Solid CO_2 towards NGC7538 IRS1

Abstract

We report the observation of the young infrared source NGC7538 IRS1 with the Short Wavelength Spectrometer (SWS) onboard the ISO satellite in the 2.4-45 mu m range. The spectrum exhibits several absorption features due to silicates and to molecular species frozen on the refractory dust. In particular the stretching and bending mode of solid CO_2 have been identified. In this paper we present a comparison of the observed absorption band at about 15.1 mu m (660 cm(-1) ) attributed to the bending mode of solid CO_2 with laboratory spectra of ion irradiated ice mixtures. 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.