The Mass-Radius Relation for Star-forming Galaxies at z ~ 1.5-3.0

Abstract

We present early results from a Hubble Space Telescope WFC3/IR imaging survey of star-forming galaxies in the redshift range 1.5 < z < 3.0. When complete, this survey will consist of 42 orbits of F160W imaging distributed amongst 10 survey fields on the line of sight to bright background QSOs, covering 65 arcmin² to a depth of 27.9 AB with a point-spread function FWHM of 0farcs18. In this contribution, we use a subset of these fields to explore the evolution of the galactic stellar mass-radius relation for a magnitude-limited sample of 102 spectroscopically confirmed star-forming galaxies (langSFRrang ~ 30 M _sun yr^-1) with stellar mass M _* ~ 10¹⁰ M _sun. Although the light profile of these galaxies often has an irregular, multi-component morphology, it is typically possible to describe the brightest component with a Sersic profile of index n ~ 1. The circularized half-light radius r _e of the brightest component is on average langr _erang = 1.66 ± 0.79 kpc (i.e., ~50%-70% the size of local late-type galaxies with similar stellar mass), consistent with recent theoretical models that incorporate strong feedback from star-forming regions. The mean half-light radius increases with stellar mass and, at fixed stellar mass, evolves with cosmic time as ~(1 + z)^-1.42, suggesting that high-redshift star-forming galaxies may evolve onto the local stellar mass-radius relation by redshift z ~ 1.