ALMA 1.3 mm Survey of Lensed Submillimeter Galaxies (SMGs) Selected by
  Herschel: Discovery of Spatially Extended SMGs and Implications
  We present an ALMA 1.3 mm (Band 6) continuum survey of lensed submillimeter
galaxies (SMGs) at $z=1.0\sim3.2$ with an angular resolution of $\sim0.2$".
These galaxies were uncovered by the Herschel Lensing Survey (HLS), and feature
exceptionally bright far-infrared continuum emission ($S_\mathrm{peak} \gtrsim
90$ mJy) owing to their lensing magnification. We detect 29 sources in 20
fields of massive galaxy clusters with ALMA. Using both the Spitzer/IRAC
(3.6/4.5 $\mathrm{\mu m}$) and ALMA data, we have successfully modeled the
surface brightness profiles of 26 sources in the rest-frame near- and
far-infrared. Similar to previous studies, we find the median dust-to-stellar
continuum size ratio to be small ($R_\mathrm{e,dust}/R_\mathrm{e,star} =
0.38\pm0.14$) for the observed SMGs, indicating that star formation is
centrally concentrated. This is, however, not the case for two spatially
extended main-sequence SMGs with a low surface brightness at 1.3 mm ($\lesssim
0.1$ mJy arcsec$^{-2}$), in which the star formation is distributed over the
entire galaxy ($R_\mathrm{e,dust}/R_\mathrm{e,star}>1$). As a whole, our SMG
sample shows a tight anti-correlation between
($R_\mathrm{e,dust}/R_\mathrm{e,star}$) and far-infrared surface brightness
($\Sigma_\mathrm{IR}$) over a factor of $\simeq$ 1000 in $\Sigma_\mathrm{IR}$.
This indicates that SMGs with less vigorous star formation (i.e., lower
$\Sigma_\mathrm{IR}$) lack central starburst and are likely to retain a broader
spatial distribution of star formation over the whole galaxies (i.e., larger
$R_\mathrm{e,dust}/R_\mathrm{e,star}$). The same trend can be reproduced with
cosmological simulations as a result of central starburst and potentially
subsequent "inside-out" quenching, which likely accounts for the emergence of
compact quiescent galaxies at $z\sim2$.
