Bands of solid CO2 in the 2-3 μm spectrum of S 140:IRS1

Abstract

We investigate the 2-3 μm ISO-SWS spectrum of the luminous protostellar object S 140:IRS1. Two narrow absorption features are detected at 2.70 and 2.77 μm, which are well fitted with laboratory spectra of the v1 + v3 and the 2v2 + v3 combination modes of solid CO2. The ice in this line of sight must have been subjected to significant heating, in agreement with previously studied CO2 bands. A combined laboratory fit to all CO2 bands detected toward S 140:IRS1 shows, among others, the need for particle shape calculations for the CO2 stretch mode. Finally, we discuss the absence of features of isolated H2O and dangling OH groups in the spectrum of S 140:IRS1.