A refined Tully-Fisher relationship and a new scaling law for galaxy discs

TL;DR

This paper refines the Tully-Fisher relation by identifying a consistent annular region in galaxy discs where similar scaling laws apply, leading to a more robust and less ambiguous galaxy scaling law.

Contribution

It introduces a new method to identify an interior annular region in galaxy discs that confirms a refined Tully-Fisher law, improving the understanding of galaxy dynamics.

Findings

Confirmation of a similar scaling law in the interior and exterior annular regions

Insight into uncertainties in defining Vmax and Rmax

A refined Tully-Fisher law largely insensitive to velocity measurement methods

Abstract

We show how the hypothesis that galaxy discs conform to self-similar dynamics leads to an objective identification, in the data, of an annular region of the optical disc which is such that, corresponding to the classical Tully-Fisher scaling law defined on the exterior annular boundary, there is a similar scaling law defined on the interior annular boundary. This result is confirmed at the level of statistical certainty over several large ORC samples. Furthermore, the same analysis provides insight into the uncertainties associated with the best way of defining Vmax, the rotation velocity used for the Tully-Fisher scaling law and Rmax, the galaxy radius at which Vmax is measured. Finally, as a direct consequence, we are led to a refined Tully-Fisher law which is largely insensitive to the means by which a galaxy's rotation velocity is defined.