Infrared spectra of protostars: Composition of the dust shells

Nearly complete 2 to 13 μm spectra are presented for 13 compact infrared sources associated with molecular clouds, as well as partial spectra of six additional objects. The spectra resemble blackbodies with superposed absorption features from 2.8 to 3.5 μm, at 6.0 and 6.8 μm, and in the silicate band centered near 9.7 μm. Correlations among the features are studied in an attempt to confirm possible identifications. A good correlation between the deepest part of the absorption at 3.1 μm, its long wavelength wing, and the 6.0 μm features suggests that all may be due to large amorphous water ice particles. The relatively poor correlation between the 3.4 and 6.8 μm optical depths adds no evidence to support the suggestion that these bands may be due to CH bonds