The GALAH Survey: Neutron-Capture Elemental Abundances for 350,000 Gaia-RVS spectra and the Chemodynamics of Accreted Structures

[2606.04567] The GALAH Survey: Neutron-Capture Elemental Abundances for 350,000 Gaia-RVS spectra and the Chemodynamics of Accreted Structures Skip to main content Search Submit Donate Log in Astrophysics > Astrophysics of Galaxies arXiv:2606.04567 (astro-ph) [Submitted on 3 Jun 2026 ( v1 ), last revised 25 Aug 2026 (this version, v2)] Title: The GALAH Survey: Neutron-Capture Elemental Abundances for 350,000 Gaia-RVS spectra and the Chemodynamics of Accreted Structures Authors: Pradosh Barun Das , Daniel B. Zucker , Aldo Mura-Guzmán , Nicholas W. Borsato , Gayandhi M. De Silva , Sven Buder , Diane Feuillet , Thomas Nordlander , Melissa K. Ness , Sarah L. Martell , Janez Kos , Joss Bland-Hawthorn , Ken C. Freeman , Andrew R. Casey , Geraint F. Lewis , Dennis Stello , Richard de Grijs , the GALAH Collaboration View PDF Abstract: We present a comprehensive data-driven spectroscopic analysis of 357,415 red giant stars using Gaia DR3 Radial Velocity Spectrometer (RVS) spectra (8460-8700 A; $R\approx11,500$), aimed at deriving homogenous stellar parameters and elemental abundances (collectively referred to as stellar labels). We employ The Cannon, a generative model based on 2747 giants in common with GALactic Archaeology with HERMES (GALAH) DR4, adopting GALAH labels ($R\approx28,000$) for training. The resulting model predicts 11 stellar labels for RVS giants: effective temperature ($T_{\rm eff}$), surface gravity ($\log g$), projected rotational velocity ($v\sin i$), and abundances of [Fe/H], [Ca/Fe], [Si/Fe], [Ni/Fe], [Ti/Fe], as well as the neutron-capture elements [Zr/Fe], [Ce/Fe], and [Nd/Fe]. Building on these results, we develop a probabilistic framework to chemically identify debris from the Gaia-Sausage-Enceladus (GSE) accretion event. A logistic regression classifier, optimized via Markov chain Monte Carlo sampling and trained on a small reference sample of GSE members and comparison stars, identifies stars with high GSE membership probabilities based solely on their chemical abundances, with the resulting candidates exhibiting distinctive abundance-ratio patterns, including [Ca/Ti], [Ti/Ce], and [Nd/Zr]. Applying independent kinematic constraints yields a robust sample of GSE candidates, demonstrating that the characteristic chemical signatures remain consistent after applying these constraints. This work demonstrates the potential of data-driven analysis techniques to extract detailed chemical information from medium-resolution spectra and establishes a framework for tracing Galactic accretion events using chemical abundances. Comments: Published in MNRAS; 24 pages, 14 figures, 8 tables. The resulting catalogues are available via the VizieR catalogue service at this https URL Subjects: Astrophysics of Galaxies (astro-ph.GA) ; Solar and Stellar Astrophysics (astro-ph.SR) Cite as: arXiv:2606.04567 [astro-ph.GA] (or arXiv:2606.04567v2 [astro-ph.GA] for this version) https://doi.org/10.48550/arXiv.2606.04567 Focus to learn more arXiv-issued DOI via DataCite Journal reference: Mon. Not. R. Astron. Soc. 550, 1-24 (2026) Related DOI : https://doi.org/10.1093/mnras/stag1142 Focus to learn more DOI(s) linking to related resources Submission history From: Pradosh Barun Das [ view email ] [v1] Wed, 3 Jun 2026 07:54:58 UTC (35,511 KB) [v2] Tue, 25 Aug 2026 06:25:24 UTC (16,381 KB) Full-text links: Access Paper: View PDF view license Current browse context: astro-ph.GA < prev | next > new | recent | 2026-06 Change to browse by: astro-ph astro-ph.SR References & Citations SciX Google Scholar Semantic Scholar export BibTeX citation Bookmark Bibliographic Tools Bibliographic and Citation Tools Bibliographic Explorer Toggle Bibliographic Explorer ( What is the Explorer? ) Connected Papers Toggle Connected Papers ( What is Connected Papers? ) Litmaps Toggle Litmaps ( What is Litmaps? ) scite.ai Toggle scite Smart Citations ( What are Smart Citations? ) Code, Data, Media Code, Data and Media Associated with this Article alphaXiv Toggle alphaXiv ( What is alphaXiv? ) Links to Code Toggle CatalyzeX Code Finder for Papers ( What is CatalyzeX? ) DagsHub Toggle DagsHub ( What is DagsHub? ) GotitPub Toggle Gotit.pub ( What is GotitPub? ) Huggingface Toggle Hugging Face ( What is Huggingface? ) ScienceCast Toggle ScienceCast ( What is ScienceCast? ) Demos Demos Replicate Toggle Replicate ( What is Replicate? ) Spaces Toggle Hugging Face Spaces ( What is Spaces? ) Spaces Toggle TXYZ.AI ( What is TXYZ.AI? ) Related Papers Recommenders and Search Tools Link to Influence Flower Influence Flower ( What are Influence Flowers? ) Core recommender toggle CORE Recommender ( What is CORE? ) IArxiv recommender toggle IArxiv Recommender ( What is IArxiv? ) Author Venue Institution Topic About arXivLabs arXivLabs: experimental projects with community collaborators arXivLabs is a framework that allows collaborators to develop and share new arXiv features directly on our website. 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