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

TL;DR

This study compares the 2D light distributions of dwarf galaxies in simulations and observations to evaluate how well simulations replicate detailed galaxy structures, highlighting discrepancies and their possible causes.

Contribution

It provides a detailed comparison of simulated and observed dwarf galaxy light profiles, emphasizing the importance of 2D structural tests for validating galaxy formation models.

Findings

Simulated dwarfs are larger, fainter, and bluer than observed counterparts.

Light profile shapes are similar between simulations and observations.

Discrepancies may stem from environmental effects, feedback, or resolution issues.

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 halos 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 on-going or up-coming surveys such as Euclid and LSST, 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.