Journal Article

Measuring unified dark matter with 3D cosmic shear

Stefano Camera, Thomas D. Kitching, Alan F. Heavens, Daniele Bertacca and Antonaldo Diaferio

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 415, issue 1, pages 399-409
Published in print July 2011 | ISSN: 0035-8711
Published online July 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.18712.x
Measuring unified dark matter with 3D cosmic shear

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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 DM-like behaviour of the scalar field can be estimated with very high precision with large-scale, 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.

Keywords: gravitation; cosmology: observations; cosmology: theory; dark energy; dark matter; large-scale structure of Universe

Journal Article.  8035 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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