A Lensing View On The Fundamental Plane

TL;DR

This paper introduces a model-independent formal velocity dispersion for lensing galaxies, confirms their virialization, and analyzes the mass-to-light relation, supporting the Fundamental Plane's consistency in galaxies but not in clusters.

Contribution

It presents a new formal velocity dispersion based on lens models, demonstrating its consistency with observed kinematic dispersions and analyzing the mass-to-light relation in lensing galaxies.

Findings

Sigma_lens is consistent with sigma_obs for galaxies and clusters.

The mass-to-light relation follows L ~ M^0.70, excluding constant M/L.

Clusters do not follow the same mass-to-light relation as galaxies.

Abstract

For lensing galaxies we introduce a formal velocity dispersion sigma_lens, based on enclosed mass and the virial theorem. This is calculated from an ensemble of pixelated lens models, and found to be fairly model independent. A sample of 18 well-known early-type lensing galaxies and two clusters is found to be consistent with the equality of sigma_lens and the kinematic velocity dispersion sigma_obs. Both the early-type lensing galaxies and the clusters can thus be determined as being virialized. In a second step we calculate the I-band luminosity and the total mass content for the sample of lensing galaxies, which enables us to analyze the mass-to-light relation L ~ M^a. We determine a = 0.70 +/- 0.08, excluding constant M/L and consistent with previous studies of the Fundamental Plane. Additionally we verify that this relation does not extrapolate to clusters, which have a much higher M/L. The sample used for this analysis comprises 9 lensing galaxies from the Sloan Lens ACS Survey (SLACS) and another 9 from the CfA-Arizona Space Telescope LEns Survey (CASTLES) as well as the lensing clusters ACO 1689 and ACO 2667.