X-ray spectroscopic constraints on cooling-flow models for clusters of galaxies

We review the general observational properties of clusters of galaxies and discuss the physics of the intracluster medium. We describe many aspects of the in- flight calibration of the Reflection Grating Spectrometers (RGS) on XMM-Newton. We describe the construction of the instrument response functions and develop a number of event correction algorithms. We discuss the formulation of multivariate Monte Carlo methods for use in fitting X-ray spectra of spatially- resolved sources. We present detailed spatially-resolved spectroscopy results of the observation of Abell 1835 using the European Photon Imaging Cameras (EPIC) and the RGS as well as high resolution X-ray spectra of 13 other putative cooling-flow clusters of galaxies obtained with the RGS. The spectra exhibit strong emission from cool plasma at just below the ambient temperature, T ₀, down to T₀/2, but also exhibit a severe deficit of emission, relative to the predictions of the isobaric cooling-flow model at lower temperatures (<T₀/3). Empirically, the differential luminosity distribution is consistent with being proportional to the temperature to the power of ≈1 to 2, instead of being independent of the temperature, as expected in the standard multi-phase model. The observations suggest a much more complicated cooling process in the cores of clusters than simple isobaric radiative cooling.