EDP Sciences
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Volume 488, Number 1, September II 2008
Page(s) 47 - 53
Section Cosmology (including clusters of galaxies)
DOI http://dx.doi.org/10.1051/0004-6361:20065067
Published online 27 May 2008

A&A 488, 47-53 (2008)
DOI: 10.1051/0004-6361:20065067

What can be learned about dark energy evolution?

M. Douspis1, Y. Zolnierowski2, A. Blanchard3, and A. Riazuelo4

1  Institut d'Astrophysique Spatiale (IAS), Univ. Paris-Sud, CNRS, Bâtiment 121, 91405 Orsay, France
    e-mail: marian.douspis@ias.u-psud.fr
2  Laboratoire d'Annecy-le-Vieux de Physique des Particules, UMR 5814 CNRS, 9 chemin de Bellevue, BP 110, 74941 Annecy-le-Vieux Cedex, France
    e-mail: zolnierowski@lapp.in2p3.fr
3  LATT, Université de Toulouse, CNRS, 14 avenue É. Belin, 31400 Toulouse, France
    e-mail: alain.blanchard@ast.obs-mip.fr
4  CNRS, UMR 7095, Institut d'Astrophysique de Paris, 75014 Paris, France; Université Pierre et Marie Curie-Paris 6, UMR 7095, 75014 Paris, France
    e-mail: riazuelo@iap.fr

Received 22 February 2006 / Accepted 22 April 2008

We examine constraints obtained from SNIa surveys on a two parameter model of dark energy in which the equation of state $w (z)
= P(z) / \rho (z)$ undergoes a transition over a period significantly shorter than the Hubble time. We find that a transition between $w \sim -0.2$ and $w \sim -1$ (the first value being somewhat arbitrary) is allowed at redshifts as low as 0.1, despite the fact that data extend beyond $z \sim 1$. Surveys with the precision anticipated for space experiments should allow only slight improvement on this constraint, as a transition occurring at a redshift as low as ~0.17 could still remain undistinguishable from a standard cosmological constant. The addition of a prior on the matter density $\Omega_{\rm m}= 0.3$ only modestly improves the constraints. Even deep space experiments would still fail to identify a rapid transition at a redshift above 0.5. These results illustrate that a Hubble diagram of distant SNIa alone will not reveal the actual nature of dark energy at a redshift above 0.2 and that only the local dynamics of the quintessence field can be inferred from a SNIa Hubble diagram. Combinations, however, seem to be very efficient: we found that the combination of present day CMB data and SNIa already excludes a transition at redshifts below 0.8.

Key words: cosmology: cosmic microwave background -- cosmology: cosmological parameters -- cosmology: observations

© ESO 2008