Near-IR Properties of Galaxy Clusters: Luminosity as a Binding Mass Predictor and the State of Cluster Baryons

Astrophysics, abstract
astro-ph/0304033

From: Joseph J Mohr <jmohr@astro.uiuc.edu>

Date: Tue, 1 Apr 2003 21:00:10 GMT   (103kb)

Authors:
Yen-Ting Lin (U Illinois),
Joseph J. Mohr (U Illinois),
S. A. Stanford (UC Davis, LLNL)

Comments: 16 pages, 9 figures, to appear in ApJ, July 10, 2003 issue

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 both the properties of
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 mlr in our ensemble increases by a factor of ~2 over the cluster mass
range (10^{14}-10^{15}M_sun). 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 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 ~30%.

We examine the stellar mass fraction, the ICM mass to stellar mass ratio and
the cluster iron mass 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.

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