We investigate various probes of luminosity evolution in the rich cluster environment , concentrating in particular on the spheroidal ( E/S0 ) galaxies , using a newly-constructed catalog of morphologically-classified Hubble Space Telescope ( HST ) images of galaxies observed in the cores of 13 clusters with redshifts 0.17 \leq z \leq 0.56 .
An important distinction of this study compared to earlier work is the availability of new near-infrared ground-based photometry for a substantial subset of our HST fields , which we have used to select and study the various populations .
We find no significant change in the characteristic luminosity , M _ { K } ^ { \ast } , of the spheroidal populations at redshifts of 0.31 and 0.56 .
As a more sensitive probe of luminosity evolution , we analyze the surface photometry of our HST -classified ellipticals by deriving effective metric radii , R _ { e } , and mean effective surface brightnesses , \langle \mu \rangle _ { e } .
At the standard condition corresponding to R _ { e } = 1 kpc , we find convincing evidence of evolutionary brightening in both rest-frame B and K light , consistent with model predictions based on the passive evolution of stellar populations .