Testing the origin of ~3.55 keV line in individual galaxy clusters observed with XMM-Newton

TL;DR

This study analyzes XMM-Newton data from galaxy clusters to investigate a mysterious 3.55 keV emission line, finding consistent signals that support the hypothesis of decaying dark matter as its origin.

Contribution

It identifies and analyzes the 3.55 keV line in multiple galaxy clusters, providing evidence consistent with dark matter decay, and compares findings across different cosmic objects.

Findings

Detected > 2 sigma line-like residuals at 3.52 keV in 8 galaxy clusters.

Line properties are inconsistent with statistical fluctuations or known astrophysical lines.

Results support a dark matter decay lifetime of approximately (3.5-6) x 10^27 seconds.

Abstract

If the unidentified emission line at ~3.55 keV previously found in spectra of nearby galaxies and galaxy clusters is due to radiatively decaying dark matter, one should detect the signal of comparable strength from many cosmic objects of different nature. By studying existing dark matter distributions in galaxy clusters we identified top-19 of them observed by XMM-Newton X-ray cosmic mission, and analyzed the data for the presence of the new line. In 8 of them, we identified > 2 sigma positive line-like residuals with average position 3.52 +/- 0.08 keV in the emitter's frame. Their observed properties are unlikely to be explained by statistical fluctuations or astrophysical emission lines; observed line position in M31 and Galactic Center makes an additional argument against general-type systematics. Being interpreted as decaying dark matter line, the new detections correspond to radiative decay lifetime tau_dm ~ (3.5-6) x 10^27 s consistent with previous detections.