ALMA FOLLOWS STREAMING OF DENSE GAS DOWN TO 40 pc FROM THE SUPERMASSIVE BLACK HOLE IN NGC 1097

We present a kinematic analysis of the dense molecular gas in the central 200 pc of the nearby galaxy NGC 1097, based on Cycle 0 observations with the Atacama Large Millimeter/submillimeter Array (ALMA). We use the HCN(4–3) line to trace the densest interstellar molecular gas ( cm−3), and quantify its kinematics, and estimate an inflow rate for the molecular gas. We find a striking similarity between the ALMA kinematic data and the analytic spiral inflow model that we have previously constructed based on ionized gas velocity fields on larger scales. We are able to follow dense gas streaming down to 40 pc distance from the supermassive black hole in this Seyfert 1 galaxy. In order to fulfill marginal stability, we deduce that the dense gas is confined to a very thin disk, and we derive a dense gas inflow rate of 0.09 M☉ yr−1 at 40 pc radius. Combined with previous values from the Hα and CO gas, we calculate a combined molecular and ionized gas inflow rate of ∼0.2 M☉ yr−1 at 40 pc distance from the central supermassive black hole of NGC 1097.

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