those involving $M_{\rm BH}$ and $N_{\rm sat}$ show greater variation, particularly in TNG-Cluster. Conditional likelihoods are nearly lognormal for many properties, including $M_{\star,\,\rm tot}$, $N_{\rm sat}$, and $\sigma_{\rm sat,\,1D}$, while $M_{\star,\,\rm BCG}$ and $M_{\star,\,\rm ICL}$ are negatively skewed. Among the properties considered here, total stellar mass is the best mass proxy, with a halo mass scatter of $7$-$14\%$, followed by $N_{\rm sat}$ with a mass scatter of $9$-$18\%$. The consistent correlation behavior of $M_{\star,\,\rm ICL}$ highlights its potential for next-generation observational studies. Finally, $\sigma_{\rm sat,\,1D}$ exhibits highly consistent scaling, with mass-independent slope and scatter and a largely neutral correlation structure, suggesting that it is relatively insensitive to astrophysical complexity.
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All authors Eddie Aljamal, August E. Evrard, Arya Farahi, Dylan Nelson

Astrophysics of Galaxies

The progenitor galaxies of the intracluster light

Rebecca J. Mayes, Facundo A. Gómez and Antonela Monachesi

Intracluster Light (ICL) is a diffuse stellar component of galaxy groups and clusters, bound to the structure's potential rather than to individual galaxies and primarily formed through the stripping and mergers of intermediate-mass galaxies. Its formation and evolution is strongly linked to the central galaxies of groups and clusters, typically the Brightest Cluster Galaxies (BCGs) in clusters. To determine the properties of the progenitor galaxies of the ICL of clusters and groups at redshift z = 0 and compare them with the progenitors of their BCGs. We select 127 clusters and groups in the hydrodynamic Illustris-TNG100 simulation above a mass of 10^{13}~$M_{\odot}$. We divide the ICL from the BCG by applying a surface brightness cut at the Holmberg radius of 26.5 mag/arcsec^{-2}, where star particles within this radius are defined as attached to the BCG, and outside, the ICL. We then determine the masses and contributions of progenitor galaxies of the ICL and BCG. We find that the number of ICL progenitors increases with structure mass, and that the ICL has more progenitors than the BCG. The ICL has a larger percentage of material from low-mass galaxies. Quenched galaxies contributed a large fraction of the ICL, and this fraction increases with galaxy mass. The mean mass radial gradient of ex-situ material in structures for the ICL and the BCG+ICL is generally negative and increases with structure mass, indicating that material from more massive progenitors is found towards the centres of clusters. The mean mass radial gradient is significantly impacted by structure formation history. ICL progenitor properties are impacted by structure history and are therefore highly individual to each system. At a given structure mass, there is diversity in the properties of the progenitors that formed the ICL. Although the BCG and the ICL co-evolve, the BCG has fewer, more massive progenitors.
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Astrophysics of Galaxies

Pushing Variability Searches to Extreme Dwarf Galaxies with the Vera C. Rubin Observatory Data Preview 2

Fan Zou, W. N. Brandt, Elena Gallo et al. (+15 more)

Galaxies with stellar masses $M_\star<10^8~M_\odot$, hereafter referred to as extreme dwarf galaxies (EDGs), represent one of the least explored regimes in the search for accreting intermediate-mass black holes. Using the recent Vera C. Rubin Observatory Data Preview 2 (DP2; covering 2025-04-25 to 2026-01-06), we present the first systematic search for variability among EDGs in the ELAIS-S1 field, the most extensively observed LSST Deep-Drilling Field in DP2. Applying single-band and cross-band variability statistics to difference-imaging light curves for $6.2\times10^4$ EDGs with archival multiwavelength characterizations, we identify seven variable EDG candidates, all brighter than $i$-band magnitude of 24 and located within $z<0.3$. The two brightest candidates are previously known AGNs, three have light curves more consistent with supernovae, and two do not have a clear nature. The sample corresponds to an apparent EDG variable fraction of $6.8_{-2.1}^{+3.1}\times10^{-4}$ at $i$-band magnitudes brighter than 24 and is expected to consist primarily of AGNs and supernovae. Compared to a magnitude-matched massive-galaxy sample with the same variability selection applied, the EDG variable fraction is comparable or at most lower by up to a factor of three. This proof-of-concept study demonstrates that Rubin will identify a statistically meaningful sample of variable EDG candidates, opening a new regime for black-hole demographics. Spectroscopic follow-up will nevertheless be required to secure redshifts and confirm individual candidates.
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All authors Fan Zou, W. N. Brandt, Elena Gallo, Franz E. Bauer, Angela Bongiorno, Colin J. Burke, Alister W. Graham, Hengxiao Guo, Lorena Hernández-García, Marcin Marculewicz, Dieu D. Nguyen, Swayamtrupta Panda, Alessandro Peca, Bindu Rani, Claudio Ricci, Ohad Shemmer, Wei Leong Tee, Zhibo Yu

Astrophysics of Galaxies · Cross-listed from astro-ph.SR

Population II Post-AGB Stars. I. Methodology, Initial Results, and the First Luminosity Function

S. Jean Feeser, Robin Ciardullo, Michael H. Siegel et al. (+2 more)

Post-asymptotic giant branch (PAGB) stars share many advantages with the tip of the red giant branch (TRGB) for Population II distance measurements, including minimal internal reddening, easy identification, a solid theoretical foundation, and an expected weak metallicity dependence. At visual wavelengths PAGB stars are the brightest members in old populations, appearing up to $\sim2$ mag brighter than the TRGB and $\sim4$ mag brighter than RR Lyrae stars. Stellar evolution theory predicts that these objects occupy a narrow luminosity strip across the top of the Hertzsprung-Russell diagram, making them excellent standard candles. Observations in Galactic globular clusters (GCs) support this prediction, but a comprehensive survey is required to define their luminosity function and test for systematic errors. In this work, we construct a multi-wavelength catalog, spanning the ultraviolet (UV) to infrared (IR), for PAGB stars in 39 Galactic GCs. We validate cluster membership with Gaia astrometry, identify 21 objects across 16 GCs using ground-based uBVI and space-based UV photometry, and perform Bayesian spectral energy distribution (SED) fitting with stellar atmosphere models to estimate their effective temperatures, luminosities, and radii. We find that PAGB stars occupy a narrow luminosity range centered at $\log(L_{\mathrm{bol}}/L_{\odot})=3.25\pm0.03$, with dispersion $\sigma=0.12$ dex, supporting their use as reliable Population II distance indicators. Comparisons with theoretical tracks show excellent agreement with evolutionary models. We confirm that PAGB stars occur preferentially in metal-poor clusters with blue horizontal branches. Our results demonstrate that PAGB stars provide a powerful probe of late stellar evolution and a promising Population II standard candle.
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All authors S. Jean Feeser, Robin Ciardullo, Michael H. Siegel, C. J. Hapich, Akshat S. Chaturvedi

Astrophysics of Galaxies

First uGMRT Constraints on Rotation Measure in the Radio-Quiet Seyfert Galaxy NGC 4235

Salmoli Ghosh, Preeti Kharb and Janhavi Baghel

We present a multi-frequency polarimetric study of the radio-quiet Seyfert galaxy NGC 4235 using the upgraded Giant Metrewave Radio Telescope (uGMRT), aimed at constraining the Faraday rotation properties of its kpc-scale radio emission. This marks the first-ever analysis of polarization across two frequency bands of the uGMRT and the first constraints on rotation measure (RM) at lower frequencies for a weak radio source (17.1$\pm$1.7 mJy at 1.3 GHz, 27.7$\pm$2.8 mJy at 663 MHz). We detect linearly polarized radio emission associated with the `core' and the extended lobes of NGC 4235. Broadband polarimetric analysis yields an RM value of {$\sim200$ rad m$^{-2}$} in the `core', indicating Faraday rotation by magnetized plasma external to the synchrotron-emitting regions. Using these RM constraints, we estimate an average electron density of the Faraday-rotating medium of $\sim$3$\times10^{-2}$ cm$^{-3}$ for a characteristic perturbation scale of $\sim$0.3 parsec within an assumed magnetized region of size $\sim$1.3 kpc, consistent with a diffuse magnetized sheath or AGN-driven wind. These results extend classical Faraday rotation diagnostics to the low-power, radio-quiet AGN regime and demonstrate the potential of uGMRT broadband polarimetry for probing magnetized environments in and around such AGN.
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Astrophysics of Galaxies

NGC 4936: abundant multi-phase medium in the central weak X-ray cool core and optically dark H I clouds in the group

Prathamesh Tamhane, Ming Sun, Hao Chen et al. (+6 more)

We present a multiwavelength analysis of NGC 4936, the central galaxy of a weak cool-core group hosting an unusually large cold/warm gas reservoir. NGC 4936 contains $\sim2\times10^8$ M$_\odot$ of molecular gas in a rotating disk of radius $\sim1$ kpc, but no detected H I, with a $3\sigma$ upper limit of $1.13\times10^7$ M$_\odot$ within $\sim2.5$ kpc. The resulting $H_2$/H I mass ratio $>17$ is consistent with a predominantly molecular medium in the high-pressure environments of central galaxies. SOAR imaging and MUSE spectroscopy reveal ionised gas extending to $\sim15$ kpc in a complex filamentary morphology that broadly follows the molecular gas kinematics while extending well beyond the CO disk. Dust filaments similarly extend to $\sim14$ kpc and appear to interact with a companion galaxy located only $\sim2.5$ kpc away in projection. NGC 4936 has a star formation rate of $0.29$ M$_\odot$ yr$^{-1}$, and its AGN shows sub-mm and X-ray variability. We favour atmospheric condensation as the primary origin of the molecular gas, although externally acquired gas may contribute. Our recalculated thermodynamic profiles reach $t_{\rm cool}/t_{\rm ff}\sim25$ in the innermost region, placing the system near the threshold for multiphase condensation. The ongoing interaction may perturb the atmosphere and promote condensation while shaping the morphology and kinematics of the multiphase medium, rather than directly supplying most of the central cold gas. We additionally detect 20 H I structures in the surrounding group environment, with masses of $\sim10^7$–$10^8$ M$_\odot$, including several with no obvious optical counterparts.
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All authors Prathamesh Tamhane, Ming Sun, Hao Chen, Thomas Connor, Megan Donahue, Mark Voit, Mpati Ramatsoku, Kokoro Hosogi, Tim Edge

Astrophysics of Galaxies

Prevalence of radio Active Galactic Nuclei in galaxy groups since z=3.5 in the COSMOS-Web field

F. Ubertosi, I. Delvecchio, I. Prandoni et al. (+30 more)

Radio active galactic nuclei (AGN) are key tracers of kinetic feedback from supermassive black holes. Although the dependence of their triggering on host stellar mass is well known, the impact of the large-scale environment across cosmic time is poorly understood. We investigate the role of the environment in triggering radio AGN activity, while also studying the dependence on stellar mass ($10\leq\log M_{\ast}\,{\rm [M_{\odot}]}\leq11.4$), radio luminosity ($22\leq\log L_{1.4}\,{\rm [W\,Hz^{-1}]}\leq26$), and redshift ($0.1\leq z \leq 3.5$). We combine the VLA-COSMOS 3 GHz Large Project with the COSMOS-Web galaxy and group catalogs, selecting radio-excess AGN and building radio luminosity functions (RLF) and radio AGN fractions separately for sources in galaxy groups (124 radio AGN) and in the field (405 radio AGN), out of the total of 20203 galaxies and 1678 galaxy groups. We fit the RLF to derive the cosmic evolution of radio AGN in different environments, and we provide a new parametric description of the radio AGN fractions as a function of environment, $M_{\ast}$, $L_{1.4}$, and z. Besides confirming the known positive correlation of radio AGN fraction with host $M_{\ast}$ in both groups and in the field, more importantly we find that the activation of a radio AGN in groups is enhanced relative to the field by a factor of 3–30 in space density and of 2 in radio AGN fraction at fixed stellar mass; the enhancement is also a function of $M_{\ast}$, $L_{1.4}$, and z. Furthermore, in all z bins, the radio AGN fractions peak within $r \leq 0.2R_{200}$. Overall, dense environments enhance radio AGN triggering out to at least z=3.5. We suggest the existence of a possible transition in the dominant triggering mechanism of radio AGN activity around z~1.5, potentially related to the intragroup medium in the core of groups at lower z and to merger and structure growth at earlier cosmic times.
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All authors F. Ubertosi, I. Delvecchio, I. Prandoni, G. Toni, G. Zamorani, E. Daddi, M. Gitti, M. Sargent, A. Traina, C. Spingola, F. Vito, L. Moscardini, G. Gozaliasl, D. Kakkad, W. Wang, S. Sanjaripour, Z. Ghaffari, M. N. Isla Llave, R. M. Samir, G. Peluso, M. Maturi, V. Smolcic, C. Casey, J. Kartaltepe, H. J. McCracken, J. Rhodes, B. Robertson, M. Franco, D. Liu, M. Shuntov, H. Akins, O. Ilbert, A. A. Khostovan

Astrophysics of Galaxies · Cross-listed from astro-ph.SR

Atypical White Dwarfs in Open Clusters

David R. Miller, Ilaria Caiazzo, Jeremy Heyl et al. (+1 more)

Open clusters are powerful laboratories for investigating the formation and evolution of white dwarfs (WDs), as their well-constrained ages link WDs to their progenitor stars. This is particularly valuable for atypical WDs, including magnetic WDs and those with non-hydrogen-dominated spectra, whose origins can be difficult to disentangle in the field. We assemble the largest sample to date of atypical WDs in open clusters: eight non-magnetic WDs with helium-dominated spectra, five with featureless spectra, and five magnetic WDs showing hydrogen or helium lines. We find no significant difference between the initial–final mass relations of hydrogen- and helium-atmosphere WDs, nor robust spatial or kinematic differences. The strongest difference from the field is a deficit of non-DAs between $0.8$ and $1.0\,\mathrm{M}_\odot$, where the field predicts $6.0^{+0.8}_{-0.7}$ WDs, yet none are observed, with a probability of only $0.37\%$. Massive magnetic WDs show a similar deficit: only one of 20 cluster WDs with $M_{\mathrm{WD}}\geq1.0\,\mathrm{M}_\odot$ and $T_{\mathrm{eff}}\geq20{,}000\,{\rm K}$ is magnetic, compared with 10 of 16 in the field. Together, these deficits are consistent with an additional field population of massive merger remnants, particularly high-mass magnetic WDs and warm/hot DQs. Such objects may be underrepresented in clusters because young systems provide limited time for certain classes of delayed mergers, while older clusters lose members or dissolve; the field accumulates binary evolution products over Galactic timescales. Magnetic cluster WDs consistent with single-star evolution further suggest mass-dependent magnetic-field emergence, with fields appearing early in some massive WDs while young lower-mass WDs remain consistent with delayed emergence.
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All authors David R. Miller, Ilaria Caiazzo, Jeremy Heyl, Pier-Emmanuel Tremblay

Astrophysics of Galaxies

A "universal" supernova efficiency to drive the HI turbulence in nearby star-forming galaxies

Lauri Sassali, Cecilia Bacchini, Aku Venhola et al. (+2 more)

The origin of cold gas turbulence in galaxies has long been debated. Supernovae (SNe), the dominant form of stellar feedback, were thought insufficient to sustain it against dissipation, especially in galactic environments with low star formation rates (SFRs). We investigate the origin of the neutral atomic gas (HI) turbulence in dwarf irregular galaxies, a challenging regime of low masses and SFRs. We build on a recent study of spirals showing that disc flaring prolongs the dissipation timescale, reducing the energy needed to sustain turbulence and making SN feedback viable. We measure the SN efficiency, that is the fraction of SN energy required to sustain HI turbulence, in 14 dwarfs, and test whether a "universal" efficiency holds across a sample representative of the star-forming main sequence. From the observed HI distributions and kinematics, we derive the radial profiles of the HI kinetic energy per unit area and model them as the sum of thermal energy and turbulent energy from SNe, constrained by the observed SFR surface density. We consider pure cold and warm neutral medium (WNM) phases as limiting cases, as well as a mixed two-phase scenario, obtaining the SN efficiency and WNM fraction via hierarchical Bayesian inference. We find that the observed HI kinetic energy in dwarfs requires only $\lesssim 3\%$ of the SN energy, and that a "universal" efficiency of $\approx 2\%$ explains the HI turbulence across our main-sequence sample. Our findings suggest that the SN efficiency remains similar across galaxies with different properties, offering valuable constraint for feedback recipes in galaxy evolution models.
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All authors Lauri Sassali, Cecilia Bacchini, Aku Venhola, Giuliano Iorio, Antonino Marasco

Astrophysics of Galaxies

Cosmic Duets II. Growth and accretion in Gaia Multi-Peak dual AGN at Cosmic Noon

M. Scialpi, F. Mannucci, D. Izquierdo-Villalba et al. (+36 more)

We present the first statistical characterization of the physical properties of Cosmic Duets: dual AGN in the redshift range 0.5 $\leq$ z $\leq$ 3.0 with projected separations of 1-7 kpc, corresponding to systems in which both AGN are expected to reside within the same merger remnant. We analyze the largest homogeneous sample currently available, consisting of 30 spectroscopically confirmed Cosmic Duets selected via the Gaia Multi-Peak technique. Using rest-frame UV-to-optical integral-field spectroscopy for all targets, primarily with VLT/MUSE, VLT/ERIS, and Keck/OSIRIS, we spatially resolve the two AGN components and extract separate spectra for each system. We decompose the continuum, emission lines, and Fe II complexes through spectral fitting. We derive black hole masses of log($M_{BH}/M_{sun}$) ~ 7.4-10.1 and bolometric luminosities of log($L_{bol}/erg s^{-1}$) ~ 44.8-47.2, consistent with those of single AGN at similar redshifts. We finally carry out the first comparison of dual AGN properties with semi-analytical models and hydrodynamical simulations, including L-GalaxiesBH and Astrid. Astrid provides a closer match to the observed black-hole mass-ratio distribution, but its selected systems are predominantly at lower redshifts, resulting in lower bolometric luminosities at fixed G-band magnitude. L-GalaxiesBH perfectly reproduce the observed parameter space, but it predicts more heterogeneous pairs, with higher primary-bolometric luminosity, lower-mass secondary SMBHs, and higher Eddington ratios, resulting in an excess of near-Eddington accreting AGN due to its adopted accretion prescription. Our results suggest that, in GMP-selected systems, secondary SMBH growth is more efficient than predicted by current models, leading to more comparable black-hole masses and accretion power between the two components.
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All authors M. Scialpi, F. Mannucci, D. Izquierdo-Villalba, A. Marconi, J. Singh, M. Volonteri, C. Marconcini, Q. D'Amato, B. Moreschini, M.V. Zanchettin, G. Tozzi, M. Ceci, L. Ulivi, E. Bertola, S. Bonoli, C. Bracci, E. Cataldi, C. Cicone, A. Ciurlo, M. Colpi, G. Cresci, A. De Rosa, M. Dotti, M. Fumagalli, M. Ginolfi, I. Lamperti, E. Nardini, M. Parvatikar, M. Perna, F. Rigamonti, K. Rubinur, B. Sala, A. Sesana, P. Severgnini, C. Spingola, D. Spinoso, G. Venturi, C. Vignali, S. Yeh

Astrophysics of Galaxies

A Multi-dimensional Analysis of the Open Clusters NGC 2423 and NGC 2482 with Gaia DR3

W. H. Elsanhoury, Deniz Cennet Ç{\i}nar and A. Ahmed

We present a homogeneous photometric, astrometric, and kinematic study of the Hyades-like open clusters NGC 2423 and NGC 2482 based on Gaia DR3 data. Cluster memberships are determined using the UPMASK algorithm in the multi-dimensional parameter space of (alpha, delta, parallax, mu_alpha cos(delta), mu_delta), with radial velocities incorporated when available. Gaussian modelling of the astrometric distributions yields mean trigonometric parallaxes of 1.060 +/- 0.035 mas and 0.735 +/- 0.061 mas, corresponding to astrometric distances of 944 +/- 31 pc and 1361 +/- 113 pc for NGC 2423 and NGC 2482, respectively. Fundamental parameters are derived through PARSEC isochrone fitting, resulting in ages of 1250 +/- 100 Myr and 445 +/- 50 Myr, observed distance moduli (m-M)_obs = 9.90 +/- 0.10 and 10.80 +/- 0.20 mag, and reddening values E(G_BP-G_RP) = 0.07 +/- 0.01 and 0.10 +/- 0.02 mag, equivalent to E(B-V) = 0.054 and 0.078. The corresponding photometric distances are 892 +/- 50 pc and 1311 +/- 146 pc. We further investigate the internal and global kinematics of both clusters using velocity-ellipsoid parameters, the convergent-point method, and action-angular-momentum diagnostics. The derived kinematic properties show that NGC 2482 closely matches the velocity-space characteristics of the Hyades stream, while NGC 2423 shares the characteristic rotational velocity and angular momentum of the Hyades-like population but is offset in its U component. Both clusters occupy the angular-momentum range associated in the literature with Hyades-like clusters and bar-related resonances, although this association is based on their present-day kinematics and action-space locations rather than a direct dynamical demonstration of resonance trapping.
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Astrophysics of Galaxies

Global and Local Infall in the ASHES Sample (GLASHES). III. Physical Parameters of Contracting Motion onto Dense Cores in 70 $\mu$m Dark Massive Clumps

Kaho Morii, Patricio Sanhueza, Qizhou Zhang et al. (+3 more)

Core growth is a key process in high-mass star formation. As part of the GLASHES (Global and Local Infall in the ASHES Sample) survey, we present infall velocities and mass infall rates derived from blue-asymmetric line profiles toward cores embedded in massive 70 \textmu m-dark clumps. Robust Hill5 model fits were obtained for 70 of the 135 cores exhibiting blue-asymmetric profiles, yielding infall velocities of 0.11–1.60 km s$^{-1}$ and mass infall rates ranging from $\sim$10$^{-5}$ to $5\times10^{-3}\,M_\odot\,{\rm yr}^{-1}$. Both quantities increase systematically from prestellar candidates to warm cores and outflow-associated cores. The inferred infall velocities are close to the cores' free-fall velocities (mean $v_{\rm in}/v_{\rm ff}\sim0.75$) and $t_{\rm in}=R/v_{\rm in}$ is comparable to the free-fall time, indicating dynamical fast contraction. Hill5 infall velocity correlates moderately with the non-thermal velocity dispersion and Mach number measured from optically thin tracers, indicating that organized infall contributes to the observed line widths. The mass infall rate follows a power-law relation with core mass, $\dot{M}=1.3\times10^{-4}\,(M/M_\odot)^{0.83\pm 0.06}\,M_\odot\,{\rm yr}^{-1}$, across $0.1\,M_\odot \lesssim M \lesssim 30\,M_\odot$. The power-law index increases from $\sim$0.65 for prestellar cores to $\sim$1.10 for outflow-associated cores, likely tracing an evolution in the dominant physical process. The Hill5 infall velocities and mass infall rates for the GLASHES cores are larger than those of cores in nearby low-mass star forming regions but smaller than those of larger scale high-mass clumps. These results provide the first statistical constraints on core-scale mass accumulation during the earliest stages of high-mass star formation.
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All authors Kaho Morii, Patricio Sanhueza, Qizhou Zhang, Philip C. Myers, James M. Jackson, Fumiaki Yoshida

Astrophysics of Galaxies · Cross-listed from astro-ph.SR

Kinematic and Dynamical Properties of Solar Neighborhood White Dwarfs from SDSS DR19 and Gaia DR3

O. Caliskan, M. Kilic and S. Bilir

We present a comprehensive kinematic and dynamical analysis of 5,837 DA white dwarfs with SDSS DR19 spectroscopy and Gaia DR3 astrometry. Using complementary spatial distributions, kinematic properties, and orbital parameters, we show that the sample is overwhelmingly dominated by the thin disk, with only minor contributions from the thick disk and the halo. Velocity dispersions and orbital eccentricities increase systematically from the thin disk to the halo, reflecting progressively hotter Galactic populations. Total stellar ages available for 4,829 white dwarfs reveal a clear age-velocity dispersion relation with power-law indices of 0.06-0.17, confirming that white dwarfs preserve the secular dynamical heating history of the Galactic disk. We derive a thin-disk scale-height of 123-229 pc and radial scale-length of 3.2-3.5 kpc, while the thick disk has a scale height of 865 pc and contributes approximately 6-7 % of the local stellar density. Reconstructed birth radii indicate that changes in the guiding radii represent an important component of the present-day radial redistribution of nearby white dwarfs, although the relative contributions of radial migration and orbital blurring cannot be uniquely separated from these displacement measures. These results establish white dwarfs as powerful tracers of the kinematic, dynamical, and structural evolution of the Milky Way.
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Astrophysics of Galaxies · Cross-listed from astro-ph.HE

Widespread steep X-ray spectra of luminous $z\simeq5.85-7.6$ quasars and their implications for future X-ray surveys

A. Tortosa, L. Zappacosta, E. Piconcelli et al. (+51 more)

Luminous quasars (QSOs) at the Epoch of Reionization (EoR, $z\gtrsim6$) host billion-solar-mass black holes assembled within the first Gyr of cosmic time. Their X-ray emission probes the innermost accreting regions and constrains the physical state of the corona during early supermassive black hole (SMBH) growth. Previous results from the HYPerluminous quasars at the Epoch of ReionizatION (HYPERION) sample of $z \gtrsim 6$ QSOs, powered by the most rapidly accreted SMBHs, suggested a link between X-ray spectral slope and long-term growth efficiency. We test whether the steep X-ray spectra of luminous z>6 QSOs are a general property of early SMBH growth or a peculiarity of the most efficiently grown SMBHs, using a sample extended mainly to the lowest growth efficiencies. We analysed the largest and most X-ray sensitive sample of 28 luminous QSOs at $z \simeq 5.85-7.56$ (26 used in the correlation analysis), combining HYPERION targets, luminous non-HYPERION sources, and QSOs powered by moderately accreting SMBHs newly observed in our XMM-Newton Large Programme. We re-derived black hole masses and growth indicators for the entire sample homogeneously, incorporating the latest JWST-based spectroscopic measurements to ensure the most consistent and high-quality characterization across all targets. We found no statistically significant correlation between coronal spectral parameters and BH growth indicators: luminous $z \gtrsim 6$ QSOs systematically show steep X-ray continua, with high photon indices and/or low high-energy cutoffs, consistent with cold coronae, possibly linked to rapid accretion. Finally, if steep X-ray slopes are common among early AGN, they may significantly reduce count rates, at fixed intrinsic luminosity, in future surveys of the EoR, affecting the detectability of steep-spectrum X-ray sources and thus the census of the early AGN population.
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All authors A. Tortosa, L. Zappacosta, E. Piconcelli, I. Saccheo, G. Lanzuisi, E. Bertola, F. Vito, M. Bischetti, M. Brazzini, M. Castellano, S. Carniani, A. Comastri, S. Gallerani, R. Gilli, F. La Franca, P. Madau, R. Maiolino, G. Miniutti, B. Musiimenta, C. Piscitelli, F. Salvestrini, F. Tombesi, R. Tripodi, C. Vignali, M. Volonteri, A. Bongiorno, L. Borrelli, M. Brusa, I. V. Chilingaria, F. Civano, S. Cristiani, V. D'Odorico, D. De Cicco, C. Done, M. Elvis, X. Fan, C. Feruglio, F. Fiore, A. Grazian, M. Guainazzi, F. Haardt, A. Luminari, N. Menci, R. Middei, F. Nicastro, M. Paolillo, M. Perna, S. Puccetti, R. Schneider, V. Testa, R. Valiante, L. Vallini, E. Vanzella, G. Vietri

Astrophysics of Galaxies

A Decade-Scale Ionization Echo of Black-Hole Accretion in Galactic Nuclei

Wei-Jian Guo, Shuo Zhai, Chen Hu et al. (+16 more)

Circumnuclear structures in active galactic nuclei respond to accretion variability over different spatial and temporal scales, but whether compact narrow-line gas responds on decade timescales has not been systematically established. We use repeat Sloan Digital Sky Survey and Dark Energy Spectroscopic Instrument spectroscopy of 473 variability-selected galactic nuclei with evidence for recent nuclear brightening. We identify 19 sources whose narrow [O III] $\lambda5007$ flux increased by more than a factor of two over rest-frame baselines of 12.0-20.4 yr, which we term narrow-line ionization echoes (NIEs). In equal-weight stacked spectra, [O III] increased by $229\pm22\%$, while lower-ionization lines remained nearly unchanged or declined, indicating an ionization-dependent response rather than uniform spectral rescaling. The NIE hosts also moved coherently toward higher excitation in optical diagnostic diagrams, with mean increases of $0.46\pm0.18$ dex in $\log([\mathrm{O III}]/\mathrm{H}\beta)$ and $0.58\pm0.13$ dex in $\log([\mathrm{O III}]/[\mathrm{O II}])$. Photoionization models reproduce this evolution with a higher ionization parameter and a harder AGN-like ionizing spectrum at fixed gas abundance. For 13 sources with well-defined mid-infrared outbursts, the integrated W1+W2 excess energy correlates strongly with the absolute [O III] luminosity change ($r=0.87$), linking the dust and narrow-line responses to the same nuclear event. The mid-infrared timescale and spectroscopic baseline constrain the variable [O III]-emitting gas to characteristic scales of 1.5-5.2 pc. Compact narrow-line gas therefore appears to form an intermediate, decade-scale response layer between the infrared dust echo and the long-lived extended narrow-line region.
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All authors Wei-Jian Guo, Shuo Zhai, Chen Hu, David M. Alexander, Bin Luo, Pu Du, Matthew J. Temple, Leah K. Morabito, Feige Wang, Jinyi Yang, Victoria A. Fawcett, Swayamtrupta Panda, Claire L. Greenwell, Yan-Rong Li, Cheng Cheng, Shengxiu Sun, Zhi-Qiang Chen, Alessandro Marconi, Jian-Min Wang

Astrophysics of Galaxies · Cross-listed from astro-ph.SR

Photometric and Spectroscopic Study of Young Stellar Objects in IC 1848E Region

Shubham Yadav, Neelam Panwar, Lalita Sharma et al. (+1 more)

We present a comprehensive analysis combining multi-epoch mid-infrared (MIR) photometric and optical spectroscopic observations of young stellar candidates associated with elongated, elephant trunk-like structures (ETLSs) in the IC 1848E star-forming region. A sample of 15 candidate YSOs, initially identified by Chauhan et al. (2011), was investigated using multi-epoch NEOWISE $W1$ and $W2$ photometry to characterize their variability properties. After imposing stringent positional and photometric quality constraints, a final set of eight robust YSOs was retained and classified into three variability categories: non-variable, secular, and stochastic. One source, Star #9, exhibits a pronounced curved variability in the MIR light-curve and color-magnitude domains, indicative of systematic evolution of its circumstellar disk and/or accretion processes. Optical spectroscopic data for this object show strong H$\alpha$ emission and prominent forbidden lines, providing clear evidence of active mass accretion and outflow phenomena. The combined photometric and spectroscopic diagnostics establish a close link between infrared variability, circumstellar disk evolution, and accretion-driven activity in YSOs associated with ETLSs in IC 1848E.
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All authors Shubham Yadav, Neelam Panwar, Lalita Sharma, C. Rishi

Astrophysics of Galaxies

Changing-look Active Galactic Nuclei from the Dark Energy Spectroscopic Instrument. VII. Testing Disk-Corona Diagnostics with eROSITA

Wei-Jian Guo, Shuo Zhai, Zhu-Heng Yao et al. (+3 more)

Changing-look active galactic nuclei (CL-AGN) have been proposed to follow an X-ray-binary-like, V-shaped relation between the optical/ultraviolet-to-X-ray spectral slope, $\alpha_{\rm OX}$, and the Eddington ratio, $\lambda_{\rm Edd}\equiv L_{\rm bol}/L_{\rm Edd}$. We test this interpretation using CL-AGN selected from the Dark Energy Spectroscopic Instrument (DESI) and control samples matched to the eROSITA all-sky survey (eRASS). We find that the apparent positive correlation between $\alpha_{\rm OX}$ and the optical-continuum-based Eddington ratio, $\lambda_{\rm Edd,opt}$, is not unique to CL-AGN, but also appears in matched non-changing-look samples. In broad-H$\alpha$ AGN, our main statistical sample, this structure is largely driven by the known dependence of $\alpha_{\rm OX}$ on ultraviolet luminosity and by the covariance between the rest-frame 2500 Angstrom luminosity, $L_{2500}$, the black-hole mass, $M_{\rm BH}$, and $\lambda_{\rm Edd,opt}$. When an X-ray-based Eddington ratio is used instead, the relation reverses sign because the X-ray luminosity, $L_X$, enters the two axes with opposite signs. An apparent $\alpha_{\rm OX}$-Eddington-ratio V-shape can therefore be induced by the luminosity estimator and is not a standalone accretion-state diagnostic. As a complementary test, we examine the eRASS effective photon index, $\Gamma_{\rm eff}$, inferred from catalogue band fluxes. In broad-line AGN, it shows a weak positive association with the X-ray-independent optical Eddington ratio. However, the weaker hard-band trend depends on the null model and does not isolate coronal softening. These results motivate further X-ray spectroscopy, combined with independently estimated Eddington ratios, to test for intrinsic changes in the disk-corona system.
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All authors Wei-Jian Guo, Shuo Zhai, Zhu-Heng Yao, Huaqing Cheng, Jingwei Hu, Jun-Jie Jin

Astrophysics of Galaxies · Cross-listed from astro-ph.EP

Two Low-Mass-Ratio Microlensing Planets from High-Magnification Events: KMT-2021-BLG-0247 and MOA-2023-BLG-169

Kansuke Nunota, Andrew Gould, Takahiro Sumi et al. (+56 more)

We present an analysis of two planetary microlensing events, KMT-2021-BLG-0247 and MOA-2023-BLG-169, both of which exhibit high magnifications and low planet–host mass ratios, but with markedly different levels of parameter constraint. For KMT-2021-BLG-0247, the finite-source effect and microlens parallax are both clearly detected, leading to unusually tight constraints on the physical properties of the lens system. The host mass and lens distance are approximately $M_{\rm L}=0.9\pm0.1\,M_\odot$ and $D_{\rm L}=6.7^{+1.0}_{-0.3}\,\mathrm{kpc}$, respectively, and the planet mass is $M_{\rm p}=41\pm5\,M_\oplus$. The projected planet–host separations are $a_\perp=3.4^{+0.7}_{-0.3}\,\mathrm{au}$ and $3.0^{+0.6}_{-0.3}\,\mathrm{au}$ for the wide and close solutions, respectively. In contrast, MOA-2023-BLG-169 involves an extremely faint source, with $I_{S,{\rm OGLE}}=26.73$, such that the light curve permits a broad family of strongly correlated solutions. We therefore construct the physical-parameter likelihood using approximate invariant combinations of the light-curve parameters and supplement it with post-event Euclid/VIS imaging from the Euclid Q2 Galactic Bulge Survey (Beaulieu et al. 2026). The Euclid data reveal a component at the event position with ${\rm VIS}_{\rm AB}=23.05\pm0.09\,{\rm mag}$. Interpreting this component as the combined light from the source and any luminous lens, the resulting posterior gives $M_{\rm L}=0.48^{+0.23}_{-0.17}\,M_\odot$, $D_{\rm L}=3.50^{+2.82}_{-1.20}\,\mathrm{kpc}$, $a_\perp=1.62^{+0.77}_{-0.43}\,\mathrm{au}$, and $M_{\rm p}=143^{+103}_{-63}\,M_\oplus$. MOA-2023-BLG-169 demonstrates that, for an extreme faint-source event, even the event timescale and angular Einstein radius can remain strongly dependent on the Galactic prior and independent flux constraints.
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All authors Kansuke Nunota, Andrew Gould, Takahiro Sumi, Ian A. Bond, Jennifer C. Yee, Valerio Bozza, Fumio Abe, David P. Bennett, Aparna Bhattacharya, Kotaro Daimon, Ryusei Hamada, Yuki Hirao, Takuto Inoue, Stela Ishitani Silva, Shuma Makida, Shota Miyazaki, Yasushi Muraki, Seiya Nakayama, Ryo Ogawa, Ryunosuke Oishi, Greg Olmschenk, Hideaki Ose, Clément Ranc, Nicholas J. Rattenbury, Yuki K. Satoh, Daisuke Suzuki, Takuto Tamaoki, Sean K. Terry, Paul J. Tristram, Chihiro Ueda, Aikaterini Vandorou, Hibiki Yama, Michael D. Albrow, Sun-Ju Chung, Cheongho Han, Kyu-Ha Hwang, Youn Kil Jung, Yoon-Hyun Ryu, In-Gu Shin, Yossi Shvartzvald, Hongjing Yang, Weicheng Zang, Dong-Jin Kim, Chung-Uk Lee, Byeong-Gon Park, Andrzej Udalski, Przemek Mróz, Radosław Poleski, Jan Skowron, Michał K. Szymański, Igor Soszyński, Paweł Pietrukowicz, Szymon Kozłowski, Krzysztof Ulaczyk, Krzysztof A. Rybicki, Patryk Iwanek, Marcin Wrona, Mariusz Gromadzki, Mateusz J. Mróz

Astrophysics of Galaxies

A Gravitationally Lensed Low-Luminosity AGN From The Cosmic Noon

Marko Mićić, Olivia Holmes, Xinyu Dai et al. (+3 more)

Strong gravitational lensing provides a unique tool of studying intrinsically faint high-redshift active galactic nuclei (AGN). In particular, low-luminosity AGN (LLAGN) can probe black-hole growth in low-mass galaxies that current X-ray surveys cannot otherwise access. We investigate the nature and physical properties of a faint X-ray source triply imaged by the galaxy cluster SDSS J2243$-$0935, and determine whether the source hosts an AGN. We combine archival Hubble Space Telescope imaging and Chandra X-ray observations with the published strong-lensing models of SDSS J2243$-$0935. We constrain the source redshift geometrically, derive magnification maps, and infer the physical properties of the host galaxy. The geometric lensing analysis gives a source redshift of $z=2.14^{+0.12}_{-0.17}$, consistent with the photometric redshift estimate, and a total magnification of $\mu=78\pm7$. The source is triply lensed and detected only in the HST F160W band, with an intrinsic magnitude of $m_{\rm AB}=28.2\pm0.2$. The rest-frame optical emission implies a stellar mass of $8.6\lesssim\log(M_\star/M_\odot)\lesssim9.4$. The unobscured star formation rate is constrained to $\mathrm{SFR}_{\rm UV}<0.009\,M_\odot\,\mathrm{yr}^{-1}$, although substantial dust obscuration remains possible. Chandra detects X-ray point-source counterparts to all three HST-detected lensed images. The combined X-ray spectrum contains $100\pm11$ net counts and is consistent with a moderately absorbed power law, with $\Gamma \simeq 1.48$ and $N_{\rm H}=(5.5\pm4.4)\times10^{22}\,\mathrm{cm}^{-2}$. After correcting for gravitational magnification, we obtain an intrinsic rest-frame $2$–$10$ keV luminosity of $L_{\rm X}=1.2\pm0.3\times10^{42}\,\mathrm{erg\,s^{-1}}$. The X-ray emission is likely dominated by an AGN hosted by a low-mass galaxy at $z\simeq2.14$, making this system a strongly lensed LLAGN at cosmic noon (abridged).
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All authors Marko Mićić, Olivia Holmes, Xinyu Dai, Kevin Hainline, Haikun Xue, Zijun Gao

Astrophysics of Galaxies

IMFIT-MW: Multiwavelength photometric decomposition with IMFIT

Ilia V. Chugunov

Photometric decomposition is often used to study galaxy structure by modelling surface brightness distribution in its components. However, most of the relevant codes are designed for single-band analysis. I present IMFIT-MW: a lightweight, open source Python tool that extends IMFIT capabilities to simultaneously model multiwavelength images. IMFIT-MW is able to set shared parameters between filters and to impose smooth variation of them with wavelength. IMFIT-MW achieves this by using IMFIT to produce model brightness distributions for given parameters, whereas hyperparameters defining their wavelength dependence are fitted by an external optimizer. The code is available on GitHub (https://github.com/IVChugunov/IMFIT-MW). I provide a few examples of use, showing that IMFIT-MW matches GALFITM in single-thread performance and can have advantage of multithreading. In a broader sense, I demonstrate the possibility to extend IMFIT features even without modifying its source code.
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Astrophysics of Galaxies

MUSE-ALMA Haloes XVI: a census of the condensed baryons in z~0.5 HI absorption-selected galaxies

T. O'Beirne, C. Péroux, M. Zwaan et al. (+16 more)

We use the MUSE-ALMA Haloes sample to build a census of the condensed baryons (stars and cold gas) to study the multiphase interstellar medium and circumgalactic medium (CGM). The sample includes 79 gas-rich galaxies at 0.2<z<1.2 located near strong HI Ly-alpha absorbers along quasar sightlines within projected separations of ~5-270 kpc and radial velocity separations of up to 500 km/s. HST spectroscopy characterises the absorbers, while HST imaging, MUSE and ALMA observations trace the stars, ionised gas and molecular gas. We find the following results. (i) HI masses inferred from optical properties show broad agreement with those derived from the CGM absorber properties for impact parameters <100 kpc, although group environments can significantly influence these estimates. (ii) The molecular gas fraction declines more steeply with stellar mass than the HI fraction. This suggests that stars build up more rapidly than the cold gas reservoir, while massive galaxies either consume their molecular gas more efficiently or convert HI into H2 less efficiently. (iii) Galaxies with high stellar surface densities exhibit the highest baryon fractions. This may reflect baryonic feedback, which can produce flatter inner dark matter profiles in high surface density systems, or aperture effects, where the ionised gas kinematic tracer probes only the innermost, baryon-dominated regions in compact sources, but extends further into the dark matter halo in sources with extended baryonic distributions. (iv) A few galaxies are consistent with being the baryon-dominated descendants of the low mass z~6 galaxies detected by JWST, while many appear to be substantially more dark matter dominated, lower mass systems with progenitors beyond JWST detection limits. This study provides a multiscale, multiphase view of the gas in and around galaxies, allowing us to probe the baryon budget across cosmic time.
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All authors T. O'Beirne, C. Péroux, M. Zwaan, C. Barfety, V. Bollo, J. Chen, A. L. Danhaive, N. M. Förster Schreiber, L. Tacconi, S. Weng, V. Kulkarni, L. Chemin, R. Augustin, B. Casavecchia, M. E. Cluver, M. Halley, A. Karki, V. A. Kilborn, O. I. Wong

Astrophysics of Galaxies

MUSE-ALMA Haloes XV: Cold molecular, ionised, and stellar kinematics of HI-rich galaxies at z $\sim$ 0.5

C. Barfety, N. M. Förster Schreiber, C. Péroux et al. (+13 more)

Spatially resolved galaxy kinematics are well studied at z $\sim$ 0 and z > 1, revealing that disks are common out to z $\sim3-6$, albeit with higher velocity dispersions. z $\sim$ 0.5 marks a key transition in the drivers of disk turbulence and baryonic-dark matter mass budgets, yet multi-tracer resolved kinematic studies remain rare beyond the local Universe. We exploit a unique dataset combining ALMA CO observations with MUSE ionised gas and stellar continuum data to study the resolved kinematics of six galaxies at 0.43 < z < 0.83, part of the MUSE-ALMA Haloes program, selected via their association with H I absorption systems and spanning stellar masses from log$(M_\star/M_\odot) = 10.1 - 11.8$. Combining new ALMA/CO data with existing MUSE H$\beta$ kinematics and HST morphologies, we classify galaxies using morpho-kinematic criteria. For rotating disks, we jointly model H$\beta$ and CO(2-1) kinematics with DYSMALPY and compare results to theoretical predictions for pressure support, while pPXF is used to fit stellar absorption features. Four of the six galaxies are classified as disks, with two having known group members. These disks show elevated gas velocity dispersions relative to z $\sim$ 0 disks, consistent with interpolated trends between z $\sim$ 0 and z > 1. The results support marginally stable gaseous disks where gravitational instability still contributes alongside stellar feedback, with tentative evidence for a dynamically hotter warm ionised phase relative to cold gas ($\sigma_{0, H\beta} \sim 1.7 \times \sigma_{0, CO}$). We derive an average dark matter fraction $\langle f_{DM} \rangle = 0.42\pm0.14$, consistent with observations at similar redshifts, stellar masses, and surface densities. This work demonstrates the value of self-consistent, multi-wavelength analyses for probing disk settling physics in a relatively unexplored redshift range.
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All authors C. Barfety, N. M. Förster Schreiber, C. Péroux, L. J. Tacconi, J. Chen, S. Weng, V. Bollo, T. O'Beirne, M. Zwaan, R. Augustin, B. Casavecchia, L. Chemin, A. L . Danhaive, N. Guerra-Varas, V. Kulkarni, R. Potlia

Astrophysics of Galaxies

MUSE-ALMA Haloes XIV: The ALMA Large Programme Data Release

Céline Péroux, Jianhang Chen, Victoria Bollo et al. (+10 more)

The interactions between gas and galaxies are of paramount importance to our understanding of structure formation. A fundamental element of such baryon cycle studies is a complete census of the condensed matter (stars and cold gas) in both galaxies and their immediate surroundings, the so-called circumgalactic medium. Of particular importance are the processes of converting molecular gas into stars and deciphering whether this <100K gas is tracing gas flows. The MUSE-ALMA Haloes survey has assembled probes of the neutral atomic gas HI, ionised gas and stellar component for a sample of 79 $z\sim0.5$ galaxies. This is achieved by combining absorption line spectroscopy of background quasars with projected impact parameter as low as 5 kpc and up to 250 kpc to probe the low density circumgalactic gas with emission line tracers of both ionised gas and stars. This paper presents the Large Programme observational set-up and releases the data characterising the molecular phase of some of the MUSE-ALMA Haloes targets so as to reach a complete census of their condensed baryons. ALMA's unique millimetre coverage and high sensitivity is ideal to characterise the CO emission of these $z\sim0.5$ HI-selected galaxies. By measuring the molecular mass, kinematics, gas flows and gas fractions, this project then: i) quantifies the role of molecular gas in HI-rich galaxies, ii) characterises the molecular phase of gas flows from morpho-kinematics analyses, and iii) establishes a census of the condensed baryons in the interstellar and circumgalactic media. Ultimately, these results will provide unique insights into the baryon cycle - a crucial component of galaxy formation.
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All authors Céline Péroux, Jianhang Chen, Victoria Bollo, Tamsyn O'Beirne, Capucine Barfety, Simon Weng, Ramona Augustin, Benedetta Casavecchia, Martin Zwaan, Linda Tacconi, Natascha Föster Schreiber, Laurent Chemin, Varsha Kulkarni

Astrophysics of Galaxies · Cross-listed from astro-ph.HE

Quasi-periodic eruption spectral-timing: EMRIs crossing warped accretion disks

Joheen Chakraborty, Andrew Mummery, Eliot Quataert et al. (+3 more)

Quasi-periodic eruptions (QPEs) are repeating X-ray transients from galactic nuclei potentially caused by a stellar-mass orbiter repeatedly colliding with the accretion disk of a supermassive black hole (SMBH) in an extreme mass-ratio inspiral (EMRI). In this picture, the eruption arrival times encode the orbit and its relativistic precessions, while the quiescent spectral energy distribution (SED) probes the same disk and SMBH, providing two independent constraints on the same orbit-disk system. We present a joint spectral-timing framework that takes advantage of this by simultaneously fitting an analytic QPE timing model built on Kerr geodesic frequencies and a warped disk geometry, coupled to a self-irradiated disk SED model sharing the same SMBH mass, spin, and disk parameters. We apply it to the QPE sources GSN 069 and eRO-QPE2, showing that the QPE timings and quiescent spectra can be reproduced simultaneously in each, providing circumstantial support for the EMRI model and warped disks in these systems. However, given the sparse timing data in both sources, neither admits a unique solution. In eRO-QPE2, we identify six physical modes which reproduce the timings and SED comparably well, motivating denser observing campaigns to identify one unambiguously. Our results demonstrate both the promise of QPE spectral-timing as a precision probe of SMBHs, their accretion disks, and orbiting companions, and the aliasing subtleties of sparsely sampled QPE timings.
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All authors Joheen Chakraborty, Andrew Mummery, Eliot Quataert, Riccardo Arcodia, Itai Linial, Erin Kara