Journal article
The GALAH survey: Data release 4
Publications of the Astronomical Society of Australia, Vol.42, e051
05/27/2025
DOI: 10.1017/pasa.2025.26
Abstract
The stars of the Milky Way carry the chemical history of our Galaxy in their atmospheres as they journey through its vast expanse. Like barcodes, we can extract the chemical fingerprints of stars from high-resolution spectroscopy. The fourth data release (DR4) of the Galactic Archaeology with HERMES (GALAH) Survey, based on a decade of observations, provides the chemical abundances of up to 32 elements for 917 588 stars that also have exquisite astrometric data from the Gaia satellite. For the first time, these elements include life-essential nitrogen to complement carbon, and oxygen as well as more measurements of rare-earth elements critical to modern-life electronics, offering unparalleled insights into the chemical composition of the Milky Way. For this release, we use neural networks to simultaneously fit stellar parameters and abundances across the whole wavelength range, leveraging synthetic grids computed with Spectroscopy Made Easy. These grids account for atomic line formation in non-local thermodynamic equilibrium for 14 elements. In a two-iteration process, we first fit stellar labels to all 1 085 520 spectra, then co-add repeated observations and refine these labels using astrometric data from Gaia and 2MASS photometry, improving the accuracy and precision of stellar parameters and abundances. Our validation thoroughly assesses the reliability of spectroscopic measurements and highlights key caveats. GALAH DR4 represents yet another milestone in Galactic archaeology, combining detailed chemical compositions from multiple nucleosynthetic channels with kinematic information and age estimates. The resulting dataset, covering nearly a million stars, opens new avenues for understanding not only the chemical and dynamical history of the Milky Way but also the broader questions of the origin of elements and the evolution of planets, stars, and galaxies.
Details
- Title: Subtitle
- The GALAH survey: Data release 4
- Creators
- Sven Buder - University of CanberraJanez Kos - University of LjubljanaXi Ella Wang - University of CanberraMadeleine McKenzie - University of CanberraMadeleine Howell - ARC Centre of Excellence for All-sky AstrophysicsSarah Martell - ARC Centre of Excellence for All-sky AstrophysicsMichael R. Hayden - ARC Centre of Excellence for All-sky AstrophysicsDaniel B. Zucker - ARC Centre of Excellence for All-sky AstrophysicsThomas Nordlander - University of CanberraBenjamin Montet - UNSW SydneyGregor Traven - University of LjubljanaJoss Bland-Hawthorn - The University of SydneyGayandhi M. De Silva - ARC Centre of Excellence for All-sky AstrophysicsKenneth Freeman - University of CanberraGeraint Lewis - The University of SydneyKarin Lind - Stockholm UniversitySanjib Sharma - Space Telescope Science InstituteJeffrey D. Simpson - ARC Centre of Excellence for All-sky AstrophysicsDennis Stello - ARC Centre of Excellence for All-sky AstrophysicsTomaz Zwitter - University of LjubljanaAnish M. Amarsi - Uppsala UniversityJoseph J. Armstrong - Chalmers University of TechnologyKirsten Banks - ARC Centre of Excellence for All-sky AstrophysicsMark Beavis - University of Southern QueenslandKevin-Luke Beeson - University of LjubljanaBoquan Chen - University of CanberraIoana Ciucă - University of CanberraGary S. Da Costa - University of CanberraRichard de Grijs - Macquarie UniversityBailey Martin - University of CanberraDavid Moise Nataf - University of IowaMelissa Ness - University of CanberraAdam D. Rains - Uppsala UniversityTim Scarr - University of CanberraRok Vogrinčič - University of LjubljanaZixian Purmortal Wang - ARC Centre of Excellence for All-sky AstrophysicsRob A. Wittenmyer - University of Southern QueenslandYi Anne Xie - University of CanberraGALAH Collaboration
- Resource Type
- Journal article
- Publication Details
- Publications of the Astronomical Society of Australia, Vol.42, e051
- DOI
- 10.1017/pasa.2025.26
- ISSN
- 1323-3580
- eISSN
- 1448-6083
- Publisher
- Cambridge University Press
- Number of pages
- 42
- Grant note
- AAT ConsortiumAustralian National UniversityUniversity of New South WalesUniversity of SydneyMacquarie UniversityWestern Sydney UniversityUniversity of MelbourneSwinburne UniversityMonash UniversityUniversity of QueenslandUniversity of Southern QueenslandUniversity of TasmaniaAustralian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D): CE170100013 Australian Research Council: DE240100150, DP220102254 UNSW Scientia ProgramSlovenian Research Agency: P1-0188 European Space Agency (PRODEX Experiment Arrangements): 4000142234, 4000143450 Swedish Research Council: VR 2020-03940 Crafoord Foundation via the Royal Swedish Academy of Sciences: CR 2024-0015
The operation of the AAT is funded by the AAT Consortium, which includes The Australian National University (operator), The University of New South Wales, The University of Sydney, Macquarie University, Western Sydney University, The University of Melbourne, Swinburne University, Monash University, The University of Queensland, The University of Southern Queensland and The University of Tasmania, with Astronomy Australia Limited (AAL) as Consortium Manager.This work was supported by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE170100013. SB acknowledges support from the Australian Research Council under grant number DE240100150. SLM, DBZ and GFL acknowledge support from the Australian Research Council through Discovery Program grant DP220102254. SLM, BTM and KB acknowledge support from the UNSW Scientia Program. JK, GT and TZ acknowledge financial support of the Slovenian Research Agency (research core funding No. P1-0188) and the European Space Agency (PRODEX Experiment Arrangements No. 4000142234 and No. 4000143450). AMA acknowledges support from the Swedish Research Council (VR 2020-03940) and from the Crafoord Foundation via the Royal Swedish Academy of Sciences (CR 2024-0015).
- Language
- English
- Date published
- 05/27/2025
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984825538702771
Metrics
18 Record Views