ALMA follows streaming of dense gas down to 40 pc from the supermassive black hole in NGC1097

TL;DR

This study uses ALMA observations to analyze dense molecular gas inflow towards the supermassive black hole in NGC1097, revealing streaming down to 40 parsecs and estimating an inflow rate of 0.09 solar masses per year.

Contribution

It demonstrates the ability of ALMA to trace dense gas inflow down to 40 pc from the black hole, combining kinematic data with an analytic inflow model for the first time.

Findings

Dense gas streams down to 40 pc from the black hole.

Inflow rate of 0.09 Msun/yr at 40 pc from the black hole.

Total inflow rate of 0.2 Msun/yr when combined with ionized gas.

Abstract

We present a kinematic analysis of the dense molecular gas in the central 200 parsecs of the nearby galaxy NGC1097, based on Cycle 0 observations with the Atacama Large Millimeter/sub-millimeter Array (ALMA). We use the HCN(4-3) line to trace the densest interstellar molecular gas, 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 disc, and we derive a dense gas inflow rate of 0.09 Msun/yr at 40 pc radius. Combined with previous values from the Ha and CO gas, we calculate a combined molecular and ionized gas inflow rate of 0.2 Msun/yr at 40 pc distance from the central supermassive black hole of NGC1097.