ASCA and ROSAT observations of nearby cluster cooling flows

We present a detailed analysis of the X-ray properties of the cooling flows in a sample of nearby, X-ray-bright clusters of galaxies using high-qualit y ASCA spectra and ROSAT X-ray images. We demonstrate the need for multipha se models to consistently explain the spectral and imaging X-ray data for t he clusters. The mass deposition rates of the cooling flows, independently determined from the ASCA spectra and ROSAT images, exhibit reasonable agree ment. We confirm the presence of intrinsic X-ray absorption in the clusters using a variety of spectral models. We also report detections of 100-mum i nfrared emission, spatially coincident with the cooling flows, in several o f the systems studied. The observed infrared fluxes and flux limits are in good agreement with the predicted values owing to reprocessed X-ray emissio n from the cooling flows. We present precise measurements of the abundances of iron, magnesium, silicon and sulphur in the central regions of the Virg o and Centaurus clusters, Our results firmly favour models in which a high mass fraction (70-80 per cent) of the iron in the X-ray gas in these region s originates from Type Ia supernovae. Finally, we present a series of metho ds which may be used to estimate the ages of cooling flows from Xray data. The results for the present sample of clusters indicate ages of between 2.5 and 7 Gyr. If the ages of cooling flows are primarily set by subcluster me rger events, then our results suggest that in the largest clusters, mergers with subclusters with masses of similar to 30 per cent of the final cluste r mass are likely to disrupt cooling flows.