Breaking Cosmological Degeneracies in Galaxy Cluster Surveys with a Physical Model of Cluster Structure
Abstract
It has been shown that in an idealized galaxy cluster survey, containing >~10,000 clusters, statistical errors on dark energy and other cosmological parameters would be at the percent level. Furthermore, through ``selfcalibration,'' parameters describing the massobservable relation and cosmology could be simultaneously determined, although at a loss in accuracy by about an order of magnitude. Here we examine an alternative approach to selfcalibration, in which a parameterized ab initio physical model is used to compute theoretical massobservable relations from the cluster structure. As an example, we use a modifiedentropy (``preheating'') model of the intracluster medium, with the history and magnitude of entropy injection as unknown input parameters. Using a Fisher matrix approach, we evaluate the expected simultaneous statistical errors on cosmological and cluster model parameters. We find that compared to a phenomenological parameterization of the massobservable relation, our physical model yields significantly tighter constraints in both surveys and offers substantially improved synergy when the two surveys are combined. In a mock Xray survey, we find statistical errors on the dark energy equation of state are a factor of 2 tighter than the phenomenological model, with Δw_{0}~0.08 and its evolution, Δw_{a}≡Δdw/da~0.23, with corresponding errors of Δw_{0}~0.06 and Δw_{a}~0.17 from a mock SunyaevZel'dovich (SZ) survey, both with N_{cl}~2.2×10^{4} clusters, while simultaneously constraining cluster model parameters to <~10%. When the two surveys are combined, the constraints tighten to Δw_{0}~0.03 and Δw_{a}~0.1, a 40% improvement over adding the individual experiment errors in quadrature and a factor of 2 improvement over the phenomenological model. This suggests that parameterized physical models of cluster structure would be useful when extracting cosmological constraints from SZ and Xray cluster surveys.
 Publication:

The Astrophysical Journal
 Pub Date:
 December 2006
 DOI:
 10.1086/508646
 arXiv:
 arXiv:astroph/0605204
 Bibcode:
 2006ApJ...653...27Y
 Keywords:

 Cosmology: Cosmological Parameters;
 Cosmology: Observations;
 Cosmology: Theory;
 Cosmology: Dark Matter;
 Galaxies: Clusters: General;
 Cosmology: LargeScale Structure of Universe;
 Astrophysics
 EPrint:
 22 pages, 8 figures, accepted to ApJ