Velocity dispersion measurements of dwarf galaxies in the Coma cluster - implications for the structure of the fundamental plane

TL;DR

This study measures velocity dispersions of dwarf galaxies in the Coma Cluster to explore their placement on the fundamental plane, revealing a flatter luminosity-velocity dispersion relation than in giant ellipticals.

Contribution

It provides new velocity dispersion measurements for dwarf galaxies, extending the fundamental plane analysis to lower luminosities and revealing a different scaling relation.

Findings

Luminosity scales with velocity dispersion as L ∝ σ^2.0.

Mass-to-light ratio varies weakly with velocity dispersion, M/L ∝ σ^0.2.

Results support models involving large-scale mass removal and structural readjustment.

Abstract

We present intermediate-resolution spectroscopic data for a set of dwarf and giant galaxies in the Coma Cluster, with -20.6 < M_R < -15.7. The photometric and kinematic properties of the brighter galaxies can be cast in terms of parameters which present little scatter with respect to a set of scaling relations known as the Fundamental Plane. To determine the form of these fundamental scaling relations at lower luminosities, we have measured velocity dispersions for a sample comprising 69 galaxies on the border of the dwarf and giant regime. Combining these data with our photometric survey, we find a tight correlation of luminosity and velocity dispersion, L \propto \sigma^{2.0}, substantially flatter than the Faber-Jackson relation characterising giant elliptical galaxies. In addition, the variation of mass-to-light ratio with velocity dispersion is quite weak in our dwarf sample: M/L \propto \sigma^{0.2}. Our overall results are consistent with theoretical models invoking large-scale mass removal and subsequent structural readjustment, e.g., as a result of galactic winds.