The Luminosity Function of E/S0 Galaxies at 0.5<z<1.0

We measure the luminosity function of morphologically selected E/S0 galaxies from z=0.5 to z=1.0 using deep high resolution Advanced Camera for Surveys (ACS) imaging data. Our data extend 2 magnitudes deeper than the Deep Groth Strip Survey (DGSS). At 0.5<z<0.75, we find M_B^*-5\log h_{0.7}=-21.1+/-0.3 and \alpha=-0.53+/-0.2, and at 0.75<z<1.0, we find M_B^*-5\log h_{0.7}=-21.4+/-0.2. Our morphologically selected luminosity functions are similar in both shape and number density to other morphologically selected luminosity functions (e.g., DGSS), but we find significant differences to the luminosity functions of samples selected using morphological proxies like colour or SED. The difference is due to incompleteness from blue E/S0 galaxies, which make up to ~30% of the sample and contamination from early-type spirals. Most of the blue E/S0 galaxies have similar structural properties to the red E/S0s and could passively evolve to form giant red ellipticals at z=0. However, the bluest, (U-V)_0<1.2, have much smaller Sersic parameters and would evolve into much fainter galaxies. These may be the progenitors of dwarf ellipticals. We demonstrate the need for both morphological and colour information to constrain the evolution of E/S0 galaxies.