Determining the Geometry and the Cosmological Parameters of the Universe through SZE Cluster Counts

Details Determining the Geometry and the Cosmological Parameters of the Universe through SZE Cluster Counts Determining the Geometry and the Cosmological Parameters of the Universe through SZE Cluster Counts

2000-11-24

arxiv.org/abs/astro-ph/0011452v1

Astronomy and Astrophysics

Astrophysics

23 pages, 7 figures, accepted by ApJ

Scientific paper

10.1086/319780

We study Sunyaev-Zeldovich Effect (SZE) cluster counts in different cosmologies. It is found that even without the full knowledge of the redshift distribution of SZE clusters, one can still readily distinguish a flat universe with a cosmological constant from an open universe. We divide clusters into a low redshift group (with redshift z<0.5) and a high redshift group (with z>1), and compute the relation r=N(z<0.5)/N(z>1), where N is the number of flux-limited (S_lim) SZE clusters. With about the same total number of SZE clusters N(z>0), the r-value for a flat universe with a consmological constant and that for an open universe occupy different regions in the S_lim -- r plot for the most likely cosmological parameters 0.25<\Omega_0<0.35 and 0.2<\Gamma<0.3, where \Gamma is the shape parameter of the initial power spectrum of density fluctuations. Thus, with a deep SZE cluster survey, the ratio r can reveal, independent of the normalization of the power spectrum, whether we are living in a low-density flat universe or an open universe. Within the flat universe scenario, the SZE cluster-normalized \sigma_8 has also been investigated in this work, where sigma_8 is the r.m.s. density fluctuations within the top-hat scale of 8 h^{-1} Mpc. A functional relation sigma_8 \sim \Omega_0^{-0.13} is found. Combining it with the X-ray cluster-normalized \sigma_8\sim\Omega_0^{-0.52+0.13\Omega_0}, one can put tight constraints on both \Omega_0 and \sigma_8 simulataneously.

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