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Constraints from the Wilkinson microwave anisotropy probe on decaying cold dark matter
Kiyotomo Ichiki1, Masamune Oguri, Keitaro Takahashi
1National Astronomical Observatory, 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan and Department of Astronomy, University of Tokyo, Tokyo 113-0033, Japan.
Abstract:
We reformulate cosmological perturbations in the decaying cold dark matter model, and calculate cosmological microwave background anisotropies. By comparing our predictions with data from the Wilkinson Microwave Anisotropy Probe, we derive a new bound on the abundance and lifetime of decaying dark matter particles. The lifetime is constrained to Gamma(- 1)> or =123 Gyr at 68% C.L. (52 Gyr at 95.4% C.L.) when cold dark matter consists only of such decaying particles. We also consider a more general case and show that the constraint generalizes to Omega(DDM )h2 less, similar -0.5(Gamma (-1)/1 Gyr) (-1)+0.12 for Gamma(- 1)> or =5 Gyr at 95.4% C.L.