ALMA 26 arcmin² Survey of GOODS-S at 1 mm (ASAGAO): Near-infrared-dark Faint ALMA Sources

Abstract

We report detections of two 1.2 mm continuum sources (S 1.2mm ∼ 0.6 mJy) without any counterparts in the deep H-and/or K-band image (i.e., K-band magnitude 26 mag). These near-infrared-dark faint millimeter sources are uncovered by ASAGAO, a deep and wide-field (≃ 26 arcmin 2 ) Atacama Large Millimeter/submillimeter Array (ALMA) 1.2 mm survey. One has a red IRAC (3.6 and 4.5 µm) counterpart, and the other has been independently detected at 850 and 870 µm using SCUBA2 and ALMA Band 7, respectively. Their optical to radio spectral energy distributions indicate that they can lie at z 3-5 and can be in the early phase of massive galaxy formation. Their contribution to the cosmic star formation rate density is estimated to be ∼ 1 × 10 −3 M ⊙ yr −1 Mpc −3 if they lie somewhere in the redshift range of z ∼ 3-5. This value can be consistent with, or greater than that

A dominant population of optically invisible massive galaxies in the early Universe

“…This suggests that while our approach yields a clean selection of H−dropouts, roughly half of the true H−dropouts have been missed simply due to chance superposition of sources, which needs to be corrected. In fact, this completeness correction is consistent with recent findings from a blind ALMA survey, which reveals four H-dropouts (with [4.5] < 24) that were not picked up by our approach within an area of 1/3 of the GOODS-South filed 32,33 , in comparison to 12 sources selected by our approach in the whole GOODS-South field. Among these four sources, 3 of them have at least one HST counterpart within 2" (with the remaining one absent from our IRAC catalog, which is shallower than the one used in 32 ), which is inconsistent with being the right counterpart of the ALMA emission based on the redshift and other physical properties.…”

Search for Optically Dark Infrared Galaxies without Counterparts of Subaru Hyper Suprime-Cam in the AKARI North Ecliptic Pole Wide Survey Field

“…If we focus on our sample with L18W and SPIRE detections, the mean SFR is 2240 M yr −1 because of requirement of FIR detection. These results are consistent with previous works reporting that SFRs of dusty galaxies tend to be high (e.g., Ikarashi et al 2017;Toba et al 2017b;Yamaguchi et al 2019;Fan et al 2020). Figure 10.…”

“…We also parameterized redshift to estimate photometric redshift (z photo ), because by definition, our sample is optically too faint to obtain spectroscopic redshifts. Since the optically-dark galaxies tend to be located at z > 2 (e.g., Franco et al 2018;Yamaguchi et al 2019;Williams et al 2019;Wang et al 2019), we optimized the range of z photo , which reduces the computing time. Aside from being an excellent SED-fitting tool, CIGALE is known to be a good estimator of z photo , since it utilizes a large number of models covering the whole SED including the MIR-FIR regime.…”

“…A more extreme DOG population, Hot DOGs (Eisenhardt et al 2012;Wu et al 2012) known as dusty AGNs at z > 2 also tend to be optically-faint. Recently, some galaxies detected by Atacama Large Millimeter/submillimeter Array (ALMA) are recognized as invisible SFGs without optical/NIR counterparts (e.g., Franco et al 2018;Yamaguchi et al 2019;Williams et al 2019;Wang et al 2019).…”

ALMA Deep Field in SSA22

“…ALMA deep surveys, which use many pointings to create a contiguous field, are another avenue of research to measure dust-obscured star-forming activity across the cosmic time (e.g., Tadaki et al 2015;Umehata et al 2015;Walter et al 2016;Dunlop et al 2017). Some of the galaxies identified by these types of surveys are known to be blank at the H-band ("HST-dark"; e.g., Franco et al 2018) and Ks-band (e.g., Umehata et al 2015;Yamaguchi et al 2016Yamaguchi et al , 2019. The existence of the near-infrareddark ALMA galaxies has also been uncovered using another approach.…”