Effects Of Mergers

It is particularly interesting to study cluster mergers with simulations since one can clearly distinguish the different stages of a cluster merger (see Figs. 8.1 and 8.2). In the pre-merger phase the subclus-ters, which are approaching each other, are still well separated units (Figs. 8.1a,b, and 8.2a,b). The collision, i.e. the moment when the cores passes through each other, is characterized by high central density and high temperature (Figs. 8.1d and 8.2d). In the subsequent post-merger stage shock waves emerge - mainly in the direction of the original collision axis - and propagate outwards (Figs. 8.1e and 8.2e). In the next paragraphs we will discuss in detail the shocks and their observational appearance since they are very important for the dynamics of the ICM and for the conversion of kinetic energy into thermal energy.

Figure 8.1. Evolution of a model cluster. Each snapshot shows ICM density contours together with the flow pattern. The contours are logarithmically spaced with Alogp = 0.2, the bold line corresponding to a density of 10-28 g/cm3. The six snapshots are taken at b) t = 0.95 Gyr, c) t = 2.7 Gyr, d) t = 3.2 Gyr, e) t = 4.4 Gyr, f) t = 6.1 Gyr after the configuration shown in a) (from Schindler & Müller 1993).

Figure 8.1. Evolution of a model cluster. Each snapshot shows ICM density contours together with the flow pattern. The contours are logarithmically spaced with Alogp = 0.2, the bold line corresponding to a density of 10-28 g/cm3. The six snapshots are taken at b) t = 0.95 Gyr, c) t = 2.7 Gyr, d) t = 3.2 Gyr, e) t = 4.4 Gyr, f) t = 6.1 Gyr after the configuration shown in a) (from Schindler & Müller 1993).

Figure 8.2. Evolution of the X-ray temperature of the same model as shown in Fig. 8.1. The temperature contours are logarithmically scaled with AlogT = 0.05, the bold contour line corresponding to a temperature of 10s K. The six snapshots are taken at the same times as in Fig. 8.1 (from Schindler & Miiller 1993).

Figure 8.2. Evolution of the X-ray temperature of the same model as shown in Fig. 8.1. The temperature contours are logarithmically scaled with AlogT = 0.05, the bold contour line corresponding to a temperature of 10s K. The six snapshots are taken at the same times as in Fig. 8.1 (from Schindler & Miiller 1993).

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