Dark energy and matter evolution from lensing tomography

Abstract

Reconstructed from lensing tomography, the evolution of the dark matter density field in the well-understood linear regime can provide model-independent constraints on the growth function of structure and the evolution of the dark energy density. We examine this potential in the context that high-redshift cosmology has in the future been fixed by cosmic microwave background measurements. We construct sharp tests for the existence of multiple dark matter components or a dark energy component that is not a cosmological constant. These functional constraints can be transformed into physically motivated model parameters. From the growth function, the fraction of the dark matter in a smooth component, such as a light neutrino, may be constrained to a statistical precision of $\ensuremath{\sigma}(f)\ensuremath{\approx}{0.0006f}_{\mathrm{sky}}^{\ensuremath{-}1/2}$ by a survey covering a fraction of sky ${f}_{\mathrm{sky}}$ with a redshift resolution $\ensuremath{\Delta}z=0.1.$ For the dark energy, a parametrization in terms of the present energy density ${\ensuremath{\Omega}}_{\mathrm{DE}},$ equation of state $w,$ and its redshift derivative ${w}^{\ensuremath{'}},$ the constraints correspond to $\ensuremath{\sigma}{(w)=0.009f}_{\mathrm{sky}}^{\ensuremath{-}1/2}$ and a degenerate combination of the other two parameters. For a fixed ${\ensuremath{\Omega}}_{\mathrm{DE}},$ $\ensuremath{\sigma}{(w}^{\ensuremath{'}}{)=0.046f}_{\mathrm{sky}}^{\ensuremath{-}1/2}.$