Near-infrared properties of galaxy clusters: Luminosity as a binding mass predictor and the state of cluster baryons

We explore the near-infrared properties of galaxies within 27 galaxy clusters using data from the Two Micron All Sky Survey (2MASS). For a subsample of 13 clusters with available X-ray imaging data, we examine the properties of both the galaxies and the intracluster medium. We show that the K-band luminosity is correlated with cluster mass, providing a binding mass estimate accurate to 45%. The mass-to-light ratio in our ensemble increases by a factor of similar to2 over the cluster mass range (10(14) - 10(15) M-.). We examine the total baryon fraction, showing that it is an increasing function of cluster mass. Using the mass-to-light ratio of massive clusters, we find that Omega(M) = 0.19 +/- 0.03; using the total baryon fraction we find that Omega(M) = 0.28 +/- 0.03, in good agreement with recent cosmic microwave background (CMB) anisotropy constraints. Differences between these two estimates suggest that the K-band mass-to-light ratio in massive clusters may be lower than that in the universe by as much as similar to30%. We examine the stellar mass fraction, the intracluster medium (ICM) mass to stellar mass ratio, and the cluster ironmass fraction. The stellar mass fraction decreases by a factor of 1.8 from low-to high-mass clusters, and the ICM to stellar mass ratio increases from 5.9 to 10.4 over the same mass range. Together, these measurements suggest a decrease of star formation efficiency with increasing cluster mass and provide constraints on models of the thermodynamic history of the intracluster medium. The cluster iron mass to total mass ratio is constant and high, suggesting that some efficient and uniform enrichment process may have taken place before the bulk of stars in cluster galaxies formed.