Shocked gas layers surrounding the WR nebula NGC 2359

¹ Departamento de Física, Universidad Europea de Madrid, Urb. El Bosque, Tajo s/n, 28670 Villaviciosa de Odón, Spain
² Observatorio Astronómico Nacional, Aptdo. Correos 1143, 28800 Alcalá de Henares, Spain
³ Departamento de Astrofísica Molecular e Infrarroja, Instituto de Estructura de la Materia, CSIC, Serrano 121, 28006 Madrid, Spain

Corresponding author: J. R. Rizzo, jricardo.rizzo@fis.cie.uem.es

Received: 11 June 2003
Accepted: 22 August 2003

Abstract

NGC 2359 is a Wolf-Rayet (W-R) nebula partially bound by a rather dense and warm molecular cloud. We present the results derived from CO and ¹³CO fully sampled maps of the molecular material with angular resolutions up to 12″. We have detected three different velocity components, and determined their spatial distribution and physical properties. The kinematics, morphology, mass and density are clearly stratified with respect to the W-R star. These features allow us to learn about the recent evolutionary history of HD 56925, because the multiple layers could be associated to several energetic events which have acted upon the surrounding circumstellar medium. Hence, a careful study of the different shockfronts contain clues in determining the present and past interaction of this evolved massive star with its surroundings. From the analysis of the mass-loss history in massive stars like HD 56925, we suggest that the multiple layers of shocked molecular gas are likely to be produced during the earlier LBV phase and/or the actual W-R stage of HD 56925.