用未来X射线团簇气体质量分数测量约束暗能量的前景
The prospects for constraining dark energy with future X-ray cluster gas mass fraction measurements
摘要：
我们研究的能力，未来的X射线天文台约束暗能量通过测量的集群X射线气体的质量分数，fgas。我们发现，fgas测量样品的~500热，X射线明亮，动态松弛的集群，到~ 5%的精度，可以用来约束暗能量与暗能量任务组（DETF）的品质因数为15-40，有可能提高这些值的40%或更多的优化目标集群的红移分布。这些限制与DETF对其他领先的、计划中的暗能量实验的预测相当。未来的fgas实验将在一个大型的X射线或SZ调查之前进行，该调查将发现热的、高红移的X射线发光团簇。用新的X射线观测站进行短时间的“快照”观测，应能确定约500个适当弛豫系统的样本。感兴趣的红移，温度和X射线光度范围已经部分地探测现有的X射线集群调查，允许合理的估计的分数集群，将适当放宽fgas工作。我们的分析使用马尔可夫链蒙特卡罗方法，充分捕捉参数之间的相关退化，并有利于在分析中纳入先验和系统的不确定性。我们探讨了这种不确定性对从乐观到悲观的情景的影响。我们的结论是，fgas实验将提供严格的约束的平均物质和暗能量密度，与峰值灵敏度的暗能量工作在红移之间的超新星和重子声学振荡/弱透镜/集群数计数实验。结合起来，这些实验应该能够精确测量暗能量的演化。（节录）
英文摘要：
We examine the ability of a future X-ray observatory to constrain dark energy via measurements of the cluster X-ray gas mass fraction, fgas. We find that fgas measurements for a sample of ~500 hot, X-ray bright, dynamically relaxed clusters, to a precision of ~5 per cent, can be used to constrain dark energy with a Dark Energy Task Force (DETF) figure of merit of 15-40, with the possibility of boosting these values by 40 per cent or more by optimizing the redshift distribution of target clusters. Such constraints are comparable to those predicted by the DETF for other leading, planned dark energy experiments. A future fgas experiment will be preceded by a large X-ray or SZ survey that will find hot, X-ray luminous clusters out to high redshifts. Short `snapshot' observations with the new X-ray observatory should then be able to identify a sample of ~500 suitably relaxed systems. The redshift, temperature and X-ray luminosity range of interest has already been partially probed by existing X-ray cluster surveys which allow reasonable estimates of the fraction of clusters that will be suitably relaxed for fgas work. Our analysis uses a Markov Chain Monte Carlo method which fully captures the relevant degeneracies between parameters and facilitates the incorporation of priors and systematic uncertainties in the analysis. We explore the effects of such uncertainties for scenarios ranging from optimistic to pessimistic. We conclude that the fgas experiment will provide tight constraints on the mean matter and dark energy densities, with a peak sensitivity for dark energy work at redshifts midway between those of supernovae and baryon acoustic oscillation/weak lensing/cluster number counts experiments. In combination, these experiments should enable a precise measurement of the evolution of dark energy. (Abridged)
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