HELIUM-LIKE IRON LINE TEMPERATURE DIAGNOSTICS IN CLUSTERS OF GALAXIES

The emission complex around approximately 6.7 keV, arising from He-lik e Fe lines and their dielectronic satellites, has been observed at low resolution in a number of clusters of galaxies. With sufficient spect ral resolution as in, e.g., solar flare observations, the ratio, G = ( x + y + z)/w, of the intercombination (x and y) and forbidden (z) to t he resonance (w) lines arising from the n = 2 level of the He-like ion , is a sensitive temperature diagnostic. We examine this role for G in the context of spatially and spectrally resolved observations of clus ters of galaxies. The temperature behavior of this ratio is strongly d ependent on the spectral resolution. We introduce an alternative defin ition for G that includes the contribution of satellite lines and impr oves the temperature fidelity of this diagnostic. We find that deproje ction of the observed value of G along a. line of sight through the cl uster can yield accurate temperature profiles for temperatures in the range 10(7)-10(8) K that do not suffer from the cluster model uncertai nties inherent in deconvolution of broad-band X-ray surface brightness profiles.