Galactic gamma-ray flux in the 0.06--5 MeV range

By using the Apollo 16 spacecraft as an occulter, the Apollo gamma-ray spectrometer (AGRS) obtained information on the spectrum and angular distribution of flux from the galactic plane. The energy range of observation was 60 keV to 5 MeV. The results show emission from the Crab nebula, Cyg X-1, and in the galactic plane extending +- 600 in galactic longitude about the galactic center. Taken with observation of Haymes et al., Wheaton, and Imhof and Nakano, the spectrum of galactic emission near 1 MeV over this range of longitudes is (1.3 +- 0.45) x 10-3(hv/1 MeV)/sup() -2.8plus-or-minus0.1/ photons cm-2 s-1 MeV-1 rad-1. This is in agreement with hard X-ray observations of the galactic central regions, suggesting that an ensemble of point sources is responsible. A simple power-law connection between the hard X-ray range and the 100 MeV range is not permitted. Apollo 16 upper limits to the cosmic 4.4 MeV line flux imply that the ratio of line strength to continuum emission for the region observed by Haymes et al. is higher than the galactic average