ANNIHILATION FOUNTAIN IN THE GALACTIC-CENTER REGION

Two different model-independent mapping techniques have been applied t o Compton Gamma Ray Observatory OSSE, SMM, TGRS, and balloon data and reveal a feature in the 0.511 MeV e(+)-e(-) annihilation radiation pat tern of our Galaxy centered at I similar to -2 degrees and b similar t o 10 degrees with a flux of approximately 5 x 10(-4) 0.511 MeV photons cm(-2) s(-1) If near the Galactic center, then positron (e(+)) source s are producing about 10(42) e(+) s(-1), which annihilate approximate to 1-2 kpc above the Galactic plane. A starburst episode within the in ner few hundred parsecs of our Galaxy would drive hot pair-laden gas i nto the halo, with the one-sidedness pointing to the site of initial p ressure release at the onset of the starburst activity. Positrons lose energy and annihilate as they are convected upward with the gas flow, and we calculate high-latitude annihilation patterns and fluxes in ac cord with the observations. Changes in the ionization state when the e scaping gas cools could give annihilation radiation substructure. The fountain of hot (similar to 10(6)-10(7) K) gas rising into the Galacti c halo would be seen through its enhanced dispersion measure, thermal emission, and recombination radiation.