The WARPS survey - IV. The X-ray luminosity-temperature relation of high-redshift galaxy clusters

We present a measurement of the cluster X-ray luminosity-temperature (L-T) relation out to high redshift (z similar to 0.8). Combined ROSAT PSPC spectra of 91 galaxy clusters detected in the Wide Angle ROSAT Pointed Survey (WARPS) are simultaneously fitted in redshift and luminosity bins. The resulting temperature and luminosity measurements of these bins, which occupy a region of the high-redshift L-T relation not previously sampled, are compared with existing measurements at low redshift in order to constrain the evolution of the L-T relation. We find the best fit to low-redshift (z < 0.2) cluster data, at T > 1 keV, to be L proportional to T3.15 +/- 0.06. Our data are consistent with no evolution in the normalization of the L-T relation up to z similar to 0.8. Combining our results with ASCA measurements taken from the literature, we find eta = 0.19 +/- 0.38 (for Omega(0) = 1, with 1 sigma errors) where L-Bol proportional to (1 + z)T-eta(3.15), or eta = 0.60 +/- 0.38 for Omega(0) = 0.3. This lack of evolution is considered in terms of the entropy-driven evolution of clusters. Further implications for cosmological constraints are also discussed.