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Physics Astrophysics Astrophysics of Galaxies

astro-ph.GA Watch Astrophysics of Galaxies

Thursday 17 September

Astrophysics of Galaxies

Intracluster light in the infall region of simulated protoclusters of galaxies

S. V. Werner, M. Jauzac, M. Montes et al. (+4 more)

Intracluster light (ICL) is a diffuse stellar component in galaxy clusters, made of stars following the potential of the cluster. Despite its potential to unveil the accretion history of clusters, the ICL in protoclusters remains poorly understood in simulations and observations. We analyse protoclusters in TNG-Cluster and Manhattan Suite simulations to investigate when ICL forms, its host progenitors, and environments where it forms. We find a considerable amount of ICL in the infall region of protoclusters at 2<z<4, ranging from $\rm 0.1\times10^{11}$<$M_{*}/M_{\odot}$<$3\times10^{11}$. ICL star formation in protoclusters peaks at 3<z<4, with stars formed in the main halo forming earlier than those born in the infall regions. We find that $74.2_{-1.7}^{+1.7}\%$ of ICL stars in TNG-Cluster and $69.2_{-3.7}^{+3.6}\%$ in Manhattan Suite were stripped from galaxies within the main halo. However, most ICL stars in protoclusters at z=2 formed in the infall region, accounting for $57.6_{-1.6}^{+1.7}\%$ and $55.6_{-2.3}^{+2.3}\%$ in TNG-Cluster and Manhattan Suite, respectively. By the time the ICL stars are stripped, their host galaxies are 3-4 times more massive than the galaxies in which the stars originally formed, implying growth of the progenitor galaxies and/or accretion of the stars onto more massive galaxies prior to stripping. The ICL stellar masses measured in simulations agree with observations at z$\leq$2. Our findings highlight the importance of investigating the diffuse light in the outer regions of protoclusters to constrain the formation and assembly of the ICL and galaxy clusters.
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All authors S. V. Werner, M. Jauzac, M. Montes, D. Rennehan, G. Mahler, A. Niemiec, Y. Jiménez-Teja

Astrophysics of Galaxies

Interstellar disparity: N- vs O-bearing molecules: A multidisciplinary perspective across interstellar environments

Mathilde Bouvier, Joan Enrique-Romero and Marta De Simone

Observations of O- and N-bearing molecules reveal systematic chemical differentiation across a wide range of interstellar environments. This pattern is peculiar and its origin likely reflects a combination of physical conditions, chemical pathways, and observational effects rather than a single mechanism. In this paper, we provide a comprehensive overview of the current understanding of the N-bearing and O-bearing species and their relative behaviour in the interstellar medium, integrating results from observations, laboratory experiments, chemical modelling, and theoretical studies. While inspired by discussions at the Lorentz Center workshop held in Leiden in August 2025, this work goes beyond a summary of the meeting and instead synthesizes the state of the field, highlights key open questions, and outlines future directions. We identify several key observational, experimental, and theoretical challenges that must be addressed to determine the origin of this chemical differentiation.
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Astrophysics of Galaxies

Thioacetaldehyde (CH3CHS) on interstellar ices: a key molecule to unravel two chemical dichotomies in the ISM

María Mallo, Miguel Sanz-Novo, Marcelino Agúndez et al. (+6 more)

Thioacetaldehyde (CH3CHS), recently detected in TMC-1, has an abundance approximately 36 times lower than its oxygen analog, acetaldehyde (CH3CHO). This makes the CH3CHS/CH3CHO pair the one with the largest column density difference among the detected oxygen/sulfur analogue pairs in this cloud. We investigate the hydrogenation pathways of CH3CHS to address two chemical dichotomies in the ISM: (i) the differenciation between CH3CHS and CH3CHO, and (ii) the apparent absence of both CH3CHS in the G+0.693-0.027 molecular cloud and ethyl mercaptan (CH3CH2SH), in TMC-1. Our results reveal a complex scheme that involves multiple competing reactions, highlighting an efficient sequence of consecutive hydrogenations that can lead to CH3CH2SH. This finding suggests that the high S/O ratio observed for thioacetaldehyde in TMC-1 (~36), and even more pronounced in G+0.693-0.027 ($\geq$112), may result from its conversion via hydrogenation on the ice surface, contrary to the case of CH3CHO, which is more resistant to that chemical process. The straightforward hydrogenation of CH3CHS on ices, which can also take place even in the gas-phase at 150 K, provides a reliable explanation for its non-detection in G+0.693-0.027, where grain-surface chemistry is expected to play an important role, favoring the conversion of CH3CHS into CH3CH2SH, which is indeed detected in G+0.693-0.027. In contrast, TMC-1 represents a more pristine gas-phase environment, where grain-surface chemistry has a lower impact. Under these conditions, CH3CHS can persist, while CH3CH2SH remains undetected. Overall, our results show the entirely different reactivity that contributes to the chemical complexity of two of the largest interstellar sulfur factories.
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All authors María Mallo, Miguel Sanz-Novo, Marcelino Agúndez, José Cernicharo, Gisela Esplugues, Víctor M. Rivilla, Izaskun Jiménez-Serra, Carlos Cabezas, Germán Molpeceres

Astrophysics of Galaxies

ELUCID. IX. Recovering the Substructures and History of the Coma Cluster

Xiong Luo, Huiyuan Wang, Weiguang Cui et al. (+7 more)

We employ constrained hydrodynamic simulations of the Coma galaxy cluster from the ELUCID project to study its substructures and assembly history. Our simulations accurately reproduce the global properties of Coma, including its position, virial mass, radius, and surrounding large-scale filaments. Using a combined HBT+SKID method, we obtain a total intracluster light (ICL) fraction of $12.2\%-23.5\%$, consistent with recent observations. The mass-weighted ICL profiles of velocity dispersion, stellar age, and iron abundance generally agree with MaNGA measurements, and its clumpy east-west elongation is closely linked to the merger history of the two brightest cluster galaxies (BCGs). The simulation also successfully reproduces the north and west intracluster filaments (ICFs) detected by weak lensing, and the surrounding galaxy groups are distributed in alignment with the directions toward the nearby A2199 and A1367 clusters. The simulation further predict a complex cluster assembly history, with two major mergers at $z=0.74$ and $0.45$, and a pericentric passage of the two BCGs occurring $\sim 0.64 \ {\rm Gyr}$ before its current state. Our results demonstrate that constrained simulations are a powerful tool for connecting observed structures to the unobservable assembly histories of individual galaxy clusters.
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All authors Xiong Luo, Huiyuan Wang, Weiguang Cui, Yipeng Jing, Weipeng Lin, Neal Katz, Romeel Davé, Houjun Mo, Xiaohu Yang, Hao Li

Astrophysics of Galaxies

The Galactic centre G+0.633-0.0604 molecular cloud: A new astrochemical gold mine: II. Chemical richness

D. San Andrés, V. M. Rivilla, L. Colzi et al. (+4 more)

In recent years, the inventory of interstellar molecules has rapidly grown, yet detections of complex species are confined to a few chemically rich sources, raising the question of whether such complexity is genuinely rare or shaped by observational biases. We present the Galactic Centre G+0.633-0.0604 molecular cloud, located in the southern part of the Sgr B2 complex, as a new and very promising laboratory for the discovery of new interstellar molecules. We analysed data from a high-sensitivity molecular line survey of G+0.633, covering nearly 100 GHz of aggregated bandwidth over the 31$-$275 GHz frequency range with the Yebes 40m, IRAM 30m and APEX radio telescopes. G+0.633 exhibits an exceptionally rich molecular feedstock comparable to that of the chemically rich G+0.693 cloud in the northern part of Sgr B2, establishing it as its 'astrochemical twin'. We report new robust interstellar detections of 15 astrochemically relevant species, most of prebiotic interest, previously identified only in G+0.693 or a very limited number of sources. These species include urea, $C$- and $N$-cyanomethanimine, ethanolamine, glycolamide, carbonic acid, and dimethyl sulphide. Our results reveal that the extraordinary molecular complexity observed in G+0.693 is not unique, but may instead reflect a natural outcome of shock-dominated chemistry in the Galactic Centre. The G+0.633 and G+0.693 clouds exhibit remarkably similar excitation conditions and comparable molecular abundances, establishing them as an ideal benchmarking pair for astrochemical studies. Moreover, G+0.633 offers a clear advantage for molecular observations over G+0.693 owing to the significantly narrower linewidths of its molecular line emission, nearly half as broad as those characteristic of G+0.693, making it an exceptionally powerful target for guiding the search for increasingly complex molecules in the ISM.
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All authors D. San Andrés, V. M. Rivilla, L. Colzi, M. Sanz-Novo, S. Martín, I. Jiménez-Serra, S. Zeng

Astrophysics of Galaxies

Water maser detections toward 70 ${\mu}$m infrared dark clumps at early star formation stage

Chao Ou, Shanghuo Li, Junzhi Wang et al. (+2 more)

Water masers provided powerful probes of shocked gas and protostellar activity during the early stages of star formation. Using VLA K-band observations of the 22 GHz water line, we report the first detections of water masers toward dense cores in five 70 ${\mu}$m infrared dark clumps, providing evidence for active star formation at an early evolutionary stage. We detected ten unresolved maser spots comprising thirteen velocity components, with peak flux densities of 13–499 mJy and deconvolved full widths at half maximum (FWHMs) of 0.51–3.54 km s-1. Eleven components had FWHMs below 1 km s-1, while their velocity offsets from the systemic velocities traced by the NH3(1,1) main line ranged from 0.83 to 50.73 km s-1. Four water maser spots were associated with 1.3 mm continuum emission, three of which were also associated with molecular outflows traced by CO 2-1 emission. No CO outflow signature was detected toward the remaining spots within the observed field of view, suggesting that water masers could trace deeply embedded protostellar activity whose outflows were not yet detectable in CO emission. For AGAL031, the non-detection of StokesV emission toward the strongest maser component yields an upper limit on the line of sight magnetic field strength on the order of a few hundred mG. Our results showed that star formation was already active in 70 ${\mu}$m infrared dark clumps and that 22 GHz water masers provided insights into early protostellar environments that remained difficult to probe with common star formation tracers.
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All authors Chao Ou, Shanghuo Li, Junzhi Wang, Ian W. Stephens, Yuqiang Li

Astrophysics of Galaxies

Revisiting the interpretation of HI Zeeman measurements in the diffuse interstellar medium

Adrien Barthas and Andrea Bracco

The HI Zeeman effect provides one of the few direct probes of magnetic field strengths in the diffuse atomic interstellar medium (ISM), yet the physical quantity recovered by the standard weak-field estimator remains uncertain in multiphase gas. This is especially relevant to the low-column-density branch of the observed magnetic field–column density relation, which is nearly flat below NH~1E22 cm-2 and remains difficult to explain theoretically. We investigate this issue using synthetic HI Zeeman observations of multiphase magneto-hydrodynamic simulations of the atomic ISM performed with RAMSES, complemented by analytical two-phase models of the thermally bistable atomic medium. We find that both emission and absorption Zeeman measurements recover the magnetic field weighted by optical depth along the line of sight, rather than the density-weighted field. The two converge only in limiting cases, such as isothermal gas or homogeneous magnetic fields across phases. In realistic multiphase media, the Zeeman-derived field statistically exceeds the density-weighted field by factors of a few, with the strongest departures when cold and warm atomic gas both contribute significantly to the column density. Our analytical models reproduce this behavior and show that thermal bistability generates both an excess and a large dispersion between Zeeman-derived and density-weighted fields, even when the intrinsic magnetic field increases monotonically with density. The effect is strongest below NH~1E22 cm-2, where the temperature contrast between cold and warm HI causes optical-depth and density weighting to diverge. We conclude that HI Zeeman observations primarily trace the optical-depth-weighted magnetic field. This intrinsic thermal weighting may contribute to the broad distribution, and possibly part of the apparent flattening, of the observed magnetic field-column density relation.
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Astrophysics of Galaxies

Electron irradiation and temperature-programmed desorption of layered ethanolamine-water-methanol ices

Tara L. Stoib, Alejandro Guerrero-Caicedo, Duncan V. Mifsud et al. (+12 more)

Ethanolamine (EtA) is a recently detected interstellar complex organic molecule and a potential precursor to more functionalised N-bearing species. We investigate the electron-driven chemistry of layered EtA–H$_2$O–CH$_3$OH ices deposited at 20~K, combining 2~keV electron irradiation with subsequent temperature-programmed desorption (TPD) while monitoring the solid phase by mid-infrared spectroscopy. These controlled irradiation conditions represent a simplified laboratory analogue of the structural and energetic conditions within interstellar grain mantles. Volatile products released during warming were followed by quadrupole mass spectrometry, and the final residue was analysed by ex situ electrospray ionisation mass spectrometry (ESI-MS). Irradiation produces abundant radiolysis products typical of processed methanol- and water-rich ices, including CO, CO$_2$, H$_2$CO, H$_2$O$_2$, NH$_3$, and OCN$^{-}$. Bands consistent with formic acid and polyoxymethylene-like material are also observed, indicating that carbonyl chemistry and formaldehyde-driven oligomerisation can occur alongside fragmentation in the layered system. Comparison with a choline chloride–H$_2$O reference reveals the emergence of features compatible with methylated EtA derivatives and/or choline-like species, while ESI-MS shows higher-$m/z$ mass families in the residue that are not reproduced in the substrate/background blank. However, spectral congestion and matrix effects preclude an unambiguous assignment of choline. Our results show that energetic processing of EtA-containing ices can generate a diverse inventory of O- and N-bearing products, providing laboratory constraints on radiation chemistry in cold, irradiated grain mantles under idealised conditions.
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All authors Tara L. Stoib, Alejandro Guerrero-Caicedo, Duncan V. Mifsud, Péter Herczku, Gergő Lakatos, Zuzana Kaňuchová, Zoltán Juhász, Béla Sulik, Nigel J. Mason, Sergio Ioppolo, Paola Caselli, Barbara Michela Giuliano, Karl E. Duderstadt, Felipe Fantuzzi, Heidy M. Quitián-Lara

Astrophysics of Galaxies

Physical properties of star-forming clumps in nearby galaxies from CLAUDS and HSC-SSP

Jürgen J. Popp, Hugh Dickinson, Stephen Serjeant et al. (+2 more)

Giant Star-forming Clumps (GSFCs) are kpc-scale regions of enhanced star-formation with stellar masses of $10^6$ to $10^{10}\,M_\odot$ that are commonly observed in high-redshift ($z \gtrsim 1$) galaxies but their formation and role in galaxy evolution remain unclear. We applied a Faster R-CNN object detection framework (FRCNN) to identify star-forming clumps in astrophysical imaging data from a mass-complete sample of $\sim$210,000 low-redshift galaxies ($z\lesssim0.32$), located in the HSC-SSP Wide and Deep fields observed by the Hyper Suprime-Cam Subaru Strategic Survey (HSC-SSP) and CFHT Large Area U-band Deep Survey (CLAUDS). We present a population of $\sim$710,000 detected clumps for which we measured the (u)grizy-photometry and derived the physical properties (stellar mass, age, dust extinction and star-formation rate) for each clump by fitting the photometric data to stellar population models. We estimate that the clump Stellar Mass Function (cSMF) for young clumps ($<100\,\mathrm{Myr}$) follows a power law with an exponent of $\alpha=1.98\pm0.02$ down to a completeness limit of $\sim10^{8}\,M_\odot$ which is consistent with an in situ formation through violent disk instabilities (VDI). The clumps show elevated star-formation rates and negative gradients in their ages and stellar masses as a function of galactocentric distance. These gradients are steeper than those measured for the intra-clump regions of the host galaxies and are robust against uncertainties introduced by different modelling assumptions. For nearby galaxies we argue that the observed low-redshift clumps are likely analogues of high-redshift GSFCs and that the inward migration of star-forming clumps directly contributes to the central bulge formation of the host galaxy.
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All authors Jürgen J. Popp, Hugh Dickinson, Stephen Serjeant, Lucy F. Fortson, Vihang Mehta

Astrophysics of Galaxies

Rapid Dark Growth of Seed Black Holes in Self-Interacting Dark Matter

Yu Rong, Shuang-Nan Zhang, Jian-Min Wang et al. (+1 more)

The rapid emergence of massive black holes in the early Universe, possibly related to Little Red Dots, challenges conventional growth from light seeds. Dark-matter accretion offers a distinct route, and self-interacting dark matter (SIDM) makes it possible by behaving as a collisional fluid. We show that gas inflow can drive strong local contraction of an SIDM halo, assembling a dense reservoir around a pre-existing black-hole seed. The seed then enters a rapid dark-growth phase and can gain several orders of magnitude in mass within less than $1$ Myr before transitioning to slower accretion. We self-consistently follow this process by solving the spherical Euler equations with SIDM self-gravity, collisional heat transport, and an absorbing black-hole sink, rather than imposing an accretion history. The growth depends most strongly on halo mass, with weaker sensitivity to inflowing gas fraction, nuclear size, and seed mass. Gas-inflow-driven SIDM accretion therefore provides an efficient pathway for producing massive black holes in the early Universe.
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All authors Yu Rong, Shuang-Nan Zhang, Jian-Min Wang, Junxian Wang

Astrophysics of Galaxies

Little Red Dots as a Transient Phase of Self-Interacting Dark Matter Assisted Black Hole Growth

Yu Rong, Shuang-Nan Zhang, Jian-Min Wang et al. (+2 more)

The discovery of Little Red Dots (LRDs) with JWST has revealed a population of compact, red galaxies hosting rapidly growing black holes at early cosmic times. Their compact morphologies, broad emission lines, weak X-ray emission, and distinctive V-shaped spectral energy distributions indicate a short-lived phase of black-hole growth within a dense nuclear environment. Here we propose that LRDs arise from a transient episode of self-interacting dark matter (SIDM)-assisted black-hole growth during galaxy assembly. In this scenario, gas inflows first establish a compact nuclear thick disk, which modifies the central SIDM distribution and provides the obscuring structure around the accreting black hole. Once the SIDM density near the seed black hole becomes sufficiently enhanced, rapid SIDM accretion drives a major increase in black-hole mass, initiating the transient LRD phase. The resulting obscured growth phase naturally suppresses direct short-wavelength emission and redistributes the radiation field, producing the red continuum and V-shaped spectral signatures of LRDs. This framework links gas inflow, SIDM dynamics, and early black-hole assembly, predicting that LRDs preferentially occur in galaxies undergoing strong nuclear inflow and evolve into ordinary AGN after this transient phase. Unlike models that require globally rare halo histories, long super-Eddington gas growth, or purely phenomenological obscuration, our model ties the overmassive black hole, X-ray weakness, spectral shape, and finite duty cycle to one local gas-triggered SIDM event.
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All authors Yu Rong, Shuang-Nan Zhang, Jian-Min Wang, Junxian Wang, Zhicheng He

Astrophysics of Galaxies

Ten years since the NGC 6334I-MM1 accretion outburst: the impact on its environment

G. C. MacLeod, A. Caratti o Garatti, W. A. Baan et al. (+11 more)

Ten years on, flaring continues in masers associated with NGC 6334I-MM1. Methanol and hydroxyl masers are nearing quiescent values, but water features remain elevated. Several more 1.665 GHz hydroxyl masers, notably, that flared during the accretion event in NGC 6334I-MM1, are identified and presented. Some hydroxyl masers appear to have been active prior to the 2015 event. Possible explanations are discussed. The radial infrared expansion speed during the accretion event is estimated to be ~1.8 AU/d. However, the expansion speed along the North-South outflow is about ten times faster (~18 AU/d). The maser flaring activity illuminated clumpy structure in NGC 6334I-MM1. Quasi-periodicity is reported after the 2015 accretion event in the total integrated 12.2 GHz methanol emission, predominantly in $v_{12.2}=[-12.0,-9.9]$ \kms, after the accretion event in NGC 6334I-MM1. It is not certain if the periodic masers are located in NGC 6334I-MM1, -MM2, or -MM3. The magnetic field, measured from the Zeeman splitting of two ground state hydroxyl lines, undergoes changes before and after the flare.
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All authors G. C. MacLeod, A. Caratti o Garatti, W. A. Baan, D. P. Smits, T. R. Hunter, C. L. Brogan, J. O. Chibueze, R. A. Burns, B. Stecklum, V. Wolf, J. M. Vorster, A. Jengis, J. Esimbek, J. Quick

Astrophysics of Galaxies

Topological Signatures of AGN Feedback in the Simba Simulations

Ryusei R. Kano, Romeel Davé, Tsutomu T. Takeuchi et al. (+1 more)

Active galactic nuclei (AGN) feedback can alter the abundance and spatial distribution of galaxies within large-scale structure. We apply topological data analysis (TDA) to Simba hydrodynamical simulations with varying AGN feedback at $z=0$ to determine which galaxy populations, environments, and spatial scales are most affected. The galaxy two-point correlation function is most sensitive to feedback at $r<1 h^{-1} Mpc$. We then use Betti curves, persistence diagrams, and the 2-Wasserstein distance to quantify feedback-dependent changes in topology. Persistence diagrams show clearer differences than Betti curves, particularly for satellite galaxies. For satellites, loop-like features show significant differences at $\alpha=0.1$–$0.4 h^{-1} Mpc$ for all feedback channels, together with a weaker cumulative difference at $\alpha=1$–$3 h^{-1} Mpc$. The differences are strongest for satellites in quenched halos with $M_h\gtrsim10^{12} M_\odot$. Optimal matching shows that they are driven mainly by shifts in the birth and death scales of loop-like features rather than by their appearance or disappearance. These results indicate that persistent homology can provide complementary constraints on AGN feedback and environmental quenching in galaxy surveys.
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All authors Ryusei R. Kano, Romeel Davé, Tsutomu T. Takeuchi, Hayato Shimabukuro

Astrophysics of Galaxies

Polarization Observations of a sample of Excited OH masers

Derck P. Smits and Paul Fallon

Spectra of 4.7 and 6.0 GHz excited OH masers from 21 pointings towards known star-forming regions are reported. The C-band observations, using the Green Bank Telescope in full Stokes mode, have measured how polarization properties vary across the maser profiles in each spectrum and vary between different epochs of observation. Seven sources had no detections of masers at any of the OH transitions. Nine sources were observed to have 4.766 GHz masers, which include two new detections in G188.946+0.886 and G196.454-1.677. No new linear or circular polarization was found in any of these masers. Seven and two sources had 6.035 and 6.031 GHz masers, respectively. All 6.035 GHz masers had some level of circular polarization, and three also had linear polarization. Both linear and circular polarization were found in the 6.031 GHz masers in G133.947+1.064, and weak, 100% LCP in G141.918+1.902. Magnetic fields have been calculated from measured Zeeman splittings. The strength and orientation of the fields agree with most previous measurements, although there are some indications that the magnetic fields could be changing. Thermal emission or absorption is seen in several of the 4.7 and 6.0 GHz transitions, many of which have not been reported before.
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Astrophysics of Galaxies · Cross-listed from astro-ph.HE

The rise and decline of a transient obscuration event in a moderately distant type-I quasar

A. Akylas, A. Georgakakis, E. Pouliasis et al. (+5 more)

Outflows of ionised material, often dubbed warm absorbers (WAs), are common in nearby Seyferts but sparse in distant and more energetic quasars (QSOs). We present multi-epoch X-ray and optical observations of the serendipitously identified type-I QSO 2MASS J14302580+4159572 at a redshift of $z=0.35$, revealing the rare rise and decline of a transient ionised absorber over a 22-year timescale. The discovery observations were obtained with XMM-Newton between 2002 and 2005. The first two observations show unremarkable X-ray spectra typical of unobscured type-I QSOs, whereas the 2005 observation reveals a pronounced suppression of the spectrum below $\sim3\,\mathrm{keV}$. Spectral analysis shows that this event is produced by a moderately ionised absorber with column density $N_{\rm H}\simeq5\times10^{22}\,\mathrm{cm^{-2}}$ and ionisation parameter $\log\xi\simeq1.4$. Joint analysis of XMM-Newton, NuSTAR, and Swift/XRT observations spanning 22 years indicates that the absorber remained stable for nearly 18 years before weakening in the 2023–2024 Swift/XRT data. Throughout this period, the intrinsic 3–10 keV continuum remained remarkably stable, indicating that the observed variability is driven by changes in line-of-sight ionised absorption rather than intrinsic luminosity fluctuations. We interpret the event as a thermally driven ionised outflow located outside the broad-line region (BLR), at sub-parsec to parsec scales, with a density of order $10^{6}\,\mathrm{cm^{-3}}$. Supporting this scenario, the high-ionisation [O\,III] $\lambda4363$ emission line varies in tandem with the X-ray absorption, suggesting that the outflow progressively modifies the ionisation state of the inner narrow-line region (NLR) on decadal timescales. These observations provide a rare view of the long-term evolution of a quasar warm absorber and its impact on the circumnuclear environment.
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All authors A. Akylas, A. Georgakakis, E. Pouliasis, I. Georgantopoulos, C. Ricci, M. Chira, A. Ruiz, E. M. Xilouris

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

On the Constancy of Binary Star Fractions in Local Star Clusters

Priya Hasan and Mohammed Saifuddin

We investigate the unresolved binary-star fraction in a complete sample of 376 open clusters located within 1 kpc of the Sun using Gaia DR3 and ASteCA based synthetic colour magnitude diagram modelling. The binary fraction is a global photometric quantity, sensitive primarily to unresolved binaries that produce measurable broadening above the single-star main sequence. We find that the median binary fraction of the sample is nearly constant, $0.29\pm 0.03$, with no clear dependence on cluster age, core radius, limiting radius or median mass. This apparent constancy suggests that the global binary content of nearby open clusters is regulated by competing dynamical processes, including disruption of soft binaries, survival and hardening of close binaries, mass segregation, evaporation of single stars, and long-term cluster dissolution. The result is consistent with theoretical expectations and previous observational studies indicating that cluster binary populations can evolve internally while maintaining a relatively stable global binary fraction. Our findings provide an observational constraint for models of open-cluster formation and dynamical evolution and highlight the need for future work combining photometric, astrometric, spectroscopic, and N-body approaches to distinguish between primordial and dynamically formed binary populations.
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Astrophysics of Galaxies

Kinematics of the System of Young Open Clusters based on Gaia DR3 Data

A.K.Dambis and A.S.Rastorguev

We use a kinematical model including circular rotation of the Milky-Way disk incorporating effects produced by a spiral density wave with constant radial and vertical components of the velocity dispersion tensor and adopted solar Galactocentric distance R_0=8.277kpc (inferred by GRAVITY collaboration in 2022) to derive the velocity field parameters for a sample of 2384 open clusters from the Hunt and Reffert (2024) catalog having ages no greater than 100 Myr almost all of which reside at Galactoaxial distances between 5 and 14 kpc. We estimate the velocity-field parameters using maximum-likelyhood method and the affine-invariant variant of the Markov chain Monte-Carlo method proposed by Goodman and Weare (2010) with both methods yieilding almost identical parameter values. The inferred rotation curve, on the whole, is consistent with the results based on our kinematical analysis of a sample of Galactic masers. We find the linear rotation velocity at the solar distance to be V=242.3+/-1.1~km/s; it reaches its maximum V~244 km/s at Galactoaxial distance of about R_g~7 kpc followed by a slow and smooth decline with V~227 km/s at R_g=14 kpc. The inferred radial and vertical components of the velocity dispersion tensor are (sigma U_0, sigma W_0)~(10.63+/-0.15, 4.56+/-0.15) km/s. We find the pitch angle and the phase of the Sun for a four-armed spiral pattern to be i~-11.7+/-0.3 degrees and chi_0~138+/-5 degrees, respectively, and the amplitudes of radial and tangential perturbations, f_R=-3.0+/-0.4 and f_{theta}=-3.1+/-0.4 km/s, respectively.
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Astrophysics of Galaxies · Cross-listed from astro-ph.EP

Delayed Methane Detection in 3I/ATLAS: GCR-Driven Subsurface Stratification and Interstellar Exposure Age Constraints

Akshat Rawat and Kinsuk Acharyya

Interstellar comet 3I/ATLAS shows unusual volatile activity, including strong H$_2$O, CO, and CO$_2$ production and a delayed post-perihelion detection of CH$_4$. In this work, we investigate the delayed CH$_4$ detection in an H$_2$O, CO$_2$, and CO ice matrix using a shape model coupled with a thermophysical nucleus model that incorporates interstellar processing by Galactic Cosmic Rays. We track the sublimation, trapping, depletion, and release of these volatiles as a function of heliocentric distance and explore the relevant parameter space through 12000 model runs to identify viable combinations of primordial volatile inventory and effective GCR exposure age that reproduce the observed production rates of these volatiles. The viable models favour a volatile-rich primordial inventory consistent with formation in an ultra-cold ($T < 20$ K) region beyond the CO snowline, followed by an effective GCR processing exposure of 0.87–3.1 Gyr during interstellar passage. GCR processing produces a continuous compositional gradient and converts part of the CO reservoir into secondary CO$_2$ and depletes near-surface CH$_4$ through radiolytic conversion. The delayed CH$_4$ detection can be explained by the survival of CH$_4$ trapped within the deeper H$_2$O matrix and its subsequent release as subsurface heating progresses after perihelion. The timing of CH$_4$ sublimation can be used to estimate the effective GCR processing age of 3I/ATLAS. The posterior distributions also reveal a degeneracy between primordial dust content and GCR exposure, where dust-rich, weakly processed and ice-rich, strongly irradiated evolutionary pathways produce processed subsurface layers with similar thermophysical properties.
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Astrophysics of Galaxies

Early steps in the hierarchical assembly of a Milky Way-mass galaxy 1 Gyr after the Big Bang

Yoshihisa Asada, Marcin Sawicki, Guillaume Desprez et al. (+14 more)

We report JWST observations of a $z_{\rm spec}=5.196$ compact group of three strongly lensed low-mass galaxies ($M_\star \sim 10^{6-7} M_\odot$ each) whose small line-of-sight velocity offsets (from $-120\pm100$ to $+160\pm110$ km s$^{-1}$) and projected separations ($\sim2$ kpc) suggest that they are undergoing merging. On the basis of abundance-matching arguments, the trio appear to be destined to evolve into a Milky Way-mass galaxy by the present day. Our spectrophotometric analysis suggests that the stellar mass growth of this system is not simply just due to the merging of its components; rather, it is being dramatically enhanced by intense bursts of star formation. Presumably initiated by tidally-induced gas inflows, these star-forming bursts boost the mass growth $2.6\pm0.5$ times that expected in straightforward merging of the existing stellar masses. These spectroscopic observations thus not only demonstrate that hierarchical assembly remains a viable formation channel in the early assembly phases of present-day massive galaxy, but also that interaction-induced bursts of star formation are a major accelerator of this assembly process.
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All authors Yoshihisa Asada, Marcin Sawicki, Guillaume Desprez, Jon Judez, Marusa Bradac, Kartheik Iyer, Nicholas S. Martis, Adam Muzzin, Gael Noirot, Ghassan T. E. Sarrouh, Chris J. Willott, Jacqueline Antwi-Danso, Seiji Fujimoto, Danilo Marchesini, Vladan Markov, Luke Robbins, Visal Sok

Astrophysics of Galaxies

On the Probability Distribution and Null-hypothesis Testing of Cross-correlation for Light Curves in Active Galactic Nuclei

Yan-Rong Li and Jian-Min Wang

Cross-correlation is crucial in studies of multiwavelength flux variability in active galactic nuclei (AGNs), especially for reverberation mapping analysis, where interpolated cross-correlation function is widely used to measure time lags between light curves. While time-lag uncertainties can be estimated via the flux randomization and random subset selection method, an appropriate framework for assessing cross-correlation significance remains lacking in the literature. Here we attempt to fill this gap by leveraging the well-established property from stochastic time series theory, namely that the probability distribution of cross-correlation coefficients for independent stochastic light curves asymptotically approaches a normal distribution. Its variance can be analytically estimated using the auto-correlation functions of the light curves. We employ Monte Carlo simulations to validate this property for irregularly sampled, red-noise AGN light curves, and then propose a fast procedure to perform null-hypothesis testing for the cross-correlation of AGN light curves. We also present exemplary applications to AGN reverberation mapping data. This procedure requires prior determination of the auto-correlation functions of light curves, which can be obtained via model fitting. The long-standing issue regarding unbiasedly recovering the auto-correlation function remains unresolved when light-curve duration is comparable to the typical variation timescale, warranting further future investigation.
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Astrophysics of Galaxies · Cross-listed from astro-ph.SR

The Contribution of Starspots to the Lithium Spread in NGC 2264

Yan Luo, Gregory J. Herczeg, Min Fang et al. (+2 more)

Star clusters with ages of a few Myr have a previously unexplained dispersion in the lithium equivalent widths. In this work, we show that much of the lithium spread of the young cluster NGC 2264 can be attributed to the observational presence of starspots. We demonstrate that the equivalent width of Li I 6708 Angstrom changes with observed spot coverage, using a sample of 15 Weak-Lined T Tauri Stars (WTTSs) with multi-epoch high-resolution ESPaDOnS spectra and photometry. To quantify the contribution of starspots, we construct an empirical two-component starspot model. When differences in visible spot coverage are taken into account, 68% of the WTTSs fall within the model-predicted EW(Li) dispersion for a range from 0-90% visible spot coverage. We find no correlation between the age spread or gravity and Li I equivalent width in NGC 2264. Our results suggest that invoking starspots can explain much of the apparent lithium spread in NGC 2264 and reduces but does not fully eliminate the need to invoke rotation-driven lithium depletion or other non-standard explanations at such young ages. Future simultaneous measurements of lithium and beryllium in young stars may provide an independent test of this scenario.
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All authors Yan Luo, Gregory J. Herczeg, Min Fang, Qinghui Sun, Xiaoting Fu

Wednesday 16 September

Astrophysics of Galaxies

The extreme Disturbed Galaxy Cluster Sample (eDGeS): Spectroscopy and Dynamical Analysis of the eROSITA-Selected Merging Galaxy Cluster Candidate 1eRASS J025859.4-193727

Anish S. Aradhey, Eleazar R. Carrasco, Alfredo Zenteno et al. (+7 more)

Addressing open questions such as the effect of galaxy cluster mergers on the evolution of galaxies and the self-interaction cross-section of dark matter requires the construction of a large, diverse sample of disturbed galaxy clusters. One contribution to such a sample is the extreme Disturbed Galaxy Cluster Sample (eDGeS), an ongoing spectroscopic study of massive disturbed and merging galaxy clusters selected from complementary surveys. Here, we present our first results from the eROSITA-selected subsample (eDGeS-eROSITA): a dynamical state analysis for the merging cluster candidate 1eRASS J025859.4-193727. We present the first spectroscopic redshift measurements for 76 galaxies in the direction of the cluster, confirming 51 as cluster members. The cluster displays a line-of-sight velocity dispersion of $\sigma_{\rm{cl}}=808^{+59}_{-66}~\rm{km~s^{-1}}$ and a dynamical mass of $M_{200}=4.47^{+0.94}_{-0.93} \times 10^{14}~M_{\rm{Sun}}$. While the cluster shows no evidence for substructure along the line of sight, the projected distribution of member galaxies reveals three subclusters, only one of which appears associated with the cluster's X-ray contours. Phase-space analysis reveals a large fraction of recently infallen member galaxies. Together, this evidence suggests a cluster merger along the plane of the sky. Assuming that the two most massive subclusters are on outgoing (incoming) trajectories after their first pericentric passage, a two-body Monte Carlo model predicts that the two subclusters collided $0.50^{+0.20}_{-0.22}~\rm{Gyr}$ ($1.24^{+0.96}_{-0.38}~\rm{Gyr}$) ago.
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All authors Anish S. Aradhey, Eleazar R. Carrasco, Alfredo Zenteno, Rogério Monteiro-Oliveira, Facundo A. Gómez, Konstantina Boutsia, Esra Bulbul, Guillermo Damke, Amelia Ramirez, Hector Cuevas

Astrophysics of Galaxies

Honoring Paris Pişmiş' Legacy: Uniform Astrophysical Properties of 14 Understudied Clusters from Gaia DR3

Seliz Koç, Neslihan Alan, Furkan Akbaba et al. (+1 more)

Open clusters are fundamental tracers of the chemical and dynamical evolution of the Galactic disc. This study presents a systematic characterisation of 14 understudied open clusters from the Pismis catalogue, selected for a well-defined stellar sequence in Gaia DR3 and spanning a wide range of ages and distances. Using high-precision Gaia DR3 astrometry, we provide a high-fidelity modernisation of these historical discoveries while testing our analytical framework across diverse stellar populations. Membership probabilities were determined via the unsupervised UPMASK algorithm using Gaia DR3 positions, proper motions, and parallaxes. To ensure high sample purity, the member samples entering the isochrone fits were restricted to P >= 0.90, with astrophysical parameters calculated through membership-weighted likelihoods. Fundamental properties – age, distance, reddening, and metallicity – were derived using a Bayesian Nested Sampling approach to isochrone fitting, chosen for its robustness against the parameter degeneracies typical of dense Galactic fields. The 14 systems exhibit a broad range of properties, with ages from approximately 11 Myr to 1.5 Gyr and distances spanning approximately 690 to 5445 pc. These refined, uniform parameters reconcile historical observations with the precision era of modern astrophysics, providing a homogeneous baseline for systems that large-scale automated surveys recover only partially. A direct cross-match against widely used automated catalogues shows that they typically contain only about a third of the members identified here, and substantially less in the most crowded fields, underscoriecific analysis. This workcontributes to a more complete census of the Galactic disc and sets out a reproducible, per-cluster licable to the manycomparable low-latitude systems still to be characterised.
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All authors Seliz Koç, Neslihan Alan, Furkan Akbaba, Olcay Plevne

Astrophysics of Galaxies

Extreme Enrichment at Cosmic Dawn: Three FeII-Strong Quasars at z > 6 from the JWST Aether survey

Anniek J. Gloudemans, Emanuele Paolo Farina, Roberto Decarli et al. (+22 more)

We present three outliers on the quasar main sequence at z>6, as revealed by JWST/NIRSpec IFU observations from the Aether survey, a program targeting ~200 quasars at cosmic dawn. The quasars, J0216-5226, J0320-3521, and J1429+5447, exhibit exceptionally strong FeII emission and weak H$\beta$ and [OIII] lines, indicating rapid chemical enrichment within the first Gyr of cosmic history. Their FeII strengths ($R_{\rm{FeII},\lambda4570} \equiv \rm{EW}_{\rm{FeII}}/\rm{EW}_{\rm{H}\beta}$) range between ~2.5-3.6, placing them among the top ~3% of SDSS quasars at ($0\lesssim z\lesssim 1$). The H$\alpha$ emission lines of J0216-5226 and J1429+5447 imply black hole masses of $\sim1-7\times10^9$ M$_{\odot}$ with $\lambda_{\rm{Edd}}\sim0.1-0.6$, comparable to typical high-z quasars, although virial black hole masses may be systematically overestimated in strong FeII emitters. In contrast, J0320-3521 hosts a lower mass black hole of $\sim0.2-2\times10^9$ M$_{\odot}$, suggesting possible super-Eddington rate accretion with $\lambda_{\rm{Edd}}$~0.5-6.0. The IFU data of J0320-3521 reveal a distinct emission-line region at a projected distance of ~1.5 kpc, consistent with either an interacting companion or ionized gas associated to the quasar. We further identify a complex environment around J1429+5447, including two candidate companion galaxies or extended ionized gas structures. These quasars with bright emission-line regions, J0320-3521 and J1429+5447, are radio-loud sources, while J0216-5226 remains undetected in radio ($R_{5\rm{GHz,} \,3\sigma}\lesssim4$). Together, these results confirm previous findings that highly enriched, rapidly growing black holes were already in place at cosmic dawn. Despite the small sample size, our results further highlight the diversity in environment and radio-jet properties among quasars that otherwise share the same extreme region of the quasar fundamental plane.
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All authors Anniek J. Gloudemans, Emanuele Paolo Farina, Roberto Decarli, Klaudia Protušová, Fabrizio Arrigoni Battaia, Eduardo Bañados, Aaron J. Barth, Silvia Belladitta, Manuela Bischetti, Hyunseop Choi, Dominika Ďurovčíková, Anna-Christina Eilers, Simona Gallerani, Thales A. Gutcke, Luca Ighina, Brian C. Lemaux, Federica Loiacono, Yoshiki Matsuoka, Chiara Mazzucchelli, Silvia Onorato, Hyewon Suh, Fabian Walter, Feige Wang, Julien Wolf, Jinyi Yang

Astrophysics of Galaxies

From observing strategies to velocity dispersion bias: forward modeling unresolved binaries in ultra-faint dwarf galaxies

Xiaowei Ou, Andrew B. Pace, Nitya Kallivayalil et al. (+9 more)

Ultra-faint dwarf galaxies (UFDs) in the Milky Way are ideal probes of low-mass galaxy formation and dark matter because they are highly dark-matter dominated. In the lowest-mass systems, however, unresolved binary orbital motion complicates dynamical mass estimates by inflating measured velocity dispersions and biasing the interpretation of the inferred masses. We develop a flexible forward-modeling pipeline, the Binary Observation Simulator, to generate mock multi-epoch radial-velocity observations of binary populations in dwarf galaxies and to quantify how binary-induced biases depend on both galaxy properties and observing strategy. We generate mock samples spanning true velocity dispersion of $\sigma_{\rm true}\sim0.75$-$3.5$ km/sec, binary fractions of $0.1$-$0.9$, and multi-epoch baselines of up to $10$ yr. We find that, while multi-epoch monitoring reduces the binary-induced bias, residual contamination remains significant for low-mass halos: even a $10$-yr baseline can leave $\sim10$-$120\%$ relative bias for systems with $\sigma_{\rm true}\lesssim1$ km/sec. We also note that small sample sizes ($\lesssim20$) introduce substantial stochastic scatter in the recovered dispersions, sometimes masking the expected improvement from longer observational baselines. Applying the framework to the real $\sim17$-yr Bootes I observing record reproduces the literature velocity dispersions, yields an empirical correction conditioned on that cadence, and shows that redistributing the same observations onto half the number of stars would have removed roughly half of the residual binary bias. These results emphasize that robust dispersion estimates for the faintest dwarfs require forward modeling of both binary populations and survey cadence.
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All authors Xiaowei Ou, Andrew B. Pace, Nitya Kallivayalil, Amery Gration, Christopher T. Garling, Nathan R. Sandford, Lina Necib, Niusha Ahvazi, Andres Almeida, Kaia R. Atzberger, Yanbo Pan, Jack T. Warfield

Astrophysics of Galaxies

Characterizing the hierarchical structure of filaments I. On the origin of the length-mass (L-M) scaling relation

Rahul Patel, Daniel Seifried and Alvaro Hacar

Aims. Filamentary structures in molecular clouds are widely recognized as fundamental components of star formation. Observations report a length-mass relation of the form $L \propto M^\alpha$ with $\alpha \simeq 0.5$. We characterize this relation in simulated molecular clouds and investigate the influence of hierarchical fragmentation and spatial resolution. Methods. We apply a two-step filament identification method to high-resolution 3D hydrodynamical and magnetohydrodynamical simulations from the SILCC-Zoom project, combining the Rolling Hough Transform with dendrogram-based segmentation for hierarchical decomposition. We analyze the resulting structures across multiple spatial resolutions. Results. The identified structures span column densities of $\sim 10^{21}$–$\sim 10^{23}\,\mathrm{cm}^{-2}$. Across multiple resolutions and, separately, the full hierarchical decomposition at the highest resolution, the ensemble exhibits a sub-linear $L-M$ relation close to $L \propto M^{0.5}$. When individual structures are traced across resolutions, the slopes remain sub-linear ($\alpha \simeq 0.45$–$0.70$), consistent with the geometric prediction $L \propto M^{0.5}$ of a fragmentation-driven random walk. In contrast, decomposing individual structures at the highest resolution yields a wide range of slopes ($\alpha \simeq 0.2$–$3$), peaking at $\alpha<1$. A simple toy model shows that this diversity arises from differences in the internal column-density distribution and segmentation geometry. Conclusions. Taken together, these results indicate that the average sub-linear length-mass relation with $\alpha \simeq 0.5$ is a robust property of the hierarchical structure and fragmentation occurring in molecular clouds.
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Astrophysics of Galaxies

Star clusters as tracers of the perturbed southern outer disk of the Large Magellanic Cloud

Matías Chiarpotti, Andrés E. Piatti, Denis M.F. Illesca et al. (+1 more)

The complex interaction history between the Large and Small Magellanic Clouds (L/SMC) has left significant imprints on their structural and chemical evolution. In this work, we use a sample of 70 star clusters located in the southern outer disk of the LMC ($R > 5^{\circ}$) to trace the magnitude of these tidal perturbations. Using deep $g,i$ photometry from the SMASH DR2 survey and the Automated Stellar Cluster Analysis (ASTeCA) code, we provide a homogeneous determination of cluster ages, metallicities, and heliocentric distances. Our results show a population with ages ranging from 1.02 to 3.34 Gyr and metallicities between -0.70 and -0.07 dex. We find that clusters at greater heliocentric distances are predominantly located toward the western regions, facing the SMC. Analysis of the vertical distribution reveals an oscillatory variation in the mean height ($\langle Z \rangle$) relative to the LMC mid-plane and an increase in intrinsic vertical dispersion ($W$) toward the West. These geometric features are consistent with a corrugated disk structure induced by recent tidal encounters with the SMC. Chemically, the clusters follow the age-metallicity relationship typical of the LMC and are well-represented by a bursting-type formation model. The lack of chemically distinct clusters suggests that while the interaction was sufficient to dynamically deform and corrugate the outer disk, it did not lead to significant cluster capture from the SMC. We conclude that the southern outer disk remains structurally and chemically part of the LMC, despite being heavily perturbed by tidal forces.
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All authors Matías Chiarpotti, Andrés E. Piatti, Denis M.F. Illesca, Roberto Butrón

Astrophysics of Galaxies

Sub-arcsecond imaging of HCN and CN in the Orion Bar. UV-driven warm Nitrogen chemistry in dense environments

M. Zannese, J. R. Goicoechea, S. Cuadrado et al. (+3 more)

Rotationally excited HCN and CN lines, due to their high critical densities, are often used as tracers of gas densities. ALMA, with its high spectral and spatial resolution, provides unique access to the spatial morphology and kinematics of HCN and CN emission to study the substructures of the molecular cloud edges. We present new sub-arcsecond imaging of HCN 4-3 and CN 3-2 lines to probe the density structure in the Orion Bar. We study their spatial distribution and compare them to other existing tracers inside the PDR. We complemented these data with multiple J lines observed with the IRAM 30m and Herschel telescopes to study HCN and CN excitation near the dissociation front (DF). We find that HCN and CN emission are more spatially extended toward the more UV-shielded cloud than C2H and H2. However, they both peak very close to the DF, in disagreement with previous lower-angular-resolution observations. This morphology can be explained by the enhanced UV-driven chemistry. In dense and irradiated environments, HCN is efficiently formed via H2+CN. Hence, its emission can also probe warmer gas near the DF. CN emission is observed in the atomic PDR, not accounted by stationary gas-phase chemistry due to the very low H2 abundances. We interpret this as photoprocessing of CN-bearing PAHs. We derive high densities near the DF when comparing observations with RADEX and Meudon PDR Code models. Finally, we do not find evidence of small-scale high-density clumps and argue that the observed density gradient could explain the variation of excitation between the different tracers. We resolve two velocity components in HCN emission: 10.5 km/s (velocity of the Bar) and 11.5 km/s. The very structured emission of HCN observed in this redshifted emission component is more compatible with the signature of the propagation of a UV-induced shock compressing the gas than clumps.
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All authors M. Zannese, J. R. Goicoechea, S. Cuadrado, J. Pety, M. Gerin, E. Chapillon

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

Extragalactic Multi-Band Exploration of Red Supergiants (EMBERS): Pipeline, Source Classification, and Bolometric Properties of 101,219 Red Supergiants from James Webb Space Telescope Imaging

Aswin Suresh, Charles D. Kilpatrick, Wen-fai Fong et al. (+6 more)

The evolution of red supergiants (RSGs), especially in their final stages before exploding as hydrogen-rich Type II supernovae (SNe), remains poorly understood, owing to small samples of well-characterized stars in the Local Group. We present the largest population study of RSGs to date using $\sim10^5$ stars with bolometric parameters inferred from archival James Webb Space Telescope/Near-Infrared Camera (NIRCam) imaging of 15 galaxies within 20 Mpc. We also present jwst123, a newly-developed general-purpose NIRCam reduction and photometry pipeline, and its application to our set of 15 galaxies. We build a simulation-based parameter inference framework to rapidly fit multi-band photometry of $\sim1.5$ million luminous stars in milliseconds per source. Using clustering in the effective temperature ($T_{\rm eff}$)-luminosity ($\log L/L_{\odot}$)-dust optical depth ($\tau_V$) phase space, we introduce a novel method to select RSGs with high completeness and purity. Leveraging the scale of our catalog, we find that the dustiest RSGs prefer metal-rich hosts, and RSG luminosities correlate with host specific star formation rate, suggesting that environment shapes RSG evolution. While most selected RSGs agree with theoretical stellar evolution tracks, we identify a new population of 1,669 RSGs that are heavily dust-enshrouded ($\tau_V>4$), overluminous ($\log(L/L_{\odot})>5.55$), or anomalously cool ($T_{\rm eff}<3000\,{\rm K}$), including analogs of known SN progenitors. Our catalog provides a population-scale baseline for understanding massive stellar evolution and connecting field RSGs to dusty progenitors of Type II SNe.
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All authors Aswin Suresh, Charles D. Kilpatrick, Wen-fai Fong, Maria R. Drout, Daichi Hiramatsu, Luca Izzo, Wynn V. Jacobson-Galán, Armin Rest, Samaporn Tinyanont

Astrophysics of Galaxies

MSA-3D: A Diversity of Dust Attenuation Profiles Across the Epoch of Thin Disk Emergence

Ivana Barišić, Tucker Jones, Naveen Reddy et al. (+13 more)

We present spatially resolved measurements of dust attenuation and star formation in 18 main-sequence star-forming galaxies at z$\sim$1 from the MSA-3D survey, obtained by mapping the Balmer emission lines at $\sim$1 kpc resolution with JWST/NIRSpec's MSA in a slit-stepping strategy. We investigate the diversity of radial attenuation profiles, and how the spatial variation affects attenuation and star formation rates (SFR) derived from single-aperture measurements. We find a notable diversity among radial attenuation profiles: some galaxies exhibit centrally peaked attenuation, but the majority exhibit flat or even positive radial profiles, with large variation at a fixed stellar mass. This diversity may reflect different evolutionary pathways shaped by various mechanisms such as disk settling, merging, and internal processes. We examine possible biases arising from single-aperture and integrated measurements and find that, while they can under- or over-estimate attenuation and SFRs for individual galaxies, the sample-averaged trends remain roughly unchanged, with the derived SFRs consistent with the star-forming main sequence, and a small scatter. From our sample, we find a median stellar-to-nebular reddening ratio f = E(B-V)$_{\rm star}$/E(B-V)$_{\rm gas}$ of 0.88 with an interquartile range of 0.51-0.96, suggesting relatively uniform dust distributions even in intermediate-mass galaxies (stellar masses $\sim 10^9$-$10^{10.5}~M_{\odot}$). Our results highlight the importance of spatially resolved attenuation measurements for accurately tracing star formation and understanding the evolving dust geometry in galaxies during a critical epoch of morphological transformation.
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All authors Ivana Barišić, Tucker Jones, Naveen Reddy, Matthew Malkan, Ryan Sanders, Alaina Henry, Ayan Acharyya, Kevin Bundy, Juan M. Espejo Salcedo, Karl Glazebrook, Themiya Nanayakkara, Danail Obreschkow, Namrata Roy, Takafumi Tsukui, Benedetta Vulcani, Xin Wang