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. Using a large set of galaxy clusters with measured iron abundances, we find a correlation between abundance and the relative deviation of a cluster from the mean LT relationship. We argue that these observations can be explained by taking into account the range of cluster formation epochs expected in a hierarchical universe. The known relationship of cooling flow mass deposition rate to luminosity and temperature is also consistent with this explanation. From the observed cluster population, 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.