Massive Molecular Gas Flows in the A1664 Brightest Cluster Galaxy

We report ALMA Early Science CO(1–0) and CO(3–2) observations of the brightest cluster galaxy (BCG) in A1664. The BCG contains 1.1 × 10 10 M ☉ of molecular gas divided roughly equally between two distinct velocity systems: one from −250 to +250 km s −1 centered on the BCG's systemic velocity and a high-velocity system blueshifted by 570 km s −1 with respect to the systemic velocity. The BCG's systemic component shows a smooth velocity gradient across the BCG center, suggestive of rotation about the nucleus. However, the mass and velocity structure are highly asymmetric and there is little star formation coincident with a putative disk. It may be an inflow of gas that will settle into a disk over several 10 8 yr. The high-velocity system consists of two gas clumps, each ∼2 kpc across, located to the north and southeast of the nucleus. Each has a line of sight velocity spread of 250–300 km s −1 . The velocity of the gas in the high-velocity system increases toward the BCG center and may be a massive flow into the nucleus. However, the velocity gradient is not smooth. These structures are also coincident with low optical–ultraviolet surface brightness regions, which could indicate dust extinction associated with each clump. The structure is complex, making a clear interpretation difficult, but if the dusty, molecular gas lies predominantly in front of the BCG, the blueshifted velocities would indicate an outflow. Based on the energy requirements, such a massive outflow would most likely be driven by the active galactic nucleus. A merger origin is unlikely but cannot be ruled out.