Simulated vs. observed cluster dwarf galaxies: New Horizon and the Fornax Cluster

Hydrodynamical simulations in cosmological volumes represent an ideal means to develop and test the theory underlying the formation and evolution of galaxies. While these simulations reproduce many integrated properties of galaxies, a more stringent test of their efficacy is to confront the predictions of the spatial distribution of baryons to observed 2D properties. Dwarf galaxies are ideal laboratories for such an exploration, as they are abundant in number, and their shallow potential wells make them especially vulnerable to all of the processes that drive star formation and morphological evolution. To this end, we compare the structural scaling relations of dwarf galaxies found in the two largest groups within the New Horizon cosmological zoom simulation with those of Fornax Cluster dwarf galaxies. New Horizon is ideal for this comparison, as it is both voluminous enough (16 Mpc^3) to contain two galaxy groups with masses comparable to Fornax (~10^13 Msun), yet high enough in both spatial (~34pc) and stellar mass (10^4 Msun) resolution to probe the dwarf galaxy regime. For a fair comparison, we measure the New Horizon dwarfs’ structural properties from mock stamps, using the exact same techniques employed in the Fornax Deep Survey. We find that, at a given stellar mass, New Horizon dwarfs are fainter, have much lower surface brightnesses, and have much larger effective radii than their Fornax counterparts. We investigate possible reasons for this, including the impact of baryonic feedback, tidal forces, and the dwarfs’ star formation histories. Our study demonstrates how data from the LSST can be used to perform novel tests of our theoretical models in the dwarf regime, which are likely to significantly advance our current understanding of galaxy evolution.