We combine high-resolution ALMA and HST/CANDELS observations of 20
submillimeter galaxies (SMGs), predominantly from the AS2UDS survey at z
≃ 2, with bright rest-frame optical counterparts
({K}{{s}}≲ 22.9) to investigate the resolved structural
properties of their dust and stellar components. We derive
two-dimensional stellar-mass distributions that are inferred from
spatial mass-to-light ratio ({\text{}}M/{L}* ) corrections
based on rest-frame optical colors. Due to the high central column
densities of dust in our SMGs, our mass distributions likely represent a
lower limit to the true central mass density. The centroid positions
between the inferred stellar-mass and the dust distributions agree
within 1.1 kpc, indicating an overall good spatial agreement between the
two components. The majority of our sources exhibit compact dust
configurations relative to the stellar component (with a median ratio of
effective radii {R}{{e},{dust}}/{R}{{e},* } =
0.6). This ratio does not change with specific star formation rate over
the factor of 30 spanned by our targets, sampling the locus of
“normal” main-sequence galaxies up to the starburst regime,
{log}({sSFR}/{sSFR}}MS})≥slant 0.5. Unlike typical spiral
galaxies in the local universe, our results imply that massive SMGs are
experiencing centrally enhanced star formation. The sizes and stellar
densities of our SMGs are in agreement with those of the passive
population at z = 1.5, which is consistent with these systems being the
descendants of z ≃ 2 SMGs.