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Inhomogeneous Galactic chemical evolution: modelling ultra-faint dwarf galaxies of the Large Magellanic Cloud

Alexander, R. K.; Vincenzo, F.; Ji, A. P.; Richstein, H.; Jordan, C. J.; Gibson, B. K.


R. K. Alexander

A. P. Ji

H. Richstein

C. J. Jordan

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Professor Brad Gibson
Head of Physics; Director, E.A. Milne Centre for Astrophysics; Director of Research, Natural Sciences; Interim Associate Dean , Science & Engineering


Ultra-faint dwarf galaxies (UFDs) are among the oldest and most metal-poor galaxies in the cosmos, observed to contain no gas and a high dark matter mass fraction. Understanding the chemical abundance dispersion in such extreme environments could shed light on the very first generations of stars. We present a novel inhomogeneous chemical evolution model, I-GETOOL, that we apply to two UFDs, Carina II and Reticulum II, both satellites of the Large Magellanic Cloud. Our model is based on the Monte Carlo sampling of the initial mass function as star formation proceeds in different gas cells of the galaxy volume. We account for the chemical enrichment of supernova (SN) bubbles as they spread in the interstellar medium, causing dispersion in the elemental abundances. We recreate the abundance patterns of α- and odd-Z elements, predicting two sequences in [C/Fe] and [N/Fe] at all metallicities. Our models underestimate [C/Fe] and [Ti/Fe] because of the large uncertainty in the adopted stellar nucleosynthesis yields. We discuss that the observed C and N abundances had likely been affected by internal mixing processes, which changed the initial surface abundances in the red giants. Our SN feedback scheme is responsible for driving galactic outflows, which quench the star formation activity at early times. We predict an average outflow mass-loading factor ≈103, which extrapolates towards very low galaxy stellar masses the trend observed at high masses. Finally, by combining our model with the MIST isochrone database, we compare our synthetic colour-magnitude diagrams to observations.


Alexander, R. K., Vincenzo, F., Ji, A. P., Richstein, H., Jordan, C. J., & Gibson, B. K. (2023). Inhomogeneous Galactic chemical evolution: modelling ultra-faint dwarf galaxies of the Large Magellanic Cloud. Monthly notices of the Royal Astronomical Society, 522(4), 5415-5433.

Journal Article Type Article
Acceptance Date Apr 27, 2023
Online Publication Date May 3, 2023
Publication Date Jul 1, 2023
Deposit Date May 17, 2023
Publicly Available Date May 18, 2023
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 522
Issue 4
Pages 5415-5433
Keywords Stars: abundances; Hertzsprung–Russell and colour–magnitude diagrams; galaxies: abundances; Galaxies: dwarf; Galaxies: evolution; Local Group
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Copyright Statement
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2023 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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