Reionization and dark matter decay

Understand

Cosmic reionization and dark matter decay can impact observations of the cosmic microwave sky in a similar way.

• A simultaneous study of both effects is required to constrain unstable dark matter from cosmic microwave background observations.
• We compare two reionization models with and without dark matter decay.
• We find that a reionization model that fits also data from quasars and star forming galaxies results in tighter constraints on the reionization optical depth $\tau_{\text{reio}}$, but weaker constraints on the spectral index $n_{\text{s}}$ than the conventional parametrization.