Making it Big: The Effect of Dust on Galaxy Morphology

Galaxy morphology is one of the fundamental and oldest observational tools used to study the formation and evolution of galaxies. Decades of observations from the ground and thousands of orbits of extragalactic imaging by the Hubble Space Telescope (HST) have constructed a picture for the relation between the sizes and masses of galaxies, which has been used to piece together the puzzle of galaxy evolution over the last 10 Gyrs. However, it is impossible to complete this puzzle using observations alone, making cosmological hydrodynamical simulations with multi-scale models of physical processes a critical deciphering tool. Despite the success of simulations in largely matching observed galaxy scaling relations, they have yet to reproduce the observed size evolution of galaxies; the sizes of galaxies are not consistent with observations, nor across different simulations. Is this because the simulations are making galaxies with the wrong sizes? Or is it because they have not yet incorporated the effect of the major culprit that is distorting our observations of galaxies - dust? In this talk I will present the effect of dust attenuation on galaxy morphology using state-of-the-art cosmological hydrodynamical simulation SIMBA with dust radiative transfer package Powderday. If true, this might remarkably change the picture of the galaxy size-mass relation as painted by HST. Resolved stellar population synthesis modelling, augmented by upcoming JWST observation, will be needed to verify our revised view of the size-mass relation of galaxies.