Oct 2014 - Sep 2015

The Galactic Center excess in gamma rays

by German Gomez-Vargas

OC218 (Ogden Centre)


Ogden Centre

Many independent groups have claimed to find an unaccounted excess over conventional diffuse backgrounds in the data collected by the Fermi-LAT from the Galactic Center. The excess is compatible with dark matter predictions, nevertheless the modelling of gamma-ray sources in the line of sight of the Milky Way’s center is full of uncertainties. I will present preliminary results of a Fermi-LAT Collaboration analysis of the diffuse emission toward to the Galactic Center that give important insight on the excess nature. Different phenomena could account for the Galactic Center excess in gamma rays. Besides the dark matter interpretation, the other phenomena that may account for the excess are: a population of yet unresolved millisecond pulsars located in the bulge of the Milky Way, and secondary emission from cosmic-ray protons or electrons injected in the Galactic Center by past events. To distinguish between an unresolved population of point sources and an intrinsic diffuse emission as the real nature of the Galactic Center excess is challenging. I will present some statistical methods proposed to shed light on this issue, in particular the 1pt-PDF (number of pixels with k counts vs k counts) to characterize the clustering properties.