Far-infrared diffuse emission - Cosecant b law and galaxy counts

The IRAS diffuse emission data at 60 and 100 microns and the Lick Observatory galaxy counts are used here to study the large-scale distribution of interstellar dust at high Galactic latitudes, the isotropic component of diffuse emission, and the spectral behavior of the absorption coefficient in the far-IR. The results confirm the existence of the cosecant b law of Galactic far-IR emission. The isotropic component of diffuse emission is found to be comparable to the instrumental offset uncertainty at 100 microns. Therefore, the cosecant b law can provide an alternative local explanation for the extragalactic background claimed by Rowan-Robinson (1986). Assuming the IR absorption efficiency spectral index lying in the range one to two, a dust temperature in the range 22-25 K is found, in agreement with previous estimates. 20 references