The GALAH Survey: Stellar parameters and abundances for 800,000 Gaia RVS spectra using GALAH DR4 and The Cannon

Abstract

Analysing stellar parameters and abundances from nearly one million Gaia Data Release 3 (DR3) Radial Velocity Spectrometer (RVS) spectra poses challenges due to the limited spectral coverage (restricted to the infrared Ca II triplet) and variable signal-to-noise ratios of the data. To address this, we use The Cannon, a data-driven method, to transfer stellar parameters and abundances from the GALAH (GALactic Archaeology with HERMES) DR4 (R ~ 28,000) catalogue to the lower resolution Gaia DR3 RVS spectra (R ~ 11,500). Our model, trained on 14,484 common targets, predicts parameters such as $T_{\text{eff}}$, $\log g$, and $[\text{Fe/H}]$, along with several other elements across approximately 800,000 Gaia RVS spectra. We utilise stars from open and globular clusters present in the Gaia RVS catalogue to validate our predicted mean $[\text{Fe/H}]$ with high precision (~0.02-0.10 dex). Additionally, we recover the bimodal distribution of $[\text{Ti/Fe}]$ versus $[\text{Fe/H}]$, reflecting the high and low $\alpha$-components of Milky Way disc stars, demonstrating The Cannon's capability for accurate stellar abundance determination from medium-resolution Gaia RVS spectra. The methodologies and resultant catalogue presented in this work highlight the remarkable potential of the RVS dataset, which by the end of the Gaia mission will comprise spectra of over 200 million stars.

Published in MNRAS, 17 pages, 15 figures. The resulting catalogue is available at CDS via anonymous ftp to https://cdsarc.u-strasbg.fr or via https://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/538/605

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• Photometric activity cycles in fast-rotating stars: Revisiting the reality of stellar activity cycle branches
• The GALAH survey: Improving chemical abundances using star clusters
• Revisiting the Galactic age-metallicity relation from wide white dwarf-main-sequence binaries
• The GALAH Survey: Neutron-Capture Elemental Abundances for 350,000 Gaia-RVS spectra and the Chemodynamics of Accreted Structures