Evolution of the stellar mass Tully-fisher relation in disk galaxy merger simulations

There is a large observational scatter toward low velocities in the stellar mass Tully-Fisher (TF) relation if disturbed and compact objects are included. However, this scatter can be eliminated if one replaces rotation velocity with S _0.5, a quantity that includes a velocity dispersion term added in quadrature with the rotation velocity. In this work, we use a large suite of hydrodynamic N-body galaxy merger simulations to explore a possible mechanism for creating the observed relations. Using mock observations of the simulations, we test for the presence of observational effects and explore the relationship between S _0.5 and intrinsic properties of the galaxies. We find that galaxy mergers can explain the scatter in the TF as well as the tight S _0.5-stellar mass relation. Furthermore, S _0.5 is correlated with the total central mass of a galaxy, including contributions due to dark matter.