The circumstellar envelope of IRC+10216 from milli-arcsecond to arcmin scales

¹ Observatoire de la Côte d'Azur, Dpt Cassiopée, CNRS-UMR 6202, BP 4229, 06304 Nice Cedex 4, France e-mail: [leao;laverny;mekarnia]@obs-nice.fr
² Departamento de Física, Universidade Federal do Rio Grande do Norte, 59072-970 Natal, RN, Brazil
³ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching b. München, Germany

Received: 23 November 2005
Accepted: 15 January 2006

Abstract

Aims.Analysis of the innermost regions of the carbon-rich star IRC+10216 and of the outer layers of its circumstellar envelope have been performed in order to constrain its mass-loss history.

Methods.We analyzed the high dynamic range of near-infrared adaptive optics and the deep V-band images of the circumstellar envelope of IRC+10216 using high angular resolution, collected with the VLT/NACO and FORS1 instruments.

Results.From the near-infrared observations, we present maps of the sub-arcsecond structures, or clumps, in the innermost regions. The morphology of these clumps is found to strongly vary from J- to L-band. Their relative motion appears to be more complex than proposed in earlier works: they can be weakly accelerated, have a constant velocity, or even be motionless with respect to one another. From V-band imaging, we present a high spatial resolution map of the shell distribution in the outer layers of IRC+10216. Shells are resolved well up to a distance of about 90'' to the core of the nebula and most of them appear to be composed of thinner elongated shells. Finally, by combining the NACO and FORS1 images, a global view is present to show both the extended layers and the bipolar core of the nebula together with the real size of the inner clumps.

Conclusions.This study confirms the rather complex nature of the IRC+10216 circumstellar environment. In particular, the coexistence at different spatial scales of structures with very different morphologies (clumps, bipolarity, and almost spherical external layers) is very puzzling. This confirms that the formation of AGB winds is far more complex than usually assumed in current models.