Thursday, June 27, 2013

1306.5725 (Chris Gordon et al.)

Dark Matter and Pulsar Model Constraints from Galactic Center Fermi-LAT Gamma Ray Observations    [PDF]

Chris Gordon, Oscar Macías
Employing Fermi-LAT gamma ray observations, several independent groups have found excess extended gamma ray emission at the Galactic center (GC). Both, annihilating dark matter (DM) or a population of about 1000 unresolved millisecond pulsars (MSPs) are regarded as well motivated possible explanations. However, there is significant uncertainties in the diffuse galactic background at the GC. We have performed a revaluation of these two models for the extended gamma ray source at the GC by accounting for the systematic uncertainties of the Galactic diffuse emission model. We also marginalize over point source and diffuse background parameters in the region of interest. We show that the excess emission is significantly more extended than a point source. We find that the DM (or pulsars population) signal is larger than the systematic errors and therefore proceed to determine the sectors of parameter space that provide an acceptable fit to the data. We found that a population of 1000-2000 MSPs with parameters consistent with the average spectral shape of Fermi-LAT measured MSPs was able to fit the GC excess emission. For DM, we found that a pure tau+ tau- annihilation channel is not a good fit to the data. But a mixture of tau+ tau- and b bbar with a of order the thermal relic value and a DM mass of around 20 to 60 GeV provides an adequate fit.
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