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Astron. Astrophys. 341, L75-L78 (1999)

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Letter to the Editor

ISO-SWS spectroscopy of IC443 and the origin of the IRAS 12 and 25 µm emission from radiative supernova remnants *

E. Oliva 1, D. Lutz 2, S. Drapatz 2 and A.F.M. Moorwood 3

1 Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy
2 Max-Planck-Institute für Extraterrestrische Physik, Postfach 1603, D-85740 Garching, Germany
3 European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei München, Germany

Received 17 November 1998 / Accepted 3 December 1998


ISO-SWS spectral observations of the supernova remnant IC443 are presented. Like other radiative SNRs, this object is characterized by prominent line-emitting filaments and relatively strong IRAS 12 and 25 µm emission which is commonly interpreted as thermal radiation from very small grains stochastically heated by collisions with the hot plasma behind the shock front. This interpretation is challenged by the data presented in this Letter which indicate that most of the 12 and 25 µm IRAS flux is accounted for by ionized line emission (mainly [NeII] and [FeII]). This result also seems to hold for other radiative SNRs. We also discuss the possible contribution of H2 lines to the IRAS 12 µm flux from the southern rim of IC443 and briefly analyze the element abundances derived from the observed ionic lines.

Key words: ISM: individual objects: IC443 – ISM: supernova remnants – 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. The SWS is a joint project of SRON and MPE.

Send offprint requests to: E. Oliva

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© European Southern Observatory (ESO) 1999

Online publication: December 16, 1998