Velocity Dispersions and Stellar Populations of the Most Compact and Massive Early-Type Galaxies at Redshift ~1

TL;DR

This study analyzes the velocity dispersions and stellar populations of four compact, massive early-type galaxies at redshift ~1, revealing their dynamical masses, stellar ages, and potential evolutionary paths to local galaxies.

Contribution

It provides new spectroscopic measurements of high-redshift compact galaxies and discusses their mass estimates and evolutionary scenarios.

Findings

Velocity dispersions range from 156 to 236 km/s.

Dynamical masses are about six times smaller than stellar masses from photometry.

Passive fading and minor mergers could evolve these galaxies into local early-type galaxies.

Abstract

We present Gran-Telescopio-Canarias/OSIRIS optical spectra of 4 of the most compact and massive early-type galaxies in the Groth Strip Survey at redshift z~1, with effective radii Reff=0.5-2.4 kpc and photometric stellar masses Mstar=1.2-4x10^11 Msun. We find these galaxies have velocity dispersions sigma=156-236 km/s. The spectra are well fitted by single stellar population models with approximately 1 Gyr of age and solar metallicity. We find that: i) the dynamical masses of these galaxies are systematically smaller by a factor of ~6 than the published stellar masses using BRIJK photometry; ii) when estimating stellar masses as 0.7xMdyn, a combination of passive luminosity fading with mass/size growth due to minor mergers can plausibly evolve our objects to match the properties of the local population of early-type galaxies.