The large scale structure of the galactic gamma-ray emissivity.

Recent results on the galactic high energy gamma-ray emission obtained from the SAS-2 data have stimulated a new attempt of deriving the gamma-ray emissivity in the Galaxy by unfolding the longitude distribution of the galactic gamma radiation. In the present paper it is found that a rather different picture of the large scale distribution of the gamma-ray emissivity emerges from these results: the relative increase of the emissivity at 5 kpc from the galactic centre does not exceed a factor of 4; also the gamma-ray emissivity appears to be preferentially distributed in accordance with a spiral pattern as seen in comparing the unfolded distribution relative to both sides of the galactic disc.