ALMA Deep Field in SSA22

Abstract

Deep surveys with the Atacama Large Millimeter Array (ALMA) have uncovered a population of dusty star-forming galaxies which are faint or even undetected at optical to near-infrared wavelengths. Their faintness at short wavelengths makes the detailed characterization of the population challenging. Here we present a spectroscopic redshift identification and a characterization of one of these near-infrared-dark galaxies discovered by an ALMA deep survey. The detection of [C I](1–0) and CO(4–3) emission lines determines the precise redshift of the galaxy, ADF22.A2, to be z = 3.9913 ± 0.0008. On the basis of a multi-wavelength analysis, ADF22.A2 is found to be a massive, star-forming galaxy with a stellar mass of M∗ = 1.1−0.6+1.3 × 1011 M⊙ and SFR = 430−150+230 M⊙ yr−1. The molecular gas mass was derived to be M(H2)[CI] = (5.9 ± 1.5)×1010 M⊙, indicating a gas fraction of ≈35%, and the ratios of L[CI](1−0)/LIR and L[CI](1−0)/LCO(4−3) suggest that the nature of the interstellar medium in ADF22.A2 is in accordance with those of other bright submillimeter galaxies. The properties of ADF22.A2, including the redshift, star-formation rate, stellar mass, and depletion time scale (τdep ≈ 0.1−0.2 Gyr), also suggest that ADF22.A2 has the characteristics expected for the progenitors of quiescent galaxies at z ≳ 3. Our results demonstrate the power of ALMA contiguous mapping and line scan, which help us to obtain an unbiased view of galaxy formation in the early Universe.

An ALMA survey of the S2CLS UDS field: optically invisible submillimetre galaxies

“…Franco et al (2018) discussed four ALMA-detected sources in the GOODS-S region which lacked 160 -detections, two of which are in the earlier Simpson et al (2014) study (see also Zhou et al 2020). Yamaguchi et al (2019) found two examples in similar ALMA observations of the same region (one previously identified by Cowie et al 2018), while Umehata et al (2020) obtained a spectroscopic redshift of = 3.99 for a near-infrared-faint source uncovered in an ALMA survey in the SSA 22 region. There have also been examples studied through the selection of sources with very red Herschel SPIRE colours (e.g.…”

FIR-luminous [C ii] Emitters in the ALMA-SCUBA-2 COSMOS Survey (AS2COSMOS): The Nature of Submillimeter Galaxies in a 10 Comoving Megaparsec-scale Structure at z ∼ 4.6

“…The confirmed [C II] emitters are near-infrared blank or faint SMGs (K s >24 ABmag). AS2COS0034.1/34.2 do not have any clear optical/ near-infrared counterparts, which is consistent with them lying at z4 (e.g., Simpson et al 2014;Wang et al 2019;Dudzevičiūtė et al 2020;Umehata et al 2020;Smail et al 2020). We use the S 870μm /S 3GHz flux ratio as a crude redshift indicator (e.g., Carilli & Yun 1999;Barger et al 2000;Smail et al 2000).…”

Tracing the evolution of dust-obscured activity using sub-millimetre galaxy populations from STUDIES and AS2UDS

“…The spread at the UV/optical wavelengths seen in Fig. 1(b) highlights the variety of the SEDs of the 450-μm sources, ranging from unobscured (A V ∼ 0) Lyman-break galaxies, through more typical A V ∼ 1 star-forming galaxies similar to those selected using the BzK criteria (Daddi et al 2004), to higher-A V systems such as Extremely Red Objects (Smail et al 2004) and the near-infrared faint populations (Simpson et al 2014;Franco et al 2018;Smail et al 2020;Umehata et al 2020).…”