The luminosity - size relation of galaxies to z = 1 ?

We use the Hubble Ultra Deep Field (UDF) to study the galaxy luminosity-size (M-R e) distribution. With a careful analysis of selection effects due to both detection completeness and measurement reliability we identify bias-free regions in the M-R e plane for a series of volume-limited samples. We also investigate the colour-log(n) distribution of these galaxies and further subdivide our data by structural type to separately study compact and diffuse objects. By comparison to the nearby Millennium Galaxy Catalogue, we present tenative evidence for evolution of diffuse, disk-like galaxies with redshift—both in mean surface brightness and the slope of the M-R e relation. In contrast we find no evidence of structural evolution in the compact galaxy M-R e relation over this redshift range, although there is a suggestion of colour evolution. We also highlight the importance of considering surface brightness dependent measurement biases in addition to incompleteness biases. In particular, the increasing, systematic underestimation of Kron fluxes towards low surface brightnesses may cause diffuse, yet luminous, systems to be mistaken for faint, compact objects.