Morphological Early-Type Galaxies at z~0.75

Nicholas Cross

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 imaging data. Our analysis covers an area of 48' and extends 2 magnitudes deeper than was possible in the Deep Groth Strip Survey (DGSS). At 0.51.7, E/S0 galaxies at brighter luminosities (M_B<-20.1), but are increasingly different at fainter magnitudes where `blue' galaxies are both smaller and have lower Sersic parameters. We find differences in both the size-magnitude relation and the photometric plane offset for `red' and `blue' E/S0s, although neither `red' nor `blue' galaxies give a good fit to the size magnitude relation. Fits of the colors to stellar population models suggest that most E/S0 galaxies have short star-formation time scales (tau<1 Gyr), and that galaxies have formed at an increasing rate from z~8 until z~2 after which there has been a gradual decline.