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

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 tau = 0.0571(-0.0006)(+0.0005) at 68%C.L. and the upper limit of epsilon(0)f(d) reads 2.7765 x 10(-2)4 at 95%C.L.. By comparison, we also constrain dark matter annihilation in the instantaneous reionization model from the same data combination except the QHII constraints and star formation rate density. We get T = 0.0559(-0.0076)(+0.0069) at 68%C.L. and the upper limit of epsilon(0)f(d) is 2.8468 x 10(-24) at 95%C.L.. This indicates various reionization models have little influence (less than or similar to 2.5%) on constraining parameters of dark matter decay or annihilation.

Automated summary

This study investigates the impact of different reionization models on constraining parameters of dark matter annihilation, finding that various reionization models have little influence (less than or similar to 2.5%) on the constraints of dark matter decay or annihilation.