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-*/M-circle dot) > 10) sample of star-forming galaxies over redshifts z - 1-7, selected from the FourStar Galaxy Evolution Survey. 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 similar to 7. At z similar to 7, we find that the average galaxy size from the mass-size relation is more compact at a fixed mass of log(M-*/M-circle dot) = 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 4 (r(e) proportional to (1 + z) (1.2 +/- 0.06)). Therefore, we conclude the LBGs likely represent a subset of highly star-forming galaxies that exhibit rapid size growth at z > 4