A ROSAT study of the cores of clusters of galaxies - I. Cooling flows in an X-ray flux-limited sample

摘要

This is the first part of a study of the detailed X-ray properties of thecores of nearby clusters. We have used the flux-limited sample of 55 clustersof Edge et al. (1990) and archival and proprietary data from the {\it ROSAT}observatory. In this paper an X-ray spatial analysis based on thesurface-brightness-deprojection technique is applied to the clusters in thesample with the aim of studying their cooling flow properties. We determine thefraction of cooling flows in this sample to be 70-90 percent and estimate thecontribution of the flow region to the cluster X-ray luminosity. We show thatthe luminosity within a strong cooling flow can account for up to 70 percent ofa cluster X-ray bolometric luminosity. Our analysis indicates that about 40percent of the clusters in the sample have flows depositing more than 100\Msunpyr throughout the cooling region and that these possibly have beenundisturbed for many Gyr, confirming that cooling flows are the natural stateof cluster cores. New cooling flows in the sample are presented and previouslyambiguous ones are clarified. We have constructed a catalogue of someintracluster medium properties for the clusters in this sample. The profiles ofthe mass deposited from cooling flows are analyzed and evidence presented forthe existence of breaks in some of the profiles. Comparison is made to recentoptical and radio data. We cross-correlate our sample with the Green Bank, NVSSand FIRST surveys and to the volume-limited sample of brightest clustergalaxies presented by Lauer and Postman (1994). Although weak trends exist, nostrong correlation between optical magnitude or radio power of the brightestcluster galaxy and the strength of the flow is found.