A geometric distance to the supermassive black Hole of NGC 3783

TL;DR

This paper combines VLTI/GRAVITY and reverberation mapping data to precisely measure the supermassive black hole's mass and the geometric distance to NGC 3783, enhancing our understanding of AGN structure and cosmology.

Contribution

It introduces a joint analysis method that improves black hole mass estimates and provides a direct geometric distance measurement to NGC 3783, testing its consistency with other distance indicators.

Findings

Black hole mass of approximately 2.54 x 10^7 solar masses.

Geometric distance to NGC 3783 of about 40 Mpc.

BLR-based distance aligns with other methods within scatter.

Abstract

The angular size of the broad line region (BLR) of the nearby active galactic nucleus (AGN) NGC 3783 has been spatially resolved by recent observations with VLTI/GRAVITY. A reverberation mapping (RM) campaign has also recently obtained high quality light curves and measured the linear size of the BLR in a way that is complementary to the GRAVITY measurement. The size and kinematics of the BLR can be better constrained by a joint analysis that combines both GRAVITY and RM data. This, in turn, allows us to obtain the mass of the supermassive black hole in NGC3783 with an accuracy that is about a factor of two better than that inferred from GRAVITY data alone. We derive $M_\mathrm{BH}=2.54_{-0.72}^{+0.90}\times 10^7\,M_\odot$. Finally, and perhaps most notably, we are able to measure a geometric distance to NGC 3783 of $39.9^{+14.5}_{-11.9}$ Mpc. We are able to test the robustness of the BLR-based geometric distance with measurements based on the Tully-Fisher relation and other indirect methods. We find the geometric distance is consistent with other methods within their scatter. We explore the potential of BLR-based geometric distances to directly constrain the Hubble constant, $H_0$, and identify differential phase uncertainties as the current dominant limitation to the $H_0$ measurement precision for individual sources.