Signature of the interaction between dark energy and dark matter in observations

We investigate the effect of an interaction between dark energy and dark matter upon the dynamics of galaxy clusters. This effect is computed through the Layser-Irvine equation, which describes how an astrophysical system reaches virial equilibrium and was modified to include the dark interactions. Using observational data from almost 100 purportedly relaxed galaxy clusters we put constraints on the strength of the couplings in the dark sector. We compare our results with those from other observations and find that a positive (in the sense of energy flow from dark energy to dark matter) nonvanishing interaction is consistent with the data within several standard deviations.

Figure 1

Probability density function (p.d.f.) for $\overline{\zeta }$ obtained with all available cluster masses. The result points to $\overline{\zeta }=0.14\pm 0.01$, that is, 14 standard deviations from the null result.

Figure 2

P.d.f.’s concerning the cluster data divided in three sets, in increasing order of the dispersion velocity (up to $600\mathrm{km}/\mathrm{s}$, from 600 to $1000\mathrm{km}/\mathrm{s}$, and above $1000\mathrm{km}/\mathrm{s}$.) The data are compatible with one another and the results point to essentially the same values of $\overline{\zeta }$, all at least 3 standard deviations from the null result.

Figure 3

P.d.f.’s concerning the cluster data divided in two sets, in increasing order of the redshift (below and above $z=0.05$). The data are compatible with one another and the results point to compatible values of $\overline{\zeta }$, at several standard deviations from a vanishing result. However, in the absence of weak lensing results the results point to a considerably higher value of the coupling compared with the previous ones.