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Physics Astrophysics Astrophysics of Galaxies

astro-ph.GA Watch Astrophysics of Galaxies

Monday 10 August

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

Impact of disk magnetic fields on the propagation of stellar-scale jets in the magnetically arrested accretion disks of active galactic nuclei

Bao-Quan Huang, Tong Liu and Jian-Fu Zhang

It is widely recognized that active galactic nucleus (AGN) disks host numerous massive stars and compact objects. Stellar-scale jets triggered by collapses of massive stars and mergers of compact objects could propagate through the disk and produce observable electromagnetic radiation. Magnetically arrested disks (MADs), supported by both numerical simulations and observations, possess strong magnetic fields (MFs). As jets travel within such environments, the MFs should regulate jet evolution and shape radiation signatures. In this work, we explore the effects of disk MFs on jet propagation and breakout emission within the MAD framework. We employ a jet-cocoon model that accounts for potential disk-MF effects, including both magnetic pressure and magnetic energy dissipation driven by magnetic reconnection. We find that magnetic pressure effectively suppresses the lateral expansion of the cocoon, which enhances jet collimation and modestly increases the jet-head velocity. Furthermore, magnetic pressure effects are more pronounced at relatively low jet powers. In this regime, the breakout luminosity of the jet-head shock is enhanced, while its breakout time is shortened. However, the magnitude of the luminosity enhancement is sensitive to the adopted regime-dependent emission prescriptions. These findings suggest that, within the explored parameter space, disk MFs can facilitate the breakout of low-power jets arising from binary black hole mergers in AGN MADs.
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Astrophysics of Galaxies

Statistical inference of fast radio burst environments using galaxy number density

Vignesh V.V. Rao, Tetsuya Hashimoto, Tomotsugu Goto et al. (+9 more)

Fast radio bursts (FRBs) are bright, millisecond-duration radio transients of unknown origin. They are categorized as repeaters and non-repeaters, possibly indicating distinct progenitor types. However, validating this distinction is difficult because of the limited number of localized FRBs. Large-scale galactic environments can provide insight into the nature of the host galaxies of FRBs and their progenitors. High-number-density regions are typically associated with old galaxies, whereas low-number-density regions are linked to young star-forming or less massive quiescent galaxies. In this study, we use galaxy number density to statistically assess the environments of 19 repeaters and 253 non-repeaters from CHIME Catalog 1, using galaxies from the WISE x PS1 catalog. A Kolmogorov-Smirnov (KS) test showed no significant difference between the two populations ($p_{\rm KS} = 0.673$). This result indicates that the statistical significance of the difference could depend on small-number statistics, highlighting the necessity of future FRB samples. Intriguingly, a comparison of FRBs with random galaxy fields suggests that FRBs may preferentially occur in underdense galactic environments, with a median $p$-value ($p_{\rm KS}$) of $2.84 \times 10^{-2}$ compared to random galaxy apertures.
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All authors Vignesh V.V. Rao, Tetsuya Hashimoto, Tomotsugu Goto, Shotaro Yamasaki, Mohanraj Madheshwaran, Sridhar Gajendran, Tomoki Wada, Simon C.-C. Ho, Terry Long Phan, Yuri Uno, Amos Y.-A.Chen, Hiroto Masaka

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

Multi-tracer mass bias in matched cosmic voids from SDSS DR7 and the ELUCID constrained simulation

Youcai Zhang, Xiaohu Yang, Hong Guo et al. (+1 more)

Cosmic voids provide a unique environment for studying the relationship between galaxies, subhaloes, and dark matter in the underdense Universe. Using the SDSS galaxy catalogue and the ELUCID constrained simulation, we establish an observationally anchored framework for measuring multi-tracer mass bias within matched cosmic voids. A sample of 102 matched void pairs is constructed to directly compare galaxy, subhalo, and dark matter mass distributions within an observationally constrained realisation of the local Universe. We find that both the galaxy-to-dark matter and subhalo-to-dark matter mass ratios decrease toward void centres, indicating that luminous and halo tracers become increasingly depleted relative to the underlying matter distribution in the deepest underdensities. In contrast, the galaxy-to-subhalo mass ratio exhibits substantially larger statistical uncertainties within the inner void regions ($r/R_{\rm v}\lesssim0.5$). By comparing measurements obtained using independent and common coordinate frameworks, we show that coordinate offsets contribute to the observed scatter but cannot fully account for the large uncertainties. The remaining uncertainty primarily arises from the severe scarcity of massive subhaloes ($\log_{10}(M_{\rm sub}/h^{-1}M_\odot)\ge11.8$) within void interiors, which greatly reduces the number of statistically valid measurements near void centres. Our results provide an empirical characterization of multi-tracer mass bias in observationally constrained cosmic environments and demonstrate the importance of accounting for coordinate consistency and tracer scarcity when interpreting such measurements in extreme underdense regions.
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All authors Youcai Zhang, Xiaohu Yang, Hong Guo, Peng Wang

Astrophysics of Galaxies

Unveiling Metal Mixing in a Grand-Design Spiral: A UV-optical multiphase spatially resolved study of M83

Adarsh Ranjan, Bethan L. James, Svea Hernandez et al. (+4 more)

We present a spatially resolved, multiphase study of chemical enrichment around young star clusters (YSCs) in the nearby grand-design spiral M83 by combining far-ultraviolet(UV) absorption-line spectroscopy from HST/COS with cospatial optical spectroscopy from VLT/MUSE and LBT/MODS. Our sample includes 18 YSCs spanning spectroscopic ages of ~1-6 Myr and galactocentric radii out to R/R_{25}=0.56. Neutral (H I) abundances were derived from UV absorption-line spectroscopy and compared with ionised (H II) abundances from reddening-corrected optical emission lines. Because auroral lines are not detected in all regions, we develop and apply an empirical multi-zone electron temperature (T_e) calibration based on strong-line diagnostics to estimate T_e and derive reliable nebular abundances. We measure oxygen(O), sulphur(S), nitrogen(N), and iron(Fe) abundance tracing enrichment from distinct nucleosynthetic channels. The alpha-elements (O and S) exhibit similar behaviour, consistent with enrichment by core-collapse supernovae, whereas Fe shows weaker variations, reflecting its delayed production by Type Ia supernovae. Nitrogen displays the largest phase offset (ionised-neutral), with enhancements of up to $Delta$N/H~1.5 dex and $Delta$N/O>1.5 dex in the ionised gas relative to the neutral phase, indicating localised enrichment by massive stars and inefficient mixing between gas phases on Myr timescales. While the ionised gas exhibits signatures of feedback-regulated chemical enrichment and large-scale abundance gradients, corresponding trends are weak or absent in the neutral gas, consistent with metals remaining largely confined to the immediate star-forming environment during the earliest stages of cluster evolution in a massive grand-design spiral.
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All authors Adarsh Ranjan, Bethan L. James, Svea Hernandez, R. Rickards Vaught, Nimisha Kumari, Alessandra Aloisi, Peter Zeidler

Sunday 9 August

Astrophysics of Galaxies

An Identifiability Audit of One-Parameter Structural Corrections to the Radial Acceleration Relation in SPARC

Lukas A. Sosna

We ask whether any one-parameter structural correction to the radial acceleration relation (RAR) can be uniquely recovered from SPARC rotation curves, and answer with an identifiability audit: each candidate is benchmarked against per-galaxy nuisance freedom, with predictive scoring against mass-only and data-quality baselines. In the full sample (N = 126) the answer is no: a hybrid compactness term improves the fit, but zero-point freedom absorbs the gain, and in cross-validation the model fails to out-predict a mass-only baseline and loses to a quality-flag baseline. One regime retains structural information: in gas-dominated, low-acceleration disks – where MOND's strict locality and $\Lambda$CDM feedback models diverge most sharply – the RAR residual correlates with compactness ($r=0.46$, $p=1.3\times10^{-4}$), remains significant under hierarchical partial pooling ($\beta=0.23$, $p=1.7\times10^{-5}$; N = 63), and survives canonical joint control for quality, sampling, mass, inclination error, and first-order pressure support ($r=0.30$, $p=0.02$). All significant results pass a Benjamini-Hochberg correction over the declared 27-test family. Three limits temper that survival: it is not significant under rank-based control over the widest proxy set; it resides in faint dwarfs independent surveys do not reach; and after mass control it is shared across the mass-size manifold. Pressure support brackets the interpretation – isotropic drift correction absorbs a quarter of the amplitude, while a Jeans treatment overcorrects resolved cases – leaving the physical origin undetermined. The audit's product is the extraction limit: claimed corrections must clear the 0.106 dex per-galaxy nuisance floor, a mass-only baseline, and data-quality stratification.
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Astrophysics of Galaxies

Exploration of UV-bright sources in Globular cluster NGC 3201 using UVIT observations

Manasi Kulkarni, Sonika Piridi, Ranjan Kumar et al. (+1 more)

We present a comprehensive study of the ultraviolet (UV)-bright stellar population in the globular cluster NGC 3201 using the Ultraviolet Imaging Telescope (UVIT) onboard AstroSat. By combining far-UV photometry of the UVIT F148W and F169M filters with Gaia and ground-based telescope optical data, we construct UV$-$optical color-magnitude diagrams (CMDs) to identify UV-bright stellar evolutionary phases. Physical parameters of all detected sources are derived by fitting stellar atmosphere models to the observed multi-wavelength spectral energy distributions (SEDs). The effective temperatures of blue horizontal branch stars (BHBs) span the range 7250$-$11250 K. We identify two extreme horizontal-branch stars (EHBs) with effective temperatures of approximately 25,000 K and 17,000 K; one lies within the cluster core radius ($r_\mathrm{c}$=1.3$'$), while the other is located outside. We also detect two candidate “gap” objects in the transitional phase between HB stars and white dwarfs, which may represent hot blue hook (BHk) stars. For the blue straggler stars (BSSs), we determine effective temperatures, radii, and luminosities through SED fittings, and estimate their masses and isochrone-equivalent ages using PARSEC isochrones. Finally, we studied the normalized cumulative radial distribution of the observed BHB stars, BSSs, MS stars, RGB stars, and variable stars along with the specific frequency of BSSs across the cluster. These results provide new insights into the late-stage stellar evolution and dynamical processes in NGC 3201.
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All authors Manasi Kulkarni, Sonika Piridi, Ranjan Kumar, Ananta C. Pradhan

Astrophysics of Galaxies

A Catalog of Giant Radio Source Candidates from TGSS ADR1 Using a Deep Learning–based Pipeline

Baoqiang Lao, Binghua Liang, Shaoguang Guo et al. (+4 more)

We present a catalog of 5,595 giant radio source (GRS) candidates, defined by a largest (projected) linear size (LLS) exceeding 0.7 Mpc. Of these, 4,566 would be new discoveries if confirmed. These candidates were identified through a systematic and automated search of the first Alternative Data Release of the TIFR GMRT Sky Survey (TGSS ADR1) using a deep learning–based pipeline that incorporates a radio sources detection model and the likelihood ratio method. Across the full sample, the LLS reaches up to $\sim$4.5~Mpc, with redshifts ranging from $z=0.056$ to at least $z=2.385$. The catalog comprises 4,210 giant radio galaxies and 1,030 giant radio quasars, with the remaining 355 candidates currently unclassified. We systematically analyze the distributions of their key physical properties, including spectral index, bending angle (BA), radio power ($P_{150}$), and $r$-band absolute magnitude. Our results show that GRS candidates are predominantly straight (a median BA of $11.0^\circ$) and follow an “L-shaped" BA–LLS distribution. The radio power vs. LLS ($P_{150}$–$D$) diagram reveals a concentration at $P_{150} < 10^{28}$ W Hz$^{-1}$, while rare high-power outliers ($>10^{28.5}$ W Hz$^{-1}$) with LLS $>$ 1 Mpc challenge self-similar evolutionary models. Additionally, 286 GRS candidates are found to be associated with cataloged galaxy clusters.
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All authors Baoqiang Lao, Binghua Liang, Shaoguang Guo, Junxiu Liu, Xiaolong Yang, Rushuang Zhao, Yang Kun

Astrophysics of Galaxies

Constructing a Hydrogen Line Library for Ly{\alpha} Emitters at Low Redshifts (z < 0.4): Estimating Dust Extinction and Assessing Paschen line Detectability with SPHEREx

Junho Song, Hyunmi Song and Hyunjin Shim

Hydrogen recombination lines, one of the strongest emission lines from star-forming galaxies, are used to probe the early Universe as indicators of star formation rates and ionizing photon production rates. Ratios between different recombination lines provide clues to estimate dust attenuation, in addition to the H II region physical diagnostics. To prepare for future near-infrared spectral surveys and optical narrow-band imaging surveys aiming for hydrogen lines in different redshifts, we construct hydrogen recombination line libraries by compiling data from published literature. Our compilation includes 260 galaxies mostly at z < 0.4, of which at least one hydrogen recombination line is observed. The specific hydrogen emission lines under investigation encompass three Balmer lines (H{\alpha}, He̱ta} and H{\gamma}) and Ly{\alpha} line. Of the compiled galaxies, we estimated dust extinction for 85 galaxies that have detections of at least two Balmer lines, by assuming the Case B recombination and Calzetti extinction curve, based on which Ly{\alpha} escape fraction is also inferred. For each of the 14 galaxies with detections of all three Balmer lines, we optimized the extinction curve so that it yields consistent E(B-V) values across the three possible Balmer line ratios, showing the variety in the slope of the dust attenuation curve. We further evaluated the feasibility of studying hydrogen emission line-selected galaxies with future spectral surveys such as SPHEREx by modeling the Paschen lines of our galaxy sample.
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Astrophysics of Galaxies

The ALMA carbon monoxide supernova (ACOS) survey II. Turbulent giant molecular clouds at the positions of core-collapse supernovae

M. Solar, M. J. Michałowski, J. Nadolny et al. (+11 more)

Context. Study of cold molecular hydrogen gas (hereafter molecular gas) provides crucial insights into its interplay with star-forming regions. However, the connection between molecular gas turbulence and the sites of massive star ($> 8~\rm{M}_{\odot}$) explosions as core-collapse supernovae (CCSNe) remains unexplored. Aims. We measure for the first time the turbulence of molecular gas in environments of CCSNe, with the aim to constrain the nature of their progenitors. Methods. In order to reach spatial resolutions of giant molecular cloud (GMC) sizes ($\sim 100~\rm{pc}$), we collected ALMA carbon monoxide $J = 2 \rightarrow 1$ spectral line ($\sim 230.54~\rm{GHz}$) observations (as a tracer of molecular gas) at the locations of 33 nearby CCSNe ($< 100~\rm{Mpc}$). Results. We found that CCSNe prefer molecular gas regions with high velocity dispersion compared to the average of their host galaxies. Conclusions. For CCSN progenitors, this observational evidence supports their increased formation in regions of high densities and/or their binary nature.
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All authors M. Solar, M. J. Michałowski, J. Nadolny, J. Sollerman, E. Zapartas, A. Oliva, L. Galbany, J. Hjorth, B. Ayala, M. Koprowski, A. Leśniewska, P. Nowaczyk, O. Ryzhov, B. Šlaus

Saturday 8 August

Astrophysics of Galaxies

GATOS: Distinct Feedback Modes in AGN Central Regions Revealed by Spatially Resolved JWST Spectroscopy

Lulu Zhang, Chris Packham, Erin K. S. Hicks et al. (+25 more)

This manuscript presents JWST MIRI/MRS observations of the central $r \approx 40-240$ pc regions of five active galactic nuclei (AGN) spanning a wide range of luminosities (${\rm log}\,L_{\rm bol}/{\rm erg\,s^{-1}} \approx 39.8-43.8$). Combining multiphase diagnostics from polycyclic aromatic hydrocarbons (PAHs), molecular hydrogen (H$_2$), and ionized gas at spatial scales of $\sim 4-24$ pc, this study presents a spatially resolved investigation into the effects of the two distinct AGN feedback modes–radiative and kinetic–on the surrounding medium. The results indicate that these two feedback modes, associated with AGN irradiation and shock processing, respectively, collectively drive the relative suppression of PAH emission in the nuclear regions of the targets studied here. Moreover, the coexistence of these two AGN feedback modes, especially the shock processing associated with either jets or outflows, in the central regions of AGN naturally explains both the bimodal distribution of PAH band ratios observed in the targets studied here and the seemingly disparate results reported in the literature. Although based on a limited sample, these findings provide new insights into calibrating star-formation rates (SFRs) from PAH emission in AGN, and more importantly, lay the groundwork for a practical framework to diagnose and quantify AGN feedback in the JWST era.
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All authors Lulu Zhang, Chris Packham, Erin K. S. Hicks, Ismael García-Bernete, Almudena Alonso-Herrero, Ric I. Davies, Martin J. Ward, Daniel E. Delaney, Takuma Izumi, Dimitra Rigopoulou, Cristina Ramos Almeida, Omaira González-Martín, Rogemar A. Riffel, Claudio Ricci, Montserrat Villar-Martín, Francoise Combes, Miguel Pereira-Santaella, Sebastian F. Hoenig, Andrew J. Bunker, Peter G. Boorman, Enrica Bellocchi, Nancy A. Levenson, Santiago García-Burillo, Fergus R. Donnan, Anelise Audibert, Lindsay Fuller, Tanio Díaz-Santos, David J. Rosario

Astrophysics of Galaxies

KCWI Discovery of a Spatially Resolved Kpc-Scale Ionized Outflow in NGC 1275

Kylie Yui Dan, Hanae Inami, Thomas Bohn et al. (+5 more)

We present new Keck Cosmic Web Imager observations of the central few kiloparsecs of NGC 1275, the brightest cluster galaxy of the Perseus Cluster. These integral field spectroscopic data reveal a warm-ionized outflow traced by H$\beta$ and the [O III] doublet extending out to $\sim2.5$ kpc from the nucleus. The warm-ionized outflow has an [O III]-derived $v_{50}$ of up to $\sim570$ km/s, $w_{80}$ of up to $3780$ km/s, and H$\beta$-derived outflowing mass of $(2.7 \pm 0.3)\times 10^6$ M$_\odot$. Our H$\beta$-derived warm-ionized outflowing mass rate of 2.7$\pm$0.7 M$_\odot$ yr$^{-1}$ is comparable to the estimated cold molecular disk accretion rate of 1$-$10 M$_\odot$ yr$^{-1}$, which could be a sign of self-regulation between the pc-scale cold gas feeding the active galactic nucleus (AGN) and the warm wind accelerated out to kpc scales. In the host galaxy, we detect an enhancement in the [O III] / H$\beta$ ratio in the direction of the receding jet, which may imply jet interaction with the host interstellar medium. The outflow component also shows a clear enhancement of [O III] / H$\beta$ that positively correlates with $w_{80}$ and $v_{50}$, indicative of AGN influence and/or fast shocks. Both the outflow and host galaxy [O III] / H$\beta$ ratio decrease with increasing distance from the center, showing that the influence of the AGN is confined to the central $\sim2$ kpc. These results are the first resolved measurements of a kpc-scale ionized wind in NGC 1275 and provide a view into how both jets and winds contribute to the feedback cycles in complex cool core cluster systems.
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All authors Kylie Yui Dan, Hanae Inami, Thomas Bohn, Sylvain Veilleux, Vivian U, Tianmu Gao, Justin Kader, Rosalie McGurk

Astrophysics of Galaxies

The Quasar Feedback Survey: Ionised Outflows in type 2 QSOs with MUSE data

M. Bianchin, C. M. Harrison, T. Costa et al. (+13 more)

We study ionised gas properties in a sample of 18 luminous (log L$_{\rm bol}\geq45$ erg/s) obscured QSOs at 0.085<z<0.2 observed with VLT/MUSE as part of the multi-wavelength Quasar Feedback Survey (QFeedS) and with VLA at low- and high-resolution data. We compare the outflow-related quantities with values reported in the literature and investigate possible correlations between the outflows and other properties of the ionised gas such as the electron density. We adopt a non-parametric approach to characterise the ionised gas kinematics, traced by the [O III]5007 emission line, and use $W_{80}$ measured from the unresolved nuclear spectra as a threshold to identify outflow-dominated spaxels. A qualitative comparison between the radio and the $W_{80}$ maps shows that, in general, the peak of the radio coincides with the peak of the $W_{80}$. The [O III]5007 is used as a proxy for the ionised gas mass, and the outflow-related properties are obtained in two different ways: the global, which uses flux-weighted velocities and radii; and the peak, relying on radial profiles. We correct the [O III]5007 flux for extinction using the Balmer decrement. We take advantage of the MUSE sensitivity and use the [Ar IV]4711,4740 doublet, only observable in the integrated r=1.5” spectra, to measure the electron density in each galaxy. We obtain $500<n_{e}{\rm[ cm^{-3}]}<27700$, leading to 0.03$<\dot{M}_{\rm out}/{\rm (M_{\odot} yr^{-1})}<$4.17 and $39<\dot{E}_{\rm kin}/{\rm [erg/s]}<42$. Our results emphasise the importance of accurate n$_e$ determination, leading to a difference of ~1 dex in the outflow rates and kinetic powers. We observe a positive correlation between $n_e$ and $V_{\rm out}$, interpreted as compression of the gas at higher velocities. This correlation should be further investigated at other luminosity and redshift ranges, but it can inform future outflow simulation studies.
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All authors M. Bianchin, C. M. Harrison, T. Costa, V. Mainieri, R. A. Riffel, G. Venturi, D. Kakkad, C. Ramos Almeida, P. H. Cezar, S. Ward, A. Girdhar, S. Molyneux, L. Ulivi, E. P. Farina, J. Mullaney, F. Arrigoni Battaia

Astrophysics of Galaxies

Kings of the Milky Way: A Homogeneous Gaia DR3 Analysis of King Open Clusters and the Galactic Disc Metallicity Gradient

Talar Yontan, Selçuk Bilir, Hikmet Çakmak et al. (+11 more)

This study aims to establish an internally homogeneous set of structural, astrophysical, and kinematical parameters for King open clusters and to assess their role as tracers of the Galactic thin disc. We present a homogeneous structural, astrophysical, and kinematical analysis of 27 King open clusters using high-precision Gaia DR3 astrometry, photometry, and spectroscopy. Cluster reddenings, distances, metallicities, and ages are determined via a homogeneous Markov Chain Monte Carlo isochrone-fitting approach applied to Gaia colour-magnitude diagrams. The derived parameters span E(G_BP-G_RP) = 0.113-1.933 mag, metallicities of [Fe/H] = -0.40 to +0.28 dex, ages from 17 to 6166 Myr, and heliocentric distances between 739 and 6272 pc. A comparison between astrometric and isochrone-based distances yields a median parallax difference of $-13\mu$as, indicating a good level of internal consistency between the photometric and astrometric distance scales within the adopted homogeneous framework. The radial metallicity behaviour of the King clusters is also examined using three complementary Galactic distance definitions and compared with the metallicity-radius relations obtained independently from 164 spectroscopically analysed open clusters from the literature. The King-cluster gradients are close to $-0.060$ dex kpc$^{-1}$ and are broadly consistent with those of the external reference sample, indicating that the homogeneously analysed King clusters follow the negative metallicity-radius trend traced by the broader thin-disc open-cluster population. Flatter gradients are found for young clusters, suggesting more homogeneous chemical enrichment at recent epochs. When dynamical constraints are applied to reduce the effects of radial migration and orbital blurring, the inferred gradient remains close to $-0.059$ dex kpc$^{-1}$.
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All authors Talar Yontan, Selçuk Bilir, Hikmet Çakmak, Olcay Plevne, Esin Soydugan, Seval Taşdemir, Remziye Canbay, Deniz Cennet Ç{\i}nar, Seliz Koç, Hülya Karagöz, Burçin Tan{\i}k Öztürk, Furkan Akbaba, Özcan Çal{\i}şkan, Timothy Banks

Astrophysics of Galaxies

A New Window on the H{\alpha} Luminosity Function and Star Formation Rate Density from 1.2 < z < 6.6 from JWST Medium-Band Photometry

Nicholas S. Martis, Chris Willott, Gregor Rihtaršič et al. (+23 more)

We present the first self-consistent measurement of the H{\alpha} luminosity function over a wide redshift range, covering cosmic noon into the epoch of reionization. Our analysis utilizes a novel method based on James Webb Space Telescope (JWST) NIRCam medium-band imaging. We combine data from the CANUCS, JWST in Technicolor, and JUMPS surveys which offer deep, uniform imaging (29.5-30 AB, 3{\sigma}) with extensive NIRCam medium-band coverage, reaching up to 29 total filters (up to 20 JWST) when including ancillary Hubble Space Telescope (HST) ACS and WFC3/UVIS data. The superb spectral energy distribution (SED) sampling enables precise, reliable photometric redshift estimation (outlier fraction 1.7%, {\sigma} N_MAD = 0.039 for this sample) as well as accurate continuum subtraction and line flux measurement verified by spectroscopic follow-up (no systematic offset, 0.23 dex scatter). We measure the H{\alpha} luminosity function (LF) from 1.25 < z < 6.6 by tracing the H{\alpha} emission line in 11 medium-band filters. The combination of depth, redshift coverage, and statistical power is unique, providing strong constraints on the shape of the LF over almost three orders of magnitude in luminosity. Our dense SED sampling enables us to reliably correct for dust attenuation and derive dust-corrected star formation rate functions as well as the evolution of the cosmic star formation rate density over the full redshift range. We recover the peak at z ~ 2 and a decrease toward z = 6, though with a higher normalization more in line with recent IR measurements than UV, though eclipsing both. This potential tension will be addressed in future work utilizing larger surveys with MIR coverage to better constrain the bright end of the luminosity function and the effects of dust.
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All authors Nicholas S. Martis, Chris Willott, Gregor Rihtaršič, Vesna Pirc Jevšenak, Roberto Abraham, Yoshihisa Asada, Maruša Bradač, Gabriel Brammer, Guillaume Desprez, Vicente Estrada-Carpenter, Kartheik Iyer, Lamiya Mowla, Adam Muzzin, Gaël Noirot, Ghassan T. E. Sarrouh, Marcin Sawicki, Sunna Withers, Giordano Felicioni, Jon Judež, Danilo Marchesini, Vladan Markov, Katherine Myers, Luke Robbins, Visal Sok, Wren Suess, Roberta Tripodi

Astrophysics of Galaxies

Diagnosing the Fe line complex of the intracluster medium by XRISM high-resolution spectroscopy

K. Fukushima, L. Hirata, N. Y. Yamasaki et al. (+17 more)

We aim to test the validity of the CIE framework in the ICM by performing line diagnostics based mainly on resolved Fe-K emission lines. Methods. We analyse Resolve full-array spectra of 17 galaxy clusters. Prominent Fe-K line components (the Fe xxv w, x, y, z, and Fe xxvi Ly{\alpha}1,2 lines) are removed from plasma emission models and instead fitted with Gaussian profiles, enabling direct measurements of line fluxes without relying on synthetic spectral models. Some cool-core systems show w/z ratios lower than predicted by about 20 per cent, and a broader w than z, consistent with resonant scattering effects. The y/x ratios exhibit marginal deviations from model predictions for some objects, suggesting possible origins of cascade process due to electron recombination and contribution from low-ionised Fe. The Fe Ly{\alpha}2/Ly{\alpha}1 ratios are globally close to the expected value of about 0.5, and the samples with good photon statistics prefer 0.55. This subtle excess is consistent with an unresolved contribution to Ly{\alpha}2 from the magnetic-dipole (M1) transition, which is absent from one of the atomic codes considered here. More interestingly, systems at around 7 keV preferentially exhibit Ly{\alpha}2/Ly{\alpha}1 ratios above 0.55. Although the statistical significance of this trend is limited, it suggests that resolved Fe Ly{\alpha} spectroscopy may provide a sensitive probe of additional atomic processes to collisional excitation, including dielectronic and radiative recombination and polarisation effects.
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All authors K. Fukushima, L. Hirata, N. Y. Yamasaki, P. Chakraborty, S. Dupourqué, Y. Fujita, L. Gu, C. Kilbourne, K. Matsushita, F. Mernier, E. D. Miller, K. Nakazawa, Y. Omiya, N. Ota, A. Sarkar, K. Sato, M. Sun, Y. Uchida, I. Zhuravleva, H. Yamaguchi

Astrophysics of Galaxies

Breathing Fire: Hot Dust in the Big Three Dragons at z = 7.15

Gitanjali Rajulal, Hiddo S. B. Algera, Yuma Sugahara et al. (+25 more)

We present new Atacama Large Millimeter/submillimeter Array (ALMA) Band 9 ($\lambda_\mathrm{obs} = 0.45\,\mathrm{mm}$) and 4 ($\lambda_\mathrm{obs} = 2.2\,\mathrm{mm}$) observations towards the Big Three Dragons, a pair of merging Lyman-break galaxies (LBGs) at $z=7.15$. The system was previously detected in ALMA Bands 6, 7 and 8 ($\lambda_\mathrm{obs} = 0.73 - 1.32\,\mathrm{mm}$), which, combined with our new observations, allows us to robustly constrain its dust temperature and obscured SFR. The unresolved Band 4 observations yield a $3.5\sigma$ detection, and the $0.4''$ Band 9 observations detect the Eastern and Western LBGs at $3.7$ and $3.5\sigma$, respectively. Through modified blackbody fitting, we infer a global dust temperature of $T_d = 78_{-23}^{+35}\,\mathrm{K}$ for the system, which implies a high IR luminosity of $\log(L_\mathrm{IR}/L_\odot) = 12.32_{-0.41}^{+0.43}$. This makes the Big Three Dragons one of the most IR-luminous systems known at $z>7$, with a total $\mathrm{SFR}_\mathrm{UV+IR} = 267_{-153}^{+418}\,M_\odot\,\mathrm{yr}^{-1}$ that is almost completely obscured ($f_\mathrm{obs} = 0.94_{-0.09}^{+0.04}$). Using resolved ALMA observations in Bands 6, 8 and 9, we confirm both LBGs have hot dust temperatures ($T_d \approx 67 - 84\,\mathrm{K}$) and correspondingly high obscured fractions ($f_\mathrm{obs} \approx 0.88 -0.95$). We find the Western LBG to fall $\sim1\,\mathrm{dex}$ above the canonical IRX-$\beta_\mathrm{UV}$ relation, suggesting patchy dust obscuration. The compact Eastern component, on the other hand, is consistent with a Calzetti- or SMC-like dust screen within the uncertainties. Together with the similarly hot dust temperature recently reported for the $z=8.31$ galaxy MACS0416-Y1, our results suggest a non-negligible fraction of star formation at the bright end of the UV luminosity function is highly dust-obscured, even at $z\gtrsim7$.
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All authors Gitanjali Rajulal, Hiddo S. B. Algera, Yuma Sugahara, Tom J. L. C. Bakx, Takuya Hashimoto, Suzuka Arai, Akio K. Inoue, Ikki Mitsuhashi, Manuel Aravena, Karin Cescon, Chian-Chou Chen, Elisabete da Cunha, Pratika Dayal, Ilse De Looze, Andreas Faisst, Yoshinobu Fudamoto, Rodrigo Herrera-Camus, Hanae Inami, Anton M. Koekemoer, Shoichiro Mizukoshi, Michael Romano, Lucie Rowland, Sander Schouws, Renske Smit, Livia Vallini, Wei-Hao Wang, Giovanni Zamorani, Anita Zanella

Astrophysics of Galaxies

First detection of C2H+ in the interstellar medium

Arshia M. Jacob, Karl M. Menten, Sandra Brünken et al. (+10 more)

Despite the detection of nearly 350 molecules in the interstellar medium, almost half of which are carbon chains, the pathways that build molecular complexity remain poorly understood. Observed abundances of carbon-chain and aromatic species are difficult to reconcile with existing top-down or bottom-up formation scenarios, due in part to limited observational constraints and incomplete theoretical understanding. In particular, small intermediary ions, key drivers of ion-molecule reactions capable of seeding larger hydrocarbons and aromatic rings, could provide critical support for the bottom-up formation scenario. Constraining the abundance and chemistry of these ions is therefore essential to test whether bottom-up growth can operate efficiently under interstellar conditions. Here, we report the first detection of the small hydrocarbon cation ethynylium, C2H+, toward the Orion Bar, based on observations with the APEX 12m sub-mm telescope of its lowest-lying J=3-2 rotational transition near 211GHz, which exhibits a unique spectroscopic fingerprint through resolved Lambda-doubling and hyperfine splitting components, as recently measured in the laboratory. Meudon PDR models successfully reproduce these values, placing C2H+ formation at the outer edges of PDR fronts. Our results link C2H+ production to CH+ and CH3+ within a network of ion-molecule reactions driven by vibrationally excited H2, a scenario now further supported by recent detections of these species in PDRs like the Orion Bar with JWST observations. The importance of C2H+ lies in its role as a key intermediate: it produces C2H2+ and subsequently C2H3+, effectively channelling small C2 building blocks toward larger hydrocarbons and facilitating bottom-up growth at the PDR surface. Targeted searches for C2H+ in other regions promise to provide a potentially decisive probe of ion-driven bottom-up chemistry in the ISM.
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All authors Arshia M. Jacob, Karl M. Menten, Sandra Brünken, Arnaud Belloche, Friedrich Wyrowski, Weslley G. D. P. Silva, Oskar Asvany, Sarwar Khan, Slawa Kabanovic, Kim Steenbakkers, Gerrit C. Groenenboom, Britta Redlich, Stephan Schlemmer

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

JWST Reveals a Galaxy-Wide Association of Red Supergiants with OB Stars in NGC 5584

Min Dai, Shu Wang and Biwei Jiang

The spatial relationship between young and evolved massive-star tracers offers a means of probing recent star formation across galactic disks. We combine JWST/NIRCam, $Swift$/UVOT UVW2, and GALEX FUV/NUV images to investigate the spatial association between red-supergiant (RSG) candidates and UV-selected star-forming complexes (SFCs) in the spiral galaxy NGC 5584. We identify 5,310 RSG candidates using colour–magnitude criteria and define 106 UV-selected SFCs from the UVOT/UVW2 morphology, with their FUV and NUV luminosities measured independently using the GALEX images. We find that 82% of the UV-selected SFCs overlap significant RSG overdensities, indicating a galaxy-wide statistical association between UV-bright SFCs and the evolved massive-star population. Among the 93 SFCs with reliable JWST coverage, the UV-$\beta$-corrected FUV and NUV luminosities correlate tightly with the JWST/NIRCam luminosities, with Pearson correlation coefficients of $r=0.962$–$0.971$. MIST isochrone comparisons for 43 RSG-rich SFCs indicate a characteristic age of $\log(\mathrm{age/yr})\simeq 7.16$. These results show that RSG overdensities and UV-selected SFCs trace related but distinct phases of recent massive-star formation. Their spatial correspondence is statistical rather than one-to-one and likely reflects differences in stellar age, dust extinction, spatial resolution, aperture coverage, and local star-formation history.
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Astrophysics of Galaxies

A Two-level Radial-velocity Zero-point Calibration for LAMOST MRS with Gaia and APOGEE and a Value-added RV Catalogue

Jinming Zhang and Haibo Yuan

The LAMOST Medium-Resolution Survey (MRS) provides a large stellar spectroscopic data set for Galactic kinematics and time-domain radial-velocity (RV) studies. However, the multi-spectrograph, multi-exposure, multi-fiber observing strategy can imprint RV zero-point (RVZP) systematics that vary across instrumental and temporal hierarchies. We construct a two-level empirical RVZP correction to LAMOST DR12 MRS using Gaia DR3 magnitude-colour-corrected RVs and APOGEE DR17 RVs as external references: a spectrograph-exposure correction in (lmjm, planid, spid) units, followed by a fiber-time correction in (spid, fiberid, time_tag) units. Within each unit, RVZPs are estimated from Gaia and APOGEE residuals using a weighted-median estimator, and are subtracted from the pipeline RVs to obtain corrected velocities. For high-S/N spectra, the scatter relative to APOGEE DR17 decreases from ~1.1 km/s to ~0.52 km/s after the full two-level correction, implying a ~2x improvement in RV precision. We release a value-added catalogue of two-level-corrected RVs for 11,129,477 blue-arm spectra, including 8,158,271 single-exposure spectra and 2,971,206 coadded spectra, enabling consistent RV analyses across exposures, spectrographs, fibers, and time.
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Astrophysics of Galaxies · Cross-listed from astro-ph.SR

NATA: a chemical-picture equation of state for stellar merger hydrodynamics

Natalia Ivanova

We present NATA (Nearly Always Truthful Approximations), a self-contained chemical-picture equation of state for hydrogen-helium-carbon-oxygen mixtures, developed for hydrodynamics calculations of stellar mergers and common envelope evolution. NATA carries bound species explicitly in ionisation and dissociation equilibrium and evaluates pressure, internal energy, and entropy from one continuous, single-physics chemical-picture solve built on analytic and semi-analytic component physics, rather than by stitching together component EOS tables. The result is smooth thermodynamics across ionisation, dissociation, and degeneracy fronts, with monotonic internal energy and no artificial energy steps at EOS seams, so the EOS inverts cleanly for codes that advance internal energy. We benchmark NATA against the blended MESA EOS, ab initio hydrogen-helium tables, and reference-independent analytic limits. NATA reproduces clean analytic limits and selected fully ionised benchmarks at the sub-percent level, while most remaining percent-level residuals are confined to partial-ionisation and dissociation fronts; these residuals are traced to identifiable picture choices, front placements, and reference-table seams or extrapolations. NATA therefore provides a well-behaved fallback in cool, low-density regimes where blended EOS tables may be stretched beyond their intended use and become physically unreliable.
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Friday 7 August

Astrophysics of Galaxies

Circumgalactic CIV Absorption Found Only Within 30 Degrees of the Minor Axis of Present-Epoch Galaxies

Mark A. Croom, Christopher W. Churchill, Bart Wakker et al. (+2 more)

We studied CIV 1548,1550 absorption in the circumgalactic medium (CGM) of 88 isolated, bright (L_B > 0.2L*_B) galaxies at z < 0.03 selected without prior knowledge of CGM absorption. The galaxies have observationally-unbiased distributions of inclination and galaxy-quasar sightline azimuthal angle. Above a 5-sigma rest-frame equivalent width detection threshold of W_r > 0.1 angstroms, we found absorption in the CGM of 9/88 of the galaxies within projected separation R_perp < 350 kpc. All nine absorbers arise within 30 deg of the projected minor axes and R_perp < 1.2R_vir of star-forming galaxies [log(sSFR/yr^-1) > -10.75]. To a confidence level of 99.998% (4.3-sigma), we can rule out that these absorbers are drawn from a random distribution of galaxy-quasar azimuthal angles. These findings suggest strong evidence for biconical polar winds related to the moderately elevated star formation in these present-epoch galaxies and we describe simple spatial-kinematic models that support this hypothesis. High specific star-formation rates may not be a sufficient condition for predicting minor-axis CIV absorption because the covering fraction of the subsample of star-forming galaxies within 30 deg of their minor axes is f_cov ~ 0.5; this may imply transient and/or patchy outflows. Incorporating studies of MgII and OVI CGM absorption, we favor a scenario in which CIV-bearing CGM gas interfaces between these low- and high-ionization regimes, comprising enriched intermediate-ionization clouds entrained and collimated in biconical stellar winds while mixing and cooling via non-equilibrium photoionization.
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All authors Mark A. Croom, Christopher W. Churchill, Bart Wakker, Glenn G. Kacprzak, Nikole M. Nielsen

Astrophysics of Galaxies

Mapping Gas Accretion and Stellar Kinematics to Sub-kiloparsec Scales in NGC 4696 with JWST/NIRSpec

Mathieu Marquis, Julie Hlavacek-Larrondo, Olivia Pereira et al. (+35 more)

We present JWST/NIRSpec IFU spectroscopy of the central $618\times618$ pc$^2$ ($\sim3''\times3''$) of NGC 4696, the BCG in the Centaurus cluster. Leveraging the $\sim0.1''$ ($20.6$ pc) pixel size of JWST, we resolve a compact circumnuclear rotating disk (radius of $\sim120$ pc) traced by Pa$\alpha$ and H$_2$ 1$-$0 S(1) emission, which allows a reassessment of the AGN position based on the kinematic centre of this disk. A central Pa$\alpha$ velocity dispersion reaching $\sigma\sim449$ km s$^{-1}$ implies a SMBH mass of $\sim10^9$ M$_\odot$, corresponding to a sphere of influence of $r_\mathrm{inf}\sim60$ pc, resolved by our observations. Position-velocity diagrams reveal an increase from $\sim-200$ to $\sim600$ km s$^{-1}$ on scales of $\sim150$ pc (a gradient of $4.7$ km s$^{-1}$ pc$^{-1}$) and an accretion rate of $\sim18$ M$_\odot$ yr$^{-1}$ feeding the CND. The Pa$\alpha$ emission shows a double-component in the core, with a high-dispersion redshifted component reaching $\sigma\sim600$ km s$^{-1}$. In contrast, MUSE H$\alpha$ observations covering the $\sim10$ kpc-scale filamentary structure recover only weak velocity gradients ($\lesssim150$ km s$^{-1}$) within $\sim300\times300$ pc$^2$ and do not resolve the disk due to larger PSFs and pixel sizes. ALMA CO(2-1) data reveal only compact molecular clumps within a $\sim410\times410$ pc$^2$ region, with no extended counterpart to the structures traced by Pa$\alpha$ and H$_2$ 1$-$0 S(1). Stellar kinematics show a smooth velocity field and broad dispersion profile, clearly decoupled from both the multiphase gas and the hot ICM probed by XRISM. These results provide a direct, spatially resolved view of gas dynamics within the inner few hundred parsecs, demonstrating the power of JWST/NIRSpec to probe SMBH feeding.
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All authors Mathieu Marquis, Julie Hlavacek-Larrondo, Olivia Pereira, Michael Reefe, Hyunseop Choi, Jorge Barrera-Ballesteros, Benjamin Vigneron, Ming Sun, Rebecca E. A. Canning, Gregory Taylor, Loïc Albert, Francesco D'Eugenio, Megan Donahue, Andrew C. Fabian, Gary J. Ferland, John S. Gallagher, Marie-Lou Gendron-Marsolais, Pierre Guillard, Minghao Guo, Nina Hatch, Ralf Kotulla, Yuan Li, Roberto Maiolino, Allison Man, Michael A. McDonald, Brian R. McNamara, Valeria Olivares, Marine Prunier, Christopher S. Reynolds, Carter Rhea, Annabelle Richard-Laferrière, Helen R. Russell, Philippe Salomé, Prathamesh Tamhane, Auriane Thilloy, Grant R. Tremblay, G. Mark Voit, Stephen A. Walker

Astrophysics of Galaxies

The large-scale ordered magnetic field in the Galactic halo and the Local Bubble

Elena Orlando

All-sky synchrotron polarization observations are the primary probe of the Galactic large-scale ordered magnetic field, which includes both coherent and ordered random components. However, magnetic-field strength estimates from synchrotron observations depend on the assumed cosmic-ray electron model, which itself depends on the magnetic-field configuration and strength throughout the Galaxy. We aim to constrain the strength of the large-scale ordered magnetic field in the Galactic halo through a self-consistent treatment of cosmic-ray electrons with the latest coherent magnetic-field configuration inferred by Xu & Han from rotation measures corrected for local contamination. We compare the Planck 30 GHz synchrotron polarization maps with our large-scale synchrotron models that jointly treat cosmic rays and magnetic fields and are constrained by direct cosmic-ray measurements and multifrequency data. Since the inferred field strength depends on the halo size, we explore different cosmic-ray propagation halo sizes. We observe a significant large-scale synchrotron excess relative to model predictions, which requires an ordered toroidal magnetic-field component in the halo with a peak strength of 3.2-4.3 microG, depending on the assumed halo size. We also find that the cosmic-ray propagation model with a 4 kpc halo size is preferred by the Planck synchrotron polarization maps. This result shows that the ordered magnetic field is 4-6 times stronger than the coherent field inferred from rotation measures by Xu & Han, establishing the presence of an ordered random field in the Galactic halo that is not traced by rotation measures. Attributing the synchrotron excess entirely to the Local Bubble would require non-standard Local Bubble properties, disfavoring this interpretation.
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Astrophysics of Galaxies

Radial Stellar Age Gradients in 42 Local Volume Dwarf Galaxies

Roger E. Cohen, Kristen B. W. McQuinn, O. Grace Telford et al. (+4 more)

We present radial stellar age gradients measured from star formation histories (SFHs) fit to resolved color-magnitude diagrams (CMDs) of 42 Local Volume dwarfs (6$\lesssim$Log M$_{\star}$/M$_{\odot}$$\lesssim$9), spatially divided into elliptical annuli. Ages in each annulus are quantified using $\tau_{90}$ and $\tau_{50}$, the lookback times to form 90% and 50% of the cumulative stellar mass. We find that radial age gradients are uncorrelated with environment, but gradients in $\tau_{90}$ are significantly correlated ($p$-values$\lesssim$0.001) with lifetime galaxy-wide "global" SFHs, in agreement with two independent cosmological zoom-in simulations. For radial gradients of $\tau_{50}$, simulation predictions differ. We demonstrate that given our large (N=42) and diverse observational sample, the strength of an observed correlation with global SFH is an actionable parameter to discriminate between different simulations with differing stellar feedback prescriptions. Overall, our results support predictions that dwarfs form inside-out like their more massive counterparts, with a combination of feedback-driven outward radial stellar migration and increasing birth radii for young stellar populations yielding present-day stellar age gradients ranging from outside-in to flat. In addition, the lack of a correlation between $\tau_{50}$ gradients and global SFH argues against recent star formation in radially outflowing gas. We also discuss the impact of differences between our observational sample and samples available in the latest simulations, highlighting areas for future investigation.
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All authors Roger E. Cohen, Kristen B. W. McQuinn, O. Grace Telford, Liese Van Zee, Laura Congreve Hunter, Andrew E. Dolphin, Suchindram Dasgupta

Astrophysics of Galaxies

Scattering from Dusty Outflows in Hot Dust-Obscured Galaxies with Blue Excess Emission

R.J. Assef, M. Stalevski, F.E. Bauer et al. (+15 more)

(Context) Hot Dust-Obscured Galaxies (Hot DOGs) are a population of hyper-luminous quasars heavily obscured by dust and gas. While most have rest UV/optical SEDs dominated by their host galaxy emission, a small fraction shows blue emission in excess of what is expected for star-formation. Detailed multi-wavelength studies from X-rays to the far-IR of these Blue Excess Hot DOGs (BHDs) have concluded the most likely origin of this blue excess is scattered light from the central engine. This scenario was confirmed by previous studies for the BHDs W0116-0505 and W0204-0506 which found highly polarized UV emission, a key signature of scattered light. (Aims) In this article we investigate this scattered light scenario in three other BHDs and further constrain the properties of the scattering material in W0116-0505. (Methods) We analyze new VLT/FORS2 imaging polarimetry observations in the $R_{\rm Special}$-band of three BHDs and additional observations of W0116-0505 in the $v_{\rm High}$- and $I_{Bessel}$-bands. (Results) We find spatially integrated polarization fractions in all three BHDs observed in the $R_{\rm Special}$-band ranging from about 6% to 15%. This confirms that their blue excess emission is due to AGN scattered light. We also find that the polarization fraction has a significant dependence with rest-frame wavelength in W0116-0505 and that it cannot be explained by Thomson scattering or by an AGN shining onto a smooth ISM. We find that a dusty bi-conical outflow acting as the scatterer can successfully explain the observations as long as the dust is dominated by graphites. This may be due to the high temperatures of the outflowing gas and the higher sublimation temperature of graphites compared to silicates.
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All authors R.J. Assef, M. Stalevski, F.E. Bauer, A. Blain, T. Diaz-Santos, P.R.M. Eisenhardt, R. Fernandez-Aranda, H.D. Jun, M. Liao, E. Shablovinskaia, A. Sarath, M. Stepney, D. Stern, C.-W. Tsai, A. Vayner, D.J. Walton, D. Wylezalek, D. Zewdie

Astrophysics of Galaxies

First Light and Assembly of GalaxieS (FLAGS) I: The JWST/NIRCam Number Counts and IGL as Constraints on Galaxy Formation Models

Jack C. Turner, Stephen M. Wilkins and Aswin P. Vijayan

JWST observations have been used in conjunction with SED fitting to infer the physical properties of galaxies throughout cosmic time, revealing tensions with the predictions of theoretical models. However, the biases associated with this process are poorly understood, which limits its true constraining power. We introduce the First Light and Assembly of GalaxieS (FLAGS) series, which will leverage forward modelling to confront models with more reliable direct observables. We describe the consistent processing of NIRCam imaging spanning $>1 \ \mathrm{deg}^{\, 2}$ across 30 independent fields, which can be used to measure the galaxy number counts from $0.9-4.4 \ \mu\mathrm{m}$. The integrated galaxy light (IGL) is constrained with a certainty of $\sim2.5\%$ at the longest wavelengths, producing novel constraints of $6.92^{\, +0.17}_{\, -0.17}$ and $3.46^{\, +0.09}_{\, -0.08} \ \mathrm{nW\,m^{-2}\,sr^{-1}}$ at $2.77$ and $4.10 \ \mathrm{\mu m}$ respectively. We compare these measurements with predictions from galaxy evolution models and find that the IGL is an unreliable measure of model performance. Comparing against the number counts directly reveals SC-SAM as the best-performing model ($\chi^{2}_{\nu}=18.6$), with its superior performance relative to SAGE attributed to efficient SNe feedback in low-mass halos. We investigate the impact of systematic photometry and forward modelling uncertainties, confirming that the number counts can be a reliable means of evaluating model predictions and performing simulation-based astrophysical parameter inference in the future.
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Astrophysics of Galaxies

GLOW II: A Census of Oxygen in Low-Mass Galaxies

Kristen B. W. McQuinn, O. Grace Telford, Andrey V. Kravtsov et al. (+12 more)

Oxygen is forged by stars and redistributed through galaxies by feedback-driven outflows, leaving a record of star formation and the baryon cycle imprinted on its present-day abundance and distribution. The Galaxies Losing Oxygen via Winds (GLOW) project quantifies the production, distribution, and retention of oxygen in 37 low-mass, low-metallicity, gas-rich galaxies in the nearby universe (D<6 Mpc) spanning a critical stellar mass range (10^6.5<Mstar<10^9.5) where feedback is expected to strongly shape galaxy evolution. We incorporate literature results to extend the analysis over 10^5<Mstar<10^11.5. We couple star formation histories derived from resolved stars with measurements of ISM metallicity and gas mass, and compares the oxygen budgets with empirical constraints in the circumgalactic medium (CGM). We find low-mass galaxies retain between 4-25% (mean 11%) of their oxygen produced by stellar nucleosynthesis, and nearly all retained oxygen residing in the gas. Galaxies exhibit increased scatter to higher oxygen retention fractions when residing in denser environments (Theta_5>0.5) and within 1 Mpc of a massive galaxy (Mstar>10^9 Msun), indicating environment likely affects the amount of oxygen retained, recycled, or accreted to galaxies. Contrary to expectations, oxygen retention does not correlate with position on the mass-metallicity relation. Although ionized oxygen is detected in the CGM, it remains unclear whether most missing oxygen resides there or has been expelled entirely. Hydrodynamical simulations, despite successfully reproducing the mass-metallicity relation, predict much higher retention fractions than measured in low-mass galaxies. Simple modeling indicates that wind mass-loading and outflow metallicity govern oxygen retention, and that low-mass galaxies accrete less baryonic material relative to the cosmic baryon fraction.
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All authors Kristen B. W. McQuinn, O. Grace Telford, Andrey V. Kravtsov, Joseph Burchett, Roger Cohen, Laura Hunter, Evan D. Skillman, Julia Roman-Duval, Danielle A. Berg, John M. Cannon, John Chisholm, Julianne J. Dalcanton, Andrew E. Dolphin, Liese van Zee, Benjamin Williams

Astrophysics of Galaxies

GLOW I: Comprehensive Measurements of Gas-Rich, Star-Forming, Low-Mass Galaxies in the Nearby Universe

Kristen B. W. McQuinn, O. Grace Telford, Roger Cohen et al. (+12 more)

Gas-rich, star-forming, low-mass galaxies in the nearby universe are powerful laboratories for studying baryonic physics in detail including: stellar mass assembly, stellar feedback, chemical enrichment, and the interplay of the interstellar medium with star formation. Investigating these disparate yet interconnected processes requires data obtained by myriad observatories. Here, we present a comprehensive atlas of uniformly processed data on 37 low-mass galaxies within 6 Mpc. The atlas includes archival data on (i) the HI from the Very Large Array observatory; (ii) resolved stars from Hubble Space Telescope optical imaging; (iii) Spitzer Space Telescope 3.6 micron imaging; and (iv) optical imaging from ground-based telescopes. We also compile measurements of (i) tip-of-the-red-giant-branch (TRGB) distances to the galaxies; (ii) direct method gas-phase oxygen abundances and nitrogen to oxygen abundance ratios; (iii) constraints on the local environment around each galaxy; and (iv) other measurements from the literature. We supplement the data with new observations where needed to complete the measurements for all galaxies in the sample. From these data, we find good agreement between stellar masses measured from color-magnitude diagrams and those estimated from 3.6 micron imaging by assuming a mass-to-light ratio. We also provide the first mapping of the HI profiles as a function of structural parameters. These data sets and measurements are the foundation for the Galaxies Losing Oxygen via Winds (GLOW) project whose main aim is to characterize the star formation - chemical enrichment cycle of low-mass galaxies by measuring the production, distribution, and retention of oxygen on a galaxy-by-galaxy basis.
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All authors Kristen B. W. McQuinn, O. Grace Telford, Roger Cohen, Liese van Zee, Laura C. Hunter, Madison Smith, Evan D. Skillman, Benjamin Williams, John M. Cannon, Joseph Burchett, Danielle A. Berg, Julianne J. Dalcanton, Andrew E. Dolphin, Suchindram Dasgupta, Avery Kiihne

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

HST imaging, pipeline modeling, and time-delay predictions of 2 triply-imaged and 15 quadruply-imaged lensed quasars

William Sheu, Tommaso Treu, Adriano Agnello et al. (+10 more)

The Hubble tension remains a significant challenge in modern cosmology, exhibiting a discrepancy between early-Universe cosmic microwave background measurements and local distance ladder observations. Strong lensing time-delay cosmography provides an independent, geometric probe of $H_0$ that can help resolve this discrepancy. Although hundreds of lensed quasars have been discovered, only a handful have been analyzed due to the resource-intensive follow-up required to measure precise time delays and break degeneracies. We present uniform gravitational lens modeling of 17 recently discovered lensed quasar systems (2 triply-imaged and 15 quadruply-imaged) to identify and prioritize the most promising candidates for future cosmological study. Using high-resolution near-infrared Hubble Space Telescope WFC3/IR F160W imaging (PID: 17916, PI: T. Treu), we perform uniform pipeline modeling with Lenstronomy. We constrain the mass and light profiles of the deflector galaxies, and assuming a fiducial cosmology, we predict their Fermat potential differences and expected time delays. Our pipeline successfully yields models and time-delay predictions for all 17 systems. Assuming ideal monitoring conditions, we estimate the total contribution from time-delay and Fermat potential modeling errors to the time-delay distance. From this, we classify the systems by estimated time-delay distance uncertainties: six "excellent" ($\leq 3\%$), five "good" ($3\%$-$7\%$), three "suitable" ($7\%$-$12\%$), and three "impractical" ($>12\%$). We recommend prioritizing follow-up campaigns on the 11 "excellent" and "good" systems, which have the potential to deliver high-precision, independent constraints on $H_0$ to help resolve the Hubble tension.
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All authors William Sheu, Tommaso Treu, Adriano Agnello, Timo Anguita, Simon Birrer, Daniel Gilman, Xiaosheng Huang, Richard G. McMahon, Nicholas D. Morgan, Veronica Motta, Anna Nierenberg, Kenneth C. Wong, Ioana Zelko

Astrophysics of Galaxies

A clear detection of proper motion confirms that the claimed $\mathbf{z\simeq32}$ galaxy candidate, "Capotauro”, is a Y-type brown dwarf

F.-Y. F. Liu, D. J. McLeod, B. J. Sutlieff et al. (+13 more)

The compact red source “Capotauro”, discovered in deep JWST imaging in 2025, has been suggested as a possible galaxy candidate at redshift $z\simeq32$ on account of its extreme NIRCam colours. However, given the lack of evidence that this source is spatially resolved, a very cool brown dwarf, at a distance consistent with the scale-height of the Milky Way stellar disc ($\simeq 500$ pc), provides an alternative explanation of the observed photometry. Here we exploit new medium-band NIRCam imaging obtained $\simeq 3.5$ years after the discovery data to test this hypothesis. Using filter-dependent point-spread-function fitting, a robust local relative astrometric frame defined by 68 compact reference sources, and a joint four-image injection-recovery analysis, we show that Capotauro has moved by $132 \pm 20$ mas over the 3.5-yr interval span of the observations, ruling out the possibility that it is an extragalactic source (galaxy, AGN, or supernova) at $> 6 \sigma$. The observed apparent proper motion is $(\mu_\xi,\mu_\eta)=(+9.4^{+6.4}_{-4.8},-35.6^{+5.1}_{-5.9})$ mas yr$^{-1}$, or $37.6^{+5.5}_{-5.6}$ mas yr$^{-1}$ in total. Through comparison of its photometric spectral energy distribution with empirical templates, we find that Capotauro is best described as a brown dwarf of spectral type Y$1.0\pm0.5$ ($T_{\rm eff}\approx350$ K) at a distance of $730\pm110$ pc (although the existing data and spectral templates are insufficient to rule out an even colder, later-type brown dwarf). Capotauro is thus one of the most distant Y dwarfs found to date, as expected given its discovery in a deep JWST extragalactic survey field. This result demonstrates the value of multi-epoch imaging for identifying substellar contaminants among the most extreme photometric-redshift candidates.
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All authors F.-Y. F. Liu, D. J. McLeod, B. J. Sutlieff, T. J. Dupuy, J. S. Dunlop, X. Chen, R. J. McLure, H.-H. Leung, S. Antonogiannaki, C. Bondestam, E. Laplace, R. Begley, A. C. Carnall, F. Cullen, C. T. Donnan, R. S. Ellis