First Results from Iso Spectra of Supernova Remnants Heavily Interacting with the Ism

ISO spectra 1 of the supernova remnant RCW103 are presented. This object is the prototype of a SNR shock heavily interacting with dense ISM (probably a molecular cloud). The spectra are dominated by prominent lines and show very little continuum at < 40 m suggesting that the 12 and 25 m IRAS emission from these types of remnant could be dominated by lines rather than continuum emission from warm dust heated by the shock as generally believed. The ISO data provide for the rst time a simple and reliable estimate of the gas phase abundances of Si and Fe which are found to be close to solar relative to non refractory species such as Ne, S and Ar. This indicates that the shock is very eeective in destroying the ISM dust and may therefore explain the absence of warm dust behind the shock. Like the optical Nickel lines, NiII]6.63 m yields Ni/Fe abundances a factor 10 above solar which we conclude results from a large underestimation of the computed Ni + collision strengths. 1 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) with the participation of ISAS and NASA. 2 E. OLIVA ET AL.