Describing the Galaxy-Halo Size Relation at Cosmic Noon in FIREbox

Galaxy sizes correlate closely with the sizes of their parent dark matter halos, suggesting a link between halo formation and galaxy growth. However, the precise nature of this relation and its scatter has not been fully explored. We analyze this galaxy-halo size relation (GHSR) during Cosmic Noon (1 < z < 5) with the help of cosmological simulations from the FIRE project. We find a strong nearly linear relation between the galaxy size and the host dark matter halo size. This relation is only weakly evolving with redshift, implying that the GHSR is roughly universal at such early times. Furthermore, the scatter of this relation is uncorrelated with any studied halo or environmental property, suggesting that instead baryonic processes and feedback are critical in setting the scatter of the GHSR.