The Evolution of Galactic Disks

Abstract

We use recent observations of high-redshift galaxies to study the evolution of galactic disks over the redshift range 0<z<1. The data are inconsistent with models in which disks were already assembled at z=1 and have evolved only in luminosity since that time. Assuming that disk properties change with redshift as powers of 1+z and analysing the observations assuming an Einstein-de Sitter universe, we find that for given rotation speed, disk scalelength decreases with z as ~(1+z)^{-1}, total B-band mass-to-light ratio decreases with z as ~(1+z)^{-1}, and disk luminosity (again in B) depends only weakly on z. These scalings are consistent with current data on the evolution of disk galaxy abundance as a function of size and luminosity. Both the scalings and the abundance evolution are close to the predictions of hierarchical models for galaxy formation. If different cosmogonies are compared, the observed evolution in disk-size and disk abundance favours a flat low-density universe over an Einstein-de Sitter universe.