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arXiv · 2007.09887

ALMA Deep Field in SSA22: A near-infrared-dark submillimeter galaxy at z=4.0

Hideki Umehata·Ian Smail·A. M. Swinbank·Kotaro Kohno·Yoichi Tamura·Tao Wang·Yiping Ao·Bunyo Hatsukade·Mariko Kubo·Kouchiro Nakanishi·Natsuki N. Hayatsu
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Abstract

Deep surveys with 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 detailed characterization of the population challenging. Here we present a spectroscopic redshift identification and characterization of one of such near-infrared-dark galaxy discovered by an ALMA deep survey. Detection of [CI](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 multi-wavelength analysis, ADF22.A2 is found to be a massive, star-forming galaxy with stellar mass Mstar = $1.1_{-0.6}^{+1.3}$ x 10^{11} Msun and SFR = $430_{-150}^{+230}$ Msun/yr. The molecular gas mass is derived to be M ($H_2$) = 5.9 +/- 1.5x10^{10} Msun, indicating a gas fraction of ~35%, and the ratios of $L_{\rm [CI](1-0)}/L_{\rm IR}$ and $L_{\rm [CI](1-0)}/L_{\rm CO(4-3)}$ suggests 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 redshift, star-formation rate, stellar mass, and depletion time scale (tau~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 to obtain an unbiased view of galaxy formation in the early Universe.

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Hideki Umehata, Ian Smail, A. M. Swinbank, Kotaro Kohno, Yoichi Tamura, Tao Wang, Yiping Ao, Bunyo Hatsukade, Mariko Kubo, Kouchiro Nakanishi, Natsuki N. Hayatsu. 2020-07-20. ALMA Deep Field in SSA22: A near-infrared-dark submillimeter galaxy at z=4.0. https://doi.org/10.1051/0004-6361%2F202038146

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