What is the origin of the different kinematic morphologies of early-type galaxies?
Abstract
Early-type galaxies (i.e. elliptical and lenticular) are divided into slow
and fast rotators according to the appearance of their maps of
line-of-sight velocity. Fast rotators show clear ordered rotation, while
slow are supported mostly by velocity dispersion. I will speak about our
work on investigation of the origin of this diversity. Inspired by
cosmological simulations, we assumed that galaxies first form as fast
rotators and then mergers transform some of them to slow rotators. We
investigated the correlations of a measure of rotational support with
various properties of galaxies that are sensitive to mergers. These
include stellar ages, the presence of tidal features, or kinematically
distinct cores. Each of these parameters is sensitive to a different type
of merger and has a different lifetime. The found correlations, or their
lack, together with observations of high-redshift universe, are explained
the easiest, if the rotation support of early-type galaxies was decreased
by multiple minor mergers more than 10 Gyr ago.