oMEGACat V: Helium Enrichment in $\omega$ Centauri as a Function of Metallicity

C. Clontz; A. C. Seth; Z. Wang; S. O. Souza; M. Häberle; M. S. Nitschai; N. Neumayer; M. Latour; A. P. Milone; A. Feldmeier-Krause; N. Kacharov; M. Libralato; A. Bellini; G. van de Ven; M. Alfaro-Cuello

arXiv · 2412.09783

oMEGACat V: Helium Enrichment in $\omega$ Centauri as a Function of Metallicity

C. Clontz·A. C. Seth·Z. Wang·S. O. Souza·M. Häberle·M. S. Nitschai·N. Neumayer·M. Latour·A. P. Milone·A. Feldmeier-Krause·N. Kacharov·M. Libralato·A. Bellini·G. van de Ven·M. Alfaro-Cuello

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Abstract

Constraining the helium enhancement in stars is critical for understanding the formation mechanisms of multiple populations in star clusters. However, measuring helium variations for many stars within a cluster remains observationally challenging. We use Hubble Space Telescope photometry combined with MUSE spectroscopic data for over 7,200 red-giant branch stars in \omc\ to measure helium differences between distinct groups of stars as a function of metallicity separating the impact of helium enhancements from other abundance variations on the pseudo-color (chromosome) diagrams. Our results show that stars at all metallicities have subpopulations with significant helium enhancement ($\Delta Y_{min} \gtrsim$ 0.11). We find a rapid increase in helium enhancement from low metallicities ($\rm{[Fe/H] \simeq -2.05}$ to $\rm{[Fe/H] \simeq -1.92})$, with this enhancement leveling out at \deltay\ $= 0.154$ at higher metallicities. The fraction of helium-enhanced stars steadily increases with metallicity ranging from 10\% at $\rm{[Fe/H] \simeq -2.04}$ to over $90\%$ at $\rm{[Fe/H] \simeq -1.04}$. This study is the first to examine helium enhancement across the full range of metallicities in \omc{}, providing new insight into its formation history and additional constraints on enrichment mechanisms.

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C. Clontz, A. C. Seth, Z. Wang, S. O. Souza, M. Häberle, M. S. Nitschai, N. Neumayer, M. Latour, A. P. Milone, A. Feldmeier-Krause, N. Kacharov, M. Libralato, A. Bellini, G. van de Ven, M. Alfaro-Cuello. 2024-12-13. oMEGACat V: Helium Enrichment in $\omega$ Centauri as a Function of Metallicity. https://arxiv.org/abs/2412.09783

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