Illuminating the 130 GeV Gamma Line with Continuum Photons

85 citations (85 excluding self-citations — zero self-citations). A timely analysis during the 130 GeV gamma-line excitement of 2012 that used continuum photon data to discriminate between dark matter explanations.

The Problem

In 2012, Weniger and others reported evidence for a monochromatic gamma-ray line at approximately 130 GeV in Fermi-LAT data from the Galactic Center. A line would be a smoking gun for dark matter annihilation — Standard Model astrophysical processes do not produce sharp spectral features at these energies. The particle physics community responded with dozens of model-building papers proposing dark matter candidates that could produce the line. But any dark matter particle that annihilates to photon pairs should also annihilate to other Standard Model particles, producing a continuum of lower-energy photons alongside the line.

The Key Idea

The paper analyzes Fermi-LAT data from the inner 3 degrees of the Galaxy down to 5 GeV, looking for the continuum emission that must accompany any dark matter line signal. The ratio of continuum photons to monochromatic line photons is a model-dependent quantity, but for neutralino dark matter (the most motivated WIMP candidate), the continuum is predicted to be substantial. The analysis places a strong bound on this ratio that is independent of uncertainties in the dark matter density profile, since both the line and the continuum scale identically with the profile. The derived constraints exclude neutralino dark matter as the source of the 130 GeV line.

Recollections

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• DOI
• arXiv:1207.0800
• INSPIRE