Resolving the nucleus of Centaurus A at mid-IR wavelengths

TL;DR

This study used mid-infrared interferometry to resolve the nuclear structure of Centaurus A at high resolution, revealing a complex, elongated disk with a significant point source contribution, advancing understanding of AGN inner regions.

Contribution

First high-resolution mid-IR interferometric imaging of Centaurus A's nucleus, modeling its structure as an elongated disk with detailed geometric parameters.

Findings

Resolved a 1.4 x 0.65 pc elongated disk in Centaurus A

Identified a 47% point source contribution at 12.5 microns

Detected complex small-scale nuclear structure in the AGN

Abstract

We have observed Centaurus A with the MID-infrared Interferometric instrument (MIDI) at the Very Large Telescope Interferometer (VLTI) at resolutions of 7 - 15 mas (at 12.5 micron) and filled gaps in the (u,v) coverage in comparison to earlier measurements. We are now able to describe the nuclear emission in terms of geometric components and derive their parameters by fitting models to the interferometric data. With simple geometrical models, the best fit is achieved for an elongated disk with flat intensity profile with diameter 76 +/- 9 mas x 35 +/- 2 mas (1.41 +/- 0.17 pc x 0.65 +/- 0.03 pc) whose major axis is oriented at a position angle (PA) of 10.1 +/- 2.2 degrees east of north. A point source contributes 47 +/- 11 % of the nuclear emission at 12.5 micron. There is also evidence that neither such a uniform nor a Gaussian disk are good fits to the data. This indicates that we are resolving more complicated small-scale structure in AGNs with MIDI, as has been seen in Seyfert galaxies previously observed with MIDI. The PA and inferred inclination i = 62.6 +2.1/-2.6 degrees of the dust emission are compared with observations of gas and dust at larger scales.