Numerical study of halo concentrations in dark-energy cosmologies

We study the concentration parameters, their mass dependence and redshift evolution, of dark-matter halos in different dark-energy cosmologies with constant and time-variable equation of state, and compare them with “standard” ΛCDM and OCDM models. We find that previously proposed algorithms for predicting halo concentrations can be well adapted to dark-energy models. When centred on the analytically expected values, halo concentrations show a log-normal distribution with a uniform standard deviation of ~0.2. The dependence of averaged halo concentrations on mass and redshift permits a simple fit of the form $(1+z)\,c=c_0\,(M/M_0)^\alpha$, with $\alpha\approx-0.1$ throughout. We find that the cluster concentration depends on the dark energy equation of state at the cluster formation redshift zcoll through the linear growth factor $D_+(z_{\rm coll})$. As a simple correction accounting for dark-energy cosmologies, we propose scaling c0 from ΛCDM with the ratio of linear growth factors, $c_0\rightarrow c_0\,D_+(z_{\rm coll})/D_{+,~\Lambda{\rm CDM}}(z_{\rm coll})$