The galactic 511 keV morphology and the old stellar population

M. Ali, S. C. Ellis, S. Sharma, J. Bland-Hawthorn

Research output: Contribution to journalConference paperResearchpeer-review

Abstract

The source of Galactic positron annihilation emission is a mystery. What is known is that photons produced in positron-electron annihilation are highly concentrated at the Galactic centre, with a slightly off-centred peak with respect to Galactic longitude. Using synthetic models of the Milky Way we find possible connections between age-bound stellar structures in the Milky Way and the 511 keV annihilation morphology. We find that in projection, the flux of the old tilted stellar bulge/bar can reproduce the Gaussian fit parameters and the apparent asymmetry observed in the radiation, supporting a large number of annihilation sources in an extended bulge/bar population. When looking at the same stars in the disk we were not able to reproduce the bulge to disk ratio in flux, indicating either a different class of sources in the disk or significant positron propagation out of the bulge.

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positron annihilation
stellar structure
longitude
positrons
projection
asymmetry
stars
propagation
photons
radiation

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Ali, M. ; Ellis, S. C. ; Sharma, S. ; Bland-Hawthorn, J. / The galactic 511 keV morphology and the old stellar population. In: Proceedings of Science. 2011 ; pp. 1-6.
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The galactic 511 keV morphology and the old stellar population. / Ali, M.; Ellis, S. C.; Sharma, S.; Bland-Hawthorn, J.

In: Proceedings of Science, 01.12.2011, p. 1-6.

Research output: Contribution to journalConference paperResearchpeer-review

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AB - The source of Galactic positron annihilation emission is a mystery. What is known is that photons produced in positron-electron annihilation are highly concentrated at the Galactic centre, with a slightly off-centred peak with respect to Galactic longitude. Using synthetic models of the Milky Way we find possible connections between age-bound stellar structures in the Milky Way and the 511 keV annihilation morphology. We find that in projection, the flux of the old tilted stellar bulge/bar can reproduce the Gaussian fit parameters and the apparent asymmetry observed in the radiation, supporting a large number of annihilation sources in an extended bulge/bar population. When looking at the same stars in the disk we were not able to reproduce the bulge to disk ratio in flux, indicating either a different class of sources in the disk or significant positron propagation out of the bulge.

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