The Evolution of the Galaxy Cluster Luminosity-Temperature Relation

We analyzed the luminosity-temperature (L-T) relation for 2 samples of galaxy clusters which have all been observed by the ASCA satellite. We used 32 high redshift clusters (0.3<z<0.6), 53 low redshift clusters (z<0.3), and also the combination of the low and high redshift datasets. This is one of two surveys to use only ASCA data, and has the largest number of high redshift clusters. We assumed a power law relation between the bolometric luminosity of the galaxy cluster and its integrated temperature (uncorrected for cooling flows) and redshift (Lbol,44=CT (1+z)). We found that for an ΩM=1.0 ΩΛ=0.0 universe, A = 1.134 −1.073±1.66, α = 2.815 −0.316±0.42, and log(C) = −1.167+0.216 −0.221±0.25, and for ΩM=0.3 ΩΛ=0.7, A = 2.052 +1.073 −1.058±1.63, α = 2.822 −0.323±0.43, and log(C) = −1.126+0.223 −0.219±0.26 (all errors at 68% confidence for one and two interesting parameters, respectively). We found the dispersion at constant kT in this relation to be ∆logL=0.282 for ΩM=1.0 ΩΛ=0.0, and ∆logL=0.283 for ΩM=0.3 ΩΛ=0.7. The results for the combined dataset and those found using the low and high redshift clusters are consistent, independent of cosmology, with previous estimates of L∼T3 found by other authors. The observed weak or zero evolution agrees with the predictions of models that produce L∼T3 incorporating an initial source of non-gravitational energy before cluster collapse.