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首页> 外文期刊>The Astrophysical journal >CHANDRA OBSERVATION OF THE MERGING CLUSTER A168: A LATE STAGE IN THE EVOLUTION OF A COLD FRONT
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CHANDRA OBSERVATION OF THE MERGING CLUSTER A168: A LATE STAGE IN THE EVOLUTION OF A COLD FRONT

机译：融合群A168的CHANDRA观测：冷锋演化的后期

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摘要

We present Chandra observations of the cool cluster A168, for which previous X-ray imaging and optical studies indicated a merger of two subclusters nearly in the plane of the sky. We derive a temperature map for A168, which shows that the merger has proceeded beyond the core passage and is near subcluster turnaround. It also reveals an unusual feature: the gas core of one of the subclusters forms a tonguelike structure extending ahead (in the direction of motion) of the subcluster center. The coolest cluster gas is found in a crescent-shaped region at the tip of this tongue and forms a cold front in pressure equilibrium with the external gas. In contrast with this feature's forward location, previously observed merger cold fronts (e.g., A3667, 1E 0657 — 56) lagged behind their host subclusters, as expected in the presence of ram pressure. We propose that A168 illustrates a much later stage in the evolution of a cold front, when its host subcluster approaches the apocenter of the merger orbit where the ram pressure on its gas drops sharply. As a result, a large chunk of the subcluster gas "slingshots" past the dark matter center, becomes unbound from the subcluster, and expands adiabatically, as seen in some recent hydrodynamic simulations.
机译：我们介绍了Chandra对A168冷星团的观测结果，先前的X射线成像和光学研究表明，这两个星团几乎在天空平面中合并。我们得出了A168的温度图，该图表明合并已经超出核心通道，并且接近子集群周转。它还显示了一个不寻常的特征：一个子群集的气芯形成了一个舌状结构，该结构在子群集中心之前（沿运动方向）延伸。最冷的团簇气体位于该舌尖的月牙形区域，与外界气体形成压力平衡的冷锋。与该功能的前方位置形成对比，先前观察到的合并冷锋（例如，A3667、1E 0657 — 56）滞后于其主子群集，这是在存在冲压压力的情况下所预期的。我们认为，A168可以说明冷锋发展的后期，当它的宿主子簇接近合并轨道的重心时，其气体的冲压压力急剧下降。结果，如近来一些水动力模拟中所看到的，大量的子团簇气体“弹弓”越过了暗物质中心，变得不受子团簇的束缚，并且绝热地膨胀。

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