The Fundamental Plane of Field Early-Type Galaxies at z = 1

Abstract

We present deep VLT spectra of early-type galaxies at z~1 in the Chandra Deep Field-South, from which we derive velocity dispersions. Together with structural parameters from Hubble Space Telescope imaging, we can study the fundamental plane for field early-type galaxies at that epoch. We determine accurate mass-to-light ratios (M/L) and colors for four field early-type galaxies in the redshift range 0.96 2). The lower mass galaxies at z~1 have a lower average M/L, and one is a genuine ``E+A'' galaxy. The M/L indicate that their luminosity-weighted ages are a factor of 3 younger at the epoch of observation, because of either a low formation redshift or late bursts of star formation contributing 20%-30% of the mass. Based on observations collected at the European Southern Observatory, Chile (169.A-0458).