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Searching for Decaying Dark Matter in Deep XMM-Newton Observation of the Draco Dwarf SpheroidalWe present results of a search for the 3.5 keV emission line in our recent very long (approx. 1.4 Ms) XMM-Newton observation of the Draco dwarf spheroidal galaxy. The astrophysical X-ray emission from such dark matter-dominated galaxies is faint, thus they provide a test for the dark matter origin of the 3.5 keV line previously detected in other massive, but X-ray bright objects, such as galaxies and galaxy clusters. We do not detect a statistically significant emission line from Draco; this constrains the lifetime of a decaying dark matter particle to tau >(7-9) × 10(exp 27) s at 95% CL (combining all three XMM-Newton cameras; the interval corresponds to the uncertainty of the dark matter column density in the direction of Draco). The PN camera, which has the highest sensitivity of the three, does show a positive spectral residual (above the carefully modeled continuum) at E = 3.54 +/- 0.06 keV with a 2.3(sigma) significance. The two MOS cameras show less-significant or no positive deviations, consistently within 1(sigma) with PN. Our Draco limit on tau is consistent with previous detections in the stacked galaxy clusters, M31 and the Galactic Centre within their 1 − 2(sigma) uncertainties, but is inconsistent with the high signal from the core of the Perseus cluster (which has itself been inconsistent with the rest of the detections). We conclude that this Draco observation does not exclude the dark matter interpretation of the 3.5 keV line in those objects.
Document ID
Document Type
Reprint (Version printed in journal)
External Source(s)
Ruchayskiy, Oleg (Copenhagen Univ. Denmark)
Boyardsky, Alex (Leiden Univ. Netherlands)
Iakbovskyi, Dmytro (Copenhagen Univ. Denmark)
Bulbul, Esra (Massachusetts Inst. of Tech. Cambridge, MA, United States)
Eckert, Domique (Geneva Univ. Geneva, Switzerland)
Franse, Jeron (Leiden Univ. Netherlands)
Malyshev, Denys (Geneva Univ. Geneva, Switzerland)
Markevitch, Maxim (NASA Goddard Space Flight Center Greenbelt, MD United States)
Neronov, Andrii (Geneva Univ. Geneva, Switzerland)
Date Acquired
April 6, 2017
Publication Date
May 1, 2016
Publication Information
Publication: Monthly Notices of the Royal Astronomical Society
Volume: 460
Issue: 2
ISSN: 0035-8711
Subject Category
Report/Patent Number
Distribution Limits
dark matter
galaxies: dwarf
line: identification
X-rays: general