Echo of interactions in the dark sector

We investigate the observational constraints on an interacting vacuum energy scenario with two different neutrino schemes (with and without a sterile neutrino) using the most recent data from cosmic microwave background (CMB) temperature and polarization anisotropy, baryon acoustic oscillations (BAO), type Ia supernovae from JLA sample and structure growth inferred from cluster counts. We find that inclusion of the galaxy clusters data with the minimal data combination $\mathrm{CMB}+\mathrm{BAO}+\mathrm{JLA}$ suggests an interaction in the dark sector, implying the decay of dark matter particles into dark energy, since the constraints obtained by including the galaxy clusters data yield a non-null and negative coupling parameter between the dark components at 99% confidence level. We deduce that the current tensions on the parameters $H_0$ and ${\sigma }_8$ can be alleviated within the framework of the interacting as well as noninteracting vacuum energy models with sterile neutrinos.

Figure 1

One-dimensional marginalized distribution, and 68% and 95% CL regions for some selected parameters of the $\nu \mathrm{IVCDM}$ model.

Figure 2

One-dimensional marginalized distribution, and 68% and 95% CL regions for some selected parameters of the ${\nu }_s\mathrm{IVCDM}$ model.

Figure 3

Constraints on ${\sigma }_8-\delta$ parametric space coloured by $H_0$ values for the $\nu \mathrm{IVCDM}$ (left panel) and ${\nu }_s\mathrm{IVCDM}$ (right panel) models from $\mathrm{CMB}+\mathrm{BAO}+\mathrm{JLA}+\mathrm{CFHTLenS}+\mathrm{SZ}$ data.

Figure 4

1D marginalized probability distributions of $H_0$ and ${\sigma }_8$ for $\nu \mathrm{IVCDM}$ (upper panel) and ${\nu }_s\mathrm{IVCDM}$ (lower panel) models. The vertical gray band in left panels corresponds to $H_0=73.24\pm 1.74\mathrm{km}{\mathrm{s}}^{-1}\mathrm{Mpc}$ [41] while in right panels it corresponds to ${\sigma }_8=0.75\pm 0.03$ [83]. CBJ stands for $\mathrm{CMB}+\mathrm{BAO}+\mathrm{JLA}$.