The 511 keV emission from positron annihilation in the Galaxy

By N. Prantzos, Céline Boehm, A. Bykov, R. Diehl, K. Ferrière, N. Guessoum, P. Jean, J. Knoedlseder, A. Marcowith, Igor V. Moskalenko and 2 more. 2010

227 citations recorded by the source corpus.

The first $\ensuremath{\gamma}$-ray line originating from outside the Solar System that was ever detected is the 511 keV emission from positron annihilation in the Galaxy. Despite 30 years of intense theoretical and observational investigation, the main sources of positrons have not been identified up to now. Observations in the 1990s with OSSE/CGRO (Oriented Scintillation Spectrometer Experiment on GRO satellite/Compton Gamma Ray Observatory) showed that the emission is strongly concentrated toward the Galactic bulge. In the 2000s, the spectrometer SPI aboard the European Space Agency's (ESA) International Gamma Ray Astrophysics Laboratory (INTEGRAL) allowed scientists to measure that emission across the entire Galaxy, revealing that the bulge-to-disk luminosity ratio is larger than observed at any other wavelength. This mapping prompted a number of novel explanations, including rather ``exotic'' ones (e.g., dark matter annihilation). However, conventional astrophysical sources, such as type Ia supernovae, microquasars, or x-ray binaries, are still plausible candidates for a large fraction of the observed total 511 keV emission of the bulge. A closer study of the subject reveals new layers of complexity, since positrons may propagate far away from their production sites, making it difficult to infer the underlying source distribution from the observed map of 511 keV emission. However, in contrast to the rather well-understood propagation of high-energy ($g\mathrm{GeV}$) particles of Galactic cosmic rays, understanding the propagation of low-energy ($\ensuremath{\sim}\mathrm{MeV}$) positrons in the turbulent, magnetized interstellar medium still remains a formidable challenge. The spectral and imaging properties of the observed 511 keV emission are reviewed and candidate positron sources and models of positron propagation in the Galaxy are critically discussed.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/c61133c2007db32eaf03c1fe0af471480ac1d00f

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In Astronomy and Astrophysics

1. Rüdiger Pakmor
2. M. Kromer
3. W. Hillebrandt
4. Stefan Taubenberger
5. S. Sim
6. M. Fink
7. I. Seitenzahl
8. A. Ruiter

In Nuclear and High Energy Physics

1. M. Fink
2. I. Seitenzahl
3. Rüdiger Pakmor
4. A. Strong
5. S. Sim
6. A. Ruiter
7. W. Hillebrandt
8. Troy A. Porter

Citations in the corpus

• Dark Matter Searches with Astroparticle Data (2011, background): “See the review by Prantzos et al. (2011) for an extensive discussion of possible origins of the 511-keV line.”
• Gamma-ray spectroscopy of Positron Annihilation in the Milky Way (2015, background): “The locations and distributions of the various possible sources within the Galaxy offer a way to constrain their relative importance, if annihilation is assumed to occur close to the respective sources (<∼100 pc) (Prantzos et al. 2011).”
• Three-dimensional delayed-detonation models with nucleosynthesis for Type Ia supernovae (2012, background): “…cold interstellar gas (e.g. Scannapieco et al. 2008), in high energy astrophysics as sources of Galactic positrons (e.g. Chan & Lingenfelter 1993; Prantzos et al. 2011), in galactic chemical evolution by enriching the inters llar gas withα, Fe-peak, and possibly p-process elements (e.g. Timmes…”