THE MASS–RADIUS RELATION FOR STAR-FORMING GALAXIES AT z ∼ 1.5–3.0

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 0.″18. 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 (〈SFR〉 ∼ 30 M☉ yr−1) with stellar mass M* ∼ 1010 M☉. 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 re of the brightest component is on average 〈re〉 = 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.