Hectospec星系团巡天的钱德拉跟踪：苛性和流体静力质量的比较和对流体静力偏差的限制
Chandra follow up of the Hectospec Cluster Survey: Comparison of Caustic and Hydrostatic Masses and Constraints on the Hydrostatic Bias
摘要：
星系团是研究宇宙学和天体物理学的强大探测器。然而，对于许多应用来说，对星系团质量的精确测量是必不可少的。系统性地低估了X射线观测的流体静力学质量（所谓的流体静力学偏差）可能是不同宇宙学测量结果之间存在矛盾的原因。我们比较X射线流体静力学质量与质量估计使用焦散方法（基于星系速度），以探讨这两种方法的系统的不确定性，并提出新的限制水平的流体静力学偏差。流体静力学和焦散质量配置文件的基础上，从Hectospec集群调查集群钱德拉观测的44个集群的样本独立确定。这是同类研究中规模最大的系统比较。使用模型在标准化半径（$R_{500}$）处比较质量，该模型包括两种质量估计值中可能的偏倚和分散。详细探讨了影响这两种质量测定方法的系统学。流体静力学的质量被发现系统高于平均焦散质量，我们发现的证据表明，焦散方法越来越低估的质量时，较少的星系被用来测量焦散。我们限制我们的分析，以14个集群的最佳采样焦散这种偏见最小化（$\ge210$星系），并发现在$R_{500}$的流体静力学焦散质量的平均比例是$M_X/M_C=1.12^{+0.11}_{-0.10}$。我们将此结果解释为对流体静力学偏倚水平的限制，有利于流体静力学偏倚的小水平或零水平（在$3σ$水平小于$20\%$）。然而，我们发现与这两种质量估计方法相关的系统不确定性仍然保持在$10-15\%$水平，这将允许显着更大的水平的流体静力学偏差。
英文摘要：
Clusters of galaxies are powerful probes with which to study cosmology and astrophysics. However, for many applications an accurate measurement of a cluster's mass is essential. A systematic underestimate of hydrostatic masses from X-ray observations (the so-called hydrostatic bias) may be responsible for tension between the results of different cosmological measurements. We compare X-ray hydrostatic masses with masses estimated using the caustic method (based on galaxy velocities) in order to explore the systematic uncertainties of both methods and place new constraints on the level of hydrostatic bias. Hydrostatic and caustic mass profiles were determined independently for a sample of 44 clusters based on Chandra observations of clusters from the Hectospec Cluster Survey. This is the largest systematic comparison of its kind. Masses were compared at a standardised radius ($R_{500}$) using a model that includes possible bias and scatter in both mass estimates. The systematics affecting both mass determination methods were explored in detail. The hydrostatic masses were found to be systematically higher than caustic masses on average, and we found evidence that the caustic method increasingly underestimates the mass when fewer galaxies are used to measure the caustics. We limit our analysis to the 14 clusters with the best-sampled caustics where this bias is minimised ($\ge210$ galaxies), and find that the average ratio of hydrostatic to caustic mass at $R_{500}$ is $M_X/M_C=1.12^{+0.11}_{-0.10}$. We interpret this result as a constraint on the level of hydrostatic bias, favouring small or zero levels of hydrostatic bias (less than $20\%$ at the $3σ$ level). However, we find systematic uncertainties associated with both mass estimation methods remain at the $10-15\%$ level, which would permit significantly larger levels of hydrostatic bias.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
