INTERPRETING THE EVOLUTION OF THE SIZE–LUMINOSITY RELATION FOR DISK GALAXIES FROM REDSHIFT 1 TO THE PRESENT

A sample of very high resolution cosmological disk galaxy simulations is used to investigate the evolution of galaxy disk sizes back to redshift 1 within the ΛCDM cosmology. Artificial images in the rest-frame B band are generated, allowing for a measurement of disk scale lengths using surface brightness profiles as observations would, and avoiding any assumption that light must follow mass as previous models have assumed. We demonstrate that these simulated disks are an excellent match to the observed magnitude–size relation for both local disks and for disks at z = 1 in the magnitude/mass range of overlap. We disentangle the evolution seen in the population as a whole from the evolution of individual disk galaxies. In agreement with observations, our simulated disks undergo roughly 1.5 mag arcsec−2 of surface brightness dimming since z = 1. We find evidence that evolution in the magnitude–size plane varies by mass, such that galaxies with M ∗ 109 M undergo more evolution in size than luminosity, while dwarf galaxies tend to evolve potentially more in luminosity. The disks grow in such a way as to stay on roughl