Quiescent Galaxy Size, Velocity Dispersion, and Dynamical Mass Evolution

TL;DR

This study investigates the evolution of quiescent galaxy properties such as size, velocity dispersion, and dynamical mass over a broad redshift range, revealing negligible evolution in velocity dispersion but significant growth in dynamical-to-stellar mass ratio.

Contribution

It provides new velocity dispersion measurements and demonstrates the increasing dark matter fraction within galaxies over cosmic time, enhancing understanding of galaxy evolution.

Findings

Velocity dispersion shows negligible evolution with redshift.

Dynamical-to-stellar mass ratio increases over time.

Dark matter fraction within effective radius grows due to minor mergers.

Abstract

We use surveys covering the redshift range $0.05 < z < 3.8$ to explore quiescent galaxy scaling relations and the redshift evolution of the velocity dispersion, size, and dynamical mass at fixed stellar mass. For redshift $z < 0.6$ we derive mass limited samples and demonstrate that these large samples enhance constraints on the evolution of the quiescent population. The constraints include 2985 new velocity dispersions from the SHELS F2 survey (Geller et al. 2014). In contrast with the known substantial evolution of size with redshift, evolution in the velocity dispersion is negligible. The dynamical-to-stellar mass ratio increases significantly as the universe ages, in agreement with recent results that combine high redshift data with the SDSS. Like other investigators, we interpret this result as an indication that the dark matter fraction within the effective radius increases as a result of the impact of the minor mergers that are responsible for size growth. We emphasize that dense redshift surveys covering the range $0.07 < z < 1$ along with strong and weak lensing measurements could remove many ambiguities in evolutionary studies of the quiescent population.