2015ApJ...799..194C

We analyze Hubble Space Telescope WFC3/H₁₆₀-band observations of a sample of 48 Atacama Large Millimeter/submillimeter Array detected submillimeter galaxies (SMGs) in the Extended Chandra Deep Field South field, to study their stellar morphologies and sizes. We detect 79%±17% of the SMGs in the H₁₆₀-band imaging with a median sensitivity of 27.8 mag, and most (80%) of the nondetections are SMGs with 870 µm fluxes of S₈₇₀< 3 mJy. With a surface brightness limit of µ_H∼ 26 mag/arcsec2, we find that 82%±9% of the H₁₆₀-band-detected SMGs at z = 1-3 appear to have disturbed morphologies, meaning they are visually classified as either irregulars or interacting systems, or both. By determining a Sérsic fit to the H₁₆₀ surface brightness profiles, we derive a median Sérsic index of n = 1.2±0.3 and a median half-light radius of r_e= 4.4_–0.5^+1.1 kpc for our SMGs at z = 1-3. We also find significant displacements between the positions of the H₁₆₀component and 870 µm emission in these systems, suggesting that the dusty starburst regions and less-obscured stellar distribution are not colocated. We find significant differences in the sizes and the Sérsic index between our z = 2-3 SMGs and z ∼ 2 quiescent galaxies, suggesting that a major transformation of the stellar light profile is needed in the quenching processes if SMGs are progenitors of the red-and-dead z ∼ 2 galaxies. Given the short-lived nature of SMGs, we postulate that the majority of the z = 2-3 SMGs with S₈₇₀ ≳ 2 mJy are early/mid-stage major mergers.