THE KINEMATICALLY PECULIAR CORES OF THE COMA CLUSTER EARLY-TYPE GALAXIES NGC-4816 AND IC-4051

The Coma cluster is one of the richest known cluster of galaxies, span ning about 4 dex in density. Hence it is the ideal place to study the structure of galaxies as a function of environmental density in order to constrain the theories of galaxy formation and evolution. For a mag nitude limited sample of 35 E and S0 galaxies we obtained long slit sp ectra to derive the rotation curves, the velocity dispersion profiles and the radial gradients of the Mg, Fe and H beta line indices. Here w e report on two early - type galaxies which turned out to host the lar gest kinematically peculiar cores yet found in ''normal'' early - type galaxies: NGC 4816 hoses a decoupled counter rotating core with a rad ial extension along the major axis of 2.7 kpc, while IC 4051 has a co- rotating peculiar core with a sizes of 3.4 kpc. We combine our data wi th HST photometry and show that both cores are flattened central stell ar disks which contribute less than 1 % to the total V band light of t he galaxies, but are nevertheless conspicuous (1 - 2 x 10(9) L.). The metallicity of the cores is 0.25 dex super solar and drops to solar an d sub solar in the outer part of NGC 4816 and IC 4051, respectively. T he mean stellar population in both central disks is old (8 - 12 Gyr) a nd highly overabundant in Mg-b relative to <Fe> (approximate to 0.5 de x). We discuss the evidence that these central disks formed via dissip ational major merger events.