X-ray temperatures of lensing clusters

If clusters of galaxies are homologous and the intracluster gas is in globa l equilibrium with the dark matter a tight relation between mass and X-ray temperature is expected in any cosmological model. We here test this relati on for 8 clusters with well-determined global temperatures measured with AS CA and masses inferred from weak and strong gravitational lensing. The data are well-fit by the predicted mass-temperature relation and are consistent with the empirical normalisation found by Evrard et al. Astrophys. J. 469, 494 (1996) using gasdynamic simulations. Thus, there is no discrepancy bet ween lensing and X-ray derived masses using this approach. The dispersion a round the relation is 22 per cent, entirely dominated by observational erro rs. These observational uncertainties may be brought down by the next gener ation of X-ray telescopes, e.g., SODART on board SPECTRUM-RG. Combined with wide-field imaging with HST such measurements could provide a sensitive te st of the normalisation and intrinsic scatter of the relation resulting in a powerful and expedient way of measuring masses of clusters of galaxies. I n addition, it is pointed out that the relation represents a new tool for d etermination of cosmological parameters, notably the cosmological constant Lambda.