IRTS observations of the unidentified infrared bands in the diffuse Galactic light

The results of IRTS observations of the unidentified infrared (UIR) bands in the diffuse galactic radiation are presented. The Near-Infrared Spectrometer (NIRS) and the Mid-Infrared Spectrometer (MIRS) on board the IRTS have unambiguously demonstrated the presence and spatial distribution of the 3.3, 3.4, 6.2, 7.7, 8.6, and 11.2 mu m UIR bands in the diffuse galactic radiation in a wide area around the galactic plane for the first time. Their intensities are correlated fairly well with the far-infrared thermal emission from classical submicron dust grains, which has been derived from the IRAS 100 mu m intensity and the 155 mu m intensity obtained from the Far-Infrared Line Mapper (FILM) also on board the IRTS. The results indicate that the UIR emitting material is well mixed with the submicron dust grains and the UIR band can be used as a useful measure for the column density of the interstellar material and the local interstellar radiation field. Possible detections of the UIRs in cirrus clouds are also presented.