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Published September 15, 2007 | Published
Journal Article Open

Constraints on radiative dark-matter decay from the cosmic microwave background


If dark matter decays to electromagnetically interacting particles, it can inject energy into the baryonic gas and thus affect the processes of recombination and reionization. This leaves an imprint on the cosmic microwave background (CMB): the large-scale polarization is enhanced, and the small-scale temperature fluctuation is damped. We use the Wilkinson Microwave Anisotropy Probe (WMAP) three-year data combined with galaxy surveys to constrain radiatively decaying dark matter. Our new limits to the dark-matter decay width are about 10 times stronger than previous limits. For dark-matter lifetimes that exceed the age of the Universe, a limit of zetaGammachi<1.7×10^-25 s^-1 (95% C.L.) is derived, where zeta is the efficiency of converting decay energy into ionization energy. Limits for lifetimes short compared with the age of the Universe are also derived. We forecast improvements expected from the Planck satellite.

Additional Information

© 2007 The American Physical Society. (Received 18 April 2007; published 18 September 2007) Our MCMC chain computation was performed on the Supercomputing Center of the Chinese Academy of Sciences and the Shanghai Supercomputing Center. This work is supported by the National Science Foundation of China under the Distinguished Young Scholar Grant No. 10525314, the Key Project Grant No. 10533010, the 973 Program No. 2007CB815401, and by the Chinese Academy of Sciences under Grant No. KJCX3-SYW-N2. M.K. was supported by DOE No. DE-FG03-92-ER40701, NASA NNG05GF69G, and the Gordon and Betty Moore Foundation. Z.Z. was supported by NASA through HF-01181.01-A from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA under Contract No. NAS 5-26555.

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