Revealing the Stellar Mass and Dust Distributions of Submillimeter
  Galaxies at Redshift 2
  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 (Ks < 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 (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 Re,dust/Re,Mstar = 0.6). This ratio does not change
with specific star-formation rate (sSFR) over the factor of 30 spanned by our
targets, sampling the locus of "normal" main sequence galaxies up to the
starburst regime, log(sSFR/sSFRMS) > 0.5. Our results imply that massive SMGs
are experiencing centrally enhanced star formation unlike typical spiral
galaxies in the local Universe. The sizes and stellar densities of our SMGs are
in agreement with those of the passive population at z=1.5, consistent with
these systems being the descendants of z~2 SMGs.
