Ionisation impact of high-mass stars on interstellar filaments

A Herschel study of the RCW 36 bipolar nebula in Vela C ^⋆,⋆⋆

¹ Laboratoire AIM Paris-Saclay, CEA/IRFU-CNRS/INSU-Université Paris Diderot, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
e-mail: vincent.minier@cea.fr
² Departamento de Astronomía, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, 36- D Casilla, Chile
³ The Rutherford Appleton Laboratory, Chilton, Didcot, OX11 0QX, UK
⁴ Department of Physics and Astronomy, The Open University, Milton Keynes, UK
⁵ School of Physics, University of New South Wales, Sydney, 2052 NSW, Australia
⁶ Laboratoire d’Astrophysique de Marseille, UMR 6110, CNRS – Université de Provence, 38 rue F. Joliot-Curie, 13388 Marseille, France
⁷ National Research Council of Canada, 5071 West Saanich Road, Victoria, V9E 2E7 BC, Canada
⁸ IAPS − Instituto di Astrofisica e Planetologia Spaziali, via Fosso del Cavaliere 100, 00133 Roma, Italy
⁹ INAF − Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monte Porzio Catone, Italy
¹⁰ Jeremiah Horrocks Institute, University of Central Lancashire, PR1 2HE, UK

Received: 16 April 2012
Accepted: 30 November 2012

Abstract

Context. Ionising stars reshape their original molecular cloud and impact star formation, leading to spectacular morphologies such as bipolar nebulae around H ii regions. Molecular clouds are structured in filaments where stars principally form, as revealed by the Herschel space observatory. The prominent southern hemisphere H ii region, RCW 36, is one of these bipolar nebulae.

Aims. We study the physical connection between the filamentary structures of the Vela C molecular cloud and the bipolar morphology of RCW 36, providing an in-depth view of the interplay occurring between ionisation and interstellar structures (bright-rims and pillars) around an H ii region.

Methods. We have compared Herschel observations in five far-infrared and submillimetre filters with the PACS and SPIRE imagers, to dedicated numerical simulations and molecular line mapping.

Results. Our results suggest that the RCW 36 bipolar morphology is a natural evolution of its filamentary beginnings under the impact of ionisation.

Conclusions. Such results demonstrate that, filamentary structures can be the location of very dynamical phenomena inducing the formation of dense clumps at the edge of H ii regions. Moreover, these results could apply to better understanding the bipolar nebulae as a consequence of the expansion of an H ii region within a molecular ridge or an interstellar filament.