paper

Quantifying scatter in galaxy formation at the lowest masses

arXiv:2101.05822 · doi:10.3847/1538-4357/ac0db6

Abstract

We predict the stellar mass -- halo mass (SMHM) relationship for dwarf galaxies, using simulated galaxies with peak halo masses of M M down into the ultra-faint dwarf range to M 10 M. Our simulated dwarfs have stellar masses of M 790 M to M, with corresponding -band magnitudes from to . For M M, the simulated SMHM relationship agrees with literature determinations, including exhibiting a small scatter of 0.3 dex. However, the scatter in the SMHM relation increases for lower-mass halos. We first present results for well-resolved halos that contain a simulated stellar population, but recognize that whether a halo hosts a galaxy is inherently mass resolution dependent. We thus adopt a probabilistic model to populate "dark" halos below our resolution limit to predict an "intrinsic" slope and scatter for the SMHM relation. We fit linearly growing log-normal scatter in stellar mass, which grows to more than 1 dex at M 10 M. At the faintest end of the SMHM relation probed by our simulations, a galaxy cannot be assigned a unique halo mass based solely on its luminosity. Instead, we provide a formula to stochastically populate low-mass halos following our results. Finally, we show that our growing log-normal scatter steepens the faint-end slope of the predicted stellar mass function.

arXiv comment16 pages, 5 figures; submitted to ApJ. arXiv admin note: text overlap with arXiv:1705.06286

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