Radial temperature profiles of X-ray-emitting gas within clusters of galaxies

Previous analyses of ASCA data of clusters of galaxies have found conflicti ng results regarding the slope of the temperature profile of the hot X-ray gas within clusters, mainly because of the large, energy-dependent point-sp read function (PSF) of the ASCA mirrors, We present a summary of all ASCA-d etermined cluster temperature profiles found in the literature and find a d iscrepancy in the radial temperature trend of clusters based on which PSF-c orrection routine is used, This uncertainty in the cluster temperature prof ile in turn can lead to large uncertainties in the amount of dark matter in clusters. In this study, we have used ROSAT PSPC data to obtain independen t relative temperature profiles for 26 clusters, most of which have had the ir temperature profiles determined by ASCA. Our aim is not to measure the a ctual temperature values of the clusters but to use X-ray color profiles to search for a hardening or softening of the spectra as a function of radius for comparison to ASCA-derived profiles. The radial color profiles indicat e that outside of the cooling flow region, the temperature profiles of clus ters are in general constant. Within 35% of the virial radius, we find that a temperature drop of 20% at 10 keV and 12% at 5 keV can be ruled out at t he 99% confidence level. A subsample of non-cooling flow clusters shows tha t the condition of isothermality applies at very small radii too, although cooling gas complicates this determination in the cooling how cluster subsa mple. The colors predicted from the temperature profiles of a series of hyd rodynamical cluster simulations match the data very well, although they can not be used to discriminate among different cosmologies. An additional resu lt is that the color profiles show evidence for a central peak in metallici ty in low-temperature clusters.