The Importance of Dry and Mixed Mergers for Early-Type Galaxy Formation

Abstract

We use semi-analytical modelling techniques to investigate the progenitor morphologies of present day ellipticals. We find that, independent of the environment, the fraction of mergers of bulge dominated galaxies (early-types) increases with time. The last major merger of bright present day ellipticals with $M_B\lesssim -21$ is preferentially between bulge dominated galaxies, while those with $M_B\sim -20$ have mainly experienced last major mergers between a bulge dominated and a disk dominated galaxy. Independent of specific model assumptions, more than 50% of present day elliptical in clusters with $M_B\lesssim -18$ had last major mergers which are not of spirals as usually expected within the standard merger scenario.

9 pages, 3 figures. submitted to APJ Letters