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

Abstract

We present high spatial resolution mid-IR images of the nuclear region of NGC 5128 (Centaurus A). Images were obtained at 8.8 μm, N band (10.4 μm), and 18.3 μm 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 μm and 3.5 pc (0.21^'') at 18.3 μm at the level of the FWHM. The most likely source of nuclear mid-IR emission is from a dusty torus and possibly a 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^'' (0.85 pc). Surrounding the nucleus is extensive low-level mid-IR emission. This paper presents to date the highest spatial resolution mid-IR images of this extended near nuclear structure, previously observed by ISO and Spitzer. Much of the emission is coincident with Paα 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.