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The distinct stellar metallicity populations of simulated Local Group dwarfs

Genina, Anna; Frenk, Carlos S; Benítez-Llambay, Alejandro; Cole, Shaun; Navarro, Julio F; Oman, Kyle A; Fattahi, Azadeh

The distinct stellar metallicity populations of simulated Local Group dwarfs Thumbnail


Authors

Anna Genina

Alejandro Benítez-Llambay

Julio F Navarro

Kyle A Oman



Abstract

A number of Local Group dwarf galaxies are known to have two spatially segregated stellar metallicity populations, a centrally concentrated metal-rich population and a more extended metal-poor population. In this work we discuss mechanisms that lead to the formation of two spatially segregated metallicity populations. Using a set of high-resolution hydrodynamical simulations of Local Group-like environments, we select a sample of satellite and field galaxies, spanning the stellar mass range 106 − 109M⊙, that exhibit bimodality in their metallicity distributions. Among those, we identify a subsample with a strong spatial segregation in the two populations. We find three distinct mechanisms for their formation. In field dwarfs and in a small fraction of satellites, a merger causes the metal-poor stars to migrate to larger radii and encourages the available gas to sink to the centre of the dwarf. Most of the gas is subsequently blown out of the halo through star formation feedback, but the remaining gas is consumed in the formation of a metal-rich population. In the exclusive case of satellites that have retained some of their gas at infall, it is the compression of this gas by ram pressure near pericentre that triggers the formation of metal-rich stars, whilst simultaneously preventing star formation at larger radii through stripping. Additionally, in a small number of field and satellite dwarfs, interactions with gaseous filaments and other galaxies can result in the formation of a metal-rich population. Regardless of the formation mechanism, a history of mergers typically enhances the spatial segregation.

Citation

Genina, A., Frenk, C. S., Benítez-Llambay, A., Cole, S., Navarro, J. F., Oman, K. A., & Fattahi, A. (2019). The distinct stellar metallicity populations of simulated Local Group dwarfs. Monthly Notices of the Royal Astronomical Society, 488(2), 2312-2331. https://doi.org/10.1093/mnras/stz1852

Journal Article Type Article
Acceptance Date Jul 2, 2019
Online Publication Date Jul 8, 2019
Publication Date Sep 30, 2019
Deposit Date Jul 18, 2019
Publicly Available Date Jul 18, 2019
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 488
Issue 2
Pages 2312-2331
DOI https://doi.org/10.1093/mnras/stz1852

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Copyright Statement
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. ©: 2019 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.





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