The evolution of disk galaxies in the GOODS-South field: Number densities and size distribution1

We examine the evolution of the sizes and number densities of disk galaxies using the high-resolution images obtained by the Great Observatories Origins Deep Survey ( GOODS) with the Advanced Camera for Surveys on the Hubble Space Telescope. The multiwavelength images are used to classify galaxies based on their rest-frame B-band morphologies out to redshift z similar to 1.25. In order to minimize the effect of selection biases, we confine our analysis to galaxies that occupy the region of the magnitude-size plane where the survey is similar to 90% complete at all redshifts. The observed size distribution is consistent with a lognormal distribution as seen for the disk galaxies in the local universe and does not show any significant evolution over the redshift range. We 0.25 less than or equal to z less than or equal to 1.25 find that the number densities of disk galaxies remains fairly constant over this redshift range, although a modest evolution by a factor of 4 may be possible within the 2 sigma uncertainties.