The central parsec of NGC 3783: a rotating broad emission line region, asymmetric hot dust structure, and compact coronal line region

TL;DR

This study uses high-resolution interferometry to map the gas and dust structures around NGC 3783's active nucleus, revealing a rotating broad line region, asymmetric hot dust, and a compact coronal line region, advancing understanding of AGN inner regions.

Contribution

First simultaneous high-resolution measurements of the BLR, hot dust, and CLR structures in NGC 3783, providing a comprehensive 0.01-100 pc view of AGN inner regions.

Findings

BLR is a rotating thick disk with a mean radius of 16 light days.

Hot dust size measured at 0.14 pc with an offset cloud detected.

CLR size is approximately 0.4 pc, located between BLR and NLR.

Abstract

Using VLTI/GRAVITY and SINFONI data, we investigate the sub-pc gas and dust structure around the nearby type 1 AGN hosted by NGC 3783. The K-band coverage of GRAVITY uniquely allows a simultaneous analysis of the size and kinematics of the broad line region (BLR), the size and structure of the near-IR continuum emitting hot dust, and the size of the coronal line region (CLR). We find the BLR probed through broad Br$\gamma$ emission is well described by a rotating, thick disk with a radial distribution of clouds peaking in the inner region. In our BLR model the physical mean radius of 16 light days is nearly twice the 10 day time lag that would be measured, which matches very well the 10 day time lag that has been measured by reverberation mapping. We measure a hot dust FWHM size of 0.74 mas (0.14 pc) and further reconstruct an image of the hot dust which reveals a faint (5% of the total flux) offset cloud which we interpret as an accreting cloud heated by the central AGN. Finally, we directly measure the FWHM size of the nuclear CLR as traced by the [CaVIII] and narrow Br$\gamma$ line. We find a FWHM size of 2.2 mas (0.4 pc), fully in line with the expectation of the CLR located between the BLR and narrow line region. Combining all of these measurements together with larger scale near-IR integral field unit and mid-IR interferometry data, we are able to comprehensively map the structure and dynamics of gas and dust from 0.01--100 pc.