Mg2 line-strength profiles of elliptical galaxies with kinematically decoupled cores

Bender, R. & Surma, P. 1992, Astr. Ap. 229, 441.

It is shown that the decoupling between central and outer parts of four presumed merger ellipticals also applies to their Mg2 profiles: in two of the four galaxies the Mg2 profile exhibits a significant change of slope at the same radius at which the peculiar core kinematics starts to become dominant. The other two galaxies show evidence of the same effect, but at a lower significance level. The decoupled core components exhibit high Mg2 line-strength indices and strong radial Mg2 gradients and are embedded in main bodies showing larger indices and weaker gradients. Attributing the gradients to changes in metallicity alone suggests that the decoupled core components have metallicities about a factor of 2 larger than those of the main bodies. While the stellar components of the progenitors violently relaxed and formed the main body of the merger remnant, a preenriched gas component efficiently lost angular momentum, settled in the central region, and underwent a strong starburst phase.