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Physics Astrophysics Astrophysics of Galaxies

astro-ph.GA Watch Astrophysics of Galaxies

Tuesday 29 September

Astrophysics of Galaxies

Morphological Identification of Dynamical Regimes in MHD Turbulence with ScaleAware-JEPA

Mengke Zhao, Guang-Xing Li and Keping Qiu

The morphology of turbulent interstellar gas reflects the coupled action of turbulence, magnetic fields, and self-gravity, but density amplitude alone does not uniquely specify dynamical state. We use ScaleAware-JEPA to learn multiscale structural coordinates from density alone and test whether these learned coordinates organize dynamical states more clearly than density-based conditioning. Clump-like, filament-like, and diffuse-like latent neighborhoods show an ordered progression in turbulent velocity scaling that is not reproduced by density-selected populations. Velocity and magnetic fields are withheld during training and used afterward as post-training physical diagnostics: MHD states occupy ordered but overlapping regions of the learned representation, and dimensionless dynamical balances vary coherently across the full latent atlas. These results show that a representation learned from density morphology can acquire a geometry that is systematically organized by established MHD diagnostics. Multiscale morphology therefore provides a useful coordinate for dynamical state beyond density amplitude alone.
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Astrophysics of Galaxies

Dynamical friction vs. subhalo heating in Cold Dark Matter haloes

Jorge Peñarrubia, Pierfrancesco Di Cintio, Eduardo Vitral et al. (+1 more)

The orbital evolution of massive stellar systems embedded in dark matter haloes is governed by competing processes. Dynamical friction removes orbital energy, whereas fluctuations in the gravitational field generated by dark matter subhaloes inject energy through stochastic heating. We investigate the balance between these two mechanisms using analytical arguments and numerical experiments. We show that, for a given host halo and subhalo population, there exists a critical mass $M_{\rm crit}$ at which heating and friction balance. Clusters with masses $M_{\rm cl}>M_{\rm crit}$ lose orbital energy and sink towards the centre of the halo, whereas those with $M_{\rm cl}<M_{\rm crit}$ gain energy and expand outwards. At $M_{\rm cl}\simeq M_{\rm crit}$, the two processes balance, leading to a cluster population that, on average, neither sinks nor expands within the host halo. In CDM haloes, the critical mass is primarily controlled by the upper end of the subhalo mass function. Since massive subhaloes are intrinsically rare, the balance between heating and friction shows substantial halo-to-halo scatter. For dark matter haloes in the mass range associated with dwarf spheroidal galaxies (dSphs), we find $M_{\rm crit}\gtrsim 10^5M_\odot$, comparable to the masses of globular clusters in the Fornax dSph. Stochastic heating by dark substructure may therefore significantly delay the orbital decay of globular clusters and help alleviate the Fornax timing problem.
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All authors Jorge Peñarrubia, Pierfrancesco Di Cintio, Eduardo Vitral, Matthew G. Walker

Astrophysics of Galaxies

Testing KMTNet–PRIME Optical–Near-Infrared Source-Color Constraints in KMT-2024-BLG-0211 and KMT-2024-BLG-1522

Kansuke Nunota, Jennifer C. Yee, Takahiro Sumi et al. (+37 more)

We present analyses of two 2024 microlensing events, KMT-2024-BLG-0211 and KMT-2024-BLG-1522, jointly observed by KMTNet in the optical and PRIME in the near-infrared. For KMT-2024-BLG-0211, the KMTNet–PRIME $I-H$ color provides a useful constraint on the angular source radius for a short-timescale finite-source event with a giant source. The event is consistent with a low-mass stellar lens, although the weak parallax constraint leaves the lens mass and distance uncertain. For KMT-2024-BLG-1522, we compare the results obtained from $V-I$, $I-H$, $V-H$, and $J-H$ color constraints. The microlensing parameters are nearly identical among the four analyses, yielding a robust binary-lens solution with nearly equal masses. However, the inferred source properties and lens physical parameters depend on the adopted source color because the different color estimates imply different angular source radii. Comparing the $(V-I)_{\rm KMT}$ versus $(I-H)_{\rm KMT,PRIME}$ plane shows that the inferred source colors lie off empirical color–color relations but within the scatter of observed stars. The prevalence of such deviations should be tested with a larger sample of KMTNet–PRIME events and this specific case can be further tested with future adaptive-optics follow-up, which can directly measure the lens–source relative proper motion and lens flux.
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All authors Kansuke Nunota, Jennifer C. Yee, Takahiro Sumi, Ryusei Hamada, Ian A. Bond, Andrew Gould, Weicheng Zang, David P. Bennett, Aparna Bhattacharya, Kotaro Daimon, Yuki Hirao, Stela Ishitani Silva, Shuma Makida, Shota Miyazaki, Tutumi Nagai, Seiya Nakayama, Ryo Ogawa, Ryunosuke Oishi, Hideaki Ose, Nicholas J. Rattenbury, Yuki K. Satoh, Daisuke Suzuki, Takuto Tamaoki, Motohide Tamura, Sean K. Terry, Chihiro Ueda, Aikaterini Vandorou, Hibiki Yama, Michael D. Albrow, Sun-Ju Chung, Cheongho Han, Kyu-Ha Hwang, Youn Kil Jung, Yoon-Hyun Ryu, In-Gu Shin, Yossi Shvartzvald, Hongjing Yang, Dong-Jin Kim, Chung-Uk Lee, Byeong-Gon Park

Astrophysics of Galaxies

Broadband reverberation mapping of quasars at cosmic noon

Juan V. Hernández Santisteban

Broadband reverberation mapping provides a powerful tool to investigate the structure of the accretion flow around supermassive black holes. The ultraviolet region of the quasar spectrum is of particular interest, as it enables the disentanglement of the relative contributions from the accretion disc and the broad-line region to the observed variability of quasars in the local Universe. Observations of quasars at cosmic noon ($z\sim 1-2$) offer the opportunity to probe the UV emission across a diverse population, spanning a broad range of black hole masses and luminosities. Here we re-analysed the 36 multi-year quasar lightcurves from the Dark Energy Survey (DES) between $z\sim0.7-2$ to retrieve interband delays and analyse their spectral energy distribution. Using PyROA, we were able to fit all multiple years of observations and the four optical bands simultaneously, significantly improving the lag detection as this method is able to interpolate over the seasonal gaps. We find robust detections of interband delays in 31/36 quasars, suggesting high-Eddington ratios for a large fraction of objects. Their spectral energy distribution is consistent with a geometrically thin disk $f_\nu\propto\lambda^{-1/3}$, with an ensemble slope of $-0.28\pm0.02$. The full sample of quasars do not show excess around the Balmer jump region, suggesting the impact of the broad-line region to the reverberation signals in high-Eddington sources could be small as documented in some AGN in the local Universe. The prospect of LSST to observe thousands of quasars in this redshift range should motivate the detailed study of the UV-rest frame of high-Eddington quasars to account for the BLR contribution and properly infer disc sizes.
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Astrophysics of Galaxies

Population search for dark matter spikes in megamaser rotation curves

Gonzalo Herrera

A black hole growing adiabatically inside a dark matter halo is expected to develop a dense spike, with a power-law slope between 1.5 and 2.5, depending on redshift and baryonic activity. Direct dynamical tests of this prediction are almost non-existent. Here we show that water megamaser disks offer one; their masers orbit within a parsec of the black hole and are mapped individually with very long baseline interferometry, so the enclosed mass at each radius can be read off the rotation curve. We develop a search method and apply it to eleven megamaser disks with public kinematics. Compared with a black hole alone, a spike is preferred in NGC 1194 and NGC 4258 and moderately improves the fit in several others. Allowing the disks to warp removes this preference in all but NGC 4258 and NGC 6264. No combination of disks, warped or not, allows a spike heavier than about ten per cent of the black hole mass, a sensitivity validated with mock injection tests. Mapping the warps with maser accelerations and detecting fainter inner masers, where a spike and a tilt differ most, can break the remaining degeneracy. Megamaser disks open a window onto dark matter around supermassive black holes, and, importantly, one that enables population statistics.
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Astrophysics of Galaxies · Cross-listed from astro-ph.EP

A Bayesian Inference Framework for Binary Lens Events Fully Incorporating Higher-Order Effects

Kansuke Nunota and Kento Masuda

Higher-order effects, such as microlensing parallax and lens orbital motion, are essential for characterizing the physical properties of microlensing planetary systems including their masses and distances. In practice, higher-order effects are often included in light-curve modeling only when their signals are strong, because their inclusion in weakly constrained cases tends to drive the inferred parameters toward regions of parameter space that are disfavored by standard Galactic models. This binary choice over physically continuous effects introduces an event-dependent selection function that complicates population-level interpretation and prevents strong and weak detections from being combined within a single uniform framework. In this work, we investigate the origin of instabilities associated with higher-order effects, and show that such instabilities can arise from a mismatch between commonly adopted uninformative priors in the light-curve parameter space and the distributions predicted by Galactic models. Motivated by this, we develop a new Bayesian framework that enables higher-order effects to be incorporated in a stable and uniform manner. As part of this framework, we introduce Galactic Prior Modeling Engine (gapmoe), a dedicated tool that enables efficient evaluation of the Galactic prior density and allows it to be incorporated directly into the light-curve inference. Using simulated events, we demonstrate that our framework robustly recovers the true physical parameters while fully accounting for microlensing parallax and lens orbital motion. This framework eliminates the need for ad-hoc model selection and provides a scalable and statistically consistent pathway for analyzing the large samples expected from next-generation surveys such as the Roman Space Telescope.
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Astrophysics of Galaxies

A 210 Megaparsec Ionized Structure at $z=6.8$ Revealed by an Astrophysics Foundation Model

Minghao Yue, Yongda Zhu, Jiani Ding et al. (+2 more)

Reionization is the last major transition in the Universe that transforms the intergalactic medium (IGM) from neutral to highly ionized, yet its spatial structure remains poorly constrained. Using an astrophysics foundation model trained for James Webb Space Telescope datasets, we identify a luminous galaxy at redshift $z=7.567$ showing significant Ly$\alpha$ transmission at $z=6.80\pm0.07$. This transmission, named “the First Ly$\alpha$ transmission in the Reionization Epoch at $z\sim7$" (FL$\alpha$RE-z7), indicates a cosmological-scale ionized structure extending over $210.5^{+55.7}_{-53.5}$ comoving Megaparsecs at cosmic dawn. The hydrogen neutral fraction of the ionized structure is $x_{\rm HI}=(2.07^{+0.29}_{-0.30})\times10^{-6}$, about $10^5$ times lower than the cosmic mean at similar redshifts $(x_{\rm HI}\approx0.4)$. Cosmological simulations suggest a probability of $\approx10^{-5}$ for a random sightline to reproduce the transmission. We find no significant galaxy overdensity associated with the transmission region, in tension with canonical inside-out reionization models. FL$\alpha$RE-z7 severely challenges existing reionization models in the standard $\Lambda$CDM Universe, indicating extreme spatial fluctuation in ionizing radiation or IGM temperature. Our result marks the first example of a foundation model discovering a previously unpredicted astrophysical phenomenon, demonstrating the power of deep learning methods for mining large astronomical datasets and finding unexpected new astrophysics.
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All authors Minghao Yue, Yongda Zhu, Jiani Ding, Xiaohui Fan, Yufeng Luo

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

Everything Everywhere All At Once: A Hierarchical Framework for Mapping Anisotropies in the Local Universe

Aryan Bansal, Edward N. Taylor, Michelle Cluver et al. (+1 more)

We present a Bayesian hierarchical forward model for mapping the local luminosity-density field from heterogeneous redshift surveys. By dividing the survey volume into angular cells and redshift shells, we model the observed galaxy distribution directly in apparent-magnitude and redshift space. This allows us to infer cell-level luminosity functions and densities while preserving each survey's unique selection function. Simultaneously, the ensemble of cells constrains the cosmic-mean luminosity function, its redshift evolution, and the hyperparameters describing cell-to-cell variation. We apply the framework to 2MRS, 6dFGS, and GAMA over $0.005<z<0.065$, combining wide sky coverage with deeper and fainter galaxy samples. The model successfully recovers global $J$-band luminosity-function parameters and a mean luminosity density consistent with previous low-redshift measurements. The inferred luminosity-density scatter decreases with volume, consistent with the cosmic-variance amplitude expected in a $\Lambda$CDM universe. Within the volume we probe, we find no evidence for a large coherent underdensity. Instead, the local Universe is broadly consistent with smooth evolution and cosmic variance. The nearest shell at $z \simeq 0.01$ is the clearest exception, lying $\simeq 0.12$~dex ($\simeq 25\%$) below the smooth global model, a $-2.6\sigma$ underdensity with a one-sided significance of $\simeq 99.5\%$. This framework offers a scalable architecture for mapping cosmic density fields with next-generation wide and deep surveys.
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All authors Aryan Bansal, Edward N. Taylor, Michelle Cluver, Matthew Colless

Monday 28 September

Astrophysics of Galaxies

How well do integral-of-motion distribution functions describe Milky Way-analogue halos?

Jason Kumar and Louis E. Strigari

We study the dark-matter phase space distribution of Milky Way-mass halos in the Auriga simulations, considering both hydrodynamic and dark-matter-only runs. In a spherically averaged potential, we test whether the coarse-grained distribution function can be approximated as a function of the integrals of motion $E$ and $L$. We find that $f(E,L)$ provides a useful description of the simulated halos: although the deviations from this form are formally statistically significant, the median fractional residuals between radial shells are typically $\lesssim 15\%$, with 90th-percentile residuals of order tens of percent. An energy-only approximation, $f(E)$, gives similar median residuals but is systematically disfavored by $\chi^2$ tests, indicating that angular momentum dependence is statistically preferred. Ultimately we find that neither $f(E)$ nor $f(E,L)$ fully describes the particle data at high precision. The remaining residuals likely reflect departures from spherical equilibrium, including anisotropy, triaxiality, substructure, and baryonic effects.
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Astrophysics of Galaxies · Cross-listed from hep-ph

LMC-Perturbed LZ Dark Matter Landscape

Nassim Bozorgnia, Samantha Contreras, Graciela B. Gelmini et al. (+3 more)

The local dark matter (DM) velocity distribution is significantly altered by the gravitational impact of the Large Magellanic Cloud (LMC), which creates a high-velocity tail. We evaluate how the LMC reshapes the DM landscape for a wide variety of theoretical models in light of the recent putative LZ DM event. We show that the LMC-induced velocity shifts substantially modify the parameter space for inelastic endothermic DM models across a broad range of possible interactions, driving the viable regions towards larger mass splittings, which are more susceptible to collider and indirect detection constraints. By contrast, models for elastically colliding DM are less impacted, and some remain viable candidates – for example, the simple light Singlet-Doublet Majorana DM candidate at the Higgs blind spot. Our work confirms that accurately accounting for LMC effects is essential when high-velocity DM is probed, rather than relying on the simplified Standard Halo Model.
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All authors Nassim Bozorgnia, Samantha Contreras, Graciela B. Gelmini, Alvine C. Kamaha, Javier Reynoso-Cordova, Yongheng Xu

Astrophysics of Galaxies

MEGATRON: The Physical Origins of Steep UV Slopes at High Redshift

Harley Katz, Nicholas Choustikov, Aayush Saxena et al. (+7 more)

The ultraviolet (UV) spectral slope, $\beta$, serves as a fundamental probe of stellar population properties and interstellar medium conditions in galaxies. At high redshift, a small sample of galaxies have been confirmed to have extremely blue spectral slopes of $\beta<-2.8$, as measured directly from spectroscopy. One explanation for such galaxies is that they are leaking copious amounts of ionizing photons such that these photons are never processed into the nebular continuum and we are observing the bluer intrinsic slopes of the stellar populations. Here, we use a detailed set of radiation hydrodynamics simulations with parsec-scale resolution and non-equilibrium chemistry to elucidate the physical origin of extremely blue UV slopes at high redshift. We show that, while some extremely blue galaxies (EBGs) do indeed have high escape fractions, a second population of EBGs has $f_{\rm esc}<1\%$. In this second population, the ISM gas densities tend to be much lower, and the timescale for ionization fronts to reach their Strömgren radii can be longer than the main-sequence lifetime of massive stars, leading to a lag in nebular emission. Our results demonstrate that extremely blue UV slopes do not uniquely imply high escape fractions, which highlights the importance of time-dependent (non-equilibrium) nebular emission for interpreting the spectra of galaxies in the early Universe.
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All authors Harley Katz, Nicholas Choustikov, Aayush Saxena, Corentin Cadiou, Martin P. Rey, Jeremy Blaizot, Alex J. Cameron, Fergus Cullen, Taysun Kimm, Kosei Matsumoto

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

Constraining reionization with persistent homology: a novel summary statistic for wide-field Lyman-$\alpha$ emitter observations

Michael M. Wyatt, Nikolaos Triantafyllou, Steven R. Furlanetto et al. (+4 more)

The spatial clustering of Lyman-$\alpha$ emitters (LAEs) is one of the most promising observables for constraining reionization. In this work, we introduce persistent homology, a popular tool in topological data analysis, and specifically the Betti-0 curve as a summary statistic to characterize the clustering of LAEs. We compare the performance of the Betti-0 curve against the angular correlation function (ACF) and void probability function (VPF) by quantifying their ability to constrain the global neutral fraction $x_{\rm HI}$ during reionization using the Fisher information. We forward model observations of LAEs using 21cmFAST by including $\mathrm{Ly}\alpha$ emission as a post-processing step and account for cosmic variance uncertainties. We focus our analysis within the framework of the SILVERRUSH. catalog at $z=5.7$ and 6.6, and find that the Betti-0 curve performs as well as or better than the ACF and VPF. We also find that the statistics are most sensitive to different physical scales and thus probe complementary information, and as a consequence that simultaneously constraining all three statistics improves constraints by a factor of $\sim 2$ compared with the ACF alone, with predicted minimum uncertainties of $\sigma_{\rm min} \sim$ 0.03 and 0.07 at $x_{\rm HI} = 0.05$ and $z=5.7$ and $x_{\rm HI} = 0.20$ and $z=6.6$, respectively. Our results show that the Betti-0 curve is a promising summary statistic to constrain reionization using LAE clustering and motivate further exploration of persistent homology for the same purpose in other wide-field surveys such as those made possible by the Nancy Grace Roman Telescope.
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All authors Michael M. Wyatt, Nikolaos Triantafyllou, Steven R. Furlanetto, Hiroya Umeda, Samuel Gagnon-Hartman, Andrei Mesinger, Masami Ouchi

Astrophysics of Galaxies

CHAMPS: Data Reduction and Detection of ~3300 Dusty Galaxies at 1.2 mm

Felix Martinez III, Jeyhan S. Karaltepe, Andreas L. Faisst et al. (+52 more)

We present the reduction and source catalogs for the \textit{COSMOS High-$z$ ALMA-MIRI Population Survey} (CHAMPS), the largest Atacama Large (Sub)Millimeter Array (ALMA) blank field survey to date at 0.2\,deg$^2$. With observing frequency centered at $250\, $GHz ($1.2\,$mm) and bandwidth of 7.5 GHz, CHAMPS covers the JWST/NIRCam+MIRI footprint in the COSMOS field, taking advantage of the rich, multiwavelength ancillary datasets in COSMOS ranging from X-ray to radio. The majority of the CHAMPS survey (90$\%$) has depths at or below 200 $\mu$Jy beam$^{-1}$ and with an average RMS of 146 $\mu$Jy beam$^{-1}$. The reduced CHAMPS mosaic has a beam size of $\theta_{\rm res} = 1.1'' \times 1.1''$. CHAMPS identifies sources via two detection methods, a blind search for high-SNR sources, and a prior-based search involving MIRI detections to identify faint sources. The blind search yields a total of 595 sources down to an SNR $\ge4.5\sigma$ while the prior catalog yields a total of 3162 source down to an SNR $\ge3\sigma$, leading to a full sample of 3355 unique objects detected across both catalogs. We identify a unique population of 385 SNR $\ge5\sigma$ sources across the two catalogs; after excluding 9 likely spurious edge detections we define a robust science sample of 376 sources above $\ge5\sigma$. These sources have a median redshift of $\langle z_{1.2 \text{ mm}}\rangle = 2.54^{+0.89}_{-1.69}$ based on optical/near-IR/mid-IR photometric redshifts and high-quality spectroscopic redshifts, and hold a median stellar mass of $\langle\log (\rm M_\star/M_\odot)\rangle = 10.79^{+0.42}_{-3.08}$. We have further identified 68/376 ($\sim18\%$) sources as candidate AGN through X-ray, UV-optical, infrared and radio selection techniques.
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All authors Felix Martinez III, Jeyhan S. Karaltepe, Andreas L. Faisst, Arianna S. Long, Jorge A. Zavala, Caitlin M. Casey, Jed McKinney, Ezequiel Treister, Maximilien Franco, Sune Toft, Manuel Aravena, John D. Silverman, Hollis B. Akins, Hiddo S. B. Algera, Jacqueline Antwi-Danso, Andrew J. Battisti, Yingjie Cheng, Olivia R. Cooper, Nicole E. Drakos, Carter Flayhart, Fabrizio Gentile, Steven Gillman, Ghassem Gozaliasl, Santosh Harish, Simon Hempel-Costello, Michaela Hirschmann, Olivier Ilbert, Bingcheng Jin, Shuowen Jin, Koki Kakiichi, Thresa Kelly, Zihao Li, Daizhong Liu, Lun-Jun Liu, Sinclaire M. Manning, Henry Joy McCracken, Romain A. Meyer, Louise Paquereau, Maria Pudoka, Jason Rhodes, Brant E. Robertson, Giulia Rodighiero, Rasha M. Samir, David B. Sanders, Marko Shuntov, Margherita Talia, Mattia Vaccari, Francesco Valentino, Aswin P. Vijayan, Feige Wang, Wuji Wang, Can Xu, Jinyi Yang, Yongda Zhu, Siwei Zou

Astrophysics of Galaxies

Snapshots of r-process production in the Milky Way disk

Sarah G. Kane, Stephanie Monty, Madeleine McKenzie et al. (+9 more)

Stars enhanced in heavy neutron capture elements like europium (Eu) provide a window into the rarest and most exotic nucleosynthetic events. Most Eu-enhanced stars discovered thus far are found among metal-poor populations, with $\mathrm{[Fe/H]}<-1.0$. Here, we report the discovery of $17$ vetted Eu-enhanced stars ($\mathrm{[Eu/Fe]}>0.7$) in the Milky Way disk with metallicities in the range $-0.87<\mathrm{[Fe/H]}<-0.21$ identified from among $74\,717$ stars in the GALAH survey. 14 of these stars additionally have $\mathrm{[Ba/Eu]}<0$, marking enhancement from the rapid neutron capture ($r$-) process and making these r-II stars. Included in their number is a star with a remarkably high $\mathrm{[Eu/H]}=1.01\pm0.09$ at $\mathrm{[Fe/H]}=-0.21$. In addition to Eu, all 17 stars show enhancements in other neutron capture elements, especially in Nd, while otherwise appearing chemically consistent with typical disk stars, particularly in their $\alpha$-element abundances. Two of the Eu-enhanced stars exhibit indications of binarity with strong enrichment in Ba and Y, marking potential signatures of the slow or intermediate neutron capture processes. This sample of 17 Eu-enhanced stars, which span both the high- and low-$\alpha$ disks, are valuable tracers of neutron capture processes, including the $r$-process, at high metallicities. Although we use criteria for Eu-enhanced stars typically applied to the halo to enable comparison to literature studies of $r$-process enhanced stars, we propose a new, metallicity-dependent selection for Eu enhancement that is better-suited to the regime of the Galactic disk.
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All authors Sarah G. Kane, Stephanie Monty, Madeleine McKenzie, HanYuan Zhang, Sven Buder, Terese Hansen, Tadafumi Matsuno, Jason Sanders, Anke Ardern-Arentsen, Vasily Belokurov, Zofia Kaczmarek, Andrew Garner

Astrophysics of Galaxies

MOCSS: Multi-Object Coronagraphy for JWST/NIRSpec Slitless Spectroscopy

Mason S. Huberty, Claudia Scarlata, Matthew J. Hayes et al. (+10 more)

We present an experimental JWST/NIRSpec observational method to obtain $R\gtrsim1000$ G140M/F100LP slitless spectroscopic observations. This "Multi-Object Coronagraphy for Slitless Spectroscopy" (MOCSS) technique involves opening essentially all microshutters on NIRSpec simultaneously while closing shutters corresponding on-sky with known bright objects. Through observations of the Hubble Ultra Deep Field, we demonstrate the discovery potential of these deep, high resolution observations without the need for target pre-selection. We obtain a catalog of 22 secure multi-line emitters at $1.3<z<4.6$, with observations of [OII], [OIII], H$\alpha$, H$\beta$ and [NII] lines, accounting for $\sim80\%$ of the emission lines identified directly in the dispersed images. The MOCSS survey provides first time spectroscopic redshifts for 18 of these sources. We also demonstrate that first order traces of the NIRSpec/G140M/F100LP observing mode extend substantially beyond the nominal $\sim1.89\rm \mu m$ red cutoff, as far as $2.94\rm \mu m$ in the most extreme case. Compared to existing NIRISS WFSS of similar exposure times, we find that the MOCSS technique can observe very faint lines while covering the full $1-2 \rm \mu m$ regime without gaps in wavelength coverage. This study describes the highest-resolution slitless spectroscopy campaign of the $1-2 \rm \mu m$ regime and emphasizes the discovery potential of this unorthodox observational technique.
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All authors Mason S. Huberty, Claudia Scarlata, Matthew J. Hayes, Alaina Henry, Danielle A. Berg, Vieri Cammelli, Richard Ellis, Anne E. Jaskot, Matilde Mingozzi, Pierluigi Monaco, Alberto Saldana-Lopez, Jonathan C. Tan, Alice Young

Astrophysics of Galaxies

An Off-Nuclear Tidal Disruption Event Discovered At Late Times: The Case Of TDE 2023mfm

Itai Sfaradi, Ryan Chornock, Yuhan Yao et al. (+24 more)

We present the discovery and analysis of the optically selected tidal disruption event (TDE) 2023mfm, which originates from a wandering massive black hole (MBH) in a massive ($\sim 10^{11} \,$M$_{\odot}$) galaxy hosting a central low-luminosity active galactic nucleus (AGN). Our analysis of the ZTF, Lick, Keck, Swift, Chandra, XMM-Newton, HST, and VLA observations reveals that TDE 2023mfm is a TDE-H from a $10^{6.2 \pm 0.5}\,$M$_{\odot}$ black hole which is offset by $0.66 \pm 0.02$" from the center of its host galaxy, corresponding to a projected distance of $1.08 \pm 0.04$ kpc. TDE 2023mfm displays all the traits of optically selected TDEs. The emission remains hot, $T_{\rm bb} \sim 22,000 \pm 1,000$ K, for more than a month after peak, and the $g$-band light curve peaks at $\left( 2.24^{+0.10} _{-0.11} \right) \times 10^{43} \, \rm erg \, s^{-1}$ and stays above half-maximum luminosity for $47.8^{+3.7}_{-3.5}$ days. The late-time optical-to-UV emission observed with the HST suggests the presence of an unresolved stellar population with a stellar mass of $10^7-10^8\,$M$_{\odot}$ at the position of the TDE, possibly being a low-mass dwarf galaxy or a stripped galaxy from a previous minor merger. The radio emission from TDE 2023mfm emerges at least a year after optical discovery, and we find it likely that it originates from a delayed outflow, however, further observations are needed to determine its true origin.
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All authors Itai Sfaradi, Ryan Chornock, Yuhan Yao, Erica Hammerstein, Jean Somalwar, Raffaella Margutti, Huei Sears, Robert Stein, Natalie LeBaron, Adelle J. Goodwin, Sjoert van Velzen, Matthew J. Graham, Kate D. Alexander, Nayana A. J., Edo Berger, Jonathan Carney, Yvette Cendes, Collin T. Christy, Walter W. Golay, Wenbin Lu, James C. A. Miller-Jones, Charlotte Ward, Eli Wiston, Tracy X. Chen, Mansi M. Kasliwal, Frank J. Masci, Jesper Sollerman

Astrophysics of Galaxies

A Systematic Assessment of Total Stellar Mass Measurements with Spatially Resolved Photometry and Medium Bands at 1 < z < 9: The Impact of Mass-to-Light Variations and Outshining

Naadiyah Jagga, Adam Muzzin, Visal Sok et al. (+16 more)

JWST NIRCam spatially resolved photometry enables studies of galaxies' stellar populations and stellar masses on sub-kpc scales. We use JWST (CANUCS, Technicolor, JUMPS) and HST data, covering wide- and medium-band UV-IR filters to study the stellar mass bias between spatially resolved and integrated photometry of $\sim$3000 galaxies at 1 $<z_{\mathrm{phot}}<$ 9. The 2D parameter maps reveal spatial variations in stellar mass and populations, showing that integrated measurements systematically underestimate stellar masses. We find that the stellar mass bias remains small for galaxies with specific star formation rate $\mathrm{sSFR} < 10^{\mathrm{-9}}$ yr$^{\mathrm{-1}}$, but increases for galaxies with $\mathrm{sSFR} > 10^{\mathrm{-8.5}}$ yr$^{\mathrm{-1}}$. For these high-sSFR galaxies, the median offset reaches $\Delta \log_{\mathrm{10}} (M_{\ast})$ $\sim$ -0.36 dex with the largest bias occurring in low-mass ($M_{\ast} \leq 10^{\mathrm{ 9.5}} M_{\odot}$) galaxies. These results are consistent with the outshining of older populations by recent star formation. High-sSFR galaxies also show spatial variations in their mass-to-light ratios ($M_{\ast}/L_{V}$): the stellar mass bias decreases with $\sigma[\log_{\mathrm{10}}(M_{\ast}/L_{V})]$ for galaxies with $10^{\mathrm{-8}} \leq \mathrm{sSFR}[\mathrm{yr}^{\mathrm{-1}}] < 10^{\mathrm{-9}}$, with the strongest trend for $10^{\mathrm{-7}} \leq \mathrm{sSFR}[\mathrm{yr}^{\mathrm{-1}}] < 10^{\mathrm{-8}}$, quantified by the Spearman correlation coefficient $\rho_{\rm S}=-0.37$. While medium bands are important for constraining stellar masses from integrated photometry, spatially resolved photometry reduces the impact of their absence, with dispersion offsets of $\Delta \log_{\mathrm{10}} (M_{\ast})$ = 0.33 dex for integrated photometry but 0.15 dex for resolved photometry when only wide-bands are included.
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All authors Naadiyah Jagga, Adam Muzzin, Visal Sok, Vivian Yun Yan Tan, Ghassan Sarrouh, Kartheik Iyer, Yoshihisa Asada, Chris J. Willott, Maruša Bradač, Nicholas S. Martis, Gaël Noirot, Gregor Rihtaršič, Marcin Sawicki, Sunna Withers, Jacqueline Antwi-Danso, Samantha C Berek, Danilo Marchesini, Maya Merchant, Katherine Myers

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

Bayesian Evidence for Inspiraling Hotspot Motion in the Galactic Center

Pablo Ruales, Maciek Wielgus, Delilah E.A. Gates et al. (+1 more)

During flaring episodes, polarimetric observations of the Galactic Center black hole Sagittarius A* (Sgr A*) reveal evolving, loop-like trajectories in the Stokes Q-U plane, the so-called Q-$U loops. Keplerian models of transiently energized orbiting features, hotspots, have been employed to reproduce these polarimetric signatures. In this work, we develop a Bayesian framework to infer the time-dependent kinematics of the hotspot from polarized light curves, using a general prescription for its motion. We model the emitting region's trajectory as a continuous, piecewise sequence of K kinematic segments, each described by radial and azimuthal velocity parameters. We perform analyses with K=1,2,3 and compare these models to millimeter-wavelength ALMA observations of Sgr A* from 2017 April 11 that include two subsequent Q-U loops, extending the observational constraints on the kinematics. We examine the effects of the local magnetic field geometry, spectral index, and kinematic profile of the hotspot's trajectory on the polarized signal. We find statistically significant evidence that the emitting region follows a non-geodesic inspiraling trajectory, and this preference over a strictly Keplerian orbit strengthens sharply when a longer data segment is modeled. The inspiraling non-Keplerian models are preferred to a purely Keplerian model based on both the Bayesian log-evidence comparison and the reduced chi-square statistic. Our results offer new insight into the nature of flaring events in the Galactic Center and the episodically produced hotspots associated with them.
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All authors Pablo Ruales, Maciek Wielgus, Delilah E.A. Gates, Alejandro Cardenas-Avendano

Astrophysics of Galaxies

CHAMPS: The COSMOS High-Redshift ALMA-MIRI Population Survey - A New Census of the Dusty Early Universe

Andreas L. Faisst, Felix Martinez III, Jeyhan S. Kartaltepe et al. (+86 more)

Understanding how dust forms and evolves over cosmic time is a key open problem in extragalactic astrophysics. Galaxies in the early Universe were once thought to be mostly dust-poor, but recent discoveries of heavily dust-obscured galaxies near the Epoch of Reionization challenge models of early dust production and raise new questions about the true cosmic star formation rate density. In this paper, we present the COSMOS High-Redshift ALMA-MIRI Population Survey (CHAMPS), which sheds light on the dusty early universe at z>4. CHAMPS is a new 144h ALMA 1.2mm (band 6) large program mapping the combined JWST/NIRCam+MIRI footprint in the COSMOS field. It covers 0.2deg2 with a synthesized beam size of 1.1" and a sensitivity of 0.14mJy/beam. It is complemented, alongside JWST, by ancillary X-ray, UV, optical, sub-mm, and radio data. CHAMPS, optimized as a blind survey, detects above 5$\sigma$ approximately 385 individual dusty high-redshift sub-mm sources, 68 dusty AGN, and a dozen dusty galaxies at z>6. The galaxies are largely not detected in JWST/F150W, making them prototypical near-IR dark galaxies. We showcase three of the highest-redshift most dusty and massive candidate galaxies detected in CHAMPS with redshifts up to z=7.5. CHAMPS also enables stacks of thousands of galaxies grouped in bins of various physical parameters. Its sub-mm coverage of dust-attenuated JWST-identified galaxies provides robust constraints on dust masses and obscured star formation rates to study early dust formation and evolution. In addition, CHAMPS enables a blind search for luminous CO line emitters at z=0.4-2.7 and [CII]158$\mu$m emitters at z=6.7.
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All authors Andreas L. Faisst, Felix Martinez III, Jeyhan S. Kartaltepe, Manuel Aravena, Caitlin M. Casey, John D. Silverman, Sune Toft, Ezequiel Treister, Jorge A. Zavala, Hiddo S. B. Algera, Andrew J. Battisti, Michele Catone, Jaclyn B. Champagne, Yingjie Cheng, Rasha M. Samir, Maximilien Franco, Kyle Finner, Carter Flayhart, Fabrizio Gentile, Ghassem Gozaliasl, Santosh Harish, Shuowen Jin, Yu-Heng Lin, Lun-Jun Liu, Arianna S. Long, Crystal L. Martin, Bahram Mobasher, Francesca Pozzi, Huimin Qu, Chuan Tian, Mattia Vaccari, Wuji Wang, Can Xu, Hollis B. Akins, Micaela B. Bagley, Angela Bongiorno, Kevin C. Cooke, Olivia R. Cooper, Simon Hempel-Costello, Ivan Delvecchio, Nicole E. Drakos, Andrea Enia, Steven L. Finkelstein, Seiji Fujimoto, Steven Gillman, Carlos Gomez-Guijarro, Jorge Gonzalez-Lopez, Michaela Hirschmann, Olivier Ilbert, Kei Ito, Knud Jahnke, Boris S. Kalita, Daichi Kashino, Vasily Kokorev, Thomas S.-Y. Lai, Erini Lambrides, Daizhong Liu, Georgios E. Magdis, Vincenzo Mainieri, Sinclaire M. Manning, Claudia Maraston, Richard Massey, Henry Joy McCracken, Jed McKinney, Wilfried Mercier, Thibaud Moutard, Masafusa Onoue, Louise Paquereau, Alvio Renzini, Jason Rhodes, R. Michael Rich, Brant E. Robertson, Giulia Rodighiero, David B. Sanders, Claudia M. Scarlata, Nick Scoville, Kartik Sheth, Marko Shuntov, Laura Sommovigo, Martin Sparre, Tomoko L. Suzuki, Margherita Talia, Benny Trakhtenbrot, Francesco Valentino, Brittany N. Vanderhoof, Eleni Vardoulaki, Aswin P. Vijayan, Katherine E. Whitaker, Stephen M. Wilkins

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

Enhanced density fluctuations: consequences for stellar dynamics and dark matter substructure

Wenzer Qin, David E. Kaplan and Neal Weiner

Enhanced density fluctuations form early dark matter halos, which serve as early gravitational potential wells for baryons. These baryons can then condense to form stars and black holes at high redshifts, $1+z \gtrsim 100$. Larger density fluctuations result in denser halos with higher virial temperatures; hence, a halo at a mass that is below the threshold for forming stars under standard astrophysical expectations may form astrophysical objects if its initial density is higher than expected, although the exact threshold for compact object formation is subject to large astrophysical uncertainties. We outline the conditions under which enhanced density fluctuations form dark (star-less) halos, early galaxies, or even star clusters. Using toy model enhancements to the primordial power spectrum that have been shown to explain the abundances of “little red dots", along with our fiducial set of astrophysical parameters, we show that the number of clusters initially captured by the Milky Way is highly sensitive to the shape of the enhancement, with the narrowly peaked enhancement resulting in $50$ clusters and the step-function enhancement resulting in $\sim 4.1 \times 10^5$. The initial stellar masses of the clusters is also $O (100) \,M_\odot$, although this range is also dependent on the shape of the enhancement. In addition, the abundance of dark matter subhalos with masses greater than $10^7 \, M_\odot$ can be enhanced by as much as a factor of $\sim 6.5$ and is denser than in $\Lambda$CDM, which will increase their detectability in future stellar stream surveys such as the Via Project.
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Astrophysics of Galaxies

COSMOS-3D: Diverse Environments and Hot-dust Signatures among Dusty Star-forming Galaxies at $z$ = 4.9-7.2

Siwei Zou, Manuel Aravena, Shaoze Geng et al. (+20 more)

Dusty star-forming galaxies (DSFGs) are expected to trace early massive-halo assembly, but the connection between dust-obscured star formation, morphology, hot dust, and environment remains unclear at $z$>4. We combine JWST/NIRCam F444W grism spectroscopy from COSMOS-3D with MIRI F1000W/F2100W imaging and a mixed ALMA-selected and ALMA-followed dusty-galaxy sample from CRISTAL, CHAMPS, REBELS, and A3COSMOS to study 18 DSFGs or DSFG candidates at z=4.9-7.2. We compare their environments with the parent spectroscopically confirmed emission-line sample and the COSMOS-Web photo-z galaxy sample using separate and combined overdensity estimators. The parent narrow-line H$\alpha$ sample has a median observed, dust-uncorrected ${\rm SFR}_{\rm H\alpha}=11.7 M_\odot~{\rm yr^{-1}}$. Within R=0.5 pMpc, DSFGs have a median $\delta_{\rm spec+phot}=0.92^{+0.06}_{-0.16}$, compared with $0.80^{+0.05}_{-0.04}$ for HAEs, with a stronger contrast on smaller scales. The strongest compact overdensities are associated with merger/interacting morphology: merging DSFGs reach $\delta_{\rm spec+phot}=4.70^{+1.61}_{-1.51}$ within R=0.5 pMpc. In contrast, MIRI-bright DSFGs do not show an enhanced number of nearby visible H$\alpha$-emitting companions, and their F2100W fluxes are difficult to explain with the 3.3 $\mu$m PAH feature alone, suggesting an additional hot-dust component. These results are consistent with a possible phase-dependent picture in which the compact line-emitter core, merger-driven dusty phase, and MIRI-bright hot-dust phase need not be spatially or temporally identical during early structure growth.
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All authors Siwei Zou, Manuel Aravena, Shaoze Geng, Romain A. Meyer, Jianwei Lyu, Jaclyn B. Champagne, Jia-Sheng Huang, Andreas L. Faisst, Shuqi Fu, Andrew J. Battisti, Hiddo Algera, Caitlin M. Casey, Xiaohui Fan, Maximilien Franco, Ghassem Gozaliasl, Linhua Jiang, Koki Kakiichi, Darshan Kakkad, Zihao Li, Lun-Jun Liu, Felix Martinez III, Jorge A. Zavala, Rasha M. Samir

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

JWST lensed quasar dark matter survey V: Hints of self-interacting dark matter from 29 quadruply imaged quasars

D. Gilman, A. M. Nierenberg, J. Gurian et al. (+21 more)

Theories of self-interacting dark matter (SIDM) predict the eventual core collapse of dark matter halos, a process that transforms these structures into extremely efficient gravitational lenses. We present a population-level inference on the abundance of core collapsed halos and subhalos in the mass range $10^6 - 10^{10.7} M_{\odot}$ using 29 quadruply imaged quasars, drawing on the collective lensing signal of many low-mass perturbers. Our structure formation model predicts the abundance of collapsed (sub)halos as a function of halo mass and redshift. We quantify how our results are affected by systematic uncertainties, including the abundance of globular clusters (GCs) and subhalos, and the internal structure of deeply collapsed halos. Our data exhibits a strong preference for core collapsed halos in the lens model, with Bayes factors disfavoring CDM relative to SIDM ranging from 8:1 to 24:1, depending on the assumed SIDM subhalo abundance and the internal structure of collapsed halos. Explaining our data without core collapse requires both a GC abundance well above expectations and more subhalos than predicted by $N$-body simulations. These results pose a challenge to the CDM paradigm. We present a particle physics interpretation of these results in a companion paper.
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All authors D. Gilman, A. M. Nierenberg, J. Gurian, H. Paugnat, C. Gannon, M. N. Martinez, T. Treu, K. N. Abazajian, T. Anguita, V. N. Bennert, A. J. Benson, S. Birrer, S. G. Djorgovski, S. F. Hoenig, R. E. Keeley, A. Kusenko, M. Millon, T. Morishita, L. A. Moustakas, P. Mozumdar, D. Paris, W. Sheu, D. Sluse, K. C. Wong

Astrophysics of Galaxies

The 1.6 $\mu\mathrm{m}$ $\rm{H^{-}}$ bump as a diagnostic of TP-AGB contributions and recent quenching. I. Insights from stellar population models

Pengjun Lu, Song Huang, Shiying Lu et al. (+3 more)

The 1.6 $\mu\mathrm{m}$ $\rm{H^{-}}$ bump arises from a minimum in the opacity of the negative hydrogen ion in cool stellar atmospheres. Although it is recognized as a common feature in galaxy spectra, its potential for studying stellar populations and recent quenching remains little explored. Its enhancement at intermediate ages is strong in some stellar population models with substantial thermally pulsing asymptotic giant branch (TP-AGB) contributions but weak or absent in others. This variation makes the feature both a potential age diagnostic and a source of model uncertainty. We use models based on the X-shooter Spectral Library (XSL) and Flexible Stellar Population Synthesis (FSPS) to examine what drives this behavior and what it can reveal about quenching. Controlled FSPS experiments show that the $\rm{H^{-}}$ bump depends on both the amount of TP-AGB light and the stellar template used to represent it. The adopted XSL and TP-AGB-on FSPS models predict a transient enhancement following rapid quenching, with a different age response from optical spectral features. Combining these diagnostics can therefore provide additional information about recent quenching, although the interpretation depends on the population model and star-formation history. An illustrative comparison with existing JWST spectra shows that models including TP-AGB contributions can describe the observed $\rm{H^{-}}$ region reasonably well. These results motivate further use of the $\rm{H^{-}}$ bump to test TP-AGB prescriptions and investigate quenching with current and forthcoming observations.
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All authors Pengjun Lu, Song Huang, Shiying Lu, Meng Gu, Li Shen, Cheng Li

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

GameDev: GPU-accelerated model for dust evolution

Jiaqing Bi

Grain growth and fragmentation through dust collisions in protoplanetary disks are strongly coupled with dust dynamics. This is because the spatial and velocity distributions of dust set the collision rates and outcomes, while dust grain sizes set the aerodynamic coupling with gas. However, existing dust evolution codes often rely on prescribed dust velocities and are mostly restricted to one or two spatial dimensions. In this work, we present GameDev, a dust evolution model accelerated by graphics processing units (GPUs) that couples independently evolved three-dimensional dust dynamics with Monte Carlo collisional evolution of dust. In GameDev, we model dust as Lagrangian representative particles in a prescribed gas disk. We integrate particle trajectories with the staggered semi-analytic method, which remains accurate for both tightly and weakly coupled dust grains. We estimate collision rates from each particle's nearest neighbors rather than on a grid, preventing physically close particles from being excluded from collision sampling because they lie across a grid boundary. Most importantly, we sample collision events against neighborhoods that remain frozen over adaptive intervals, enabling massive parallelization across particles. These implementations make GameDev an accurate and efficient tool for studying dust evolution in protoplanetary disks. GameDev supports both NVIDIA CUDA and AMD ROCm platforms, provides a smaller-scale standalone Eulerian dust fluid model, and is publicly available on GitHub.
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Astrophysics of Galaxies · Cross-listed from astro-ph.SR

Discovery of over a thousand variable stars in Terzan 5 and Liller 1 with JWST

Kevin B. Burdge, Ilaria Caiazzo, Malina M. Desai et al. (+18 more)

The Bulge Fossil Fragments Terzan 5 and Liller 1 host some of the densest stellar environments in the Galaxy, yet their variable star populations have remained largely unexplored due to crowding and heavy obscuration. Here, we identify 1,315 variable sources in these two systems in what is to our knowledge the first JWST time-series variability census of a globular cluster-like object. By differencing consecutive non-destructive reads within each NIRCam integration, we transform sample-up-the-ramp imaging into an infrared movie sampled every 21 seconds. More than a century of observations has cataloged 5,604 variables, the majority of them pulsating stars, across 151 Galactic globular clusters. Our census alone amounts to 23 percent of that total and contains more photometrically variable binaries than had previously been cataloged in all globular clusters combined. The field of Liller 1, with zero previously known variables, now hosts 915, nearly double the count in the runner-up $\omega$ Centauri. We detect dramatic infrared variability from the Rapid Burster, revealing the counterpart sought since 1976 (see Desai et al. 2026), and blindly recover a signal coincident with the prototype redback pulsar PSR J1748-2446A at its radio-timed orbital period, identifying the first optical or infrared counterpart to any of Terzan 5's pulsars. More broadly, we present a technique that recovers group-level time-series photometry from JWST observations, enabling time-domain studies with an observatory whose field of view is naturally matched to the Galaxy's densest stellar systems.
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All authors Kevin B. Burdge, Ilaria Caiazzo, Malina M. Desai, Cristina Pallanca, Vera L. Berger, Kaley Brauer, Matteo Correnti, Paul Draghis, Kareem El-Badry, Francesco R. Ferraro, Denis González-Caniulef, Kyle Kremer, Barbara Lanzoni, Dongzi Li, Jessica R. Lu, Geoffrey Mo, Mason Ng, Roger W. Romani, Kaitlyn Shin, Daniel R. Weisz, Giorgia Zullo

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

LIMFAST. V. Probing Reionization with the Synergy Between 21 cm and Photometric Galaxy Surveys

Guochao Sun, Adam Lidz, Tzu-Ching Chang et al. (+4 more)

Cross-correlating the 21\,cm signal from intergalactic neutral hydrogen with the galaxy distribution is a powerful probe of the Epoch of Reionization and the physical mechanisms driving it. While upcoming surveys with the SKA-Low radio telescope and the Roman Space Telescope offer ideal synergies for this measurement, foreground mitigation of 21\,cm data requires exquisite redshift precision of galaxies, effectively excluding the rich photometrically selected samples of Lyman-break galaxies (LBGs) with typical redshift uncertainties $\sigma_z \gtrsim 0.1$. We overcome this challenge using a squared statistic of the foreground-cleaned 21\,cm signal. Squaring the filtered 21\,cm signal couples surviving high $k_\parallel$ modes into low $k_\parallel$ fluctuations accessible to photometric LBG surveys. This higher-order cross-correlation statistic remains measurable even when direct cross-correlations are strongly suppressed. Applying Fisher matrix analysis to this LBG–21\,cm$^2$ cross-correlation signal simulated by the LIMFAST code over $6 \lesssim z \lesssim 10$, we investigate the prospects for constraining EoR physics combining SKA-Low 21\,cm measurements and Roman photometric galaxy samples. For an overlapping survey area covering 10\,deg$^2$, we find that the LBG–21\,cm$^2$ cross-correlation is detectable at high significance across much of the EoR through 1000\,hours of SKA-Low integration with 15\,MHz bandwidth and a Roman photometric galaxy sample from the High-Latitude Wide-Area Survey (HLWAS) reaching $m_\mathrm{AB,lim}=27$ and photo-$z$ uncertainties of $\sigma_z \sim 0.1$–0.3. The characteristic sign evolution of the large-scale cross-power spectrum—driven primarily, though not exclusively, by the evolving neutral fraction—provides strong constraints on the physical parameters governing the ionization and thermal history of the IGM.
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All authors Guochao Sun, Adam Lidz, Tzu-Ching Chang, Claude-André Faucher-Giguère, Steven R. Furlanetto, Aritra Kundu, Jordan Mirocha

Astrophysics of Galaxies

GA-NIFS view of LAP1: Assembly of Pop~III stellar clusters during EoR

J. Scholtz, R. Maiolino, S. Carniani et al. (+28 more)

Lensed and Pristine 1 (LAP1) is one of the most promising candidates for the detection of so-called Pop~III stars at $z\sim6.6$. In this work, we present new high-spectral-resolution ($R \sim 2700$) \jwst NIRSpec-IFS observations of the system along with a detailed re-analysis of all archival \jwst and VLT/MUSE data. We confirm the very low metallicity of the system, with $12+\log(\text{O/H})=6.5\text{--}6.8$ (1–2% Z$_{\odot}$), and its low stellar mass, with $M_{*}= 10^{3\text{--}4}$ \Msun, based on the non-detection in \jwst/NIRCam filter stacks and the \Hbeta luminosity. The high-resolution IFS data allow us to constrain the upper limits on the dynamical masses ($\log_{10}(M_{*}/M_{\odot})$) of the A and B components to $<6.6\text{--}7.6$ and $<5.6\text{--}6.6$, respectively. Based on the metallicity and the high equivalent width of \Halpha (EW $>1200$\,Å), we estimate the possible range of the LAP1 stellar population ages to be $2\text{--}5$~Myr, consistent with the first burst of star formation in a pristine environment. Based on the size ($<10$~pc) and mass of the system, we discuss the nature of LAP1 as representing the formation of the first stellar clusters in a larger undetected galaxy, similar to other low-metallicity Pop~III candidates in the literature.
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All authors J. Scholtz, R. Maiolino, S. Carniani, E. Vanzella, R. J. Terlevich, H. Übler, M. Perna, S. Arribas, E. Bertola, P. Bergamini, T. Böker, A. Bolamperti, A. Bunker, S. Charlot, M. Curti, F. D'Eugenio, C. Grillo, L. R. Ivey, X. Ji, G. C. Jones, M. Meneghetti, M. M. Messa, R. Pascalau, B. Rodríguez Del Pino, P. Rosati, E. Rusta, S. Salvadori, E. Terlevich, G. Venturi, S. Zamora, A. Zanella

Astrophysics of Galaxies

Massive Population III Galaxies Near a GN-z11 Analog: The Role of the Baryon-Dark Matter Streaming Velocity

Eli Visbal, Greg L. Bryan and Ryan Hazlett

Recently the James Webb Space Telescope (JWST) detected Hebe, a Population III (Pop III) candidate located ${\sim}3$ kpc in projection from the massive $z=10.6$ galaxy GN-z11. This raises the question of whether Pop III star formation is expected in the vicinity of massive high-redshift galaxies or whether it would be prevented by early metal enrichment. We address this with a semi-analytic model of Pop III and metal-enriched star formation applied to a zoom-in N-body simulation of a highly overdense region surrounding a GN-z11 analog. The zoom-in region resolves the minihalos where the first stars form. We find that Pop III and metal-enriched star formation both occur earlier, and with a higher star formation rate density, than in a typical mean-density environment. The majority of Pop III star formation in minihalos ends by $z\sim15$; however, we identify a distinct population of late-forming Pop III galaxies that form near the central galaxy. These systems have their star formation delayed due to ionizing feedback from the central GN-z11 analog and experience a Lyman-Werner (LW) intensity of ${\sim}10$ - $100~J_{21}$, potentially leading to massive Pop III starbursts similar to Hebe. Interestingly, the abundance of these Pop III galaxies depends strongly on the baryon-dark matter streaming velocity, $v_{\rm bc}$, because a higher streaming velocity allows halos to remain chemically pristine for longer. None of these late-forming Pop III sources occur for $v_{\rm bc}=0$, while many form at high $v_{\rm bc}$. Averaging over the expected distribution of streaming velocities, we predict that of order four GN-z11-like galaxies would need to be surveyed at $z\sim11$ to expect to find one such source. We also note these environments may provide a natural formation site for heavy black hole seeds.
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Astrophysics of Galaxies

Photoelectron and electron microscopy investigation of laboratory grown Mg-silicate space dust analogues

Steffen Friis Holleufer, Mie Andersen, Frederik Granzow Doktor et al. (+9 more)

The atomic structure at the surface of interstellar silicate dust particles likely plays a key role in a variety of chemical processes occurring in star- and planet-forming regions of the interstellar medium (ISM). Here, we use the photoelectric effect to characterize, in situ, the local chemical structure of Mg-silicate nanoparticulate films, and ex situ electron microscopy to trace changes to morphology resulting from different starting compositions. Nanoparticulate films are prepared via co-deposition of Si, Mg and O atoms on a graphitic substrate under ultra-high vacuum (UHV) and are characterised with X-ray photoelectron spectroscopy and near edge X-ray absorption fine structure measurements. Analysis, supported by density functional theory calculations, shows that adjusting the Mg-to-Si ratio from 3.5 to 1.8 changes particle composition from a mixture of MgO and Mg-silicate towards predominantly Mg-silicate. Annealing in UHV also pushes the composition towards Mg-silicate, however, non-stoichiometric chemical motifs are always observed, presenting a distribution of potentially catalytically active sites. Electron microscopy images show composition-dependent film morphologies that restructure differently upon thermal annealing. The Mg-silicate nanoparticulate films presented here are characterised as a 2D version of ISM analogue dust particles prepared via laser ablation and are therefore a more readily suitable model for surface science investigations into the catalytic properties of interstellar Mg-silicate dust.
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All authors Steffen Friis Holleufer, Mie Andersen, Frederik Granzow Doktor, Lars Eric Borchert, Martin Wibrand Larsen, Duncan S. Sutherland, Zheshen Li, Alexei Preobrajenski, Jeppe Vang Lauritsen, Cornelia Jäger, Liv Hornekær, Andrew Cassidy

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

Reconstructing Implicit Scientific Knowledge: Evaluating LLM Agents through End-to-End Reproduction of Astronomy

Yuehui Wang, Xinyu Qi, Guirong Xue et al. (+4 more)

The integration of large language models (LLMs) into scientific workflows is accelerating, yet their ability to reconstruct the reasoning underlying published research remains unexplored. Papers specify explicit procedures while leaving many methodological dependencies-data selection, calibration corrections, priors, and domain assumptions-implicit. This ambiguity complicates the evaluation of LLM-based agents, since a failure to reproduce a result may reflect either limitations of the agent or underspecification in the source. We present a framework that evaluates agents through end-to-end reproduction, separating execution from verification and computational failure from methodological ambiguity. We apply it to fourteen astronomy studies: a case study from The Astrophysical Journal and thirteen papers published in Nature. Eleven of the thirteen contained an ambiguity preventing a uniquely specified reproduction path. In a controlled case study, twelve predefined paths, a 3x2x2 sensitivity analysis over sample definition, sky masking, and parallax zero-point treatment-gave estimates from 2.16 to 3.53 kpc for the same quantity, with only one recovering the published value (about 2.70 kpc). The published value was never used as an optimization target, selection criterion, or stopping condition; the matching path was found only after all twelve had run. Crucially, the decisive information (a +0.02 mas parallax zero-point correction) was already in the paper, but the agents did not recognize its causal relevance until the analysis made the effect visible. Matching a published outcome therefore does not validate reconstruction of the underlying reasoning, and the bottleneck is as often a failure to connect relevant information as to retrieve it. End-to-end reproduction thus serves both as a test of reproducibility and as a framework for evaluating implicit scientific knowledge in AI systems.
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All authors Yuehui Wang, Xinyu Qi, Guirong Xue, Cheng Wang, Yangbin Xie, Xiaoyu Tang, Cong Sun