We determine colour gradients of β0.15Β±0.08 magnitudes per decade in
radius in F450WβF606W and β0.07Β±0.06 magnitudes per decade in radius in
F606WβF814W for a sample of 22 E/S0 galaxies in Abell 2218. These gradients
are consistent with the existence of a mild (βΌβ0.3 dex per decade in
radius) gradient in metal abundance, (cf. previous work at lower and higher
redshift for field and cluster galaxies). The size of the observed gradients is
found to be independent of luminosity over a range spanning Mββ1 to
Mβ+1.5 and also to be independent of morphological type. These results
suggest a fundamental similarity in the distributions of stellar populations in
ellipticals and the bulges of lenticular galaxies. These results are not
consistent with simple models of either monolithic collapse or hierarchical
mergers.Comment: accepted by MNRA