We perform a maximum likelihood analysis of the cluster abundance measured in
the SDSS using the maxBCG cluster finding algorithm. Our analysis is aimed at
constraining the power spectrum normalization σ8, and assumes flat
cosmologies with a scale invariant spectrum, massless neutrinos, and CMB and
supernova priors Omega_m*h^2=0.128+/-0.01 and h=0.72+/-0.05 respectively.
Following the method described in the companion paper Rozo et al. 2007, we
derive \sigma_8=0.92+/-0.10$ (1-sigma) after marginalizing over all major
systematic uncertainties. We place strong lower limits on the normalization,
sigma_8>0.76 (95% CL) (>0.68 at 99% CL). We also find that our analysis favors
relatively low values for the slope of the Halo Occupation Distribution (HOD),
alpha=0.83+/-0.06. The uncertainties of these determinations will substantially
improve upon completion of an ongoing campaign to estimate dynamical, weak
lensing, and X-ray cluster masses in the SDSS maxBCG cluster sample.Comment: 10 pages, 6 figures, ApJ Submitte
