Astron. Astrophys. 358, 708-716 (2000)

Silicate emission in Orion ^*

D. Cesarsky ^1,2, A.P. Jones ¹, J. Lequeux ³ and L. Verstraete <sup>1

1</sup> Institut d'Astrophysique Spatiale, Bat. 121, Université Paris XI, 91405 Orsay CEDEX, France (ant@ias.fr; verstra@ias.fr)
² Max-Planck-Institut für Extraterrestrische Physik, 85741 Garching, Germany (diego.cesarsky@mpe.mpg.de)
³ DEMIRM, Observatoire de Paris, 61 Avenue de l'Observatoire, 75014 Paris, France (james.lequeux@obspm.fr)

Received 7 December 1999 / Accepted 26 January 2000

Abstract

We present mid-infrared spectro-imagery and high-resolution spectroscopy of the Orion bar and of a region in the Orion nebula. These observations have been obtained in the Guaranteed Time with the Circular Variable Filters of the ISO camera (CAM-CVF) and with the Short Wavelength Spectrometer (SWS), on board the European Infrared Space Observatory (ISO). Our data shows emission from amorphous silicate grains from the entire H II  region and around the isolated O9.5V star  Ori A. The observed spectra can be reproduced by a mixture of interstellar silicate and carbon grains heated by the radiation of the hot stars present in the region. Crystalline silicates are also observed in the Orion nebula and suspected around  Ori A. They are probably of interstellar origin. The ionization structure and the distribution of the carriers of the Aromatic Infrared Bands (AIBs) are briefly discussed on the basis of the ISO observations.

Key words: ISM: individual objects: Orion nebula ISM: individual objects: Orion bar stars: individual: 2  Ori A ISM: H ii regions ISM: dust, extinction 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.

Send offprint requests to: james.lequeux@obspm.fr

© European Southern Observatory (ESO) 2000

Online publication: June 8, 2000

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