Does the reionization model influence the constraints on dark matter decay or annihilation?

Abstract

If dark matter decay or annihilate, a large amount of energy and particles would be released into the cosmic plasma. Therefore, they could modify the thermal and ionization history of our universe, then leave footprints on the cosmic microwave background power spectra.In this paper, we take dark matter annihilation as an example and investigate whether different reionization models influence the constraints on dark matter annihilation.We consider the ionization history including both dark matter annihilation and star formation, then put constraints on DM annihilation.Combining the latest Planck data, BAO data, SNIa measurement, Q HII constraints from observations of quasars, as well as the star formation rate density from UV and IR data, the optical depth is τ = 0.0571+0.0005 -0.0006 at 68%C.L. and the upper limit of ϵ0 f d reads 2.7765 × 10-24 at 95%C.L..By comparison, we also constrain dark matter annihilation in the instantaneous reionization model from the same data combination except the Q HII constraints and star formation rate density. We get τ = 0.0559+0.0069 -0.0076 at 68%C.L. and the upper limit of ϵ0 f d is 2.8468 × 10-24 at 95%C.L.. This indicates various reionization models have little influence (≲ 2.5%) on constraining parameters of dark matter decay or annihilation.