Advances in Astronomy and Space Physics, Volume 6, Issue 1, PP. 3-15 (2016)
doi: 10.17721/2227-1481.6.3-15

Observation of the new emission line at ~3.5 keV
in X-ray spectra of galaxies and galaxy clusters

D. A. Iakubovskyi

Discovery Center, Niels Bohr Institute, Blegdamsvej 17, Copenhagen, Denmark
Bogolyubov Institute of Theoretical Physics, Metrologichna Str. 14-b, 03680, Kyiv, Ukraine

Abstract
The detection of an unidentified emission line in the X-ray spectra of cosmic objects would be a `smoking gun' signature for the particle physics beyond the Standard Model. More than a decade of its extensive searches results in several narrow faint emission lines reported at 3.5, 8.7, 9.4 and 10.1 keV. The most promising of them is the emission line at ~3.5 keV reported in spectra of several nearby galaxies and galaxy clusters. Here I summarize its up-to-date status, overview its possible interpretations, including an intriguing connection with the radiatively decaying dark matter, and outline future directions for its studies.

Keywords:
X-rays: general, dark matter, line: identification