We report the redshift of an unlensed , highly obscured submillimetre galaxy ( SMG ) , HS1700.850.1 , the brightest SMG ( S _ { 850 \mu m } =19.1 mJy ) detected in the JCMT/SCUBA-2 Baryonic Structure Survey , based on the detection of its ^ { 12 } CO line emission .
Using the IRAM PdBI-WIDEX with 3.6 GHz band width , we serendipitously detect an emission line at 150.6 GHz .
From a search over 14.5 GHz in the 3-mm and 2-mm atmospheric windows , we confirm the identification of this line as ^ { 12 } CO ( 5–4 ) at z = 2.816 , meaning that it does not reside in the z \sim 2.30 proto-cluster in this field .
Measurement of the 870 \mu m source size ( < 0.85 ^ { \prime \prime } ) from the Sub-Millimeter Array ( SMA ) confirms a compact emission in a S _ { 870 \mu m } = 14.5 mJy , L _ { IR } \sim 10 ^ { 13 } L _ { \odot } component , suggesting an Eddington-limited starburst .
We use the double-peaked ^ { 12 } CO line profile measurements along with the SMA size constraints to study the gas dynamics of a HyLIRG , estimating the gas and dynamical masses of HS1700.850.1 .
While HS1700.850.1 is one of the most extreme galaxies known in the Universe , we find that it occupies a relative void in the Lyman-Break Galaxy distribution in this field .
Comparison with other extreme objects at similar epochs ( HyLIRG Quasars ) , and cosmological simulations , suggests such an anti-bias of bright SMGs could be relatively common , with the brightest SMGs rarely occupying the most overdense regions at z = 2–4 .