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Probing the extreme low-mass limits of galaxy formation with FIRE simulations

Presentation #145.07 in the session Dwarf and Irregular Galaxies — iPoster Session.

Published onJun 29, 2022
Probing the extreme low-mass limits of galaxy formation with FIRE simulations

Dwarf Galaxies provide physicists and astronomers with one of the best tests of our cosmological model, Lambda-Cold Dark Matter (LCDM). Despite the general success of the LCDM model, several small-scale challenges have arisen in recent years – the most well-known being the Missing Satellites Problem (MSP), where the counts of galaxies predicted by the assignment of stellar mass to dark-matter-only simulations of Milky Way mass galaxies are an overestimate of currently observed dwarf galaxies around the Milky Way. While it is currently unknown if there is a well-defined halo mass scale under which galaxy formation ceases to occur, the severity of the MSP exhibits a sensitivity to the low-mass edge of galaxy formation. We use ultra-high resolution cosmological zoom-in FIRE simulations of dwarf galaxies at two different resolutions (Mgas = 30Msun is high resolution, Mgas = 250Msun is standard resolution) to investigate the properties of the smallest ultra-faint dwarf galaxies (Mstar< 105 Msun), including how different mass or star particle cuts affect predictions for the counts and properties of these dwarfs. Every dark matter halo more massive than 5.3×107Msun forms at least one star particle, while halos with mass > 1.5×108 Msun host at least 15 star particles. Independent of this cut, our standard and high-resolution models show how our simulated UFDs possess uniformly ancient stellar populations (with most star formation occurring before z = 2). We relate these star formation histories to the properties of the gas to better understand how conditions like those observed came to be. We also investigate a large gas void in the central galaxy (m10q), likely caused by supernovae explosions.

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