The SXDF-ALMA 2 arcmin2 Deep Survey: stacking rest-frame near-infrared selected objects

We present stacking analyses on our ALMA deep 1.1 mm imaging in the Subaru/XMM-Newton Deep Survey Field using 1.6 and 3.6 μm selected galaxies in the CANDELS WFC3 catalog. We detect a stacked flux of ∼0.03–0.05 mJy, corresponding to {L}{IR}\lt {10}11 {L}ȯ and a star formationrate (SFR) of ∼ 15 {M}ȯ yr‑1 at z = 2. We find that galaxies that are brighter in the rest-framenear-infrared tend to also be brighter at 1.1 mm, and galaxies fainter than {m}3.6μ {{m}}=23 do not produce detectable 1.1 mm emission. This suggests a correlation between stellar mass and SFR, but outliers to this correlation are also observed, suggesting strongly boosted star formationor extremely large extinction. We also find tendencies that redder galaxies and galaxies at higher redshifts are brighter at 1.1 mm. Our field contains z∼ 2.5 Hα emitters and a bright single-dish source. However, we do not find evidence of bias in our results caused by the bright source. By combining the fluxes of sources detected by ALMA and fluxes of faintsources detected with stacking, we recover a 1.1 mm surface brightnessof up to 20.3 ± 1.2 Jy deg‑2, comparable to the extragalactic background lightmeasured by COBE. Based on the fractions of optically faintsources in our and previous ALMA studies and the COBE measurements, we find that approximately half of the cosmic star formationmay be obscured by dust and missed by deep optical surveys. Much deeper and wider ALMA imaging is therefore needed to better constrain the obscured cosmic star formationhistory.