Decaying Dark Matter and Lyman-α forest constraints

Decaying Cold Dark Matter (DCDM) is a model that is currently under inves-tigation regarding primarily the S8 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 euro = (1 - m2/M2)/2 between the mother and massive daughter particle as well as the lifetime T. 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 S8 tension can be well compatible with the Lyman-alpha forest. Nevertheless, for values of the degeneracy parameter euro -0.1 - 0.5%, for which the power suppression occurs within the scales probed by BOSS Lyman-alpha data, we find improved constraints compared to previous CMB and galaxy clustering analyses, obtaining T >= 18 Gyrs for small mass splitting. Furthermore, our analysis of the BOSS Lyman-alpha flux power spectrum allows for values T ti 102 Gyrs, euro 1%, that have been found to be preferred by a combination of Planck and galaxy clustering data with a KiDS prior on S8, and we even find a hint for a marginal preference within this regime.

Automated summary

Investigated the impact of the Decaying Cold Dark Matter (DCDM) model on the tension between cosmic microwave background (CMB) and large-scale structure measurements. Found that the Lyman-alpha forest data is compatible with the DCDM model and can provide improved constraints under certain parameter values.