AAS 201st Meeting, January, 2003
Session 23. Cosmology: The Fundamental Parameter
Oral, Monday, January 6, 2003, 10:00-11:30am, 608-609

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[23.01] The Cluster Mass Function and Cosmological Implications

N. Bahcall, F. Dong, P. Bode (Princeton University), SDSS Collaboration

The mass function of clusters of galaxies from 400 deg2 of the Sloan Digital Sky Survey is determined using ~ 300 clusters at z = 0.1 to 0.2. Comparison of the mass function with cosmological simulations yields a best-fit cluster normalization relation of sigma(8)*omega(m) = 0.33 +- 0.03 (for omega(m) in the range 0.1-0.4). This amplitude is significantly lower than the previous canonical value, implying that either omega(m) is lower than previously expected (omega(m) = 0.16 if sigma(8) = 1) or sigma(8) is lower than expected (sigma(8) = 0.7 if omega(m) = 0.3), as suggested by recent results. The shape of the cluster mass function partially breaks this degeneracy ; we find best-fit parameters of omega(m) = 0.19 (+0.08, -0.07) and sigma(8) = 0.9 (+0.3, -0.2). High values of omega(m) (>~0.4) and low sigma(8) (<~0.6) are excluded ati >~2sigma. We compare the results with cosmological constraints obtained from other independent methods including the evolution of cluster abundance with time, which yields consistent results.

The SDSS is a joint multi-institutional project. Funding for the project has been provided by the Alfred P. Sloan Foundation, the SDSS member institutions, NASA, NSF, DOE, Japanese Monbukagakusho, and the Max Planck Society. The SDSS web-site is http://www.sdss.org

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