C. Moutou 1, K. Sellgren 2, L. Verstraete 3 A. Léger 3 D. Rouan 4, & M. Werner 5
1 Observatoire de Haute Provence
2
3 IAS, Orsay. France
4 Observatoire de Meudon, France
5 JPL
We have obtained SWS and LWS spectra of reflection nebulae, in order to test the hypothesis that the photoelectric effect on tiny grains/PAHs is responsible for the heating of interstellar gas clouds. We selected reflection nebulae with exciting stars of different spectral types, from cool stars (3,600K) to hot stars (22,000K). Gas cooling lines such as [CII] and [OI] were observed, as well as the energy emitted at long wavelengths by large dust grains, and at short wavelengths by tiny grains/PAHs. We are searching for correlations between the strength of gas cooling lines and mid-infrared aromatic emission features, to test whether the photoelectric effect on tiny grains/PAHs is responsible for gas heating. Our preliminary results are promising.