Possible Evidence for MeV Dark Matter In Dwarf Spheroidals

Abstract

It has been recently proposed that the observed 511 keV emission from the Galactic bulge could be the product of very light (1-100 MeV) annihilating dark matter particles. Other possible explanations for this signal are associated with stellar objects, such as hypernovae. In order to distinguish between annihilating light dark matter scenario and more conventional astrophysical sources for the bulge emission, we here propose the study of dwarf spheroidals such as Sagittarius. These galaxies have typical luminosities of $10^5{L}_{\odot }$ but mass-to-light ratios of $\sim 100$. As there are comparatively few stars, the prospects for 511 keV emission from standard astrophysical scenarios are minimal. The dwarf spheroidals do, however, contain copious amounts of dark matter. INTEGRAL/SPI has observed the Sagittarius region. Analysis of this data for 511 keV emission will provide a test of MeV dark matter which can distinguish between annihilating dark matter and more standard astrophysics. The observation of such a signal from Sagittarius should be a ``smoking gun'' for MeV dark matter.

4 pages, no figures. Version accepted by Physical Review Letters

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• Dark Matter Dynamics and Indirect Detection
• Cosmological bounds on dark matter-neutrino interactions
• Constraining DM properties with SPI
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• The impact of the phase-space density on the indirect detection of dark matter
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• Annihilation vs. Decay: Constraining dark matter properties from a gamma-ray detection
• The effect of early dark matter halos on reionization
• Metastable dark matter mechanisms for INTEGRAL 511 keV $\gamma$ rays and DAMA/CoGeNT events
• Impact of Dark Matter Annihilation on the High-Redshift Intergalactic Medium
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• The new interaction suggested by the anomalous ${}^8$Be transition sets a rigorous constraint on the mass range of dark matter
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• Perspective of Galactic dark matter subhalo detection on Fermi from the EGRET observation