Evidence for Impact of Galaxy Mergers on Stellar Kinematics of
  Early-type Galaxies
  We provide observational evidence that galaxy mergers significantly affect
stellar kinematics of early-type galaxies (ETGs) such as specific stellar
angular momentum within the half-light radius ($\lambda_{R_e}$) and kinematic
misalignment ($\psi_\mathrm{mis}$), using MaNGA integral field unit
spectroscopic data that are in the Stripe 82 region of the Sloan Digital Sky
Survey. In this study, tidal features around ETGs, which are detected in deep
coadded images, are used as direct evidence for mergers that occurred recently.
In the case of ETGs that do not have dust lanes, $\lambda_{R_e}$ is lower in
ETGs with tidal features than in those without tidal features (median
$\lambda_{R_e}$: $0.21$ versus $0.39$) in all stellar mass and S\'ersic index
ranges except the most massive bin, so that the fraction of ETGs with tidal
features in slow rotators is more than twice as large as that in fast rotators
($42\%$ versus $18\%$). Moreover, ETGs with tidal features have larger
$\psi_\mathrm{mis}$ than those without tidal features (mean
$\psi_\mathrm{mis}$: $28^\circ$ versus $15^\circ$). By contrast, ETGs with dust
lanes are fast rotators, and ETGs with both dust lanes and tidal features have
the highest $\lambda_{R_e}$ (median $\lambda_{R_e}$: $0.59$) among all ETG
categories. In addition, ETGs with dust lanes have small $\psi_\mathrm{mis}$
regardless of the existence of tidal features ($\psi_\mathrm{mis}<7.5^\circ$).
Our results can be explained if mergers with different gas fractions generate
merger remnants that have different kinematic properties.
