The correlation function of galaxy clusters and detection of baryon   acoustic oscillations
  We calculate the correlation function of 13,904 galaxy clusters of z \leq 0.4 selected from the cluster catalog of Wen, Han & Liu. The correlation function can be fitted with a power-law model \xi(r)=(r/R_0)^{\gamma} on the scales of 10h^(-1)Mpc \leq r \leq 50h^(-1)Mpc, with a larger correlation length of R_0=18.84\pm0.27 h^(-1)Mpc for clusters with a richness of R \geq 15 and a smaller length of R_0=16.15 \pm 0.13 h^(-1)Mpc for clusters with a richness of R \geq 5. The power law index of \gamma=2.1 is found to be almost the same for all cluster subsamples. A pronounced baryon acoustic oscillations (BAO) peak is detected at r ~ 110 h^(-1)Mpc with a significance of ~ 1.9\sigma. By analyzing the correlation function in the range of 20 h^(-1)Mpc \leq r \leq 200 h^(-1)Mpc, we find the constraints on distance parameters are D_v(0.276)=1077\pm55(1\sigma) Mpc and h=0.73 \pm 0.039 (1\sigma), which are consistent with the WMAP 7-year cosmology. However, the BAO signal from the cluster sample is stronger than expected and leads to a rather low matter density \Omega_m h^2=0.093\pm0.0077 (1\sigma), which deviates from the WMAP 7-year result by more than 3 \sigma. The correlation function of the GMBCG cluster sample is also calculated and our detection of the BAO feature is confirmed. 
T. Hong, J. L. Han, Z. L. Wen, L. Sun, and H. Zhan
astro-ph.CO