Constraints on the nuclear emission from the Circinus galaxy: the torus

Abstract

In the context of the unified model of Seyfert galaxies, we use observations from the literature and a radiative transfer model to investigate the near-IR to mm emission produced by the presumed torus in the Circinus galaxy, from 2microns to 1.3mm. From the infrared SED modelling, we find that the total luminosity (L_{IR}) in this wavelength range, consists of similar contributions from the torus and starburst with a ratio of nuclear luminosity to starburst luminosity (L_{NUC}/L_{SB}) approx. 0.8. By using a similar torus model to that of NGC1068, but without the conical dust, we find an upper limit to the outer torus radius of approx. 12pc with a best fit of approx. 2pc. The upper limit torus size estimated from the radiative transfer modelling is consistent with the 16pc torus radius estimated from near-IR imaging polarimetry of Circinus.