A Low-Redshift Galaxy Cluster X-Ray Temperature Function Incorporating Suzaku Data

We present the first results of a survey of 14 low-redshift galaxy clusters using Suzaku. Although luminous (L_x > 1 × 10⁴³ erg s^-1 (0.1-2.4 keV)), these clusters have no prior pointed X-ray data. Together with 47 other systems they form a flux-limited sample (f_x > 1.0 × 10^-11 erg s^-1cm^-2 (0.1-2.4 keV)) with z <= 0.1 in the northern celestial hemisphere. Using this total sample, we evaluate the local L-T relationship and the local cluster temperature function. Suzaku temperature measurements appear to be in accord with those of other missions. General agreement is found with other published estimates of the low-redshift cluster temperature function; however, the sample used here exhibits slightly lower space densities at gas temperatures below 4-5 keV. We find a corresponding deficit in the number of clusters with temperatures between approximately 4.5 and 5.5 keV. Although at low significance, a similar feature exists in previous low-redshift cluster data sets. We suggest that low-redshift cluster samples, while crucial for calibrating precision cosmology measurements, must be used with caution due to their limited size and susceptibility to the effects of cosmic variance.