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Session 13 - Galaxies & Globular Clusters.
Oral session, Monday, June 09
North Main Hall F/G,
In addition to the bulge and disk components of the diffuse galactic annihilation radiation, a new region of annihilation radiation roughly centered at -3 degrees galactic longitude and +7 degrees galactic latitude has been discovered with OSSE (Purcell et al. 1997; Cheng et al. 1997). If this region is in the galactic center region, then annihilation is occurring \approx 1 kpc off the galactic plane. We model this result by treating positron injection, transport, and annihilation in inhomogeneous moving media. Positrons are injected with specified energy distributions over a range of heights above the galactic plane, where they are trapped in the background fluid and rise with the flow. Energy losses due to thermalization, bremsstrahlung, synchrotron radiation, Thomson scattering, and adiabatic expansion are considered. We apply our results to two scenarios. In the first, a prolonged episode of starburst formation in the central kpc of our galaxy results in a fountain of hot pair-laden gas. In the second, we consider pair injection from black-hole jets. Results of the calculations are compared with the OSSE observations.
