Measuring unified dark matter with 3D cosmic shear
Abstract
We present parameter estimation forecasts for future 3D cosmic shear surveys for a class of Unified Dark Matter (UDM) models, where a single scalar field mimics both Dark Matter (DM) and Dark Energy (DE). These models have the advantage that they can describe the dynamics of the Universe with a single matter component providing an explanation for structure formation and cosmic acceleration. A crucial feature of the class of UDM models we use in this work is characterized by a parameter, c_{∞} (in units of the speed of light c= 1), that is the value of the sound speed at late times, and on which structure formation depends. We demonstrate that the properties of the DMlike behaviour of the scalar field can be estimated with very high precision with largescale, fully 3D weak lensing surveys. We found that 3D weak lensing significantly constrains c_{∞}, and we find minimal errors Δc_{∞}= 3.0 × 10^{5}, for the fiducial value c_{∞}= 1.0 × 10^{3} and Δc_{∞}= 2.6 × 10^{5}, for c_{∞}= 1.2 × 10^{2}. Moreover, we compute the Bayesian evidence for UDM models over the ΛCDM model as a function of c_{∞}. For this purpose, we can consider the ΛCDM model as a UDM model with c_{∞}= 0. We find that the expected evidence clearly shows that the survey data would unquestionably favour UDM models over the ΛCDM model, for the values c_{∞}≳ 10^{3}.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 July 2011
 DOI:
 10.1111/j.13652966.2011.18712.x
 arXiv:
 arXiv:1002.4740
 Bibcode:
 2011MNRAS.415..399C
 Keywords:

 gravitation;
 cosmology: observations;
 cosmology: theory;
 dark energy;
 dark matter;
 largescale structure of Universe;
 Astrophysics  Cosmology and Extragalactic Astrophysics
 EPrint:
 12 pages, 5 figures