Astronomy and Astrophysics – Astrophysics
Scientific paper
May 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993a%26a...272..137s&link_type=abstract
Astronomy and Astrophysics, Vol. 272, p. 137 (1993)
Astronomy and Astrophysics
Astrophysics
174
Scientific paper
We present simulations of the evolution of galaxy clusters including both collisionless matter (galaxies and dark matter) and intra- cluster gas. The simulations have been performed using a direct N-body integrator for the collisionless component combined with a finite difference scheme (PPM) for the gas dynamics. With this combined method we have investigated the collision of subclusters as well as the subsequent quasi-equilibrium state by calculating several models with different initial conditions. The collision of subclusters produces several shock waves of varying strength depending on the mass of the colliding subclusters. In particular, the collision of two large subclusters causes a lens-shaped shock front. After merging the model cluster is not isothermal, but shows a hot central region (T >= 3 10^8^K) and temporarily cool regions (T <= 5 10^7^K). We have also calculated the X-ray image of the model cluster when it would be observed by ROSAT. The collision of large subclusters gives rise to distorted X-ray contours at the moment of collision and to lens-shaped contours when the strong shock front resulting from the collision begins to expand. We have also calculated X-ray temperature maps which are expected to be observable with the next generation of X-ray telescopes. We find that these temperature maps show many details of the collision, e.g., the heated gas between two subclusters shortly before their collision and the steep temperature gradients at shock fronts. Thus, the evolutionary state of a cluster can be characterized much better when these temperature data are available. An investigation of the so-called β-discrepancy shows no discrepancy in our cluster models. Our results further show that a frequent occurance of cooling flows can be one of the reasons for the β-discrepancy.
Mueller Ewald
Schindler Sabine
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