MPIK: One Trace of Dark Matter Vanishes

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[img3="Charge exchange instead of dark matter: An X-ray signal from clusters of galaxies, which researchers have so far not been able to explain, could be produced when highly charged sulfur captures an electron. A sulfur nucleus (S16+) approaches a hydrogen atom (A) and attracts the electron (B), which ends up in a high energy level of S15+ (C) before falling back into the ground state (D), emitting X-rays as it does so.
(© 2016 MPIK)"]https://www.mpi-hd.mpg.de/personalhomes ... BCD-v2.png[/img3]

One Trace of Dark Matter Vanishes
Max Planck Institute for Nuclear Physics | 2016 Sep 05

A mysterious X-ray signal most likely originates from sulfur ions which capture electrons

A mysterious X-ray signal from clusters of galaxies recently caused some excitement among astronomers: Does it perhaps originate from dark matter, which makes up around 80 percent of the matter in the universe, but which scientists have not yet been able to detect? In order to help answering this question, physicists at the Max Planck Institute for Nuclear Physics in Heidelberg checked an alternative explanation. Accordingly, the search for this form of matter, which is difficult to detect, must go on, as the mysterious X-ray signal seems to originate from highly charged sulfur ions that capture electrons from hydrogen atoms.

Around two years ago, the XMM-Newton X-ray satellite radioed data back to Earth which fired up great hopes with astrophysicists. It had picked up weak radiation from several galaxy clusters at an energy of around 3.5 kiloelectronvolts (keV) which the researchers were not immediately able to explain with the aid of the known X-ray spectra. Speculation quickly arose that they could be signals of decaying particles of dark matter – this would have been the first concrete trace of the long-sought form of matter. Hope was soon dampened, however: The regions in which XMM-Newton observed the X-ray radiation did not match the spatial distribution which astrophysical analyses predicted for dark matter.

In addition, there are still a large number of physical processes for which astronomers do not know the corresponding fingerprints in X-ray spectra, and so cannot yet be excluded as the possible cause of the mysterious signal. Fact is, the spectral data in the collection of tables which researchers use to evaluate astronomical spectra are still incomplete. They are sometimes based on theoretical assumptions and are correspondingly unreliable. ...

Laboratory Measurements Compellingly Support Charge-Exchange
Mechanism for the ‘Dark Matter’ ~3.5 keV X-ray Line - Chintan Shah et al

• arXiv.org > astro-ph > arXiv:1608.04751 > 16 Aug 2016