Fingerprints of the hierarchical building up of the structure on the gas
  kinematics of galaxies
  Recent observational and theoretical works have suggested that the
Tully-Fisher Relation might be generalised to include dispersion-dominated
systems by combining the rotation and dispersion velocity in the definition of
the kinematical indicator. Mergers and interactions have been pointed out as
responsible of driving turbulent and disordered gas kinematics, which could
generate Tully-Fisher Relation outliers. We intend to investigate the gas
kinematics of galaxies by using a simulated sample which includes both, gas
disc-dominated and spheroid-dominated systems. Cosmological hydrodynamical
simulations which include a multiphase model and physically-motivated Supernova
feedback were performed in order to follow the evolution of galaxies as they
are assembled. Both the baryonic and stellar Tully-Fisher relations for gas
disc-dominated systems are tight while, as more dispersion-dominated systems
are included, the scatter increases. We found a clear correlation between
$\sigma / V_{\rm rot}$ and morphology, with dispersion-dominated systems
exhibiting the larger values ($> 0.7$). Mergers and interactions can affect the
rotation curves directly or indirectly inducing a scatter in the Tully-Fisher
Relation larger than the simulated evolution since $z \sim 3$. Kinematical
indicators which combine rotation velocity and dispersion velocity can reduce
the scatter in the baryonic and the stellar mass-velocity relations. Our
findings also show that the lowest scatter in both relations is obtained if the
velocity indicators are measured at the maximum of the rotation curve.
Moreover, the rotation velocity estimated at the maximum of the gas rotation
curve is found to be the best proxy for the potential well regardless of
morphology.
