2009/12/31 by Alexander Kusenko, Michael Loewenstein · 1 citation
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Dark Matter and Cosmic Phenomena #Particle physics theoretical and experimental studies #astro-ph.CO #astro-ph.HE #hep-ph
paper · pdf · doi:10.1088/0004-637x/714/1/652
published as Astrophys.J.714:652-662,2010 · 34 pages, including 20 figures; accepted for publication in ApJ; substantially expanded discussion session, results unchanged
openalex publication_date 2010/04/13 · arxiv created 2010/05/12 · arxiv updated 2014/11/20 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
We report the results of a search for an emission line from radiatively decaying dark matter in the Chandra X-ray Observatory spectrum of the ultra-faint dwarf spheroidal galaxy Willman 1. 99% confidence line flux upper limits over the 0.4–7 keV Chandra bandpass are derived and mapped to an allowed region in the sterile neutrino mass–mixing angle plane that is consistent with recent constraints from Suzaku X-ray Observatory and Chandra observations of the Ursa Minor and Draco dwarf spheroidals. A significant excess to the continuum, detected by fitting the particle-background-subtracted source spectrum, indicates the presence of a narrow emission feature with energy 2.51 ± 0.07(0.11) keV and flux [3.53 ± 1.95(2.77)] × 10 −6 photons cm −2 s −1 at 68% (90%) confidence. Interpreting this as an emission line from sterile neutrino radiative decay, we derive the corresponding allowed range of sterile neutrino mass and mixing angle using two approaches. The first assumes that dark matter is solely composed of sterile neutrinos, and the second relaxes that requirement. The feature is consistent with the sterile neutrino mass of 5.0 ± 0.2 keV and a mixing angle in a narrow range for which neutrino oscillations can produce all of the dark matter and for which sterile neutrino emission from the cooling neutron stars can explain pulsar kicks, thus bolstering both the statistical and physical significance of our measurement.