Black hole mass measurement using ALMA observations of [CI] and CO emissions in the Seyfert 1 galaxy NGC 7469

We present a supermassive black hole (SMBH) mass measurement in the Seyfert 1 galaxy NGC 7469 using Atacama Large Millimeter/submillimeter Array (ALMA) observations of the atomic-[CI](1-0) and molecular-(CO)-C-12(1-0) emission lines at the spatial resolution of approximate to 0 ''.3 (or approximate to 100 pc). These emissions reveal that NGC 7469 hosts a circumnuclear gas disc (CND) with a ring-like structure and a two-arm/bi-symmetric spiral pattern within it, surrounded by a starbursting ring. The CND has a relatively low sigma(gas)/V approximate to 0.35 (r less than or similar to 0 ''.5) and approximate to 0.19 (r > 0 ''.5), suggesting that the gas is dynamically settled and suitable for dynamically deriving the mass of its central source. As is expected from X-ray dominated region (XDR) effects that dramatically increase an atomic carbon abundance by dissociating CO molecules, we suggest that the atomic [CI](1-0) emission is a better probe of SMBH masses than CO emission in active galactic nuclei (AGNs). Our dynamical model using the [CI](1-0) kinematics yields a M-BH = 1.78(-1.10)(+2.69) x 10(7) M-circle dot and M/L-F547M = 2.25(-0.43)(+0.40) (M-circle dot/L-circle dot). The model using the (CO)-C-12(1-0) kinematics also gives a consistent M-BH with a larger uncertainty, up to an order of magnitude, i.e. M-BH = 1.60(-1.45)(+11.52) x 10(7) M-circle dot. This newly dynamical M-BH is approximate to 2 times higher than the mass determined from the reverberation mapped (RM) method using emissions arising in the unresolved broad-line region (BLR). Given this new M-BH, we are able to constrain the specific RM dimensionless scaling factor of f = 7.2(-3.4)(+4.2) for the AGN BLR in NGC 7469. The gas within the unresolved BLR thus has a Keplerian virial velocity component and the inclination of i approximate to 11.0 degrees(+2.2)(-2.5), confirming its face-on orientation in a Seyfert 1 AGN by assuming a geometrically thin BLR model.

Automated summary

This study presents a SMBH mass measurement in the galaxy NGC 7469 using ALMA observations, revealing new features and proposing a new method for mass derivation. The new mass result is higher than previous methods and can be used to determine the RM dimensionless scaling factor for the AGN BLR.