2D light distributions of dwarf galaxies – key tests of the implementation of physical processes in simulations

ABSTRACT Cosmological simulations provide much of the theoretical framework within which we interpret extragalactic observations. However, even if a given simulation reproduces the integrated properties of galaxies well, it may not reproduce the detailed structures of individual galaxies. Comparisons between the 2D light distributions of simulated and observed galaxies – particularly in the dwarf regime, where key processes like tidal perturbations and baryonic feedback most strongly influence galaxy structure – thus provide an additional valuable test of the simulation’s efficacy. We compare scaling relations derived from mock observations of simulated galaxies, drawn from the two largest haloes in the high-resolution NewHorizon cosmological simulation, with galaxies in the Fornax Cluster. While Fornax is significantly more massive than either group, it is the lowest mass cluster in the local Universe and contains a well-studied population of spatially resolved dwarfs, hence serves as a useful benchmark. Per unit stellar mass, NewHorizon dwarfs are systematically larger in half-light radius, much fainter in surface brightness, and bluer in colour than their Fornax counterparts, albeit with similar light profile shapes. We discuss potential reasons for these discrepancies, including environmental effects, baryonic feedback, resolution, or couplings of these factors. As observations of dwarfs outside of the local Universe become more plentiful through ongoing or upcoming surveys such as Euclid and Legacy Survey of Space and Time, 2D comparisons such as these, where properties are measured in the same way across both simulations and observations, can place strong constraints on processes that alter the spatial distribution of baryons in galaxies.