Probing the Dark Matter Nature of the 3.5 keV Line with Draco

In recent months, much excitement has been generated in the scientific communityby the detection of an Xray line at 3.5keV in galaxy clusters, M31, and theGalactic Center that is consistent with a decay product of light dark matter. Itis very difficult to explain the properties of this line across all of thesetargets consistently with any known atomic transition line or instrumentalanomaly. An important check on the nature of this signal may be obtained byobserving classical dwarf spheroidals, which are strongly dark matter dominatedand contain very little, if any, hot gas. We thus propose a 1.3Msec observationof the Draco dwarf galaxy, which we show to be a sufficient exposure to eitherdetect a dark matter decay line or robustly exclude the dark matter hypothesis. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]