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Physics Astrophysics Astrophysics of Galaxies

astro-ph.GA Watch Astrophysics of Galaxies

Wednesday 19 August

Astrophysics of Galaxies

The progenitors of $z\gtrsim10$ JWST galaxies in the COLIBRE simulations

Evgenii Chaikin, Andrew Pontzen, Carlos S. Frenk et al. (+4 more)

JWST has revealed a large population of luminous galaxies ($M_{\rm UV}\lesssim -20$) at redshifts $z \gtrsim 10$, widely interpreted as posing a challenge to models of galaxy formation within the $\Lambda$CDM cosmology. Here, we search for counterparts of the JWST galaxies in the COLIBRE simulations of galaxy formation. Although these simulations have not been tuned to reproduce any $z > 0$ observations, we find a population of COLIBRE galaxies with properties similar to those of the JWST galaxies, and trace them to their earliest evolutionary phases, $z\simeq25$, to investigate the onset of galaxy formation. We study the evolution of galaxy stellar masses, sizes, star formation rates, UV magnitudes, metallicities, central black hole masses, and molecular gas and dust content, finding good agreement with observationally inferred properties at $z > 10$, except for UV magnitudes and dust masses, which COLIBRE underpredicts and overpredicts, respectively. Our results indicate that the standard galaxy formation physics and $\Lambda$CDM cosmology adopted in COLIBRE are sufficient to reproduce a broad range of properties of the most extreme $z > 10$ JWST galaxies - including their compact sizes, stellar masses, gas content, and metallicities. We show that the discrepancies with the UV magnitudes and dust masses can both be attributed to the uncertain rate of grain growth at high redshift, possibly alongside a top-heavy stellar initial mass function. These findings provide strong evidence that the standard cosmological model can naturally explain even the most extreme galaxies in the early Universe.
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All authors Evgenii Chaikin, Andrew Pontzen, Carlos S. Frenk, Joop Schaye, Shengdong Lu, Robert A. Crain, Anna Durrant

Astrophysics of Galaxies

The efficient star-forming regions of stripped-envelope supernovae

M. Solar, M. J. Michałowski, J. Nadolny et al. (+13 more)

Massive stars ($> 8~\rm{M}_{\odot}$) play a key role in shaping the interstellar medium of galaxies through stellar feedback. However, how these stars form and evolve before exploding as core-collapse supernovae (SNe) remains elusive. We compute for the first time the star-formation efficiencies (SFEs) at the locations of hydrogen-rich (H-rich) SNe and stripped-envelope SNe (SESNe) to constrain their progenitor properties. We used VLT/MUSE and ALMA observations of H$\alpha$/H$\beta$ and CO(2-1) emission lines to trace the components of the warm ionised gas and cold molecular gas, respectively. Both observations resolve individual H II regions and giant molecular clouds at spatial resolutions on cloud-scales ($\sim$100 pc). This combined data allows us to compute the SFE from the star formation rate (SFR) and the molecular gas mass (M$_{\rm{mol}}$) as SFE = SFR/M$_{\rm{mol}}$. We find that SESNe explode in environments that are currently forming stars eight times more efficiently than those of H-rich SNe (higher SFR for SESNe with similar M$_{\rm{mol}}$). On one hand, this is consistent with the scenario in which the majority of SESNe are produced from very massive stars ($> 20~\rm{M}_{\odot}$) if the initial mass function is top-heavy. On the other hand, most of SESN progenitor channels are formed from interacting binaries ($< 20~\rm{M}_{\odot}$) if an increased binary system formation rate is connected with turbulences and, in turn, with the boost to SFE. Then, an increased binary fraction could explain the enhanced H$\alpha$ luminosities. In summary, SESNe preferentially occur in regions of intense, efficient star formation rather than simply higher gas content.
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All authors M. Solar, M. J. Michałowski, J. Nadolny, L. Galbany, J. P. Anderson, J. Sollerman, T. Pessi, E. Zapartas, B. Šlaus, J. Alexander, O. Ryzhov, J. Hjorth, C. Jiménez-Palau, P. Nowaczyk, D. Somawanshi, A. Leśniewska

Astrophysics of Galaxies

Size-Mass Relation Shows Its Colours: Contrasting Physical Imprints of Galaxy Evolution in Rest-Frame UV and Optical

Angelo George, Marcin Sawicki and Ivana Damjanov

The galaxy size-mass relation (SMR) is a key scaling relation used to constrain the physical processes that build galaxy structure, yet it is almost always measured in a single rest-frame optical band, where the light traces the bulk of the old stellar mass. Tracing younger populations with flux-weighted ages of ~100-500 Myr and low-metallicity stars, the rest-frame near-ultraviolet opens a new stellar window on this scaling relation. Because each process redistributes the light of young and old stars differently, the same mechanism shifts the slope and zero point of the SMR by different amounts in the two wavelength regimes. Here we review and synthesize the effects of main physical processes on the form of the SMR for star-forming and quiescent galaxies in the rest-UV and optical. For each process, we start from its underlying physics, the galaxy stellar masses it affects, and the light it adds/removes/rearranges, anchoring the predictions to observations and simulations. We validate the predicted imprints with forward Monte Carlo modelling. The two-wavelength view breaks several degeneracies that single-band analyses cannot, most notably between minor mergers, dry major mergers, and adiabatic expansion. These results motivate joint rest-UV and optical SMR measurements with current and upcoming wide-field imaging surveys.
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Astrophysics of Galaxies

The Total and Polarized Radio Emission from the Innermost Jets of a High-Redshift Quasar and a Candidate at Parsec-Scale Resolution

Bence Husvéth, Krisztina É. Gabányi, Tao An et al. (+4 more)

High-frequency very long baseline interferometry (VLBI) polarimetry probes synchrotron-emitting plasma closer to the central engines of radio-loud active galactic nuclei (AGNs), but observations above 43 GHz are technically demanding. We present 22-GHz European VLBI Network observations of the $z=4.31$ quasar J1510+5702 and J1606+3124, whose published spectroscopic redshift, $z=4.56$, is uncertain; a photometric estimate gives $z_{\rm phot}=0.9\pm0.1$. For the published $z>4$ redshifts, 22 GHz corresponds to rest-frame frequencies above 118 GHz. Polarized emission is detected in J1510+5702, and a low-level polarized signal is recovered from the brightest feature of J1606+3124. Adopting $z=4.56$, that feature has a brightness temperature of $T_{\mathrm{b,VLBI}}=(7.4\pm0.8)\cdot10^{10}$ K, allowing a mildly Doppler-boosted interpretation, while the young compact-source scenario also remains viable. The core of J1510+5702 has $T_{\mathrm{b,VLBI}}=(1.08\pm0.15) \cdot10^{12}$ K, implying a Doppler factor of ${\sim}22$ under the equipartition assumption. This component has a ${\sim}3.5$ % fractional polarization. These observations show that cm-wavelength VLBI can access rest-frame millimeter-band polarization in bright $z>4$ jets.
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All authors Bence Husvéth, Krisztina É. Gabányi, Tao An, Sándor Frey, Jun Yang, Iván Agudo, Yingkang Zhang

Astrophysics of Galaxies

Hector Galaxy Survey: Falling in Between - Infalling Galaxies in the Midst of the Abell 3667 Merger

Oğuzhan Çak{\i}r, Matt Owers, Gabriella Quattropani et al. (+38 more)

Whether cluster mergers enhance ram pressure stripping (RPS) and accelerate member galaxy evolution remains an open question. Here, we investigate galaxy populations in the nearby merging cluster Abell 3667 ($z\simeq0.0553$) using spatially resolved data from the Hector Galaxy Survey. We define an RPS sample combining Hector-selected galaxies with ionised gas disturbances (e.g., asymmetric tails or truncated disks) and supplementary, optically identified jellyfish galaxies lacking Hector data. Most of the RPS sample ($\sim 71^{+10}_{-7}\%$; 20/28) lies within $R_{200}$, where the merger impact is greater. Most asymmetric galaxies ($\sim 73^{+14}_{-8}\%$; 11/15), especially those with extreme RPS signatures, are concentrated in the inner cluster ($R \lesssim 0.6\, R_{200}$), along the merger axis between two shock-tracing radio relics. These central asymmetric galaxies show two spatial and kinematic groups: one at the North-West (NW) subcluster, downstream of its radio relic in a region of high-velocity intracluster medium (ICM) bulk motion, with blueshifted line-of-sight velocities; and a mostly redshifted population near the main cluster (MC), which also shows a turbulent ICM. Despite their projected association with the MC core and NW substructure, both samples' velocities indicate they are not bound to them. Tail orientations give insight into orbital histories: NW tails point away from the cluster centre and often align with the merger axis, suggesting merger-driven stripping, while MC tails show neither pattern clearly. Tails are broadly westward, with MC tails tracing due west and NW tails shifted northwest, pointing to two distinct filamentary accretion events for the NW and MC populations. Together, our results indicate enhanced RPS in the heart of A3667, driven mainly by infalling galaxies accreted along nearby filaments interacting with the merger-driven turbulent environment.
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All authors Oğuzhan Çak{\i}r, Matt Owers, Gabriella Quattropani, Mina Pak, Stefania Barsanti, Joss Bland-Hawthorn, Julia Bryant, Scott Croom, Pratyush Kumar Das, Caroline Foster, Madusha Gunawardhana, Hyunjin Jeong, Jong Chul Lee, Joon Hyeop Lee, Yifan Mai, Kyuseok Oh, Sree Oh, Andrei Ristea, Sarah Sweet, Sujeeporn Tuntipong, Gurashish Bhatia, David Brodrick, Rebecca Brown, Elton Cheng, Robert Content, Fred Crous, Tony Farrell, Peter Gillingham, Ellen Houston, Jon Lawrence, Helen McGregor, Mahesh Mohanan, Seong-Sik Min, Barnaby Norris, Naveen Pai, Ayoan Sadman, Will Saunders, Sudarshan Venkatesan, Adeline Wang, Ross Zhelem, Jessica Zheng

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

Investigating the properties of nearby young moving groups using GaiaDR3

Mamta Lad, Ujjwal Krishnan, Blesson Mathew et al. (+4 more)

Moving groups, which are gravitationally unbound collections of stars spread over large portions of the sky, pose challenges to their identification. Analyzing the three-dimensional spatial motion of stars is one method to identify their members. Despite several studies in the past, a reliable and conclusive catalog of moving group stars is currently lacking. Our objective is to present a most recent and updated catalog of nearby young moving group (NYMG) candidates in the solar neighborhood and investigate their properties using updated science data from the Gaia Data Release 3 (DR3). We searched for candidates of twelve NYMGs within a distance of 150 pc using Gaia DR3. To determine the membership, we employed the Bayesian algorithm BANYAN-Sigma. We compiled a total list of 3,153 NYMG candidates, of which 1,651 were new candidates. We also assessed the credibility of the literature defined 'Good-box' criterion with the latest comprehensive catalog of NYMGs from our study. We homogeneously estimated the ages of the NYMG candidates using Gaia DR3 photometry data. The analysis revealed that our NYMG candidates display a large scatter on the CMDs resulting in a large range of estimated ages from isochrones. Additionally, we conducted an infrared (IR) excess analysis to identify disk candidates among our final sample. Our spectral energy distribution (SED) analysis found 51 stars with IR excess. We present a largely inclusive list of all the NYMG candidates within 150 pc of Solar neighbourhood using Gaia DR3. The wide range of ages obtained from isochrone fitting underscores the need for more robust age analysis techniques to accurately determine the ages of NYMG members. The presence of IR excess in the 51 stars confirms the existence of disks indicating that they could be potential candidates for exoplanet detections.
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All authors Mamta Lad, Ujjwal Krishnan, Blesson Mathew, Raksha Olakal, Arun Roy, Sreeja Kartha, Vineeth Valsan

Astrophysics of Galaxies

Kinematics and Dynamics of the Open Cluster NGC 2302

Yuna Lee, Jongsuk Hong and Beomdu Lim

Open clusters are ideal observational testbeds to understand the dynamics of stellar systems. We present a dynamical study of the young open cluster NGC 2302. The latest Gaia data and $UBVIJHK_s$ photometric data are used in this study. A total of 117 stars are selected as the genuine members using the Gaia data. This cluster is, on average, reddened by $<E(B-V)> = 0.24 \pm 0.06$ (s.d.). The ratio of total-to-selective extinction ($R_V$) in the direction of NGC 2302 is $2.8 \pm 0.1$. The cluster distance is determined to be $1.16 \pm 0.08$ kpc using Gaia parallaxes. Theoretical isochrone fitting for $Z = 0.008$ on color-magnitude diagrams yields an age of $80 \pm 20$ Myr. The relative proper motions of individual members show no significant radial expansion or contraction. NGC 2302 contains a total stellar mass of $333 \pm 48 M_{\odot}$. The one-dimensional velocity dispersion is approximately 0.26 km s$^{-1}$, which is comparable to the viral velocity dispersion of 0.27 km s$^{-1}$ derived from its total mass. Its relaxation time is estimated to be approximately 90 Myr, which is similar to the age of the cluster within the uncertainty in age estimation. Finally, we report a pattern of mass segregation in the radial distribution of stellar masses. Our results suggest that NGC 2302 is virialized and currently approaching a state of dynamical relaxation. However, because no definitive evidence of kinetic energy equipartition is found, the possibility of the in-situ formation of high-mass stars within the central region should be carefully considered.
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Astrophysics of Galaxies

Beyond Idealized PAHs: Infrared Signatures of Carbon-Chain Defects from Shock Synthesis

Xiaoting Tan, Zhao Wang, Zu-Jia Lu et al. (+2 more)

Polycyclic aromatic hydrocarbons (PAHs) are widely recognized as carriers of the aromatic infrared bands (AIBs). However, most spectral models rely on idealized structures that fail to capture the energetic environments of interstellar PAH formation. This work investigates the infrared (IR) signatures of PAHs formed under shock conditions and explores whether produced defective structures can explain observational features unpredicted by standard, idealized models. We combine two-stage reactive molecular dynamics simulations of PAH formation via condensation and shock processing with density functional theory spectral calculations, and compare our theoretical results with James Webb Space Telescope (JWST) observations of NGC 7023 and MRK 1066. Shock processing produces PAHs featuring fullerene-like carbon skeletons and linear carbon-chain attachments. These structural defects yield distinct IR signatures, including prominent carbon-chain stretching features at 4.6-5.5 micron that is absent in ideal PAHs, and significantly enhanced out-of-plane skeletal modes in the 14.5-20 micron regime. Our findings attribute the observed 5.2 micron band in NGC 7023 and MRK 1066 to carbon-chain vibrations and the 15-18 micron emission to curved skeletal modes, providing observational support for the prevalence of defective, shock-formed PAHs in the interstellar medium.
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All authors Xiaoting Tan, Zhao Wang, Zu-Jia Lu, Houda Haidar, Dimitra Rigopoulou

Astrophysics of Galaxies

A model for the enhanced production rate of early-type hypervelocity stars in the Galactic halo

Chunyang Cao, F.K. Liu, Xian Chen et al. (+1 more)

About twenty late B-type hypervelocity stars (HVSs) traveling faster than the Galactic escape velocity have been discovered in the Galactic halo, many of which were ejected from the Galactic center (GC). Recently, we have advocated that these HVSs most likely formed in the nuclear star cluster (NSC) $150$–$500\, \rm{Myr}$ ago and were predominantly ejected via the gravitational slingshot of a past intermediate-mass black hole (IMBH) orbiting the supermassive black hole (SMBH) Sgr~A$^{*}$. Here we explore the constraints of the production rate of young HVSs on the star formation region of the NSC. We propose that the young HVS progenitors are born in a lopsided eccentric disk that is comparable in radius to the NSC. By numerically tracking the orbital evolution of disk stars, we find that they undergo rapid angular momentum relaxation at formation due to eccentric disk instability, and that their slingshot interactions with the SMBH-IMBH binary at distances $\simeq 100\, \rm{au}$ produce HVSs at a rate of $10^{-5}$–$10^{-4}\, \rm{yr}^{-1}$. The rate is expected to trace the disk formation history, increasing with the accumulation of disk stars and dropping rapidly after the star formation stopped at $150\, \rm{Myr}$ ago. The rate is consistent with the observation and orders of magnitude higher than that expected for an old relaxed population in the literature, enhanced due to the gravitational torque from the non-spherical GC potential and radial velocity anisotropies of the disk stars. Our results imply that young HVSs should have a distinct radial and angular distribution from old ones.
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All authors Chunyang Cao, F.K. Liu, Xian Chen, Shuo Li

Astrophysics of Galaxies

The MAGPI Survey: Emission Line Products Data Release and the Role of Spectroscopic Aperture Covering Fraction on the Balmer Decrement-Stellar Mass Relation

A. J. Battisti, E. G. M. Muller, E. Wisnioski et al. (+27 more)

The Middle Ages Galaxy Properties with Integral field spectroscopy (MAGPI) survey is a Large Program on the European Southern Observatory Very Large Telescope using the MUSE instrument. This paper presents the data release for the MAGPI emission line products and includes emission line maps for 836 galaxies at $0.05\leq z_\mathrm{spec}\leq 0.424$ ($\mathrm{H}\alpha$-window) and aperture-based emission line measurements for 2,607 galaxies at $0.05\leq z_\mathrm{spec}\leq 1.50$ (upper bound is [OII] cut-off), both based on the GIST software, for all 56 MAGPI fields. We use these data to examine dust attenuation, which represents a major source of uncertainty in the derived properties of galaxies that are critical to constrain models of galaxy evolution. We examine the role that the spectroscopic aperture covering fraction ($f_c$) has on the relationship between the Balmer decrement ($\mathrm{BD}=F(\mathrm{H}\alpha)/F(\mathrm{H}\beta)$; a common proxy for dust attenuation) and the total stellar mass ($M_\star$). Several studies have suggested that the BD-$M_\star$ relation may be redshift invariant; however, the compared surveys often have different $f_c$ due to their differing fibre or slit sizes that can cause systematic offsets. Our results indicate that $f_c$ has a significant impact on this relationship, due to galaxies having negative BD radial gradients, which are more negative for more massive galaxies at $z\lesssim0.4$. Comparing spectroscopic surveys with $\left<f_c\right> \gtrsim 0.5$, we find that the BD-$M_\star$ relation shows a preference for redshift evolution and is roughly consistent with the behaviour of UV stellar continuum attenuation redshift evolution ($A_\mathrm{FUV}$-$z$), with the average dust attenuation in galaxies peaking at $z\sim1.2$ and decreasing at lower and higher redshifts.
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All authors A. J. Battisti, E. G. M. Muller, E. Wisnioski, J. T. Mendel, C. Foster, C. D. P. Lagos, K. E. Harborne, I. U. Aalia, S. Barsanti, I. Breda, D. Calzetti, S. M. Croom, P. K. Das, A. Ferré-Mateu, T. Gao, E. Gjergo, K. Grasha, Y. Mai, A. Mailvaganam, T. Mukherjee, M. Mun, R.-S. Remus, G. Sharma, S. M. Sweet, S. Thater, L. M. Valenzuela, J. van de Sande, G. van de Ven, T. Zafar, B. Ziegler

Tuesday 18 August

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

The Cross-Survey Decade: A Call to Action

Gioia Rau, Robert Benjamin, Federica Bianco et al. (+24 more)

By 2027, three flagship wide-field surveys will be operating simultaneously from ground and space, observing overlapping sky and representing more than $6 billion in US and European public investment. Together they will produce overlapping petabyte-scale datasets across thousands of square degrees. This is a different class of challenge: the observations are no longer the bottleneck; realizing their joint scientific return now depends on shared computational infrastructure and coordination. Decades of community studies show that combining these datasets does more than improve precision. For science ranging from weak lensing to transient discovery and Galactic-plane astronomy, joint processing and analysis can unlock capabilities no single survey provides alone. Yet the required infrastructure – joint pixel-level processing, cross-calibration and validation, interoperable data access, and the people to build and sustain it – falls outside any single mission or institution's mandate. We issue a call to action for cross-survey science infrastructure, built around four pillars: (1) joint pixel-level processing and validation; (2) an AI-ready data substrate for scientific foundation models; (3) standardized, interoperable data access across surveys, democratizing participation in astrophysical discovery; and (4) dedicated personnel and career pathways. We outline concrete steps for policymakers, agencies, observatories, universities, the research community, and philanthropy, and argue that the moment to act is now, while foundational technical choices can still be aligned at a fraction of the cost of reconciling them later.
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All authors Gioia Rau, Robert Benjamin, Federica Bianco, Ranga-Ram Chary, Andy Connolly, Cecilia Garraffo, Suvi Gezari, Leanne P. Guy, Željko Ivezić, Stephanie Juneau, Vicky Kalogera, Mansi M. Kasliwal, François Lanusse, Zack Li, Rachel Mandelbaum, Peter Melchior, Stella Offner, Antonella Palmese, Jason Rhodes, Edward Schlafly, Kartik Sheth, Rachel Street, Michael Troxel, Tony Tyson, Beth Willman, Michael Wood-Vasey, Yuanyuan Zhang

Astrophysics of Galaxies

Dynamics of tidal dwarf galaxies in the system Arp 72

Osvan M. Portilla-Narvaez, Javier Zaragoza-Cardiel, Gisela N. Ortiz-León et al. (+6 more)

Some interactions between galaxies produce tidal tails primarily composed of material from their disks. Within these tails, concentrations of gas and stars can form, resembling dwarf galaxies. These tidal objects often begin to form stars and become dynamically independent of their parent galaxies, leading to their classification as Tidal Dwarf Galaxies (TDGs). By definition, TDGs should consist solely of baryonic material, with a negligible dark matter fraction. In this study, we analyze the dynamics of two TDGs in the Arp 72 system using high-resolution H{\alpha} observations obtained with the MEGARA multi-spectrograph at the GTC (Gran Telescopio Canarias) and neutral hydrogen (HI) data from the GMRT (Giant Metrewave Radio Telescope). The HI data were also used to determine the gas mass. We derived the rotation curves and velocity dispersion from the kinematic data, which allowed us to estimate the dynamical mass of the systems. The TDGs were modeled through 3D fitting as rotating disks with additional pressure support, assuming a mass distribution following an exponential law. The gas mass was combined with the stellar mass to determine the total baryonic mass. Under specific dynamical considerations, we established the relationship between the dynamical mass and the baryonic mass. Additionally, we used the pressure-support corrected circular velocity to compare the behavior of TDGs in the context of the baryonic Tully-Fisher relation (BTFR) with the literature, showing how detached TDGs fall off the relation. The two studied objects are consistent with the expected properties of a TDG.
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All authors Osvan M. Portilla-Narvaez, Javier Zaragoza-Cardiel, Gisela N. Ortiz-León, Y. D. Mayya, Beverly J. Smith, Chandreyee Sengupta, Mark L. Giroux, S. Comerón, Luz I. Alvarez-Cruz

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

The Inbound Gas and Dust Evolution of Interstellar Comet 3I/ATLAS from Optical Spectroscopy and Multi-band Photometry

Toni Santana-Ros, Alexey Sergeyev, Oleksandra Ivanova et al. (+9 more)

Interstellar objects (ISOs) provide direct constraints on the composition and evolution of extrasolar planetary systems. As the third confirmed ISO, comet 3I/ATLAS offers a rare opportunity to study pristine material from another star system. We present a systematic multi-band monitoring campaign conducted from 2025 July to September. To minimize systematic uncertainties, we utilized a homogeneous dataset of SDSS $g', r', i', z_s$ and Johnson-Cousins $BVR$ imaging obtained with MuSCAT3/4 on the 2.0-m Faulkes Telescopes and the 1.5-m Maidanak telescope. We employed a novel multi-aperture technique providing a robust, distance-independent characterization of the coma, alongside optical spectroscopy from SALT and the Nordic Optical Telescope. 3I/ATLAS exhibited a stable reddish color with no significant secular variation during its inbound journey. Spectroscopic analysis reveals carbon-chain depletion, with CN as the only prominent molecular emission. Coma morphology, analyzed via azimuthal averaging and rotational gradient filters, shows a persistent sunward jet at a position angle of $\sim$280$^{\circ}$, indicating sustained and localized outgassing from a high-latitude active region. Light-scattering modeling demonstrates that the observed colors and polarization are consistent with dense aggregates of organic matter and silicate minerals, while water ice sublimation remained insufficient to alter the optical properties. The stability of the coma structures and the homogeneous nature of our dataset indicate that 3I/ATLAS underwent a steady activation phase, preserving a volatile-rich but carbon-chain-poor composition. This characterization points to an object formed in a distinct protoplanetary environment and provides a definitive record of its pre-perihelion evolution.
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All authors Toni Santana-Ros, Alexey Sergeyev, Oleksandra Ivanova, Sofiia Mykhailova, Johannes Markkanen, Igor Luk'yanyk, Tomasz Kwiatkowski, Dagmara Oszkiewicz, Antti Penttilä, Nicolas Erasmus, Kamoliddin Ergashev, Yurij Krugly

Astrophysics of Galaxies

Continuum Variability in AGN: Evidence for Systematically Suppressed Fluctuations in the BAL Population

A. Aliaga, P. Arévalo, M.L. Martínez-Aldama et al. (+2 more)

We aim to compare the flux variability of Broad Absorption Line quasars (BAL) to non-BAL quasars, controlling for black hole parameters to inform models concerning the generation of the BAL phenomenon. Using SDSS DR16 and ZTF $g$- and $r$-band light curves, we select quasars with $1.57 \leq z \leq 2.00$ and $18.5 \leq rmag \leq 19.8$. This redshift range ensures that the $g$-band covers the C IV emission line (and trough in BALs) while the $r$-band probes continuum variability, and allows black hole mass (MBH) estimates via Mg II. We quantify variability using excess variance and damped random walk (DRW) parameters ($\sigma_{\mathrm{DRW}}$, $\tau_{\mathrm{DRW}}$). We also compared the DRW metrics in bins of MBH and Eddington ratio (REdd) to isolate the influence of the BAL phenomenon in objects with the same physical properties. Excess variance and $\sigma_{\mathrm{DRW}}$ are consistently smaller for BALs, confirming lower long-term variability, while the $g$-band exhibits higher variability than the $r$-band across both populations. These differences persist in fixed bins of MBH and REdd, indicating that the suppressed variability in BALs is not simply driven by differences in these properties between BAL and non-BAL samples. These results show that BAL quasars are systematically less variable than non-BAL quasars in both bands, confirming that this suppression is an intrinsic feature of the continuum rather than an effect of emission or absorption line contamination. The samples could be made to agree if BAL MBH values were systematically overestimated by a factor $\gtrsim 4$, implying a significantly higher REdd. Alternatively, the lower variability in BALs can be related to their lower X-ray luminosities, or to significant nuclear obscuration, if the inner part of the accretion disc were more obscured in BALs and more variable than the rest of the disc.
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All authors A. Aliaga, P. Arévalo, M.L. Martínez-Aldama, W. Zuo, B. Muñoz-Bravo

Astrophysics of Galaxies

Accretion of AGN Stars under Influence of Disk Geometry II: The Adiabatic Regime and Runaway Collapse Induced by Self-gravity

Yi-Xian Chen, Yan-Fei Jiang and Jeremy Goodman

Accretion onto massive stars embedded in Active Galactic Nuclei (AGN) disks around supermassive black holes (SMBHs) is regulated to the stellar Eddington rate in the fast-diffusion or radiatively-efficient limit, $c/\tau > c_s$, where $\tau$ is the optical depth of the accretion flow and $c_s$ the sound speed. However, when the ambient density is sufficiently high, the opposite slow-diffusion limit applies. In this regime, accretion proceeds quasi-adiabatically and forms a hydrostatic circumstellar envelope (CSE) that stalls further mass inflow in the absence of self-gravity. We perform 3D hydrodynamic simulations in the adiabatic limit to investigate the structure and evolution of such envelopes. For low thermal mass ratios, $q_{\rm th} \equiv M_\star/M_{\rm th}$ where $M_{\rm th}=c_s^3/(G\Omega)$ is the thermal mass, the CSE boundary smoothly matches the ambient disk entropy and density without forming a shock. In contrast, when $q_{\rm th} \gg 1$, a strong shock develops at the envelope boundary, substantially increasing the entropy of the envelope and thereby regulating its structure and mass, $M_{\rm env}$. In marginally self-gravitating disks with Toomre parameter $Q \sim 1$, we find that at sufficiently large $q_{\rm th}$ the envelope mass satisfies $M_{\rm env}/M_\star \gtrsim 1$. This condition is equivalent to stating that the post-shock material entering the envelope possesses lower radiation entropy than the characteristic stellar value, which triggers dynamical runaway growth on a dynamical timescale once envelope self-gravity is included in our simulations. In realistic AGN disk environments with SMBH mass $\sim 10^8M_\odot$, runaway may occur close to the minimum self-gravitating radii and produce supermassive stars of $\sim 10^5M_\odot$.
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Astrophysics of Galaxies

Automated Assignment and Prediction of Molecules in Astronomical Line Surveys Using Machine-Learning-Based Chemical Embeddings

Zachary T. P. Fried, Ryan A. Loomis, Jes K. Jørgensen et al. (+6 more)

Modern radio telescopes generate vast amounts of observational data, offering valuable insights into the molecular composition of interstellar sources. Identifying the molecules within these datasets typically involves time-consuming and labor-intensive manual analysis. This paper presents an automated method for assigning molecules in interstellar line surveys. The algorithm operates in two main stages. First, it automatically determines key parameters of the data, including excitation temperature, line width, and source velocity. Next, it assigns the observed spectral peaks by evaluating the spectroscopic match of the molecular candidates along with analyzing their chemical relevance to the interstellar source. The chemical relevance is determined by leveraging machine-learning-based molecular embedding techniques to analyze the regions of chemical space occupied by the observed species. Following the line assignment, this information is then used to generate new molecular candidates that occupy the same regions of chemical space. These newly generated species serve as promising targets for further investigation in the observational data. The algorithm was validated on spectral line surveys of the dark molecular cloud TMC-1 and the star-forming region IRAS 16293-2422B. In both cases, it identified at least 67 molecular species, accounting for over 90 percent of the analyzed line intensity, in 17 minutes or less while maintaining a high level of accuracy.
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All authors Zachary T. P. Fried, Ryan A. Loomis, Jes K. Jørgensen, Andrew Lipnicky, Ci Xue, Gabi Wenzel, Thomas H. Speak, Michael C. McCarthy, Brett A. McGuire

Astrophysics of Galaxies

Quasar Impostors: Two Extremely UV-Bright ($M_{\rm UV}\approx-23.5$) Reionisation-Epoch Galaxies Powered by Very Massive Stars

Daming Yang, Joseph F. Hennawi, Sarah E. I. Bosman et al. (+20 more)

The extreme bright end of the galaxy UV luminosity function during reionisation remains poorly constrained, particularly where the galaxy and quasar luminosity functions overlap and source classification becomes ambiguous. We present JWST/NIRSpec and ALMA Band-6 observations of J1450-0144 ($z=6.627$) and J1429-0104 ($z=6.796$), two $M_{\rm UV}\simeq-23.5$ sources originally classified as faint quasars by SHELLQs. NIRSpec reveals blue UV continua, strong P Cygni profiles in N V, Si IV, and C IV, broad He II $\lambda1640$ emission with rest-frame equivalent widths of $8.8\pm1.2$ and $3.7\pm1.1$ Å, respectively, and narrow nebular lines, reclassifying both as extremely UV-luminous galaxies. Standard population-synthesis models cannot simultaneously reproduce the strong He II and wind features, whereas models incorporating very massive stars (VMS; $M\gtrsim100\,M_\odot$) with dedicated wind prescriptions can. These models favor a star-formation duration of 2-4 Myr for J1450-0144, with a broader allowed range for J1429-0104, stellar masses of $\log(M_\star/M_\odot)\approx9.2$-$9.9$, and star-formation rates of $\simeq300$-$540\,M_\odot\,{\rm yr}^{-1}$. Under the same VMS wind models, equivalent-width diagnostics imply $M_{\rm up}\gtrsim225\,M_\odot$ for J1429-0104, while J1450-0144 lies beyond even the $M_{\rm up}=475\,M_\odot$ grid. ALMA detects luminous [C II] 158 $\mu$m emission in both systems, with $L_{\rm [CII]}\approx0.8$ and $4.1\times10^{9}\,L_\odot$, respectively. J1429-0104 additionally shows bright dust continuum, with both [C II] and dust offset by $\sim5.4$ kpc from its UV emission. These sources demonstrate that VMS can power some of the most UV-luminous galaxies at cosmic dawn and show that source classifications, and hence the inferred demographics of both galaxies and quasars in the crossover regime, need revisiting.
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All authors Daming Yang, Joseph F. Hennawi, Sarah E. I. Bosman, Frederick B. Davies, Rychard Bouwens, Timo Kist, Eduardo Bañados, Jiamu Huang, Alice E. Shapley, Marianne Vestergaard, Hiddo S. B. Algera, Silvia Belladitta, Anna-Christina Eilers, Xiaohui Fan, Francesco Guarneri, Xiangyu Jin, Romain A. Meyer, Elia Pizzati, Huub Röttgering, Jan-Torge Schindler, Mauro Stefanon, Feige Wang, Jinyi Yang

Astrophysics of Galaxies

Recurrent Multi-year Mg II BAL Variability in SDSS J1333+0012

M. Vivek, P. Aromal, R. Srianand et al. (+3 more)

We present a long-term spectroscopic study of Broad Absorption Line (BAL) variability in the quasar J1333+0012 (\zem = 0.9197) using an extensive multi-epoch dataset spanning nearly two decades. The dataset comprises multi-epoch observations from multiple observatories, delivering nearly uniform temporal coverage of the Mg II BAL profile, with close to one spectroscopic observation per year spanning the period from 2008 to 2025. We identify recurrent multi-year variability in the BAL absorption strength, characterized by a rest-frame timescale of $\sim$4 yr. Because the well-sampled baseline covers only a small number of candidate cycles, we present J1333+0012 as a candidate quasi-periodic BAL system. In contrast, contemporaneous optical photometric light curves from CRTS, Pan-STARRS, ZTF, and PTF show no statistically significant correlated variability on comparable timescales. However, ionization-driven variability cannot be ruled out, as the observed optical continuum does not directly trace the unobserved extreme-UV ionizing continuum. The coherence of the variability across distinct velocity components, coupled with the absence of large-scale profile reshaping, is consistent with a geometric origin. We interpret the observed behavior as modulation of the line-of-sight absorption by the rotation of an inhomogeneous shielding-gas structure.
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All authors M. Vivek, P. Aromal, R. Srianand, K.A. Anjali, S. C. Gallagher, Rachana

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

The impact of recombination during tidal disruption events

Simona Pacuraru, Clément Bonnerot and Martin E. Pessah

During a tidal disruption event, the resulting debris stream cools down adiabatically due to the tidal stretching. As the temperature drops, the gas is expected to undergo chemical processes, which can release thermal energy into the stream, potentially affecting the subsequent gas evolution. For the first time, we investigate in detail this effect and its dynamical impact on the early-time evolution of the stream by making use of three dimensional hydrodynamic simulations coupled with a realistic equation of state. We find that a few days after disruption, the energy injected by hydrogen recombination and molecular hydrogen formation causes the stream thickness to grow much more rapidly. In the bound debris, this effect stops the stream's confinement by self-gravity before the gas reaches apocentre. As a result, the maximum stream thickness increases by a factor that ranges from a few, for the most bound gas, to a few tens for the near-parabolic gas, reaching $\approx 30 \, R_{\star} $ around the peak of the mass fallback rate. We discuss how this accelerated stream expansion may affect the subsequent evolution of the gas, estimate the luminosity powered by recombination in the unbound debris, and evaluate the potential influence of non-ideal magneto-hydrodynamic effects. By characterizing the thermodynamic and hydrodynamic properties of the stream before its return near pericentre, our results provide physically motivated initial conditions to self-consistently model the later stages of tidal disruption events, offering a promising pathway to unveiling the physical origins of their observed emission.
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Astrophysics of Galaxies

The Spin Angular Momentum and Black Hole Mass Components of Sagittarius A*

Ruth A. Daly

The dimensionless spin angular momentum, dimensionless spin function, and blackhole mass components of Sagittarius A* (Sgr A*) were obtained by Daly et al. (2024) by applying the outflow method to six independent sets of simultaneously or contemporaneously obtained X-ray and radio data. Here, results obtained for Sgr A* with the outflow method are reviewed. Consistent results were obtained with each data set. Set I (the preferred data set) indicates that Sgr A* has a dimensionless spin angular momentum $a_* = (0.90 ~\pm~ 0.06)$ and a dimensionless spin function $F = (0.62 ~\pm~ 0.10)$. The results are consistent with the value of $a_* = (0.93~\pm~ 0.15)$ obtained with the outflow method applied to an independent data set (Daly 2019). The application of the outflow method to a weak compact radio source such as Sgr A* in its current state is most accurately determined with simultaneous or contemporaneous radio and X-ray measurements.
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Astrophysics of Galaxies · Cross-listed from astro-ph.IM

Vera C. Rubin LSST Synthetic Magnitudes derived from Gaia XP Spectra

Oleksandra Razim, Krešimir Tisanič and Lovro Palaversa

Context. In the context of Milky Way studies, the Vera C. Rubin Observatory's Legacy Survey of Space and Time is often described as a deep extension of the Gaia survey. In the future, joint analysis of the Gaia and LSST data promises to bring new insights into our understanding of the Galaxy's structure and formation history. However, the relatively small overlap in the magnitude ranges of the two surveys raises the question of how to perform a joint calibration of these datasets. Aims. In this paper, we produce high-quality synthetic LSST photometry from Gaia XP low-resolution spectra, using SDSS and DES observed photometry to calibrate the spectra. Methods. We develop a method of empirical correction of Gaia XP spectra using SDSS Stripe 82 photometry. We project sources for which Gaia XP data are available onto a magnitude-magnitude grid and calculate residuals between uncorrected synthetic and observed SDSS magnitudes, which are then used to derive correction coefficients across spectral regions corresponding to each photometric band. Results. The correction significantly reduces systematic trends and scatter in the synthetic magnitudes: the median residuals decrease by an order of magnitude (e.g., for the u band the improvement is from 0.038 to 0.002 mag), and the standard deviation of residuals typically becomes up to factor of two smaller (e.g., for the u band from 0.2 to 0.07 mag). Conclusions. Our correction approach improves the reliability of synthetic photometry derived from Gaia XP spectra and enables joint analysis of Gaia and LSST data for studies of Galactic structure and stellar populations.
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Astrophysics of Galaxies

The segmented spiral structure of the Solar neighbourhood traced by young clustered populations

M. Carmen Sánchez-Gil and Emilio J. Alfaro

The Milky Way spiral pattern remains poorly constrained, and the youngest tracers in the solar neighbourhood do not always follow a few smooth, continuous logarithmic arms. We analyse young open clusters, both independently and combined with young stellar object (YSO)-based groups, to test whether they define continuous spiral-arm ridges or shorter, partially connected structures. In the (theta_G, ln R_G) plane, we identify local overdensities using a density-supported Bayesian Gaussian Mixture Model (BGMM), introducing published Perseus, Local, Sagittarius, and Scutum arm tracks only afterwards as reference curves. We then apply a Minimum Spanning Tree (MST) analysis in the heliocentric (X,Y) plane to examine spatial connectivity. The open-cluster sample already resolves into several local components, while the addition of YSO-based groups highlights branches and intermediate regions without producing continuous arms. The MST likewise shows distinct local branches at small pruning scales that progressively merge as the linking scale increases. The Local–Sagittarius region provides the clearest agreement between both diagnostics: the BGMM identifies an intermediate component between the reference arms, while the MST connects neighbouring branches through the same region. Overall, young structures near the Sun appear as fragmented, spiral-like segments with partial links rather than smooth continuations of a few grand-design arms. Determining whether this morphology reflects spiral-arm formation mechanisms or subsequent evolution will require additional age, vertical, and kinematic information.
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Astrophysics of Galaxies

Concerns regarding recurrent fluorescence's impact on smaller diffuse ISM aromatics

Daniel Majaess, Cercis Morera-Boado, Tina A. Harriott et al. (+1 more)

Recent research implied that recurrent fluorescence (RF) could bolster smaller aromatics against fragmentation in the diffuse ISM, yet that hypothesis is contested by timescales for unrelenting dissociative recombination (electrons), and unceasing dissociating photons. Specifically, neutral cyanonaphthalene can sustain $13.6$ eV photoionization, and the ensuing cation's excess energy is channeled through intramolecular vibrational redistribution (IVR), with RF providing the radiative stabilization pathway ($\simeq7$ eV negligible survival limit). However, that cation endures dissociative recombination every $\tau\approx0.5^{+5.6}_{-0.4}$ years, which deposits $\simeq 8.6$ eV and exceeds the limit. Moreover, that is paired with $7-13.6$ eV photodestruction each $\tau\approx16^{+223}_{-14}$ years (total visual dust extinction $A_V=0-1$, and $\tau\approx4^{+7}_{-2}$ years for $A_V\approx0$). Recent laboratory characterizations of RF were seminal, but the mechanism may not overturn models indicating a gap in smaller $N_C\approx7-11$ diffuse ISM aromatics, nor support those molecules as viable diffuse interstellar band carriers.
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All authors Daniel Majaess, Cercis Morera-Boado, Tina A. Harriott, Cherif F. Matta

Astrophysics of Galaxies

The Stellar Population of NGC 346 in the Small Magellanic Cloud with JWST

J. Jaspers, P. Kavanagh, G. De Marchi et al. (+13 more)

NGC 346 is a massive star-forming region located at a distance of $\sim$62 kpc, in the Small Magellanic Cloud (SMC). Due to its low metallicity (Z $\sim$1/5 Z$_{\odot}$), it is an ideal environment to study star formation and stellar population analogues to those at Cosmic Noon. In this work, we produce a combined JWST NIRCam and MIRI photometric catalogue of NGC 346. We characterise different stellar populations in the region: the upper main sequence (UMS), red giant branch (RGB), and red clump (RC), as well as pre-main sequence (pre-MS) stars and young stellar objects (YSOs). We performed point-spread function (PSF) weighted photometry in 11 wavelength bands across NIRCam and MIRI and utilised multiple colour-magnitude-diagrams to identify the various stellar populations in the field. Our final photometric catalogue of NGC 346 comprises 249,519 unique sources, including 2,024 UMS stars, 2,755 RGB stars and 742 RC stars. In addition, we identified 6,274 candidate pre-MS stars, 7,350 candidate YSOs and 23,819 IR-excess sources. Combining these three categories, we characterised 1,583 strong and 3,761 likely pre-MS/YSO candidates. By utilising the F115W-F200W vs F115W-F187N colour-colour diagram, we found 239 non-spurious sources with Pa$\alpha$ excess, indicating accretion and star formation in NGC 346. Using JWST NIRCam and MIRI observations, we produced the deepest catalogue to date of the star formation region NGC 346 in the near- and mid-IR range (1-21$~\mu$m). Our catalogue and characterisations of the young and old populations will provide the basis for detailed follow-up studies.
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All authors J. Jaspers, P. Kavanagh, G. De Marchi, C. Nally, O. Jones, N. Habel, P. Zeidler, M. Meixner, E. Sabbi, A. Hirschauer, K. Biazzo, L. Lenkic, O. Nayak, M. Roberto, C. Rogers, B. Sargent

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

eROSITA cosmology with galaxy groups: Hot gas budget out to the virial radius

H. Khalil, A. Finoguenov, D. Eckert et al. (+4 more)

Non-gravitational processes that expel hot gas beyond the virial regions of groups and clusters of galaxies, known collectively as baryonic feedback, play a key role in reshaping the matter distribution of the Universe on Mpc scales. We use eROSITA observations of a complete sample of 25 galaxy groups selected from the first public release of the eROSITA-DE data (eRASS1) and identified with the Two Micron Redshift Survey optical group catalogue (2MRS). We extract and fit surface brightness (SBx) profiles and present hot gas mass and hot gas fraction profiles out to $R_{200}$. We perform a Bayesian analysis of $M_{\mathrm{gas}}-M_{\mathrm{tot}}$, $L_{\mathrm{X}}-M_{\mathrm{tot}}$, and $L_{\mathrm{X}}-M_{\mathrm{gas}}$ relations, taking into account the aperture covariance effects. At $R_{500}$, we report uniformly flat SBx profiles with a mean $\beta$ parameter of $0.38 \pm0.04$, steepening to $\beta = 0.76\pm0.19$ beyond $R_{500}$. We measure a sub-cosmic hot gas fraction at the median mass of our sample $M_{500} = 2.54\times10^{13}M_{\odot}$ of $ f_{\mathrm{gas,500}} = 4.32\pm0.42\%$. Similarly, at $R_{200}$ and the median mass $M_{\mathrm{ 200}} = 3.69\times10^{13}M_{\odot}$, we obtain $f_{\mathrm{gas,200}}=5.78\pm0.69\%$. Our $f_{\mathrm{gas}}-M_{\mathrm{tot}}$ and $L_{\mathrm{X}}-M_{\mathrm{tot}}$ relations show significant deviations from the predictions of the strong feedback variants of the FLAMINGO simulation ($2.5\sigma$ to $8.0\sigma$ tension), while fiducial FLAMINGO and BAHAMAS provide the closest match to our measurements. Using our measured baryon fractions and the SP(k) model, we infer a $10\%-15\%$ reduction in the matter power spectrum at $k = 5\ h\ \mathrm{Mpc}^{-1}$ relative to a dark matter-only universe, in agreement with fiducial FLAMINGO and BAHAMAS, while revealing a growing tension on smaller scales with the strong feedback variants.
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All authors H. Khalil, A. Finoguenov, D. Eckert, R. Seppi, E. Tempel, L. Lovisari, F. Gastaldello

Astrophysics of Galaxies

$R_{\rm e}$, or not $R_{\rm e}$: Developing $R_5\equiv R_{-2}$ as a scale radius for galaxy sizes, masses, and mass-to-light ratios

Alister W. Graham

The effective half-light radius $R_{\rm e}$ marks an arbitrary 50-per-cent light boundary, and scaling relations involving such effective radii and their associated surface brightnesses, $\mu_{\rm e}$, systematically (and undesirably) vary as the percentage changes. Here, the projected radius $R_5\equiv R_{-2}$, where the logarithmic slope of the surface-brightness and intensity profile equals $5.00\,\text{mag\,dex}^{-1}$ and $-2$, respectively, and where the luminosity contributed per logarithmic radial interval is maximal, is developed as an alternative. It can be measured non-parametrically or with a parametrized fit. For the Sérsic $R^{1/n}$ family, the exact relation $R_5=(2n/b_n)^n\,R_{\rm e}$ is derived, with $R_5/R_{\rm e}\rightarrow{\rm e}^{1/6}\approx1.181$ as $n\rightarrow\infty$. Reparameterizing the (now $b_n$-free) $R^{1/n}$ model in terms of the observable pair $(R_5,\mu_5)$ removes the non-linear $R_{\rm e}$–$n$ coupling, and because the local slope is $5\,\text{mag\,dex}^{-1}$ at $R_5$, correlated measurement errors in $R_5$ and $\mu_5$ largely cancel when deriving the inferred total magnitude. Additionally, an exact single-integral identity is provided to relate any projected light fraction to the fraction within a sphere of the same radius. The directly observable $R_5$ is shown to be connected, through a weakly $n$-dependent factor to the anisotropy-insensitive intrinsic radius $r_{-3}$, yielding a refined $n$-dependent Wolf-type mass estimator $M_{-3}$ and spatial mass-to-light ratio $(M_{\rm dyn}/L)_{-3}$. Specifically, $M_{-3}\approx4\,G^{-1}\langle\sigma_{\rm los}^2\rangle\,R_{-2}\approx4.72\,G^{-1}\langle\sigma_{\rm los}^2\rangle\,R_{\rm e}$. Past half-light substitutions in dynamical mass estimators introduce systematic Sérsic-dependent offsets of 12–18 per~cent in enclosed mass and offsets spanning $>20$ per~cent in the mass-to-light ratio.
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Astrophysics of Galaxies · Cross-listed from astro-ph.CO

Dianoga simulations of galaxy clusters and groups: Properties of the baryonic components

Stefano Borgani, Alice Damiano, Elena Rasia et al. (+12 more)

We introduce the Dianoga set of cosmological simulations of galaxy clusters and groups, specifically aimed at studying the impact of the implementation of AGN feedback and star formation. Using the OpenGadget3 code, we carry out simulations of 28 regions centred on massive galaxy clusters, and of a cosmological box. This generates a sample of 293 halos with M_{200}> 1.5 x 10^{13} M_{\odot}. Parameters of AGN feedback in the reference implementation were minimally calibrated exclusively to match the local relation between SMBH masses and stellar masses of host galaxies. Simulations are compared to observed galaxy stellar mass function (GSMF), stellar mass fraction in clusters and groups, BCG masses, scaling relations between ICM/IGM properties and profiles of their thermodynamical properties. In the appendix, we show how results vary as we modify the reference feedback model in six alternative configurations. Our reference model predicts a GSMF in general agreement with observations, albeit overestimated in the high end. BCG stellar masses and mass fractions are higher than observed in massive clusters, while being closer to observations for groups. Predicted properties of the ICM/IGM are in general agreement with observations, with the core regions of simulated clusters having entropy and temperature profiles that are slightly less "cool-cored" than observed. A comparison with other implementations of AGN feedback highlights that models including thermal evaporation of the sub-resolution interstellar medium succeed to bring BCG masses and stellar mass fractions closer to observation, and to increase the cool-coreness of simulated clusters. Our results demonstrate that the details of the interface between AGN energy injection and the sub-resolution interstellar medium model are at least as critical as the total feedback efficiency itself.
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All authors Stefano Borgani, Alice Damiano, Elena Rasia, Tiago Castro, Michela Esposito, Ilaria Marini, Giuseppe Murante, Milena Valentini, Veronica Biffi, Klaus Dolag, Gian Luigi Granato, Antonio Ragagnin, Cinthia Ragone-Figueroa, Alex Saro, Luca Tornatore

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

From Variability to SED Modeling: A Multiwavelength Study of the Neutrino Blazar TXS 0506+056

Shiyu Du, Hanxiao Xia, Jianghua Wu et al. (+1 more)

The blazar TXS 0506+056 is the first source that was reported to be associated with high-energy extragalactic neutrino events and is one of the major targets for multi-messenger studies. We carried out multi-wavelength optical monitoring of this object on 24 nights in the period from 2018 to 2023. The overall light curves exhibit a dimming trend superposed by some small-amplitude fluctuations, and intraday variability was detected on four nights. Bluer-when-brighter behaviors were observed on both intraday and long timescales and were more pronounced on long timescales, while a weak redder-when-brighter trend was detected on one night. No significant time lags were found between variations at different optical wavelengths. We also retrieved the multi-broadband data from some monitoring programs. The data reveal complex, asynchronous flaring in different wavebands. A cross-correlation analysis shows that the high-energy emission (optical to gamma-ray) is co-spatial and leads the radio emission by a substantial time of about 800 to 900 days, suggesting that the radio emission originates from a downstream region of the jet. We performed time-dependent lepto-hadronic modeling of the spectral energy distributions for three representative epochs, the 2017 neutrino-associated flare, a post-flare phase, and a deep quiescent state, revealing an evolution in the radiative properties of the emission regions. The modeling results provide a phenomenological framework for interpreting the long-term multiwavelength behavior of TXS 0506+056 in a multi-messenger context.
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All authors Shiyu Du, Hanxiao Xia, Jianghua Wu, Yue Fang

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

Modelling s-process chemical clocks: insights from high-precision Kepler data

G. Casali and M. Molero

We present Galactic chemical evolution (GCE) models for the chemical clocks [Zr/Ti] and [Ce/Ti], tracing first- and second-peak s-process nucleosynthesis, and compare them with a high-precision sample of 68 Kepler red giant stars with asteroseismic ages from individual-mode frequencies and high-resolution spectroscopy. Using a multi-zone GCE framework, we explore variations in metallicity-dependent asymptotic giant branch (AGB) nucleosynthetic yields, including proposed enhancements to high-metallicity Ce production. Our baseline model reproduces [Zr/Ti] and the high-$\alpha$ sequence in both age and metallicity space, but systematically underestimates [Ce/Ti] at young ages and intermediate metallicities, indicating a persistent deficit in second-peak s-process enrichment over the last $\sim6$ Gyr of Galactic disc evolution. Increasing second-peak yields from high-metallicity AGB stars only partially reduces this discrepancy, suggesting that simple yield rescaling is insufficient and more fundamental revisions to s-process nucleosynthesis at high metallicity, alongside a self-consistent treatment of stellar dynamics, may be required. In fact, models reproduce abundance trends more tightly in metallicity than in age space, with additional age scatter partly attributed to radial migration. This Letter highlights the diagnostic power of precise asteroseismic ages for GCE studies and the limitations of current models in capturing the complex interplay between s-process nucleosynthesis and stellar dynamics.
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Astrophysics of Galaxies · Cross-listed from astro-ph.SR

Ejecta clumps revealed by study of reverse-shocked ejecta through MUSE integral field spectroscopy of SNR 0509-67.5

Priyam Das, Ivo Seitenzahl, J. Martin Laming et al. (+3 more)

We report the discovery of a spatially resolved clumpy ejecta structure in the reverse-shocked ejecta of SNR 0509-67.5, revealed through multiple faint and broad forbidden coronal emission lines in deep MUSE observations. We also identify two new broad coronal emission lines not reported before in this remnant, [Fe xi] 7894 A and [Fe x] 6374.5 A , which extend the set of previously reported [Fe xv] 7059.59 A, [Fe xiv] 5302.86 A , [Fe ix] 8236.55 A , [Ca xv] 5695 A, and [S xii] 7611.0 A. Near-continuous ionisation states of Fe allow us to follow the ionisation progression behind the reverse shock. We use a 1D analytical model to evolve Fe charge states following reverse shock interaction to compare with observations, indicating the need for preshock clumping or over-density in order to reproduce the observed surface brightness of the [Fe xiv] line. Additionally, we report the spatially resolved distribution of ejecta clumps and show that reverse-shock interaction drives their compression and fragmentation. We also find a clear trend of decreasing velocity width with increasing Fe ionisation state, from the broadest [Fe ix] emission to the narrowest [Fe xv], with intermediate-ionisation species ([Fe x], [Fe xi], [Fe xiv]) showing intermediate widths. Finally, we compare our observations to a dynamically driven double-degenerate double detonation (D6) 3D remnant model at similar Fe and S ionisation states and conclude that the observed clumps are predominantly due to Rayleigh-Taylor instabilities.
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All authors Priyam Das, Ivo Seitenzahl, J. Martin Laming, Gilles Ferrand, Simon J. Murphy, Ashley Ruiter