Sizes and surface brightness profiles of quiescent galaxies at z ~ 2

TL;DR

This study uses deep HST imaging to analyze the size, surface brightness profiles, and evolution of quiescent galaxies at z ~ 2, revealing their compactness, structural similarity to local ellipticals, and the extent of size growth needed over cosmic time.

Contribution

It provides detailed surface brightness profiles of z ~ 2 quiescent galaxies and compares their structures to local counterparts, highlighting size evolution and mass accretion processes.

Findings

z ~ 2 quiescent galaxies follow Sersic profiles with median n=3.7

Their effective radii are about 4 times smaller than local galaxies of similar mass

Size growth from z ~ 2 to 0 is at least a factor of 2 for these galaxies

Abstract

We use deep Hubble Space Telescope Wide Field Camera 3 near-infrared imaging obtained of the GOODS-South field as part of the CANDELS survey to investigate a stellar mass-limited sample of quiescent galaxies at 1.5 < z < 2.5. We measure surface brightness profiles for these galaxies using a method that properly measures low surface brightness flux at large radii. We find that quiescent galaxies at z ~ 2 very closely follow Sersic profiles, with n_{median} = 3.7, and have no excess flux at large radii. Their effective radii are a factor ~ 4 smaller than those of low-redshift quiescent galaxies of similar mass. However, there is significant spread in sizes (sigma_{log r_e} = 0.24), with the largest z ~ 2 galaxies lying close to the z = 0 mass-size relation. We compare the stellar mass surface density profiles with those of massive elliptical galaxies in the Virgo cluster and confirm that most of the mass-growth which occurs between z ~ 2 and z = 0 must be due to accretion of material onto the outer regions of the galaxies. Additionally, we investigate the evolution in the size distribution of massive quiescent galaxies. We find that the minimum size growth required for z ~ 2 quiescent galaxies to fall within the z = 0 size distribution is a factor ~ 2 smaller than the total median size growth between z ~ 2 and z = 0.