Abstract
We present a search for -ray emission from the direction of the newly discovered dwarf galaxy Reticulum II. Using Fermi-LAT Collaboration data, we detect a signal that exceeds expected backgrounds between and is consistent with annihilation of dark matter for particle masses less than a few . Modeling the background as a Poisson process based on Fermi-LAT diffuse models, and taking into account trial factors, we detect emission with value less than (). An alternative, model-independent treatment of the background reduces the significance, raising the value to (). Even in this case, however, Reticulum II has the most significant -ray signal of any known dwarf galaxy. If Reticulum II has a dark-matter halo that is similar to those inferred for other nearby dwarfs, the signal is consistent with the -wave relic abundance cross section for annihilation.
- Received 8 March 2015
DOI:https://doi.org/10.1103/PhysRevLett.115.081101
© 2015 American Physical Society
Viewpoint
Deciphering Gamma Rays from a Dwarf Galaxy
Published 17 August 2015
Are gamma rays from a nearby dwarf galaxy a beacon of dark matter or a false alarm?
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