New UBVRI color distributions in E-type galaxies -: II.: Central and mean metallicities

Central and mean metallicities are calculated for a sample of 40 early-type galaxies, whose color gradients were reported in a previous paper (Idiart et al. 2002). The present color-metallicity calibration was derived from a grid of evolutionary models which fit the color-magnitude sequence of ellipticals in Coma and Virgo clusters. The mean metallicity gradient derived from our data is (Delta[Fe/H]/Delta log r) = -0.26 +/- 0.08 and the mean sample average metallicity is < [Fe/H] > = 0.01 +/- 0.11 (rmsd). Central and mean metallicities are correlated with the central velocity dispersion, consistent with the interpretation by metallicity variations of the color-magnitude sequence and of color gradients. Age effects are also discussed, in particular concerning the interpretation of the Hbeta line strength in those objects.