A Maximum Entropy Map of the 511 [CLC]ke[/CLC]V Positron Annihilation Line Emission Distribution Near the Galactic Center

Open Access
Publisher Website
Google Scholar
Abstract
We have applied the maximum entropy method to a large data set based on Compton Gamma Ray Observatory (CGRO)/OSSE, Solar Maximum Mission, Transient Gamma-Ray Spectrometer, Gamma-Ray Imaging Spectrometer, HEXAGONE, and FIGARO observational results of the Galactic center 511 keV radiation in order to produce a map of the 511 keV line emission. This map suggests two components: a central bulge with a flux of 5.7 ± 0.29 × 10-4 photons cm-2 s-1 and a Galactic plane (GP) component with a flux of 2.2 ± 0.4 × 10-4 photons cm-2 s-1. The central bulge is located at l = -047 ± 024, b = 01 ± 018, and FWHM = 528 ± 048. We note that the position of the GP component coincides with a strong hot spot in the COMPTEL map of 1.8 MeV26Al line emission. A comparison between CGRO/OSSE and other instruments with larger field of view suggests an extended diffuse 511 keV emission. An interesting hot spot at l = -4°, b = 7° with a flux of ~2 × 10-4 photons cm-2 s-1 is shown on our map. A bootstrap test indicates that the significance level of this feature is 3.5 σ.