科研之友
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摘要
The rich galaxy cluster Abell 2204 exhibits edges in its X-ray surface brightness at similar to 65 and 35 kpc west and east of its center, respectively. The presence of these edges, which were interpreted as sloshing cold fronts, implies that the intracluster medium (ICM) was recently disturbed. We analyze the properties of the ICM using multiple Chandra observations of Abell 2204. We find a density ratio of n(in)/n(out) = 2.05 +/- 0.05 and a temperature ratio of. T-out/T-in = 1.91 +/- 0.27 (projected, or 1.87 +/- 0.56 deprojected) across the western edge, and correspondingly n(in)/n(out) = 1.96 +/- 0.05 and T-out/T-in= 1.45 +/- 0.15 (projected, or 1.25 +/- 0.26 deprojected) across the eastern edge. These values are typical of cold fronts in galaxy clusters. This, together with the spiral pattern observed in the cluster core, supports the sloshing scenario for Abell 2204. No Kelvin-Helmholtz eddies are observed along the cold front surfaces, indicating that they are effectively suppressed by some physical mechanism. We argue that the suppression is likely facilitated by the magnetic fields amplified in the sloshing motion. and deduce from the measured gas properties that the magnetic field strength should be greater than 24 +/- 6 mu G and 32 +/- 8 mu G along the west and east cold fronts, respectively.
- 出版日期2017-3-20
- 单位南京大学
