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

Abstract

This is the first part of a study of the detailed X‐ray properties of the cores of nearby clusters. We have used the flux‐limited sample of 55 clusters listed by Edge et al., and archival and proprietary data from the ROSAT observatory. In this paper an X‐ray spatial analysis based on the surface‐brightness‐deprojection technique is applied to the clusters in the sample with the aim of studying their cooling flow properties. We determine the fraction of cooling flows in this sample to be 70–90 per cent, and estimate the contribution of the flow region to the cluster X‐ray luminosity. We show that the luminosity within a strong cooling flow can account for up to 70 per cent of a cluster X‐ray bolometric luminosity. Our analysis indicates that about 40 per cent of the clusters in the sample have flows depositing more than 100 M⊙ yr−1 throughout the cooling region, and that these possibly have been undisturbed for many Gyr, confirming that cooling flows are the natural state of cluster cores. New cooling flows in the sample are presented, and previously ambiguous ones are clarified. We have constructed a catalogue of some intracluster medium properties for the clusters in this sample. The profiles of the mass deposited from cooling flows are analysed, and evidence is presented for the existence of breaks in some of the profiles. Comparison is made to recent optical and radio data. We cross‐correlate our sample with the Green Bank, NVSS and FIRST surveys, and with the volume‐limited sample of brightest cluster galaxies presented by Lauer &38; Postman. Although weak trends exist, no strong correlation between optical magnitude or radio power of the brightest cluster galaxy and the strength of the flow is found.

Halo and relic sources in clusters of galaxies

“…Both these clusters are characterized by signatures of recent merger events (Markevitch 1997, Markevitch et al 1998. No cooling flow is detected in A 2218, whereas the cluster A 2142 has a massive cooling flow (Peres et al 1998) centered on the diffuse radio source. The presence of a radio halo in a cooling flow cluster is quite uncommon (Feretti 2000).…”

Cosmological Parameters from Observations of Galaxy Clusters

“…The fraction of the total flux coming from r < 0.05r 500 can be as large as 50%, and correlates strongly with other observable signatures of cool cores such as central cooling time and cuspiness of the surface brightness profile (Mantz 2009; see also Andersson et al 2009). Interestingly, the fractions of cool-core systems identified using this criterion are comparable in X-ray flux-selected samples, at least within z < 0.5 (∼ 40%; see Figure 21; Peres et al 1998;Bauer et al 2005;Sanderson, Ponman & O'Sullivan 2006;Chen et al 2007;Mantz 2009), although these fractions are biased relative to the full population due to selection effects. Cool cores are also common in X-ray selected samples at high redshift (Santos et al 2008; 0.7 < z < 1.4).…”

Temperature and total mass profiles of the A3571 cluster of galaxies

“…The cooling flow found in the center of A3571 (Peres et al 1998) contributes a comparable amount of flux to the ambient gas in the central bin. To study this more we added a cooling flow model (mkcflow in XSPEC) fixing the lower boundary of the continous temperature range to 0.1 keV and forcing the upper boundary to equal the ambient temperature.…”