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Metallicity of Dwarf Galaxies: Bimodal age-related Metallicity Distributions in Simulated Dwarf Galaxies

Presentation #147.11 in the session “Dwarf & Irregular Galaxies”.

Published onJan 11, 2021
Metallicity of Dwarf Galaxies: Bimodal age-related Metallicity Distributions in Simulated Dwarf Galaxies

Metallicity is an informative property of dwarf galaxies, offering insight into a dwarf galaxy’s history of gas accretion, loss, and star formation, which helps us understand the dynamics of galaxy formation. We studied the metallicity, stellar age, and halo environment of satellite dwarf galaxies in the Justice League high-resolution cosmological SPH simulations. There were four simulations in total, each containing one large Milky-Way like halo and about 10-50 dwarf galaxies with a virial mass greater than 108 solar masses. We found that the simulated dwarf halos conformed to a fundamental plane relating metallicity, star formation rate, and stellar mass, which was preserved over the entire course of the simulations. When analyzing the metallicities of individual star particles, we discovered a bimodal distribution in the metallicity of stars in each halo. Before around 4 GYR in the galaxies’ star-formation histories, the stars rapidly increased in their metal content. However, stars formed after that point tended to have a more uniform metallicity. Reionization was considered as a causal factor in the bimodal distributions of star formation, since it would have caused many galaxies to lose much of their gas and slowed down metal enrichment. We further analyzed metal enrichment during the later stages of dwarf galaxy evolution and found that the metal flux into and out of the dwarf galaxies ceased almost immediately after each halo entered the halo of its host.


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