Title: The Mystery of the σ-Bump -- A new Signature for Major Mergers in 
Elliptical Galaxies?

Authors: Anna Schauer, Rhea-Silvia Remus, Andreas Burkert, Peter H. Johansson

Abstract: The stellar velocity dispersion of an elliptical galaxy can generally 
be well approximated by a power law σ α r^ß. However, some observed dispersion 
profiles show a deviation from this fit in the medium-range regime, usually 
between 6 and 17 kpc, where the velocity dispersion remains constant with 
radius, showing a bump-like behavior, which we term the'σ-'bump. To understand 
the origin of this σ-bump, we study a set of simulated elliptical galaxies 
formed in major mergers. We find the σ-bump in all of our simulated 
ellipticals, with the size and position of the bump slightly varying from 
galaxy to galaxy. The feature can be seen both in the intrinsic and projected 
stellar velocity dispersions. In contrast to shells that form during the merger 
event but evolve with time and finally disappear, the σ-bump stays nearly 
constant with radius and is a permanent feature that is preserved until the end 
of the simulation. The σ-bump is not seen in the dark matter and gas components 
and we therefore conclude that it is a purely stellar feature of the merger 
remnants.