THE LUMINOSITY FUNCTION OF GALAXIES TO MB g v riz ∼-14 IN z ∼ 0.3 CLUSTERS

We present deep composite luminosity functions (LFs) in B, g, V, r, i, and z for six clusters at 0.14 < z < 0.40 observed with the Hubble Space Telescope Advanced Camera for Surveys. The LFs reach to an absolute magnitude of similar to - 14 + 5 log h mag and are well fitted by a single Schechter function with M* (Bg)v(riz) = - 19.8, - 20.9 - 21.9, - 22.0, - 21.7, - 22.3 mag, respectively, and alpha similar to - 1.3 ( in all bands). The observations suggest that the galaxy LF is dominated by objects on the red sequence to at least 6 mag below the L* point. Comparison with local data shows that the red sequence is well established at least at z similar to 0.3 down to similar to 1/600th of the luminosity of the Milky Way and that galaxies down to the regime of dwarf spheroidals have been completely assembled in clusters at this redshift. We do not detect a steepening of the LF at M > - 16, as is locally observed. If the faint-end upturn is real, the steepening of the LF must be due to a newly infalling population of faint dwarf galaxies.