Fermi Gamma-ray Space Telescope

Dark matter constraints from dwarf galaxies: a data-driven analysis

Pasquale Serpico
(Francesca Calore, Bryan Zaldivar)


Dwarf galaxies represent a powerful probe of annihilating dark matter particle models, with gamma-ray data setting some of the best bounds available. A major issue in improving over existing constraints consists in the limited knowledge of the astrophysical background (mostly diffuse photons, but also unresolved sources). Perhaps more worrisome, several approaches in the literature suffer of the difficulty of assessing the systematic error due to background mis-modeling. We propose a data-driven method to estimate the background at the dwarf position and its uncertainty, relying on an appropriate use of the whole-sky data, via an optimization procedure of the interpolation weights. We also report the bounds based on latest Fermi-LAT data and updated information for J-factors for both isolated and stacked dwarfs. We discuss the impact of profiling over the J-factor as well as over the background probability distribution function, with the latter resulting for instance crucial in drawing conclusions of compatibility with dark matter interpretations of the so-called Galactic Centre Excess.