SXDF-ALMA 2 arcmin² deep survey: Resolving and characterizing the infrared extragalactic background light down to 0.5 mJy

We present a multiwavelength 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 Subaru/XMM-Newton Deep Survey Field (SXDF)-UDS-CANDELS field (2 arcmin², 1σ = 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_-3.0Jy 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 multiwavelength 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 ≃ 1 × 10¹², L_⊙; or SFR ≃ 100 M_⊙ yr^-1). By fitting the spectral energy distributions 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) × 10¹⁰ M_⊙. We also derived their star formation rates (SFRs) and specific SFRs as ≃30-200 M_⊙ yr^-1 and ≃0.8-2 Gyr^-1, respectively. These values imply that they are main sequence star-forming galaxies.