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For more than 50 years, the rate and distribution of positron (anti-electron) annihilation in the Milky Way has puzzled gamma ray astronomers. Positrons with low (~MeV) initial energies are predominantly produced by beta+ unstable radioactive elements, however, the observed rate of positron annihilation in the Milky Way far exceeds the inferred rate of positron production by ’conventional sources’ such as core-collapse and Type Ia supernovae. Moreover, the observed distribution of positron annihilation in the Milky Way appears to trace the older stellar populations of the Galaxy (the Galactic bulge and thick disk), while radioactive material is predominantly synthesised in the thin disk of the Galaxy. My PhD has focused both on investigating the transport of positrons in the interstellar medium, to constrain the production sites of this Galactic antimatter, as well as investigating phenomena associated with SN1991bg-like supernovae, which have been implicated as potential antimatter factories in the Milky Way. In this talk I will discuss some of my exciting new results on positron transport, and SN1991bg-like supernovae, and the implications of this work beyond high-energy astrophysics. |
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