Constraints on Dark Matter annihilations from reionization and heating of the intergalactic gas

Understand

Dark Matter annihilations after recombination and during the epoch of structure formation deposit energy in the primordial intergalactic medium, producing reionization and heating.

• We investigate the constraints that are imposed by the observed optical depth of the Universe and the measured temperature of the intergalactic gas.
• We find that the bounds are significant, and have the power to rule out large portions of the `DM mass/cross section' parameter space.
• The optical depth bound is generally stronger and does not depend significantly on the history of structure formation.