Positron Annihilations at the Galactic Center: Generating More Questions Than Answers
arXiv:astro-ph/0609139 · doi:10.1016/j.nuclphysbps.2007.08.031
Abstract
The bulge of our Galaxy is illuminated by the 0.511 MeV gamma-ray line flux from annihilations of nonrelativistic positrons. The emission is strongly concentrated at the Galactic Center, in contrast to gamma-ray maps tracing nucleosynthesis (e.g., the 1.809 MeV line from decaying ^26Al) or cosmic ray processes (e.g., the 1-30 MeV continuum), which reveal a bright disk with a much less prominent central region. If positrons are generated at relativistic energies, higher-energy gamma rays will also be produced from inflight annihilation of positrons on ambient electrons. The comparison of the gamma-ray spectrum from inflight annihilation to the observed diffuse Galactic gamma-ray data constrains the injection energies of Galactic positrons to be less than 3 MeV.
arXiv commentTo be published in the proceedings of the 7th international UCLA symposium on sources and detection of dark matter and dark energy in the universe (DM 2006) 2006, Marina del Rey, California, 22-24 Feb 2006
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