The emergence of the faint nature of Low Surface Brightness Galaxies in the IllustrisTNG simulation

Abstract We employ a simulated sample of galaxies drawn from the IllustrisTNG suite to study the emergence of the diffuse and extended nature of ~12, 000 low surface brightness galaxies (LSBGs) within a wide stellar mass range (M* = 109 − 1012M⊙). We employ merger trees to follow the evolution of their physical properties such as stellar surface density, specific angular momentum and halo spin parameter, finding that the central low density nature of LSBGs is mainly a consequence of an increase in their angular momentum and (inner) halo spin parameter. We also find that star formation histories of LSBGs are quite similar to their high surface brightness (HSBGs) counterparts, with significant differences not in the time, but in the spatial distribution in which new stars are forming. We conclude that the mechanisms that favor the emergence of the low surface brightness nature are strongly related with variations in the spin parameter of host halos and their angular momentum, deviating the stellar distribution of galaxies from their inner regions to their outskirts, leading to a decrease in their central surface brightness. Once the LSBG nature is established, galaxies are less likely to experience strong variations in their central surface densities and morphology.