Systematic bias in an estimate of the cluster mass and the fluctuation amplitude from cluster abundance statistics

摘要

We revisit an estimate of the mass fluctuation amplitude, us, from the observational X-ray cluster abundance. In particular., we examine the effect of the systematic difference between the cluster virial mass estimated from the X-ray spectroscopy, M-vir,M-spec, and the true virial mass of the corresponding halo, M-vir. Mazzotta et al. (2004, MNRAS, 354, 10) recently pointed Out the possibility that alpha(M) M-vir,M-spec/M-vir is systematically lower than unity. We performed a statistical analysis by combining the latest X-ray cluster sample and the improved theoretical models, and found that sigma(8) similar to 0.76 +/- 0.01 + 0.50(1 - alpha(M)) for 0.5 < alpha(M) < 1. where the quoted errors are only statistical. Thus, if alpha(M) similar to 0.7, the value of sigma(8) from cluster abundance alone is now in better agreement with other cosmological data. including the cosmic microwave background, the galaxy power spectrum and the weak lensing data. The current study also illustrates the importance of possible systematic effects in mapping real clusters to underlying dark halos, which changes the interpretation of cluster abundance statistics.