The Mystery of the $\sigma$-Bump -- A new Signature for Major Mergers in
  Early-type Galaxies?
  The stellar velocity dispersion as a function of the galactocentric radius of
an early-type galaxy can generally be well approximated by a power law $\sigma
\propto r^{\beta}$. However, some observed dispersion profiles show a deviation
from this fit at intermediate radii, usually between one and three
$R_{\mathrm{eff}}$, where the velocity dispersion remains constant with radius,
showing a bump-like behavior, which we term the "$\sigma$-"bump. To understand
the origin of this $\sigma$-bump, we study a set of simulated early-type
galaxies formed in major mergers. We find the $\sigma$-bump in all of our
simulated early-type galaxies, with the size and position of the bump slightly
varying from galaxy to galaxy, leading to the assumption that the bump is a
characteristic of the major merger formation scenario. 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 $\sigma$-bump stays nearly constant with radius and is a
permanent feature that is preserved until the end of the simulation. The
$\sigma$-bump is not seen in the dark matter and gas components and we
therefore conclude that it is a purely stellar feature of merger remnants.
