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Dwarf Galaxies: The Milky Way

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Simulations of galaxy formation based on the Lambda Cold Dark matter (ΛCDM) cosmological model predict that a large galaxy such as the Milky Way should have many (~ 200) dwarf satellite galaxies. However, only about 20 or 30 have been identified. Where are the rest? Warm dark matter, constituting of sterile neutrinos, is lighter and since dwarf galaxies consisting mainly of dark matter are so difficult to find by visible light, there could be enough of them to reconcile the large number of dwarf galaxies that simulations predict to exist with the small number actually observed. We are looking for a weak unidentified emission line at E = (3.55−3.57) ±0.03 keV in a stacked XMM-Newton spectrum of Dwarf galaxies, which are the satellite galaxies of our Milky Way.…show more content…
(2014) using XMM-Newton observations of galaxy clusters. The signal was detected in five independent samples, including observations both of single objects and stacked cluster spectra. Subsequently, the presence of an unidentified line at E~3.52 keV was confirmed by a re-analysis of XMM data of the Perseus cluster, and also reported from an analysis of XMM observations of M31 by Boyarsky et.al. XMM blank-sky observations do not reveal any evidence for any feature at the energy of interest. Furthermore, when detected in clusters, the line is observed to have a redshift consistent with that of the host cluster, helping to rusle out an obvious instrumental
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