Deep XMM Observations of Draco rule out at the 99% Confidence Level a Dark Matter Decay Origin for the 3.5 keV Line

TL;DR

Deep XMM observations of Draco do not detect the 3.5 keV line, strongly challenging the hypothesis that this line originates from dark matter decay, with results ruling out this origin at over 99% confidence.

Contribution

This study provides the most stringent constraints to date on the dark matter decay origin of the 3.5 keV line using deep observations of Draco.

Findings

No 3.5 keV line detected in Draco data.

Upper limits exclude dark matter decay as the source of the 3.5 keV line.

Results are consistent with background-only models.

Abstract

We searched for an X-ray line at energies around 3.5 keV in deep, ~1.6 Msec XMM-Newton observations of the dwarf spheroidal galaxy Draco. No line was found in either the MOS or the PN detectors. The data in this energy range are completely consistent with a single, unfolded power law modeling the particle background, which dominates at these energies, plus instrumental lines; the addition of a ~3.5 keV line feature gives no improvement to the fit. The corresponding upper limit on the line flux rules out a dark matter decay origin for the 3.5 keV line found in observations of clusters of galaxies and in the Galactic Center at greater than 99% C.L..