ForumSpringer[A&A-EE Home Page]
ForumWhats NewSearchOrdersTable of Contents

Astron. Astrophys. 315, L289-L292 (1996)

SWS observations of IR emission features towards compact HII regions*

P.R. Roelfsema1,4, P. Cox2, A.G.G.M. Tielens3, L.J. Allamandola3, J.-P. Baluteau5, M.J. Barlow6, D. Beintema1,4, D.R. Boxhoorn1,4, J.P. Cassinelli7, E. Caux8, E. Churchwell7, P.E. Clegg9, Th. de Graauw1, A.M. Heras4, R. Huygen10, K.A. van der Hucht11, D.M. Hudgins3, M.F. Kessler4, T. Lim4,9, and S.A. Sandford3

1 SRON, P.O. Box 800, 9700 AV Groningen, The Netherlands
2 Institut d'Astrophysique Spatiale, Bât. 120, Universit'e de Paris XI, F-91405 Orsay, France
3 NASA Ames Research Center, MS: 245-6, Moffett Field, CA 94035, USA
4 ISO Science Operations Centre, Astrophysics Division of ESA, P.O. Box 50727, E-28080 Madrid/Villafranca, Spain
5 Laboratoire d'Astronomie Spatiale, CNRS, BP 8, F-13376 Marseille Cedex 12, France
6 Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
7 Department of Astronomy, University of Wisconsin-Madison 475 N Charter Street, Madison, WI 53706-1582, USA
8 Centre d'Etude Spatiale des Rayonnements, CESR/CNRS-UPS, BP 4346, F-31029 Toulouse Cedex, France
9 Queen Mary and Westfield College, University of London, Mile End Road, London E1 4NS, UK
10 Instituut voor Sterrenkunde, Universiteit van Leuven, Celestijnenlaan 200B, B-3001 Heverlee, Belgium
11 SRON, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands

Received 31 July 1996 / Accepted 29 August 1996

Abstract. We present ISO Short Wavelength Spectrometer (SWS**) grating spectra of six compact HII regions. In addition to strong emission lines from atomic species these spectra display infrared bands attributed to Polycyclic Aromatic Hydrocarbons (PAHs). The continuous spectral coverage of the present observations and the high spectral resolution allow to describe the detailed structure of the emission bands: the 7.7 img14.gif band is composed of two bands at 7.6 and 7.8 img14.gif , the 6.2 img14.gif band has a long wavelength extension, there is a plateau of emission between 6 and 7 img14.gif and a new feature is reported at 11.0 img14.gif in addition to the well-known 11.2 img14.gif band. These observations also reveal large variations in the relative intensities of the dust bands, in particular between the 7.7 and 8.6 img14.gif bands. In one extreme case, the 8.6 img14.gif band is stronger than the 7.7 img14.gif band. These observations are compared to a mixed population of ionized PAHs, using new laboratory measurements.

Key words: ISM: dust - ISM: HII regions - ISM: molecules - infrared: ISM: lines and bands

* 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 the participation of ISAS and NASA.
**SWS is a joint project of SRON and MPE (DARA grants no 50 QI9402 3 and 50 QI8610 8) with contributions from KU Leuven, Steward Observatory, and Phillips Laboratory.

Article in PDF format
Article in (gzipped) PS format

Last change: December 16, 1996
© European Southern Observatory (ESO) 1996