We present stacking analyses on our ALMA deep 1.1 mm imaging in the SXDF using 1.6 {\mu}m and 3.6 {\mu}m selected galaxies in the CANDELS WFC3 catalog. We detect a stacked flux of ~0.03-0.05 mJy, corresponding to LIR < 10^11 Lsun and a star formation rate (SFR) of ~ 15 Msun/yr at z = 2. We find that galaxies brighter in the rest-frame near-infrared tend to be also brighter at 1.1 mm, and galaxies fainter than m[3.6um] = 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 formation or 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 H-alpha 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 faint sources detected with stacking, we recover a 1.1 mm surface brightness of up to 20.3 +/- 1.2 Jy/deg, comparable to the extragalactic background light measured by COBE. Based on the fractions of optically faint sources in our and previous ALMA studies and the COBE measurements, we find that approximately half of the cosmic star formation may 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 formation history.
@article{arxiv.1609.08772,
title = {SXDF-ALMA 2-arcmin^2 Deep Survey: Stacking of Rest-Frame Near-Infrared Selected Objects},
author = {Wei-Hao Wang and Kotaro Kohno and Bunyo Hatsukade and Hideki Umehata and Itziar Aretxaga and David Hughes and Karina I. Caputi and James S. Dunlop and Soh Ikarashi and Daisuke Iono and Rob J. Ivison and Minju Lee and Ryu Makiya and Yuichi Matsuda and Kentaro Motohara and Kouichiro Nakanish and Kouji Ohta and Ken-ichi Tadaki and Yoichi Tamura and Tadayuki Kodama and Wiphu Rujopakarn and Grant W. Wilson and Yuki Yamaguchi and Min S. Yun and Jean Coupon and Bau-Ching Hsieh and Sebastien Foucaud},
journal= {arXiv preprint arXiv:1609.08772},
year = {2016}
}