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Galaxies 2018, 6(2), 39;

Positron Transport and Annihilation in the Galactic Bulge

Research School of Astronomy and Astrophysics, Australian National University, Canberra 2611, Australia
Received: 29 January 2018 / Revised: 14 March 2018 / Accepted: 17 March 2018 / Published: 21 March 2018
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The annihilation of positrons in the Milky Way Galaxy has been observed for ∼50 years; however, the production sites of these positrons remains hard to identify. The observed morphology of positron annihilation gamma-rays provides information on the annihilation sites of these Galactic positrons. It is understood that the positrons responsible for the annihilation signal originate at MeV energies. The majority of sources of MeV positrons occupy the star-forming thin disk of the Milky Way. If positrons propagate far from their sources, we must develop accurate models of positron propagation through all interstellar medium (ISM) phases in order to reveal the currently uncertain origin of these Galactic positrons. On the other hand, if positrons annihilate close to their sources, an alternative source of MeV positrons with a distribution that matches the annihilation morphology must be identified. In this work, I discuss the various models that have been developed to understand the origin of the 511 keV line from the direction of the Galactic bulge, and the propagation of positrons in the ISM. View Full-Text
Keywords: astroparticle physics; gamma rays-ISM; nucleosynthesis astroparticle physics; gamma rays-ISM; nucleosynthesis
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Panther, F.H. Positron Transport and Annihilation in the Galactic Bulge. Galaxies 2018, 6, 39.

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