We combine HST imaging from the GEMS Galaxy Evolution from Morphologies and SEDs survey with photometric redshifts from COMBO-17 to explore the evolution of disk-dominated galaxies since z \lesssim 1.1 .
The sample is comprised of all GEMS galaxies with Sérsic indices n < 2.5 , derived from fits to the galaxy images .
We account fully for selection effects through careful analysis of image simulations ; we are limited by the depth of the redshift and HST data to the study of galaxies with M _ { V } \lesssim - 20 , or equivalently \log \left ( \mathcal { M } / \mathcal { M } _ { \odot } \right ) \gtrsim 10 .
We find strong evolution in the magnitude–size scaling relation for galaxies with M _ { V } \lesssim - 20 , corresponding to a brightening of \sim 1 mag arcsec ^ { -2 } in rest-frame V -band by z \sim 1 .
Yet , disks at a given absolute magnitude are bluer and have lower stellar mass-to-light ratios at z \sim 1 than at the present day .
As a result , our findings indicate weak or no evolution in the relation between stellar mass and effective disk size for galaxies with \log \left ( \mathcal { M } / \mathcal { M } _ { \odot } \right ) \gtrsim 10 over the same time interval .
This is strongly inconsistent with the most naive theoretical expectation , in which disk size scales in proportion to the halo virial radius , which would predict that disks are a factor of two denser at fixed mass at z \sim 1 .
The lack of evolution in the stellar mass–size relation is consistent with an “ inside-out ” growth of galaxy disks on average ( galaxies increasing in size as they grow more massive ) , although we can not rule out more complex evolutionary scenarios .