The mass function of clusters of galaxies is determined from 400 deg 2 of early commissioning imaging data of the Sloan Digital Sky Survey using ∼300 clusters in the redshift range z = 0.1-0.2. Clusters are selected using two independent selection methods: a matched filter and a red-sequence color-magnitude technique. The two methods yield consistent results. The cluster mass function is compared with large-scale cosmological simulations. We find a best-fit cluster normalization relation of σ 8Ωm0.6 = 0.33 ± 0.03 (for 0.1 ≲ Ωm ≲ 0.4) or, equivalently, σ8 = (0.16/Ωm)0.6. The amplitude of this relation is significantly lower than the previous canonical value, implying that either Ωm is lower than previously expected (Ωm = 0.16 if σ8 = 1) or σ8 is lower than expected (σ8 = 0.7 if Ωm = 0.3). The shape of the cluster mass function partially breaks this classic degeneracy. We find best-fit parameters of Ωm = 0.19±0.07 0.08 and σ8 = 0.9±0.2 0.3. High values of Ωm (≳ 0.4) and low σ8 (≲ 0.6) are excluded at ≳ 2 σ.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science