Cosmic microwave background constraints of decaying dark matter particle properties

If a component of cosmological dark matter is made up of massive particles - such as sterile neutrinos - that decay with cosmological lifetime to emit photons, the reionization history of the universe would be affected, and cosmic microwave background anisotropies can be used to constrain such a decaying particle model of dark matter. The optical depth depends rather sensitively on the decaying dark matter particle mass m_dm, lifetime τ_dm, and the mass fraction of cold dark matter f that they account for in this model. Assuming that there are no other sources of reionization and using the Wilkinson Microwave Anisotropy Probe 7-year data, we find that 250eV ≲ m_dm ≲ 1 MeV, whereas 2.23 × 10³ yr ≲ τ_dm/f ≲ 1.23 × 10¹⁸ yr. The best-fit values for m_dm and τ_dm/f are 17.3 keV and 2.03 × 10¹⁶ yr, respectively. Copyright © 2012 The American Astronomical Society. All rights reserved.