THE GALAXY CLUSTER LUMINOSITY-TEMPERATURE RELATIONSHIP AND IRON ABUNDANCES - A MEASURE OF FORMATION HISTORY

Both the X-ray luminosity-temperature (L-T) relationship and the iron abundance distribution of galaxy clusters show intrinsic dispersion. U sing a large set of galaxy clusters with measured iron abundances, we find a correlation between abundance and the relative deviation of a c luster from the mean LT relationship. We argue that these observations can be explained by taking into account the range of cluster formatio n epochs expected in a hierarchical universe. The known relationship o f cooling flow mass deposition rate to luminosity and temperature is a lso consistent with this explanation. From the observed cluster popula tion, we estimate that the oldest clusters formed at z greater than or similar to 2. We propose that the iron abundance of a galaxy cluster can provide a parameterization of its age and dynamical history.