ar X iv : a st ro - p h / 05 08 40 3 v 2 3 1 O ct 2 00 5 Disk evolution since z ∼ 1 in a

Increasingly large populations of disk galaxies are now being observed at increasingly high redshifts, providing new constraints on our knowledge of how such galaxies evolve. Are these observations consistent with a cosmology in which structures form hierarchically? To probe this question, we employ SPH/N-body galaxy scale simulations of late-type galaxies. We examine the evolution of these simulated disk galaxies from redshift 1 to 0, looking at the mass-size and luminosity-size relations, and the thickness parameter, defined as the ratio of scale height to scale length. The structural parameters of our simulated disks settle down quickly, and after redshift z = 1 the galaxies evolve to become only slightly flatter. Our present day simulated galaxies are larger, more massive, less bright, and redder than at z = 1. The inside-out nature of the growth of our simulated galaxies reduces, and perhaps eliminates, expectations of evolution in the size-mass relation. Subject headings: galaxies: evolution — galaxies: formation — galaxies: disks — galaxies: structure — numerical methods