Constraints on the dark energy with barotropic equation of state: assessing the importance of different observations

For dynamical dark energy with the barotropic equation of state we determine the mean values of parameters and their confidence ranges together with other cosmological parameters on the basis of different combined datasets. The used observations include Planck data on CMB temperature anisotropy, E-mode polarisation and lensing, BICEP2/Keck Array data on B-mode polarisation, BAO from SDSS and 6dFGS, power spectrum of galaxies from WiggleZ, weak lensing from CFHTLenS and SN Ia data from the JLA compilation. We find that all but one mean models are phantom, mean values of the equation of state parameter at current epoch are close to −1 and constraints on the adiabatic sound speed of dark energy are weak. We investigate the effect of CMB polarisation data on the dark energy parameters estimation. We discuss also which type of data on the large scale structure of the Universe allows to determine the dark energy parameters most precisely.