Astrophysics of Galaxies · Cross-listed from gr-qc
From Density to Mass: A New Parametrized Framework for Dark Matter Environment Around Black Holes
Rajes Ghosh, Nicholas Speeney, Avijit Chowdhury et al. (+3 more)
Astrophysical black holes (BHs) are not isolated
vacuum objects but are expected to reside within complex environments, such as dark matter (DM)
halos and baryonic distributions. Such environments can modify the spacetime geometry surrounding the BH and leave observable imprints on gravitational-wave (GW) signals, including shifts in the quasinormal mode (QNM) spectrum, tidal Love numbers (TLNs), and the inspiral dynamics of extreme-mass-ratio inspirals (EMRIs). We develop a general framework for describing DM-dressed BH spacetimes by parameterizing the geometry directly in terms of the enclosed mass function, rather than the traditional density-based profile. This mass-based formulation is naturally connected to the total gravitational field, accommodates several common
halo profiles as limiting cases, and incorporates basic physical consistency requirements such as regularity, causality, and appropriate asymptotic behavior. Within this framework, we investigate the environmental imprints on QNMs, TLNs, and GW fluxes from EMRIs. We find a complementary sensitivity to the
halo structure: QNMs predominantly probe the inner regions of the environment, whereas static TLNs are more sensitive to its outer structure. EMRI fluxes, in contrast, probe the matter distribution through its influence on the orbital motion and GW propagation. Our results establish the enclosed-mass formulation as a flexible and physically controlled framework for connecting astrophysical environment models with precision GW observables.
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All authors Rajes Ghosh, Nicholas Speeney, Avijit Chowdhury, Chiranjeeb Singha, Miguel A. S. Pinto, Emanuele Berti
Astrophysics of Galaxies
The abundance and emission of PAHs from the local to early Universe
Massimiliano Parente, Desika Narayanan, Paul Torrey et al. (+8 more)
We present the first large-volume cosmological simulation of
galaxy evolution with a model for the abundance and luminous emission of Polycyclic Aromatic Hydrocarbons (PAHs) across a wide range of
cosmic time ($0 < z \lesssim 6$). The simulation is built on a semi-analytic model (SAM) that includes a treatment of dust size distribution, with PAHs being identified with the smallest carbonaceous grains ($< 15$ A) residing in the diffuse ISM of
galaxies. PAH emission is computed by post-processing the simulation output with the radiative transfer code GRASIL. In our model, where
stars only inject large grains, the PAH abundance emerges from the growth and shattering of dust grains in the ISM, naturally reproducing the observed correlation between the PAH mass fraction ($q_{\rm PAH}$) and both
metallicity and specific
star formation rate (sSFR). We derive a relation to infer $q_{\rm PAH}$ from $L_{\rm PAH}$, $L_{\rm IR}$, and sSFR, with a relatively small scatter (a factor of $\approx 1.3$). Simulated PAH emission correlates well with key
galaxy properties such as SFR and molecular gas content, and reproduces observational constraints. Taken together, these results support the viability of a top-down formation scenario for PAHs. We extend our model predictions to higher
redshifts, which can be exploited for future missions such as PRIMA. This work is a significant step toward leveraging PAH observations as a tool for studying
galaxy evolution.
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All authors Massimiliano Parente, Desika Narayanan, Paul Torrey, Gian Luigi Granato, Brandon S. Hensley, Jed McKinney, Alexandra Pope, Gergö Popping, Irene Shivaei, Laura Silva, J.D.T. Smith
Astrophysics of Galaxies
Precise C-N-O Abundances of Individual Galaxies in the First Billion Years from Ultra-Deep, Rest-UV-to-Optical JWST Spectroscopy
Raunaq Singh Rai, Guido Roberts-Borsani, Ryan Sanders et al. (+8 more)
We present ultra-deep JWST/NIRSpec $R\sim1000$ spectroscopy of nine
star-forming
galaxies at $z=6.0-8.3$ in the GOODS-N field, drawn from the Origins of Metal Enrichment in
Galaxies at
cosmic dAwn (OMEGA) survey. Paired with ancillary ultra-deep G140M observations, the G395M integrations from OMEGA yield continuous rest-frame UV-to-optical coverage and the full suite of diagnostics needed for precise characterisations and measures of the chemical abundances of these systems. Crucially, the auroral [O\,{\scriptsize III}]\,$\lambda$4363 line is detected in every
galaxy, enabling the determination of electron temperatures and direct oxygen abundances of $12+\log(\mathrm{O/H})=7.14-8.18$, independent of strong-line calibrations that dominate systematics at these
redshifts. We couple direct oxygen abundances with measurements of rest-frame UV emission-line strengths and ratios to infer the physical properties of our sample. Most importantly, we trace the relationship between oxygen abundance and both C/O and N/O abundance ratios with high fidelity, demonstrating robustly that $z=6.0-8.3$
galaxies follow the local trend in C/O vs. O/H, and that inferences regarding N/O are sensitive to the choice of rest-frame UV (\niv] or \niii]) or optical ([\nii]) tracers. This pilot study demonstrates the power of combining ultra-deep JWST/NIRSpec $R\sim1000$ rest-frame UV and optical spectroscopy, which now requires statistical samples to uncover the nebular properties of the full population of $z\geq 6$
star-forming
galaxies.
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All authors Raunaq Singh Rai, Guido Roberts-Borsani, Ryan Sanders, Alice E. Shapley, Leonardo Clarke, Pascal A. Oesch, Daniel Schaerer, Rui Marques-Chaves, Romain A. Meyer, Emma Giovinazzo, Shreya Karthikeyan
Astrophysics of Galaxies
Diverse Metallicities in Protoclusters at $z \sim 3.4$ detected by Deep Learning
Yoshihiro Takeda, Nobunari Kashikawa, Kei Ito et al. (+12 more)
We present spectroscopic follow-up observations with Subaru/MOIRCS of four protocluster candidate regions identified by the deep-learning model PCFNet. In three candidate regions, we confirm four protoclusters at $z =$ 3.316, 3.403, 3.408 and 3.425, exhibiting
galaxy density peaks over five times the uniform distribution. The detection rate of confirmed members aligns with PCFNet's predictions, underscoring its effectiveness. Analysis of spectral energy distributions (SEDs), incorporating up to ten photometric bands $(uu^*grizyJHK)$, reveals that protocluster members lie on the
star-formation main sequence. The masses of the most massive
halos in the protoclusters are estimated from the most massive stellar mass of the member
galaxies, yielding $\log M_\mathrm{halo}/M_\odot=12.4$-$12.8$, which are consistent with those at this
redshift predicted by cosmological simulations and are comparable to those of the progenitors of typical local clusters ($M_\mathrm{halo}^{z=0}\sim10^{14}M_\odot$). Using the Voronoi Tessellation Monte Carlo technique based on the probability of protocluster membership from PCFNet, we find that our protoclusters exhibit a significantly higher SFRD than the
cosmic SFRD at $z\sim3.4$. Based on the [Oiii]/H$\beta$ emission line ratio, two protoclusters show marginally ($1.4$-$2\sigma$) higher average
metallicities than the field, while the other protoclusters are statistically consistent with the field. These diverse
metallicities highlight the environmental impact within protoclusters detected by PCFNet, likely reflecting the complex opposing interplay between metal-rich gas recycling and metal-poor gas inflow, which may depend on the surrounding environment of each protocluster. This work demonstrates PCFNet's capability to unveil diverse samples of high-
redshift protoclusters, paving the way for a more comprehensive understanding of their role in
galaxy evolution.
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All authors Yoshihiro Takeda, Nobunari Kashikawa, Kei Ito, Jun Toshikawa, Mariko Kubo, Rieko Momose, Yongming Liang, Takehiro Yoshioka, Junya Arita, Hiroki Hoshi, Shunta Shimizu, Hisakazu Uchiyama, Satoshi Kikuta, Ryo Emori, Kentaro Koretomo
Astrophysics of Galaxies · Cross-listed from astro-ph.IM
Source–Line Associations in JWST/NIRSpec Dense-Shutter Spectroscopy
Zihao Wu, Daniel J. Eisenstein, Francesco D'Eugenio et al. (+9 more)
We demonstrate the feasibility of source–line association in JWST/NIRSpec dense-shutter spectroscopy, with $\sim$2000 sources observed simultaneously per pointing regardless of spectral overlap. While JWST wide-field slitless spectroscopy (WFSS) can disentangle overlapping spectra using two grisms with perpendicular dispersion directions, NIRSpec can achieve this using gratings with different dispersions. Compared with WFSS, NIRSpec dense-shutter spectroscopy offers substantially higher sensitivity and broader wavelength coverage. We develop a
Bayesian framework that combines cross-dispersion offsets, wavelength consistency, and changes in relative line positions between gratings to jointly determine source associations and
redshifts. We test the method using mock observations based on the observed source distribution and emission-line fluxes from the JWST Advanced Deep Extragalactic Survey (JADES), accounting for the NIRSpec optical model, MSA operability, measurement noise, false-positive detections, and bad pixels. Although the spectral traces overlap extensively, fewer than 0.5% of the simulated emission lines are blended with another line on the detectors in NIRSpec grating spectroscopy. Applying our method to these simulations, we obtain
redshifts, at an accuracy of 98%, for the $\sim$1800 sources that have detectable emission lines, of which $\sim$1500 are classified as confident and are 99.9% accurate. We further investigate how the association accuracy depends on the number of grating configurations. By combining high multiplexing, high sensitivity, and broad wavelength coverage, NIRSpec dense-shutter spectroscopy enables efficient, highly complete spectroscopic surveys for the high-
redshift Universe.
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All authors Zihao Wu, Daniel J. Eisenstein, Francesco D'Eugenio, Erica Nelson, Benjamin D. Johnson, Andrew J. Bunker, Zhiyuan Ji, Pierluigi Rinaldi, Brant Robertson, Sandro Tacchella, Christopher N. A. Willmer, Joris Witstok
Astrophysics of Galaxies
Extreme MgII Emission in Recently-Quenched Galaxies: A New Sample of Intermediate-Redshift Post-Starburst Quasars from the DESI Early Data Release
Margaret E. Verrico, Aayan Verma, K. Decker French et al. (+8 more)
Post-starburst
galaxies are
galaxies which have recently and rapidly shut off
star formation. AGN activity is often invoked to explain this rapid quenching, but most post-starburst selection methods select against optical AGN, motivating searches for "post-starburst
quasars." We present DESI observations of ten post-starburst
quasars with significant MgII emission ($L_{\text{MgII}} \geq 3 \times 10^{41}$ erg/s). This is the first sample of post-starburst
quasars to be selected from a post-starburst
galaxy parent sample rather than a
quasar catalog.
Quasars make up $4.6^{+1.6}_{-1.2}\%$ of the post-starburst parent sample at $0.49 \leq z \leq 1.39$. Using multiwavelength AGN diagnostics, we find that $26^{+3.0}_{-2.8}\%$ of post-starbursts in the parent sample host AGN. We find that post-starburst selection methods are biased against AGN with $\text{L}_{\text{Bol}}\gtrsim10^{45} \textrm{erg s}^{-1}$, potentially removing the
quasars responsible for driving outflows that aid in quenching. Finally, we find that 9/10 post-starburst
quasars in our sample have no detected broad H$\beta$, similar to so-called "MgII emitters" that may be the remnants of fading
quasars; if confirmed, these objects suggest a link between post-starburst
galaxies and variable AGN. Our new sample of post-starburst
quasars provides a link between previously reported local and high
redshift post-starburst
quasars during the epoch when
star formation throughout the universe was declining.
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All authors Margaret E. Verrico, Aayan Verma, K. Decker French, David J. Setton, Omar Almaini, Jenny E. Greene, Stephanie LaMassa, Yuanze Luo, Pallavi Patil, Kate Rowlands, Dharlenny Soto
Astrophysics of Galaxies
ViCTORIA project: A pilot study of the M49 region in the Virgo cluster in polarisation
A. Spasic, A. Benati, M. Brüggen et al. (+7 more)
Large-scale
magnetic fields permeate the Intracluster Medium (ICM) of
galaxy clusters. Understanding these fields gives an insight into the origin of
cosmic magnetic fields and the interaction of cluster
galaxies with the ICM. Using MeerKAT observations of the Virgo cluster as part of the ViCTORIA project, we probe
magnetic fields via Rotation Measure (RM) synthesis. The aim of this work is to characterise the
magnetic fields in and around the infalling group M49 in the Virgo cluster. We will probe the interaction of M49 with its surrounding medium through its imprint on the polarised emission and Faraday rotation. We use L-band MeerKAT data in full polarisation calibrated with the ViCTORIA MeerKAT Survey (ViMS) pipeline, which is designed for the calibration, imaging, mosaicking and RM Synthesis of the fields in the Virgo cluster, to achieve high-fidelity reconstruction of, both, total intensity and polarised emission. We analyse the background sources of the cluster for potential local changes in the
magnetic field, by calculating the RM distribution. In the final polarised image, consisting of four pointings of 45 min, we reach a noise level of $23.3 \mu \textrm{Jy/beam}$. We detect 101 background sources in the $\sim 2.5\, \textrm{deg}^2$ region around M49, corresponding to a source density of 40 sources/$ \textrm{deg}^2$. Across the $112\, \textrm{deg}^2$ observations of the Virgo cluster, this implies a total number of 4000 polarised sources. In M49 we find structured, diffuse polarised emission extending in the direction of the total intensity
radio tails. A higher polarisation fraction across the upper edge of the source indicates the effect of
magnetic field draping. Around M49 we find a larger RM scatter (at $3.8\sigma$) in the wake of M49 compared to the region in front of it. This can inform the modelling of the
turbulence created by galactic motions.
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All authors A. Spasic, A. Benati, M. Brüggen, H. W. Edler, F. De Gasperin, V. Gustafsson, P. Serra, A. Bonafede, A. Boselli, H. McCall
Astrophysics of Galaxies
The 2MIG isolated AGNs – 4. Linking hot-dust reverberation to spectroscopically predicted BLR scales in IC~5287 and Mrk~845
I.O. Izviekova, I.B. Vavilova, O.V. Kompaniiets et al. (+2 more)
We investigate the relation between directly measured hot-dust reverberation scales and spectroscopically predicted broad-line region (BLR) scales in the isolated Seyfert
galaxies IC~5287 and Mrk~845 (MCG+09-25-022), combining ZTF optical light curves, WISE/NEOWISE monitoring, and archival SDSS spectroscopy. Both
nuclei show BWB optical variability, RWB MIR behaviour, and delayed MIR responses consistent with circumnuclear dust reprocessing. For IC~5287, interpolated cross-correlation function analysis with flux-randomisation/random-subset-selection uncertainties yields a rest-frame W1 delay of $106_{-39}^{+24}$~d, corresponding to $0.089_{-0.033}^{+0.020}$~pc. The median W2 response occurs at a longer delay, but the lag distributions overlap substantially. The SDSS decomposition reveals strong host dilution and BLR reddening, $E(B-V)_{\rm BLR}=0.612_{-0.066}^{+0.067}$~mag. Applying the same colour excess to the AGN continuum as an illustrative scenario increases the predicted H$\beta$ BLR lag from approximately 4.8 to 11.7~d and reduces the dust-to-predicted-BLR radius ratios from approximately 20–25 to 8–10. For Mrk~845, transfer-function modelling gives a rest-frame W1 delay of $157_{-8}^{+19}$~d, corresponding to $0.132_{-0.007}^{+0.016}$~pc. Its W2 response occurs at a longer delay, with $P(\tau_{\rm W2}>\tau_{\rm W1})=0.963$, supporting wavelength-dependent hot-dust structure. The SDSS spectrum shows more moderate BLR reddening, $E(B-V)_{\rm BLR}=0.197_{-0.039}^{+0.046}$~mag. The comparatively large dust-to-predicted-BLR radius ratios in both
galaxies therefore primarily reflect the spectroscopically predicted BLR scales. These results emphasise the need to distinguish directly measured dust reverberation radii from BLR radii inferred from single-epoch spectroscopy when interpreting the BLR–dust hierarchy.
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All authors I.O. Izviekova, I.B. Vavilova, O.V. Kompaniiets, O. Zamora, R. Clavero
Astrophysics of Galaxies
Probing Spatial Variations in IGM Transmission: Higher Ly$\alpha$ Visibility in an H$\alpha$-Selected Galaxy Overdensity at $z\simeq6.2$
Shunta Shimizu, Nobunari Kashikawa, Junya Arita et al. (+13 more)
The visibility of Ly$\alpha$ emission during the epoch of reionization depends on both
galaxy properties and the transmission of Ly$\alpha$
photons through the intergalactic medium (IGM). Using JWST/NIRCam F470N imaging, we identify a prominent projected overdensity of H$\alpha$ emitters (HAEs) at $z\simeq6.2$ in CEERS field. We use Subaru/HSC NB872 imaging to measure their Ly$\alpha$ fluxes and compare the Ly$\alpha$ visibility of
galaxies within $2'$ of the density center with that of
galaxies outside this region. The Ly$\alpha$-emitter (LAE) fraction is $0.41^{+0.15}_{-0.14}$ in the inner region and $0.27^{+0.19}_{-0.15}$ in the outer region. Stacking the H$\alpha$ and Ly$\alpha$ images gives median Ly$\alpha$ escape fractions of $0.100^{+0.091}_{-0.053}$ and $0.063^{+0.130}_{-0.063}$ in the inner and outer regions, respectively. Both measures indicate higher Ly$\alpha$ visibility in the inner region, although only at modest significance. HAEs closer to the density center are systematically more massive and have redder UV slopes, which instead favor lower Ly$\alpha$ escape. The environmental difference in Ly$\alpha$ visibility is therefore difficult to explain solely by variations in underlying
galaxy population. Our results are consistent with reduced Ly$\alpha$ attenuation through a more highly ionized IGM in the overdense region, as expected if large H\,ii bubbles preferentially form around such
galaxy overdensities. The wide-field LAE distribution provides complementary support for this scenario, as the HAE-defined density center coincides with the strongest LAE overdensity across the $1.4\,{\rm deg}^2$ HSC field. These findings highlight the importance of spatial variations in IGM attenuation in shaping Ly$\alpha$ visibility near the end of reionization.
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All authors Shunta Shimizu, Nobunari Kashikawa, Junya Arita, Ryo Emori, Kohei Inayoshi, Akio K. Inoue, Kei Ito, Satoshi Kikuta, Kentaro Koretomo, Mariko Kubo, Yongming Liang, Rieko Momose, Kentaro Nagamine, Masafusa Onoue, Rhythm Shimakawa, Hisakazu Uchiyama
Astrophysics of Galaxies · Cross-listed from astro-ph.CO
MATISSE in the era of GRAVITY+
Florentin Millour, Anthony Soulain, Stéphane Lagarde et al. (+28 more)
MATISSE, the mid-infrared spectro-interferometric imager of the Very Large
Telescope Interferometer (VLTI), has been feeding on the light corrected by the
GRAVITY+ Adaptive Optics (GPAO) systems since the retirement of MACAO on the four Unit
Telescopes in 2024. We report the assessment of the new MATISSE performance with GPAO, based on commissioning observations obtained in 2024 and 2025 and compared with archival MACAO observations of the same stellar sources. The instrumental visibility transfer function is more stable in the L band, while its typical value in the L and N bands is unchanged; the visibility signal-to-noise ratio is consistent with, or better than, the values reported at the initial MATISSE commissioning. The correlated flux increases by 20–30% in GRA4MAT mode thanks to a better fringe tracking performance, and the total flux injected into the instrument increases by a factor of 1.3 to 1.4 (up to 1.7) in the L band at low spectral resolution, with no measurable loss in the N band. Combined with the new K-band fringe-tracking limits enabled by GPAO, this translates into a sensitivity gain of a factor 2 to 6 in the L and M bands, a confirmation of the N-band limits similar to the MACAO era. We then report the performances of MATISSE with the GPAO's
laser guide
stars in November and December 2025. The updated noise figures follow the exposure time calculator predictions in LM LOW and MED and come out better than them in N LOW, the L-band transfer function is stable at the few percent level between observing blocks an hour apart, and correlated fluxes, differential phases and closure phases are recovered down to a 10\,mJy target. Embedded young stellar objects and AGN are now within reach, thanks to the better performances on red targets brought by the
lasers. We finally discuss the science cases opened by this gain and the case for a future upgrade of the instrument.
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All authors Florentin Millour, Anthony Soulain, Stéphane Lagarde, Alexis Matter, Valentin Fleury, Farin Drewes, Mathis Houllé, Jules Scigliuto, Bruno Lopez, Anthony Meilland, G. Petrov Romain, Philippe Berio, Anthony Berdeu, Guillaume Bourdarot, Sylvestre Lacour, Mathias Nowak, Jean-Baptiste Le Bouquin, Antoine Mérand, Frank Eisenhauer, Julien Woillez, Miguel Montargès, Diogo Ribeiro, Taro Shimizu, Jens Kammerer, Xavier Haubois, Stefan Gillessen, Pierre Cruzalèbes, Frédéric Gonté, Walter Jaffe, James Leftley, Nicole Nesvadba
Astrophysics of Galaxies
Far-Ultraviolet diffuse emission as a tracer of Galactic extinction at the North Galactic Pole
Swagat Bordoloi, P. Shalima, Rupjyoti Gogoi et al. (+2 more)
Interstellar extinction at high Galactic latitude is often traced by thermal dust emission, but the conversion from infrared surface brightness to reddening is sensitive to grain properties and temperature. We test dust-scattered far-ultraviolet (FUV) and near-ultraviolet (NUV) diffuse emission as a high-resolution extinction tracer towards the North Galactic Pole (NGP), where E(B-V) < 0.1 mag. Using the GALEX diffuse maps of Murthy (2014), we build FUV and NUV intensity maps at 6' resolution over the region b > 70 deg and compare them with the Planck E(B-V) map at matched resolution. A direct pixel-to-pixel regression gives only moderate correlations (rho = 0.536 for FUV, 0.243 for NUV) owing to high per-pixel scatter from H2 fluorescence, line emission, and
photon-counting noise; we therefore construct per-pixel GALEX uncertainty maps and apply a centroid-fitting method that fits the mean intensity in bins of E(B-V) after rejection of outliers via iterative sigma-clipping, recovering tight relations (rho = 0.993 for FUV, 0.976 for NUV). We find the best-fit relations for the FUV and NUV intensity per 6'x6' pixel: FUV = 2285.3 E(B-V) + 278.6 and NUV = 1517.6 E(B-V) + 547.2 (
photons/cm^2/s/sr/A), inverted to produce a 601x601 GALEX reddening map. GALEX E(B-V) correlates strongly with HI column density from the all-sky HI4PI survey (rho = 0.991). We validate the maps using SDSS
quasars as extragalactic extinction calibrators:
quasar extinctions from the GALEX and Planck maps agree with a correlation of 0.99 and a slope of 0.986. Comparison with the Pan-STARRS1 stellar reddening map of Schlafly et al. (2014) shows the GALEX-based values have a smaller mean difference (0.039 mag) than the Planck-based values (0.064 mag). These results establish dust-scattered FUV diffuse emission as a viable alternative to thermal-dust extinction maps at high Galactic latitude.
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All authors Swagat Bordoloi, P. Shalima, Rupjyoti Gogoi, Jayant Murthy, Oleg Malkov
Astrophysics of Galaxies
Exploring the observed properties of JWST Little Red Dots with cosmological simulations and dust radiative transfer
Saksham Chandna, Fabio Di Mascia, Simona Gallerani et al. (+6 more)
JWST has uncovered compact high-
redshift (z>=4) sources, dubbed Little Red Dots (LRDs), characterised by a distinct V-shaped continuum. Their nature remains debated since broad-line AGN signatures coexist with non-AGN continua, marked by weak X-ray and mid-IR emission. We investigate which properties of LRDs naturally emerge within simulations of massive AGN host
galaxies and which require additional physics. We post-process two cosmological zoom-in simulations of the same massive
halo, one including black hole growth and AGN feedback (AGNfid) and the other with only
star formation and stellar feedback (SFonly). We analyse snapshots spanning z=6-9 to probe different evolutionary stages. Using SKIRTv8, we develop a forward-modelling framework exploring various dust models, dust-to-metal ratios, and intrinsic AGN spectra. We generate mock spectra and images to apply JWST observational LRD selection criteria. Not designed to model LRDs, our AGNfid simulations naturally reproduce their properties: V-shaped continua, compact morphologies with rest-UV complexity, UV luminosities, attenuations, overmassive BHs, sub-Eddington
accretion, and Balmer break strengths (~1-2) typical of most LRDs. Spectral decomposition reveals that the rest-UV continuum is dominated by stellar emission, whereas the optical continuum stems from a dust-attenuated AGN. Dust geometry and AGN-to-stellar contribution drive photometric differences between LRDs and Little Blue Dots. Our results suggest that LRDs do not necessarily represent a distinct class of objects. Instead, their defining properties can arise in massive AGN host
galaxies from the interplay between stellar emission, an obscured central engine, and dust geometry. Super-Eddington
accretion, dust-free gas columns, evolved stellar populations, and photoionisation modelling are required to test whether this framework reproduces the diversity of observed LRDs.
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All authors Saksham Chandna, Fabio Di Mascia, Simona Gallerani, Stefano Carniani, Pierluigi Rinaldi, Roberta Tripodi, Milena Valentini, Alessia Tortosa, Luca Zappacosta
Astrophysics of Galaxies
DREAMS: Taking the Temperature of a Massive Galaxy at z ~ 11
L. Parente, E. Vanzella, M. Messa et al. (+15 more)
We present a detailed photometric and spectroscopic analysis of Janus-11, a $z=10.7933 \pm 0.0006 $
galaxy magnified by a factor 1.6 by the
galaxy cluster MACS J0416. It was observed with JWST/NIRCam as part of the PEARLS program and with JWST/NIRSpec MSA as part of the DREAMS program. It has M$_{\rm UV}=-19.78^{+0.12}_{-0.11}$, and its stellar mass of log(M*/M_sun) = 8.75 (+0.08/-0.10) places it among the most massive known $z>10$
galaxies, while its $A_V=0.54\pm0.09$ mag and UV slope of $\beta=-1.71\pm0.26$ are compatible with a red monster classification, albeit among the least obscured members of this population: this could hint at a transition from the red monster to the blue monster phase. Moreover, the [OIII]4363 detection allows for the highest-
redshift metallicity measurement based on the [OIII]4363 direct method to date of $12 + \log(O/H) = 7.74^{+0.11}_{-0.10}$, together with an electron temperature of $T_e$(O$^{++}$) = $(2.1 \pm 0.2)\times10^4$ K. Its spatially resolved nature, with an effective radius of $136 \pm 9$ pc, together with the narrow FWHM of the emission lines ($\lesssim 230$ km s$^{-1}$, or $\sigma_v \lesssim 100$ km s$^{-1}$), and the lack of significant detections of high-ionization emission lines and broad components, favor an SFG classification, although an AGN contribution cannot be excluded. Janus-11 joins the small sample of spectroscopically confirmed and characterized sources at $z>10$, providing new information on massive systems with non-negligible dust attenuation and well-measured
metallicity in this epoch.
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All authors L. Parente, E. Vanzella, M. Messa, A. Zanella, K. Nakajima, M. Ouchi, R. A. Windhorst, M. Talia, Y. Harikane, Y. Ono, A. M. Koekemoer, P. Bergamini, M. Meneghetti, P. Rosati, Y. Xu, H. Umeda, Y. Zhang, Y. Isobe
Astrophysics of Galaxies
Before fragmentation: from uniform clouds to stellar clusters
A. Giannetti, T. Pillai, J. Kauffmann et al. (+4 more)
Our study of the early stages of fragmentation in massive clumps has revealed a striking anomaly: $\sim15\%$ of the CoCoA sample exhibit no fragmentation at all. These sources could represent the initial conditions before core formation. We investigate whether these sources are indeed at the onset of core formation, and whether
gravity or
turbulence dominates their early fragmentation. We study the transition from uniform gas to active cluster formation, and compare contrasting predictions of
turbulence- and
gravity-dominated models of clump fragmentation through ALMA observations of three massive clumps spanning this phase. The fragmented source exhibits higher average $n$(H$_2$) and a core-to-envelope density contrast 5-6 times larger than the minimally fragmented sources. All sources display pc-scale velocity differences comparable to their linewidths and gravitational velocities. This suggests that the linewidth is dominated by the large-scale motions, and that the latter are driven by
gravity. The high CH$_3$OH abundances and the mass build-up timescales align with astrochemical models where complex molecules form at intermediate densities before the appearance of cores. All independent diagnostics in our analysis are consistent with the minimally fragmented clumps being an early evolutionary phase, potentially marking the onset of core fragmentation. If
turbulence were the primary driver of fragmentation, sources with comparable Mach numbers should exhibit similar structural properties. Instead, we observe significant variations in density contrast and fragmentation. These findings challenge
turbulence-supported models and lend support to hierarchical,
gravity-driven models of clump fragmentation, where large-scale ordered motions account for a significant fraction of the observed linewidths and drive the
evolution of the clump toward increasingly dense and fragmented states.
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All authors A. Giannetti, T. Pillai, J. Kauffmann, A. Palau, E. Vazquez-Semadeni, K. Morii, P. Sanhueza
Astrophysics of Galaxies
KiDS-DR5: Exploring dust transport in dark matter halos of galaxies
Eray Genc, Angus H. Wright, Hendrik Hildebrandt et al. (+12 more)
We analyse a well-defined sample of
galaxies from the final data release of the Kilo-Degree Survey (KiDS-DR5), selected using magnitude, photometric
redshift, and stellar mass cuts, to measure their mean
halo mass and circumgalactic dust content as a function of stellar mass. Our goal is to provide empirical constraints on dust transport mechanisms, such as stellar- and AGN-driven outflows, operating in
galaxy halos. We develop and validate a new measurement and modelling framework using the MICE2 simulation, incorporating a realistic circumgalactic dust extinction scenario. Using this framework, we jointly model multiband ($ugriZYJHK_{\rm s}$) magnitude shifts and
galaxy–
galaxy lensing signals to infer the mean
halo mass and dust mass of lens
galaxies at $z_{\rm B} < 0.4$, analysed in five stellar-mass bins in KiDS-DR5. The modelling jointly describes the
halo mass distribution and dust extinction, including dust associated with neighbouring
halos. We demonstrate that the inclusion of a satellite fraction and dust extinction from neighbouring
halos is required by the data. We find a linear relation between stellar mass and dust mass, consistent with previous observational studies, but flatter than predictions from the semi-analytic model Dusty-SAGE. This difference may indicate that current implementations of dust-related feedback in
galaxy formation models require further refinement.
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All authors Eray Genc, Angus H. Wright, Hendrik Hildebrandt, Dian P. Triani, Dominik J. Bomans, Benjamin Stölzner, Marika Asgari, Henk Hoekstra, Benjamin Joachimi, Shahab Joudaki, Konrad Kuijken, Lauro Moscardini, Mario Radovich, Robert Reischke, Ziang Yan
Astrophysics of Galaxies
Discovery of Kolmogorov-like turbulence in the inner shell of SNR HB 9
Li Xiao, Ming Zhu, Xiao-Hui Sun et al. (+2 more)
We investigated the scaling relation of the magnetohydrodynamic
turbulence in the inner and outer shells of the
supernova remnant HB 9 using multi-tracers. For the eastern inner shell section, one-dimensional structure function and power spectrum analyses of the
radio total intensity, H-alpha emission, and polarized intensity consistently show a Kolmogorov-like scaling of l^2/3 over the inertial range. The two-dimensional power spectrum for the entire inner region follows k^-8/3 of all tracers, including the polarization gradient. It indicates that fully developed, trans-Alfvenic Kolmogorov
turbulence is present in the inner shell of HB 9. We estimated the strength of random
magnetic field therein from the low fractional polarization (5%), and obtained a upper limit delta B of 18 micro G. The
turbulence in the inner shock shell is most likely driven by the Richtmyer-Meshkov instability.
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All authors Li Xiao, Ming Zhu, Xiao-Hui Sun, Wolfgang Reich, Patricia Reich
Astrophysics of Galaxies
R Coronae Borealis fadings: a dusty gas cloud eclipse model
Mark A. Walker, Artem V. Tuntsov and Arthur G. Suvorov
R Coronae Borealis
stars (RCBs) are hydrogen-deficient supergiants that undergo deep fading events due to transient extinction by dust. First observed over two centuries ago, that behaviour remains poorly understood. Our aim is to investigate the possibility that the fading events are eclipses by orbiting, dusty gas clouds. We construct a simple physical model of the dust wind that is driven from the cloud surface by the stellar radiation field, and we calculate the extinction and scattered light from wind and cloud. We consider a broad range of dust compositions. For the model that best matches the data, we sketch out implications for the RCB phenomenon more broadly. Our calculations show that conventional dust materials like graphite and silicate produce eclipses whose ingress is too slow and whose morphology too symmetric to account for RCB fadings. But dust made of solid H2 yields a good match: the eclipses are deep and strongly asymmetric, with rapid onset and slow recovery, and event timescales are about right if the clouds' periastra are within a few tens of AU. Such close approaches imply tidal stripping/disruption of each cloud, with hydrogen-deficient debris accreting onto the
star via a disk. Starlight incident on the disk creates a metal-ion
plasma that emits a powerful bremsstrahlung continuum, peaking in the mid-IR. We conclude that eclipses by orbiting, dusty clouds could be the cause of RCB fading events, but only if the dust is made of solid H2, in which case both the unusual, hydrogen-deficient nature of the
stars and their mid-IR excess follow naturally. It is, however, challenging to account for the high eclipse rates that are observed; we propose a scenario in which the progenitor
star is a wide binary inside a massive
halo of clouds, suggesting a connection to the Galactic "missing mass" problem.
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Astrophysics of Galaxies
Toward Resolution Convergence for Star Formation and Galactic Winds in Galaxy Simulations
Xue-Fu Li, Weishan Zhu, Tian-Rui Wang et al. (+2 more)
The predictive power of hydrodynamic simulations of
galaxies is often hampered by the resolution dependence of sub-grid models for
star formation (SF) and stellar feedback. We present three-dimensional hydrodynamic simulations of an M82-like low-mass starburst
galaxy at resolutions of 4, 8, 16, 32 pc and develop optimized sub-grid prescriptions to mitigate these numerical inconsistencies. For
star formation, we adopt a $\sim20$ pc physical-scale control volume, corresponding to the typical size of giant molecular clouds (GMCs), for gas
accretion onto sink particles, reducing its dependence on numerical resolution. We further incorporate an empirical, resolution- and density-dependent
star formation scheme that accounts for variations in gas surface density across spatial scales, as suggested by observations. Furthermore, we refine the
supernova feedback coupling by anchoring the injection volume to the physical cooling radius of the
supernova remnant ($R_{\rm cool}$) and utilizing a resolution-dependent thermal-to-kinetic energy partition. These improvements substantially enhance convergence across 4 to 32 pc: variations in the total stellar mass formed and kinetic energy are reduced to $\sim20\%$, while relative errors in the cool-phase mass outflow rate and integrated X-ray luminosity decrease to below $\sim40\%$. The warm and hot outflow phases remain less well converged, with variations of $\sim50\%$ and $\sim75\%$, respectively. The upgraded model also improves the convergence of normalized wind properties, with relative errors below $\sim50\%$, $\sim80\%$, and $\sim20\%$ for the time-averaged mass loading factor, energy loading factor, and X-ray emission efficiency, respectively. Our results provide a practical framework for achieving more robust simulations of starburst
galaxies.
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All authors Xue-Fu Li, Weishan Zhu, Tian-Rui Wang, Huan Chen, Long-Long Feng
Astrophysics of Galaxies
A Study on the Evolution of NGC6822. I. Investigating the Star Formation History through Evolved Stellar Populations
Fatemeh Khatamsaz, Mahdi Abdollahi, Atefeh Javadi et al. (+4 more)
NGC6822 is an isolated dwarf irregular
galaxy in the Local Group at a distance of $\sim$ 490 kpc . In this paper, we derived the
star formation history (SFH) of NGC6822 employing a method based on evolved asymptotic giant branch (AGB)
stars, known as long-period variable (LPV)
stars. We utilized a
dataset of 329 LPVs in JHK$_s$ bands to estimate the
star formation rate (SFR) over time and reconstructed the SFH of the
galaxy. In addition to obtaining the SFH assuming constant
metallicity values within the range of 0.0001 $<$ Z $<$ 0.012, we also adopted three distinct age-
metallicity relations (AMRs) to account for variations in the chemical content of the
galaxy throughout its lifetime. The SFH has been investigated in two regions. The bar region encloses a central area of 189 arcmin$^{2}$, and the outer region encircles a field beyond the bar region, extending to the radial distance of 3 kpc. In the bar region, we identified three episodes of
star formation peaking at $t \sim$ 4.7 Gyr (log $t = 9.67$), $t \sim$ 1.6 Gyr (log $t = 9.21$), and $t \sim$ 48 Myr (log $t = 7.63$), where $t$ is the look-back time. In the outer region, we found one episode of
star formation occurring at $t \sim$ 4.6 Gyr. The significant peak observed $\sim$ 4-5 Gyr ago further supports the hypothesis suggested by the previous research, indicating that NGC6822 passed through the virial radius of the Milky Way in the past.
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All authors Fatemeh Khatamsaz, Mahdi Abdollahi, Atefeh Javadi, Hamidreza Mahani, Jacco Th. van Loon, Hedieh Abdollahi, Sepideh Ghaziasgar
Astrophysics of Galaxies
Improving Lens Modelling from Ground-Based Imaging with Deconvolution
Eric Paic, Kenneth C. Wong, Anupreeta More et al. (+1 more)
Accurate and precise mass modelling of strong
lensing systems is essential for extracting insights into cosmology,
galaxy environments, and the nature of dark matter. The Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP), which has mapped $\sim$1000 square degrees of the sky, discovered over 1000 definite or probable
galaxy-scale gravitational lens candidates. As the resolution of ground-based imaging poses challenges for accurate lens modelling, high-resolution imaging is traditionally sought after for detailed analyses of these systems. In this work, we instead propose applying the STARRED
algorithm, which leverages starlet wavelet regularisation, as a preprocessing step before lens modelling to maximise the scientific output of the large HSC-SSP sample. We test this approach on seven HSC-like mock
lensing systems with different
lensing configurations. Our results show that the resolution boost from $\sim$0.6" to $\sim$0.15" enables improved accuracy and sub-3% precision measurements of key
lensing parameters such as the Einstein radius and the mass axis ratio for ground-based images. These results pave the way for accurate measurements of key strong
lensing quantities from a large sample of ground-based observations.
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All authors Eric Paic, Kenneth C. Wong, Anupreeta More, Anton T. Jaelani
Astrophysics of Galaxies
Trigonometric Parallaxes of Maser Sources toward the Far Side of the Milky Way
Z. H. Lin, Y. Xu, M. Reid et al. (+2 more)
We present trigonometric parallaxes and proper motions for eight maser sources associated with high-mass
star-forming regions. Four 22 GHz H$_2$O masers and four 6.7 GHz CH$_3$OH masers were observed over eight epochs between 2024 and 2025. Combining parallax, proper-motion, and radial-velocity information, we determine distances and spiral-arm assignments for these sources. The newly measured far-side masers extend the known distributions of the Sagittarius and Perseus arms toward Galactic longitudes as small as $\ell\sim10^\circ$. Their locations and kinematics agree well with recently updated spiral-arm models based on maser astrometry. In particular, the new measurements show that the far-side Sagittarius and Perseus arms tend to converge toward a common spiral feature in the inner
Galaxy. This configuration is consistent with the bifurcation scenario proposed for the Milky Way spiral structure, although an unresolved inter-arm structure provides an alternative interpretation that cannot yet be excluded.
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All authors Z. H. Lin, Y. Xu, M. Reid, J. J. Li, S. B. Bian
Astrophysics of Galaxies
Large-Scale Spiral Structure of the Milky Way Traced by Young Classical Cepheids
Z. H. Lin, C. J. Hao, D. J. Liu et al. (+5 more)
Using 985 classical Cepheids younger than 100 Myr, we investigate the large-scale spiral structure of the Milky Way by comparing their spatial and kinematic distributions with the R19 (four-arm) and X23 (multiple-arm) spiral-arm models. Both models provide reasonably good descriptions of the current sample: R19 yields slightly smaller point-to-arm distances, whereas X23 has a higher supported-arm fraction, but the descriptive statistics do not provide a decisive preference between them. Model-dependent arm assignment and refitting suggest that the distribution of the youngest Classical Cepheids (20–60 Myr) is consistent with an X23-like multiple-arm in which the Perseus and Norma arms form two dominant inner arms extending toward the ends of the Galactic bar, the Sagittarius and Centaurus segments are possible branches of these inner arms, and Local, Outer, and other features constitute additional arm segments. The updated model improves the constraints on the southern spiral structure, yielding smaller point-to-arm distances and a higher supported-arm fraction. Some of these structures extend to heliocentric distances of approximately 15~kpc.
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All authors Z. H. Lin, C. J. Hao, D. J. Liu, Y. J. Li, J. J. Li, Y. W. Dong, Y. X. He, Jarken Esimbek
Astrophysics of Galaxies
Morphological Statistic of Milky Way-like Galaxies
Zehao Lin, Junye Wei, Ye Xu et al. (+5 more)
We analyze the spiral morphology of 1,738 nearby
galaxies with similar Hubble type of the Milky Way ($i<60^\circ$, $z<0.048$) using multi-band optical images from the Sloan Digital Sky Survey and Digitized Sky Survey. Multiple-arm systems dominate, comprising $\sim$50-60% of the sample and $\sim$75% of large
galaxies ($d_{\rm max} \geqslant 18~\mathrm{kpc}$). In $90\pm3$% of multiple-arm
galaxies, two inner arms extend into multiple outer arms; three-arm inner structures occur in $9\pm2$%, and four or more are rare ($<1$%). Morphology and inner-arm counts are consistent across bands at $\sim$80%. Bifurcation points, marking the transition from two inner arms to multiple outer arms, occur in up to $\sim$40% of
galaxies, are more prominent in bluer bands tracing younger stellar populations, and cluster within 4-7~kpc of
galaxy centers. These statistics suggest that the Milky Way's inner two-arm and outer multiple-arm morphology, including bifurcations at similar radii, is broadly consistent with that of a typical multiple-arm spiral
galaxy.
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All authors Zehao Lin, Junye Wei, Ye Xu, Yingjie Li, Chaojie Hao, Dejian Liu, Yiwei Dong, Zhen-yu Wu
Astrophysics of Galaxies · Cross-listed from astro-ph.HE
Comment on "Fermi-LAT Galactic Center Excess Morphology of Dark Matter in Simulations of the Milky Way Galaxy"
Kevork N. Abazajian, Jason Kumar and Oscar Macias
Muru et al. [Phys. Rev. Lett. 135, 161005 (2025)] conclude from the HESTIA constrained simulations that the $\gamma$-ray morphologies of the Galactic Center Excess predicted by dark matter annihilation and by an old stellar population are essentially indistinguishable. Their "quadratic dark matter" maps, however, show the square of the mass projected along the line of sight, $\bigl[\int\rho\,s^{2}\,ds\bigr]^{2}$, rather than the annihilation integral $\int\rho^{2}\,ds$. Squaring a nonnegative map preserves its isophote shapes at corresponding intensity levels, as confirmed by the reported contour axis ratios. The corrected calculation on the same simulations does not support their conclusion.
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Astrophysics of Galaxies
PEGASUS (Pfs Emission-line GAlaxy SUrvey with Subaru): II. Metal Poor AGNs in High Equivalent-Width Narrow-Band Emitters
Hisakazu Uchiyama, Tohru Nagao, Mariko Kubo et al. (+19 more)
We present Subaru 'Ōnohi'ula
Prime Focus Spectrograph (PFS) optical–NIR spectroscopic follow-up of high-equivalent-width (EW) narrow-band (NB) emission-line
galaxies selected from Hyper Suprime-Cam Subaru Strategic Program, to assess whether high-EW sources preferentially host low-
metallicity AGNs. PFS spectroscopy yielded secure identifications for 583 targets, including 581 sources with reliable PFS
redshift solutions and two manually identified $z\sim4$ interlopers. We construct BPT diagnostics for the 70 objects with significant detections in all four BPT lines. Among them, $\sim34\%$ are located in the AGN region of the BPT diagram, suggesting that AGNs constitute a significant fraction of the sample. A non-negligible fraction does not populate the classical AGN branch; instead, it lies in the intermediate “valley” between the
star-forming and AGN sequences. Comparison to Cloudy models suggests that the valley population is consistent with sub-solar
metallicities. Three He II/[Ne V]-detected sources are also found in the
star-forming region of the BPT diagram and extend to lower-
metallicity solutions, consistent with $Z/Z_{\odot}\approx0.25-0.5$ ($12+\log({\rm O/H})\approx8.1-8.4$). One object shows a clear broad H$\alpha$ component; a multi-component fit yields $M_{\rm BH}\approx8.8\times10^{6} M_{\odot}$ and $\lambda_{\rm Edd}\approx0.035$, consistent with near-solar narrow-line region
metallicity. The fraction of point-like sources in the parent target sample ($22\%\pm2\%$) is intermediate between those of
star-forming
galaxies ($12\%\pm5\%$) and AGN ($33\%\pm10\%$), consistent with a contribution from compact components. Stacked [O III] line profiles show no clear evidence for strong outflows. Our findings suggest that high-EW NB selection efficiently identifies candidates for metal-poor AGNs.
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All authors Hisakazu Uchiyama, Tohru Nagao, Mariko Kubo, Tadayuki Kodama, Rhythm Shimakawa, Akio Inoue, Masayuki Tanaka, Jialai Wang, Ronaldo Laishram, Yuma Sugahara, Masato Onodera, Kazuki Daikuhara, Ko Ishida, Ryo Albert Sutanto, Haruka Kusakabe, Yoshiki Matsuoka, Alberto Rodriguez-Ardila, Yuta Suzuki, Yoshiki Toba, Xinfeng Xu, Yongquan Xue, Yongming Liang