Strong Optimized Conservative Fermi-LAT Constraints on Dark Matter Models from the Inclusive Photon Spectrum

TL;DR

This paper uses Fermi-LAT gamma-ray data to set conservative limits on dark matter annihilation and decay, disfavoring certain WIMP models without modeling astrophysical foregrounds.

Contribution

It introduces a robust, conservative method to constrain dark matter models using the inclusive photon spectrum without foreground subtraction.

Findings

Constraints are competitive with existing limits.

Disfavors typical WIMP cross sections for certain dark matter distributions.

Method can be applied to various final states and assumptions.

Abstract

We set conservative, robust constraints on the annihilation and decay of dark matter into various Standard Model final states under various assumptions about the distribution of the dark matter in the Milky Way halo. We use the inclusive photon spectrum observed by the Fermi Gamma-ray Space Telescope through its main instrument, the Large-Area Telescope (LAT). We use simulated data to first find the "optimal" regions of interest in the gamma-ray sky, where the expected dark matter signal is largest compared with the expected astrophysical foregrounds. We then require the predicted dark matter signal to be less than the observed photon counts in the a priori optimal regions. This yields a very conservative constraint as we do not attempt to model or subtract astrophysical foregrounds. The resulting limits are competitive with other existing limits, and, for some final states with cuspy dark-matter distributions in the Galactic Center region, disfavor the typical cross section required during freeze-out for a weakly interacting massive particle (WIMP) to obtain the observed relic abundance.