2025/11/26 by Brown, Shaun T., Fattahi, Azadeh, Gutcke, Thales A. +6 · 1 citation
Engineering · Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics of Galaxies (astro-ph.GA) #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Space Technology and Applications
paper · doi:10.48550/arxiv.2511.21824
openalex publication_date 2025/11/26 · openalex created_date 2025/12/03 · openalex updated_date 2026/07/28
We present a suite of zoom-in cosmological hydrodynamical simulations of dwarf galaxies using the LYRA galaxy formation model with an extremely high mass resolution of 4 \mathrmM\odot, evolved to z=0. The suite contains 65 haloes selected from Local Group like environments, spanning M200c=107 to 5×109 \mathrmM\odot. The sample includes small ultra-faints with M_∗∼100 \mathrmM\odot through to classical dwarfs with M_∗ ∼ 5×106 \mathrmM\odot, as well as haloes that remain dark to the present day. We explore two prescriptions for the high-redshift (z>7) Lyman-Werner background (LWB), differing in intensity and redshift evolution. Star formation begins early (z\gtrsim8) in progenitors with M200c∼105-106 \mathrmM\odot, where molecular hydrogen enables warm moderate-density gas to efficiently cool. The LWB strongly influences the z=0 halo occupation fraction, shifting the dark-to-luminous transition from M200c∼107 \mathrmM\odot (weaker LWB) to M200c∼108 \mathrmM\odot (stronger LWB). Galaxies with M_∗\gtrsim105 \mathrmM\odot are mostly insensitive to the LWB choice, whereas lower mass systems respond strongly, producing markedly different stellar mass-halo mass (SMHM) relations. The weaker LWB yields a very shallow SMHM slope with nearly constant scatter, while the stronger LWB introduces a pronounced break at M200c∼109 \mathrmM\odot, where haloes of similar mass host galaxies with M_∗∼103 to 105 \mathrmM\odot or remain dark. Both models produce a minimum stellar mass floor at M_∗∼103 \mathrmM\odot, originating from galaxies that undergo a single burst of star formation at high redshift before self-quenching from their first supernovae.