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Astrophysics Colloquium

Dark Matter and Astrophysical Model Constraints from Galactic Center Fermi-LAT Gamma Ray Observations
Presented by Chris Gordon
University of Canterbury, New Zealand

Thursday, October 10, 2013
4:00 P.M. in 169-336

Employing Fermi Large Area Telescope (LAT) gamma ray observations, several independent groups have found excess extended gamma ray emission at the Galactic center. Both annihilating dark matter or a population of about 1000 unresolved millisecond pulsars are regarded as well motivated possible explanations. However, there are significant uncertainties in the diffuse galactic background. We reevaluated the data accounting for the systematic uncertainties of the Galactic diffuse emission model and marginalized over point source and diffuse background parameters in the region of interest. We found that a population of 1000-2000 millisecond pulsars with parameters consistent with the average spectral shape of Fermi-LAT measured millisecond pulsars was able to fit the Galactic center excess emission. For dark matter, we found that a pure lepton annihilation channel is not a good fit to the data. But a mixture of leptons and quarks with a cross-section of order the thermal relic value and a dark matter mass of around 20 to 60 GeV provides an acceptable fit.

JPL Contact: Jenny Siegal-Gaskins (

SVCP Astrophysics

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