Cosmological constraints on neutrino plus axion hot dark matter

Understand

We use observations of the cosmological large-scale structure to derive limits on two-component hot dark matter consisting of mass-degenerate neutrinos and hadronic axions, both components having velocity dispersions corresponding to their respective decoupling temperatures.

• We restrict the data samples to the safely linear regime, in particular excluding the Lyman-alpha forest.
• Using standard Bayesian inference techniques we derive credible regions in the two-parameter space of m_a and sum(m_nu).
• Marginalising over sum(m_nu) provides m_a < 1.2 eV (95% C.L.).