NOEMA Redshift Measurements of the Brightest Submillimeter Galaxies in the GOODS-N

We report spectroscopic redshift measurements for three bright submillimeter galaxies (SMGs) in the GOODS-N field, each with SCUBA-2 850 μm fluxes > 10 mJy, using the Northern Extended Millimeter Array (NOEMA). Our molecular linescan observations of these sources, which occupy a ∼ 7 arcmin area outside of the HST/ACS region of the field, reveal that two lie at z ∼ 3.14 and thus likely belong to a previously-unknown overdensity of rare galaxies, which we shall refer to as a protocluster. In the remaining object, which is the brightest SCUBA-2 source in the entire GOODS-N, we detect line emission consistent with CO(7–6), [C i], and H2O at z = 4.42. The far-infrared spectral energy distributions of these galaxies, constrained by SCUBA-2, NOEMA, and Herschel/SPIRE, indicate instantaneous SFRs ∼ 4000 M yr−1 in the z = 4.42 galaxy and ∼ 2500 M yr−1 in the two z ∼ 3 galaxies. These occupy a co-moving volume ∼ 30 Mpc, making the protocluster one of the most compact, spectroscopically-confirmed episodes of simultaneous dusty starbursts. Based on our sources’ CO line luminosities, we estimate Mgas ∼ 10M and find gas depletion timescales of τdepl ∼ 50 Myr, consistent with findings in other high-redshift SMG protoclusters.