Decaying Dark Matter and Lyman-$\alpha$ forest constraints

Understand

Decaying Cold Dark Matter (DCDM) is a model that is currently under investigation regarding primarily the $S_8$ tension between cosmic microwave background (CMB) and certain large-scale structure measurements.

• The decay into one massive and one (or more) massless daughter particle(s) leads to a suppression of the power spectrum in the late universe that depends on the relative mass splitting $\epsilon=(1-m^2/M^2)/2$ between the mother and massive daughter particle as well as the lifetime $\tau$.
• In this work we investigate the impact of the BOSS DR14 one-dimensional Lyman-$\alpha$ forest flux power spectrum on the DCDM model using a conservative effective model approach to account for astrophysical uncertainties.
• Since the suppression of the power spectrum due to decay builds up at low redshift, we find that regions in parameter space that address the $S_8$ tension can be well compatible with the Lyman-$\alpha$ forest.