Measurement of the Black Hole Mass in NGC 1332 from ALMA Observations at 0.044 Arcsecond Resolution

TL;DR

This study uses high-resolution ALMA observations of CO emission in NGC 1332 to measure the supermassive black hole's mass by modeling the circumnuclear gas disk's kinematics.

Contribution

First to successfully measure black hole mass in NGC 1332 using ALMA's 0.044 arcsecond resolution CO observations and detailed disk modeling.

Findings

Black hole mass estimated at 6.64 x 10^8 solar masses.

ALMA can resolve gas kinematics on scales smaller than the black hole's radius of influence.

Disk models fit well within 200 pc of the nucleus.

Abstract

We present Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 3 observations of CO(2-1) emission from the circumnuclear disk in the E/S0 galaxy NGC 1332 at 0.044" resolution. The disk exhibits regular rotational kinematics and central high-velocity emission (+/-500 km/s) consistent with the presence of a compact central mass. We construct models for a thin, dynamically cold disk in the gravitational potential of the host galaxy and black hole, and fit the beam-smeared model line profiles directly to the ALMA data cube. Model fits successfully reproduce the disk kinematics out to r=200 pc. Fitting models just to spatial pixels within projected r=50 pc of the nucleus (two times larger than the black hole's gravitational radius of influence), we find M_BH=6.64(-0.63,+0.65)*10^8 solar masses. This observation demonstrates ALMA's powerful capability to determine the masses of supermassive black holes by resolving gas kinematics on small angular scales in galaxy nuclei.