Die difffuse Gammastrahlung des lokalen Spiralarms.

To test the suggestion that the gamma brightness of the local spiral arm should be proportional to the visual absorption, the gamma isophotes are compared with isophotes of the local 21 cm radiation and suitable isopleths of the zone of avoidance. The correlations are very good. The gamma emissivity amounts to 1.3 x 10 to the -25th photons per H atom and molecule per second or 0.0001 photons per magnitude of absorption per second. The emissivity of the arm amounts to 1.7 x 10 to the 39th photons per kpc arm-length per second. The distribution of the gamma intensity as well as similar runs of local gas distribution and absorption prove the concept of the local spiral arm to be a better description of anticenter phenomena than the more formal great circle of Gould's belt. The descending node of the gamma brightness is at 155 deg, while Gould's belt crosses the galactic equator at 112 deg.