Tracing stars in Milky Way satellites with A-SLOTH

Abstract

We study the stellar mass-to-halo mass relation at z = 0 in 30 Milky Way-like systems down to the ultra-faint (M * < 10 5 M ) regime using the semi-analytic model a-sloth.A new model allows us to follow star formation and the stochastic stellar feedback from individually sampled Pop II stars. Our fiducial model produces consistent results with the stellar mass-to-halo mass relation derived from abundance matching and the observed cumulative stellar mass function above the observational completeness. We find a plateau in the stellar mass-to-halo mass relation in the ultra-faint regime. The stellar mass of this plateau tells us how many stars formed before supernovae occur and regulate further star formation, which is determined by the Pop II star formation efficiency. We also find that the number of luminous satellites increases rapidly as M * decreases until M * ≈ 10 4 M . Finally, we find that the relative streaming velocity between baryons and dark matter at high redshift is important in determining the number of ultra-faint dwarf galaxies at z = 0. The new model in a-sloth provides a framework to study the stellar properties and the formation history of metal-poor stars in Milky Way and its satellites.

A-SLOTH: Ancient Stars and Local Observables by Tracing Halos

“…These models differ widely in their scope, and often they are specifically geared towards addressing a specific issue or question. With A-SLOTH, we offer a highly capable semi-analytical model that can make predictions in numerous areas, ranging from 21-cm cosmology to metal-poor stars in the Milky-Way (Chen et al, 2022;Hartwig et al, 2015Hartwig et al, , 2018Hartwig, Latif, et al, 2016;Mattis Magg et al, 2022;Tarumi et al, 2020). This model was originally based on the Extended-Press-Schechter algorithm and more specifically the GALFORM code (Parkinson et al, 2008) but has since evolved to use merger trees from numerical simulation.…”