Merger Frequency Of Rosat Clusters

The result of computing power ratios for the brightest ~ 40 ROSAT clusters is displayed in Figure 3.8. It is immediately apparent that there is a marked deficiency of highly disturbed clusters (complex and double). These brightest clusters therefore lack young members and are instead dominated by mostly evolved clusters with only small-scale (< 500 kpc) substructure. Since such highly evolved clusters are usually associated with cooling flows it should be expected that cooling flows dominate the brightest clusters as has been suggested before on different grounds (e.g., Arnaud 1988; Forman & Jones 1990; Edge et al. 1992; Peres et al. 1998).

In Figure 3.9 the quantitative connection between cooling flows and cluster morphology is shown by the anti-correlation of the mass deposition rate (M) and Pi/Pq- This represents the first quantitative description of the anti-correlation of substructure with the strength of a cooling flow. Note the large scatter for systems that have significant substructure (i.e., large P2/P0). Analysis of this correlation and its large scatter should shed light on how cooling flows are disrupted by mergers and are subsequently re-established.

Vid Xyz Mpc
Figure 3.8. Power ratios of the brightest ~ 40 clusters (Buote & Tsai 1996) computed within apertures of 0.5 Mpc (Left) and 1 Mpc (Right).
Vid Xyz Mpc
Figure 3.9. As Figure 3.8 for the 1 Mpc aperture except that the cooling flow mass deposition rate has been plotted on the vertical axis.
Figure 3.10. ROSAT HRI images of (Left) RX J1347.5-1145 from Schindler et al. (1997) and (Right) CI 0024+17 from Böhringer et al. (2000).

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