Metallicity of the double Red Clump in the Milky Way Bulge

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Main Authors: Budzik, Zofia, Łukaszewicz, Matylda, Poleski, Radosław
Format: Preprint
Published: 2025
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author Budzik, Zofia
Łukaszewicz, Matylda
Poleski, Radosław
author_facet Budzik, Zofia
Łukaszewicz, Matylda
Poleski, Radosław
contents We present a reanalysis of the metallicity of the double red clump (RC) stars from the Milky Way bulge. Two leading explanations for the existence of the double RC concern possible differences in chemical composition (multiple populations of stars) or distance (X-shaped bulge). We aim to verify the chemical composition hypothesis by determining the mean metallicity of each RC. We use infrared photometric data and metallicities from a previous study (that are based on the Michigan/Magellan Fiber System spectra). In contrast with previous studies, we assign stars to RCs or the red giant branch using a Bayesian approach. Our resulting difference between mean metallicity of the two RCs equals: $0.23^{+0.19}_{-0.24}$ or $0.28^{+0.17}_{-0.18}~\mathrm{dex}$, if the red giant branch bump is included or not, respectively. Because of the high statistical error, the result does not confirm the multiple populations hypothesis.
format Preprint
id arxiv_https___arxiv_org_abs_2509_03402
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Metallicity of the double Red Clump in the Milky Way Bulge
Budzik, Zofia
Łukaszewicz, Matylda
Poleski, Radosław
Astrophysics of Galaxies
We present a reanalysis of the metallicity of the double red clump (RC) stars from the Milky Way bulge. Two leading explanations for the existence of the double RC concern possible differences in chemical composition (multiple populations of stars) or distance (X-shaped bulge). We aim to verify the chemical composition hypothesis by determining the mean metallicity of each RC. We use infrared photometric data and metallicities from a previous study (that are based on the Michigan/Magellan Fiber System spectra). In contrast with previous studies, we assign stars to RCs or the red giant branch using a Bayesian approach. Our resulting difference between mean metallicity of the two RCs equals: $0.23^{+0.19}_{-0.24}$ or $0.28^{+0.17}_{-0.18}~\mathrm{dex}$, if the red giant branch bump is included or not, respectively. Because of the high statistical error, the result does not confirm the multiple populations hypothesis.
title Metallicity of the double Red Clump in the Milky Way Bulge
topic Astrophysics of Galaxies
url https://arxiv.org/abs/2509.03402