The Size Evolution of Star-forming Galaxies Since z~7 Using ZFOURGE
  For the first time, we present the size evolution of a mass-complete
(log(M*/Msol)>10) sample of star-forming galaxies over redshifts z=1-7,
selected from the FourStar Galaxy Evolution Survey (ZFOURGE). Observed H-band
sizes are measured from the Cosmic Assembly Near-Infrared Deep Extragalactic
Legacy Survey (CANDELS) Hubble Space Telescope (HST)/F160W imaging.
Distributions of individual galaxy masses and sizes illustrate that a clear
mass-size relation exists up to z~7. At z~7, we find that the average galaxy
size from the mass-size relation is more compact at a fixed mass of
log(M*/Msol)=10.1, with r_1/2,maj=1.02+/-0.29 kpc, than at lower redshifts.
This is consistent with our results from stacking the same CANDELS HST/F160W
imaging, when we correct for galaxy position angle alignment. We find that the
size evolution of star-forming galaxies is well fit by a power law of the form
r_e = 7.07(1 + z)^-0.89 kpc, which is consistent with previous works for normal
star-formers at 1<z<4. In order to compare our slope with those derived Lyman
break galaxy studies, we correct for different IMFs and methodology and find a
slope of -0.97+/-0.02, which is shallower than that reported for the evolution
of Lyman break galaxies at z>4 (r_e\propto(1 +z)^-1.2+/-0.06). Therefore, we
conclude the Lyman break galaxies likely represent a subset of highly
star-forming galaxies that exhibit rapid size growth at z>4.
