Evolution of the Stellar Mass Tully-Fisher Relation in Disk Galaxy Merger Simulations

TL;DR

This study uses galaxy merger simulations to explain the observed tight correlation between stellar mass and a combined velocity measure, S_0.5, which accounts for both rotation and dispersion, reducing scatter seen in the traditional Tully-Fisher relation.

Contribution

The paper demonstrates that galaxy mergers can produce the observed S_0.5-stellar mass relation and explains the scatter in the traditional Tully-Fisher relation through simulations.

Findings

Galaxy mergers explain the tight S_0.5-stellar mass relation.

S_0.5 correlates with total central mass including dark matter.

Mergers reduce scatter in the Tully-Fisher relation.

Abstract

There is a large observational scatter toward low velocities in the stellar mass Tully-Fisher relation if disturbed and compact objects are included. However, this scatter can be eliminated if one replaces rotation velocity with $\rm S_{\rm 0.5}$, 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 $\rm S_{\rm 0.5}$ and intrinsic properties of the galaxies. We find that galaxy mergers can explain the scatter in the TF as well as the tight $\rm S_{\rm 0.5}$-stellar mass relation. Furthermore, $\rm S_{\rm 0.5}$ is correlated with the total central mass of a galaxy, including contributions due to dark matter.