Physics PAN Seminar : "Foreground Mismodeling and the Point Source Explanation of the Fermi Galactic Center Excess" by Dr. Malte Buschmann (UMich)

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Date: March 20, 2020
Time: 3:30 p.m. - 4:30 p.m.
Location: Physics #312 | Map
666 W. Hancock
Detroit, MI 48201
Category: Seminar

Title: Foreground Mismodeling and the Point Source Explanation of the Fermi Galactic Center Excess


The Fermi Large Area Telescope has observed an excess of ~GeV energy gamma rays from the center of the Milky Way, which may arise from near-thermal dark matter annihilation. Firmly establishing the dark matter origin for this excess is however complicated by challenges in modeling diffuse cosmic-ray foregrounds as well as unresolved astrophysical sources, such as millisecond pulsars. Non-Poissonian Template Fitting (NPTF) is one statistical technique that has previously been used to show that at least some fraction of the GeV excess is likely due to a population of dim point sources. These results were recently called into question, but we show that this is largely due to foreground mismodelling. We repeat the NPTF analyses using a state-of-the-art model for diffuse gamma-ray emission in the Milky Way and introduce a novel statistical procedure, based on spherical-harmonic marginalization, to provide an improved description of the Galactic diffuse emission in a data-driven fashion. With these improvements, we find that the NPTF results continue to robustly favor the interpretation that the Galactic Center excess is due, in part, to unresolved astrophysical point sources across the analysis variations that we have explored.


Raghav Kunnawalkam Elayavalli




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