The Rest-frame Ultraviolet Structure of 0.5 < z < 1.5 Galaxies

We present the rest-frame UV wavelength dependence of the Petrosian-like half-light radius (r ₅₀), and the concentration parameter for a sample of 198 star-forming galaxies at 0.5 < z < 1.5. We find a ~5% decrease in r ₅₀ from 1500 Å to 3000 Å, with half-light radii at 3000 Å ranging from 0.6 kpc to 6 kpc. We also find a decrease in concentration of ~0.07 (1.9 < C ₃₀₀₀ < 3.9). The lack of a strong relationship between r ₅₀ and wavelength is consistent with a model in which clumpy star formation is distributed over length scales comparable to the galaxy's rest-frame optical light. While the wavelength dependence of r ₅₀ is independent of size at all redshifts, concentration decreases more sharply in the far-UV (~1500 Å) for large galaxies at z ~ 1. This decrease in concentration is caused by a flattening of the inner ~20% of the light profile in disk-like galaxies, indicating that the central regions have different UV colors than the rest of the galaxy. We interpret this as a bulge component with older stellar populations and/or more dust. The size-dependent decrease in concentration is less dramatic at z ~ 2, suggesting that bulges are less dusty, younger, and/or less massive than the rest of the galaxy at higher redshifts.