A novel scenario for the possible X-ray line feature at ~3.5 keV Charge exchange with bare sulfur ions

Motivated by recent claims of a compelling ~3.5 keV emission line from nearby galaxies and galaxy clusters, we investigate a novel plasma model incorporating a charge exchange component obtained from theoretical scattering calculations. Fitting this kind of component with a standard thermal model yi...

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Published inAstronomy and astrophysics (Berlin) Vol. 584; p. L11
Main Authors Gu, L, Kaastra, J, Raassen, A J J, Mullen, P D, Cumbee, R S, Lyons, D, Stancil, P C
Format Journal Article
LanguageEnglish
Published 01.12.2015
Subjects
Charge exchange
Clouds
Clusters
Diagnostic systems
Emission analysis
Fittings
Grounds
Sulfur
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Summary:Motivated by recent claims of a compelling ~3.5 keV emission line from nearby galaxies and galaxy clusters, we investigate a novel plasma model incorporating a charge exchange component obtained from theoretical scattering calculations. Fitting this kind of component with a standard thermal model yields positive residuals around 3.5 keV, produced mostly by S XVI transitions from principal quantum numbers n > or = 9 to the ground. Such high-n states can only be populated by the charge exchange process. In this scenario, the observed 3.5 keV line flux in clusters can be naturally explained by an interaction in an effective volume of ~1 kpc super(3) between a ~3 keV temperature plasma and cold dense clouds moving at a few hundred keV super(-1). The S XVI lines at ~3.5 keV also provide a unique diagnostic of the charge exchange phenomenon in hot cosmic plasmas.
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content type line 23
ISSN:0004-6361
1432-0746
DOI:10.1051/0004-6361/201527634