SAS-2 Observations of Gamma Rays from the Galactic Plane

The SAS-2 -ray experiment has made measurements on the high-energy (>30 MeV) -rays coming irom the galactic-center region. The -radiation in this region is very much more intense than in the anticenter region, in agreement with the observations made with the OSO-3 experiment of Kraushaar et al., and exhibits a narrow distribution (the 2 width is no more than 6 ) along the plane which is nearly uniform in intensity from 330' to 30'. The average value, induding present uncertainties other than statistical is (1.15 [+0.40, -O.35J) X 10- photons (cm2 radian s) -1 The energy spectrum in the range from 35 to 210 MeV is quite flat, consistent with a 0-decay spectrum due to interactions between cosmic rays and interstellar matter, or a mixture of this spectrum and a spectrum formed by Compton radiation from cosmic-ray electrons. The intensity of the radiation in the anticenter direction is consistent with that expected if the origin is interactions between cosmic rays and interstellar matter, namely, 0.2 X 10- photons (cm2 radian s) 1 Subject headings:Galaxy, The - gamma rays