Detection of solid ammonia, methanol, and methane with ISOPHOT.

Abstract

We report on a search for the NH₃ inversion band at 9.0 mu m, the CH₄ band at 7.7 mu m, and the CH₃OH band at 9.7 mu m in the spectra of 10 heavily obscured stellar objects taken with the spectrophotometer ISOPHOT-S aboard the Infrared Space Observatory (ISO). Four of them show indications of the NH₃ inversion band at 9.0 mu m superimposed on the always strong silicate band. The results show that ammonia ice may be abundant in some cool and dense molecular circumstellar regions. The 9.7 mu m band of solid CH₃OH was detected in 5 of the sources, and also the 7.7 mu m band of solid CH₄ was found in 5 sources. The PHT-S detections were cross-checked against ISO-SWS spectra from archive data. Considering the different beam sizes (24 x 24 sq arcsec versus 14 x 20 sq arcsec ), there is good agreement. 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.