Constraining dark sector perturbations II: ISW and CMB lensing tomography

• Published in: Journal of Cosmology and Astroparticle Physics
• Main Authors: Soergel, B, Giannantonio, T, Weller, J, Battye, R A
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2015
• Subjects: modified gravity; galaxy clustering; integrated sachs-wolfe effect; dark energy theory; microwave background anisotropies; baryon acoustic-oscillations; south-pole telescope; digital sky survey; cosmological constant; systematic uncertainties; field-equations; power spectra; high-redshift; South Pole; South pole
• Online Access: https://research.manchester.ac.uk/en/publications/f38f94da-d9e0-4734-864b-b92817af11d0; https://doi.org/10.1088/1475-7516/2015/02/037

Any Dark Energy (DE) or Modified Gravity (MG) model that deviates from a cosmological constant requires a consistent treatment of its perturbations, which can be described in terms of an effective entropy perturbation and an anisotropic stress. We have considered a recently proposed generic parameterisation of DE/MG perturbations and compared it to data from the Planck satellite and six galaxy catalogues, including temperature-galaxy (Tg), CMB lensing-galaxy (phi g) and galaxy-galaxy (gg) correlations. Combining these observables of structure formation with tests of the background expansion allows us to investigate the properties of DE/MG both at the background and the perturbative level. Our constraints on DE/MG are mostly in agreement with the cosmological constant paradigm, while we also find that the constraint on the equation of state w (assumed to be constant) depends on the model assumed for the perturbation evolution. We obtain w = -0.92(-0.16)(+0.20) (95% CL; CMB+gg+Tg) in the entropy perturbation scenario; in the anisotropic stress case the result is w = -0.86(-0.16)(+0.17). Including the lensing correlations shifts the results towards higher values of w. If we include a prior on the expansion history from recent Baryon Acoustic Oscillations (BAO) measurements, we find that the constraints tighten closely around w = -1, making it impossible to measure any DE/MG perturbation evolution parameters. If, however, upcoming observations from surveys like DES, Euclid or LSST show indications for a deviation from a cosmological constant, our formalism will be a useful tool towards model selection in the dark sector.