Gemini Imaging of Mid-IR Emission from the Nuclear Region of Centaurus A

TL;DR

This paper provides high-resolution mid-IR images of Centaurus A's nucleus, revealing a compact core, surrounding dust structures, and star-forming regions, advancing understanding of the galaxy's nuclear environment and emission sources.

Contribution

It presents the highest spatial resolution mid-IR images of Centaurus A's nuclear region, analyzing the structure and emission sources with detailed modeling and multi-wavelength comparisons.

Findings

Unresolved core size limits: 3.2 pc at 8.8 micron, 3.5 pc at 18.3 micron

Mid-IR emission likely from dusty torus, narrow line region, and jet-related synchrotron emission

Extended mid-IR emission coincides with star-forming regions and jet activity

Abstract

We present high spatial resolution mid-IR images of the nuclear region of NGC 5128 (Centaurus A). Images were obtained at 8.8 micron, N-band (10.4 micron), and 18.3 micron using the mid-IR imager/spectrometer T-ReCS on Gemini South. These images show a bright unresolved core surrounded by low-level extended emission. We place an upper limit to the size of the unresolved nucleus of 3.2 pc (0.19") at 8.8 micron and 3.5 pc (0.21") at 18.3 micron at the level of the FWHM. The most likely source of nuclear mid-IR emission is from a dusty torus and possibly dusty narrow line region with some contribution from synchrotron emission associated with the jet as well as relatively minor starburst activity. Clumpy tori models are presented which predict the mid-IR size of this torus to be no larger than 0.05" (0.85pc). Surrounding the nucleus is extensive low-level mid-IR emission. Previously observed by ISO and Spitzer, this paper presents to date the highest spatial resolution mid-IR images of this extended near nuclear structure. Much of the emission is coincident with Pa-alpha sources seen by HST implying emission from star forming areas, however evidence for jet induced star formation, synchrotron emission from the jet, a nuclear bar/ring, and an extended dusty narrow emission line region is also discussed.