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This paper presents spectra in the 2 to 20 micron range of quiescent cloudmaterial located in the IC 5146 cloud complex. The spectra were obtained withNASA's Infrared Telescope Facility (IRTF) SpeX instrument and the Spitzer SpaceTelescope's Infrared Spectrometer. We use these spectra to investigate dust andice absorption features in pristine regions of the cloud that are unaltered byembedded stars. We find that the H2O-ice threshold extinction is 4.03+/-0.05mag. Once foreground extinction is taken into account, however, the thresholddrops to 3.2 mag, equivalent to that found for the Taurus dark cloud, generallyassumed to be the touchstone quiescent cloud against which all other densecloud and embedded young stellar object observations are compared. Substructurein the trough of the silicate band for two sources is attributed to CH3OH andNH3 in the ices, present at the ~2% and ~5% levels, respectively, relative toH2O-ice. The correlation of the silicate feature with the E(J-K) color excessis found to follow a much shallower slope relative to lines of sight that probediffuse clouds, supporting the previous results by Chiar et al. (2007).

Ices in the Quiescent IC 5146 Dense Cloud