SXDF-ALMA 2 Arcmin^2 Deep Survey: Resolving and Characterizing the
  Infrared Extragalactic Background Light Down to 0.5 mJy
  We present a multi-wavelength analysis of five submillimeter sources (S_1.1mm
= 0.54-2.02 mJy) that were detected during our 1.1-mm-deep continuum survey in
the SXDF-UDS-CANDELS field (2 arcmin^2, 1sigma = 0.055 mJy beam^-1) using the
Atacama Large Millimeter/submillimeter Array (ALMA). The two brightest sources
correspond to a known single-dish (AzTEC) selected bright submillimeter galaxy
(SMG), whereas the remaining three are faint SMGs newly uncovered by ALMA. If
we exclude the two brightest sources, the contribution of the ALMA-detected
faint SMGs to the infrared extragalactic background light is estimated to be ~
4.1^{+5.4}_{-3.0} Jy deg^{-2}, which corresponds to ~ 16^{+22}_{-12}% of the
infrared extragalactic background light. This suggests that their contribution
to the infrared extragalactic background light is as large as that of bright
SMGs. We identified multi-wavelength counterparts of the five ALMA sources. One
of the sources (SXDF-ALMA3) is extremely faint in the optical to near-infrared
region despite its infrared luminosity (L_IR ~ 1e12 L_sun or SFR ~ 100 M_sun
yr^{-1}). By fitting the spectral energy distributions (SEDs) at the
optical-to-near-infrared wavelengths of the remaining four ALMA sources, we
obtained the photometric redshifts (z_photo) and stellar masses (M_*): z_photo
~ 1.3-2.5, M_* ~ (3.5-9.5)e10 M_sun. We also derived their star formation rates
(SFRs) and specific SFRs (sSFRs) as ~ 30-200 M_sun yr^{-1} and ~ 0.8-2
Gyr^{-1}, respectively. These values imply that they are main-sequence
star-forming galaxies.
