标题： 高红移下是否存在冷核星系团？ 钱德拉结果及WFXT的前景 显示英文标题

标题： Are there cool-core clusters at high-redshift? Chandra results and prospects with WFXT

摘要： 在本次贡献中，我们使用钱德拉望远镜的高分辨率数据，追踪了冷却核心星系团在红移z~1.3范围内的演化情况。我们的分析基于表面亮度（SB）集中度c_SB的测量，它与中心冷却时间强烈反相关，使我们能够在低信噪比数据中表征冷却核心的强度。我们确认了随着红移增加，冷却核心星系团的比例呈负演化趋势，尤其是对于非常强的冷却核心。尽管如此，我们发现红移z ~ 1处存在大量形成良好的冷却核心。一旦获得大样本的高红移星系团数据，这种分析在限制冷却核心的本质和演化方面具有潜在的高效性。在这方面，我们探讨了提出的广域X射线望远镜（WFXT）任务在解决这一科学问题上的潜力。我们得出结论，WFXT在角分辨率、灵敏度和覆盖立体角之间提供了最佳的权衡，以便发现并完全表征到z=1.5范围内的冷却核心星系团群体。 显示英文摘要

摘要： In this contribution we trace the evolution of cool-core clusters out to z~1.3 using high-resolution Chandra data of three representative cluster samples spanning different redshift ranges. Our analysis is based on the measurement of the surface brightness (SB) concentration, c_SB, which strongly anti-correlates with the central cooling time and allows us to characterize the cool-core strength in low S/N data. We confirm a negative evolution in the fraction of cool-core clusters with redshift, in particular for very strong cool-cores. Still, we find evidence for a large population of well formed cool-cores at z ~ 1. This analysis is potentially very effective in constraining the nature and the evolution of the cool-cores, once large samples of high-z clusters will be available. In this respect, we explore the potential of the proposed mission Wide Field X-ray Telescope (WFXT) to address this science case. We conclude that WFXT provides the best trade-off of angular resolution, sensitivity and covered solid angle in order to discover and fully characterize the cool-core cluster population up to z=1.5.