Shape and kinematics of elliptical galaxies: evolution due to merging at z < 1.5

Abstract

Aims:In this study we investigate the evolution of shape and kinematics of elliptical galaxies in a cosmological framework. Methods: We use a set of hydrodynamic, self-consistent simulations operating in the context of a concordance cosmological model where relaxed elliptical-like objects (ELOs) were identified at redshifts z=0, z=0.5, z=1 and z=1.5. Results: The population of elliptical systems analysed here present a systematic change through time, i.e. evolution, by becoming rounder in general at z=0 and, at the same time more velocity dispersion supported. This is found to be primarily due to major dry mergers where only a modest amount of angular momentum is involved into the merger event. Despite the general trend, in a significant amount of cases the merger event involves a higher specific angular momentum, which in general causes the system to acquire a higher rotational support and/or a more oblate shape. These evolutionary patterns are still present when we study our systems in projection, mimicking real observations, and thus they should become apparent in future observations.