Yu-Yen Chang (ASIAA) et al.
I will present structural parameters and morphological properties of faint 450-um selected submillimeter galaxies (SMGs) by JCMT SCUBA-2 in the COSMOS-CANDELS region. We specifically investigate stellar structures of 170 faint 450-um sources (S450=2.8-29.6 mJy) at z<3 using HST near-infrared observations. Based on our spectral energy distribution fitting, about half of such faint SMGs (LIR~10^11.65 Lsun) lie above the main sequence in the star-formation rate/stellar mass plane. The size-mass relation shows that these SMGs are generally similar to less-luminous star-forming galaxies by color-color selection. Because of the intrinsic luminosity, the rest frame optical emission in 850-um sources are more extended than 450-um sources, and 450-um sources are more extended than less luminous star-forming galaxies in the same redshift range. For the stellar mass and star formation rate (SFR) matched sample, the size differences are marginal between faint SMGs and the matched comparison galaxies. Moreover, faint SMGs have similar Sersic indices and projected axis ratios as star-forming galaxies with the same stellar mass and SFR at z~2. Both SMGs and the stellar mass and SFR matched star-forming galaxies show high fractions (~70%) of disturbed features, and the fractions depend on the SFRs. Our results suggest that galaxy merging is related to star formation activity, and the stellar structures of SMGs are similar to those of star-forming galaxies. We show that the depth of submillimeter surveys are now starting to approach the lower luminosity end of star-forming galaxies, allowing us to detect galaxies on the main sequence statistically. Therefore, we are able to understand the nature of dusty galaxies over cosmic time.