Dark matter and the Tully-Fisher relations of spiral and S0 galaxies

TL;DR

This study models 28 S0-Sb galaxies to compare their dark matter content and Tully-Fisher relations with spirals, revealing differences that challenge simple transformation scenarios and suggest structural distinctions.

Contribution

The paper provides detailed mass models and demonstrates that S0 galaxies are systematically fainter and less massive than spirals at the same rotational velocity, indicating structural differences.

Findings

S0 galaxies are 0.5 mag fainter than spirals at Ks-band.

S0s are 0.2 dex less massive for a given velocity.

Results challenge simple star formation truncation transformation scenarios.

Abstract

We construct mass models of 28 S0-Sb galaxies. The models have an axisymmetric stellar component and a NFW dark halo and are constrained by observed Ks-band photometry and stellar kinematics. The median dark halo virial mass is 10^12.8 Msun, and the median dark/total mass fraction is 20% within a sphere of radius r_1/2, the intrinsic half-light radius, and 50% within R_25. We compare the Tully-Fisher relations of the spirals and S0s in the sample and find that S0s are 0.5 mag fainter than spirals at Ks-band and 0.2 dex less massive for a given rotational velocity. We use this result to rule out scenarios in which spirals are transformed into S0s by processes which truncate star formation without affecting galaxy dynamics or structure, and raise the possibility of a break in homology between spirals and S0s.