http://arxiv.org/abs/2212.11639
Context: In the latest Gaia data release (DR3), the GSP-Spec module has provided stellar parameters and chemical abundances measured from the RVS spectra alone. However, very metal-poor stars (VMP stars; $[\mathrm{Fe/H}]<-2$) suffer from parameter degeneracy due to a lack of information in their spectra, making it difficult to obtain reliable stellar parameters and metallicities for many of them. Aim: We aim to improve metallicity estimates for VMP stars analysed by the GSP-Spec module. Methods: We compute the Ca triplet equivalent widths from the published set of GSP-Spec stellar parameters. We then convert these obtained equivalent widths to metallicities adopting photometric temperatures and surface gravities that we derive based on Gaia and 2MASS catalogs. Results: Comparison to high-resolution studies shows that our approach drastically reduces the cases where the estimated metallicities are far off for VMP stars. Now only $23\%$ of VMP stars have a metallicity different by more than $0.5\,\mathrm{dex}$ from a high-resolution value, while this fraction is $76\%$ with the original metallicity estimates by the GSP-Spec module. We explore possible ways to remove stars with poor metallicity estimates while keeping as many stars with reliable metallicity as possible. Our improved metallicity estimates and new quality cut result in producing a catalog of bright ($G\lesssim 13$) metal-poor stars, containing 57 stars at $[\mathrm{Fe/H}]<-3$ and 2202 VMP stars. These numbers increase to 174 and 2794 if one allows a low level of metal-rich contaminants. Conclusion: The inclusion of photometric information greatly contributes to breaking parameter degeneracy, enabling precise metallicity estimates for VMP stars from Gaia RVS spectra. We produce a publicly-available catalog of bright metal-poor stars suitable for high-resolution follow-up.
T. Matsuno, E. Starkenburg, E. Balbinot, et. al.
Fri, 23 Dec 22
2/58
Comments: The catalog will be publicly made available when accepted, or before upon reasonable request
You must be logged in to post a comment.