The DEEP Groth Strip Survey X: Number Density and Luminosity Function of   Field E/S0 Galaxies at z < 1
  We present the luminosity function and color-redshift relation of a magnitude-limited sample of 145 mostly red field E/S0 galaxies at z < 1 from the DEEP Groth Strip Survey (GSS). Most of the E/S0s (86%) form a red envelope in the redshift-color diagram, consistent with predictions of spectral synthesis models in which the dominant stellar population is formed at redshifts z > 1.5. Constructing a luminosity function of the full sample of   145 E/S0s, we find that there is about 1.1--1.9 magnitude brightening in rest-frame B band luminosity back to z = 0.8 from z=0, consistent with other studies.   Together with the red colors, this brightening favors models in which the bulk of stars in red field E/S0s formed before z_{for} > 1.5 and have been evolving rather quiescently with few large starbursts since then.   Evolution in the number density of field E/S0 galaxies is harder to measure, and uncertainties in the raw counts and their ratio to local samples might amount to as much as a factor of two.   Within that uncertainty, the number density of red E/S0s to z = 0.8 seems relatively static, being comparable to or perhaps moderately less than that of local E/S0s depending on the assumed cosmology. A doubling of E/S0 number density since z = 1 can be ruled out with high confidence (97%) if \Omega_{m}=1.   Taken together, our results are consistent with the hypothesis that the majority of luminous field E/S0s were already in place by z = 1, that the bulk of their stars were already fairly old, and that their number density has not changed by large amounts since then. 
Myungshin Im, L. Simard, S. M. Faber, D. C. Koo, K. Gebhardt, C. N. A.   Willmer, A. Phillips, G. Illingworth, N. P. Vogt, a...