New UBVRI colour distributions in E-Type
galaxies
II. Central and mean metallicities «
T.P. Idiart, R. Michard and
J.A. de Freitas Pacheco
ABSTRACT
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. 2001). 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 (D[Fe/H]/ Dlog r) = -0.26±0.08 and the mean sample average metallicity is <[Fe/H]> = 0.01±0.11.Central and mean metallicities are correlated with the central dispersion velocity, consistent with the interpretation of metallicity variations along the color-magnitude sequence and color gradients. Age effects are also discussed, in particular concerning the interpretation of the Hb line strength in those objects.