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Astron. Astrophys. 341, 667-674 (1999)

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A barred spiral at the centre of the giant elliptical radio galaxy Centaurus A *

I.F. Mirabel 1,2, O. Laurent 1, D.B. Sanders 3, M. Sauvage 1, M. Tagger 1, V. Charmandaris 4, L. Vigroux 1, P. Gallais 1, C. Cesarsky 1 and D.L. Block 5

1 CEA/DSM/DAPNIA Service d'Astrophysique F-91191 Gif-sur-Yvette, France
2 Instituto de Astronomía y Física del Espacio, cc 67, suc 28. 1428 Buenos Aires, Argentina
3 Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
4 Observatoire de Paris, DEMIRM, 61 Av. de l'Observatoire, F-75014 Paris, France
5 Department of Computational and Applied Mathematics, University of the Witwatersrand, Private Bag 3, WITS 2050, South Africa

Received 7 October 1998 / Accepted 12 October 1998

Abstract

We report observations at mid-infrared and sub-millimeter wavelengths of Centaurus A (Cen A, NGC 5128), the giant elliptical galaxy that harbors the closest radio loud Active Galactic Nucleus (AGN) to Earth. The dust emission from the deep interior of Cen A reveals a bisymmetric structure with a diameter of [FORMULA] (5 kpc), centred at the AGN. This structure is remarkably similar to that of a barred spiral galaxy, with the bar lying in a plane that is tilted [FORMULA] [FORMULA] from the line of sight. The true nature of the distribution of dust in the inner regions of Cen A is noticeably displaced from the more chaotic and widespread optical obscuration. The barred spiral is a quasi-stable structure formed at the center of the giant elliptical from the tidal debris of a gas-rich object(s) accreted in the past 109 years. The total size and mass of interstellar gas in the barred spiral at the center of Cen A is comparable to the small Local Group spiral galaxy Messier 33. The observation of this remarkable structure opens the more general question on whether the dusty hosts of giant radio galaxies like Cen A, are "symbiotic" galaxies composed of a barred spiral inside an elliptical, where the bar serves to funnel gas toward the AGN.

Key words: galaxies: active – galaxies: individual: NGC 5128=Cen A – galaxies: kinematics and dynamics – galaxies: structure – infrared: galaxies

* Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with participation of ISAS and NASA.

Send offprint requests to: I.F. Mirabel
(mirabel@discovery.saclay.cea.fr)

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© European Southern Observatory (ESO) 1999

Online publication: December 16, 1998
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