Open AccessA near‐infrared polarized bipolar cone in the Circinus galaxy
Author(s) -
Ruiz M.,
Alexander D. M.,
Young S.,
Hough J.,
Lumsden S. L.,
Heisler C. A.
Publication year - 2000
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2000.03454.x
Subject(s) - physics , torus , astrophysics , galaxy , astronomy , flux (metallurgy) , luminous infrared galaxy , active galactic nucleus , infrared , polarization (electrochemistry) , extinction (optical mineralogy) , optics , geometry , chemistry , mathematics , materials science , metallurgy
We present near‐infrared broad‐band polarization images of the nuclear regions of the Circinus galaxy in the J , H and K bands. For the first time the south‐eastern reflection cone is detected in polarized light, which is obscured at optical wavelengths behind the galactic disc. This biconical structure is clearly observed in J ‐ and H ‐band polarized flux, whilst in the K band a more compact structure is detected. Total flux J − K and H − K colour maps reveal a complex colour gradient toward the south‐east direction (where the Circinus galactic disc is nearer to us). We find enhanced extinction in an arc‐shaped structure, at about 200 pc from the nucleus, probably part of the star formation ring. We model the polarized flux images with the scattering and torus model of Young et al., with the same basic input parameters as used by Alexander et al. in the spectropolarimetry modelling of Circinus. The best fit to the polarized flux is achieved with a torus radius of ∼16 pc, and a visual extinction A V , through the torus, to the near‐infrared emission regions of >66 mag.