Resolving a merger in a hyper-luminous submillimeter galaxy at z=2.82

We present the resolved properties of the z = 2.82 Hyper Luminous Infrared Galaxy (HyLIRG) HS1700.850.1, the brightest 850μm source found in the SCUBA-2 followup to the Keck Baryonic Structure Survey fields (S850μm =19.5 mJy), and amongst the most luminous starbursts known at any redshift. Using the IRAM-NOEMA interferometer in the highest resolution A-configuration, we resolve the source into two components separated by ∼8 kpc, visible as blue shifted and red shifted 12CO(5-4) lines, exhibiting the expected kinematic properties of a major merger between two gas-rich galaxies. The combined merger system is traced over 2.3″ or 18.4 kpc. Each component of the merger shows ordered gas motions suggestive of a massive, turbulent disk. We measure the dynamical masses of the blue and red disks as (1.5 ± 0.2) × 1011 M⊙ and (0.71 ± 0.22) × 1011 M⊙ respectively. The more massive disk component shows broad wings in the CO line, offset by ∼3 kpc from the disk centroid along the major axis, and extending to velocities ∼±1000 km $\rm {s^{-1}}$ from systemic velocity. We interpret this as either a possible bipolar outflowing component, or more likely a warping or tidal structure in the CO disk. Comparing the properties of HS1700.850.1 to other submillimeter detected galaxies with comparably bright 850μm luminosities suggests that ongoing gas-rich mergers, or at least a clustered/group environment lead to these most extreme starburst phases.