标题： 类星体-星团关联与大尺度物质团块的引力透镜效应 显示英文标题

标题： Quasar-Cluster Associations and Gravitational Lensing by Large-Scale Matter Clumps

摘要： 受最近发现的前景星系团背后背景亮类星体显著过量分布的激励（在$10$弧分尺度上），我们研究了将类星体-星系团关联归因于大尺度物质非均匀性引力透镜效应的可能性。基于传统的透镜模型，我们表明，报告的类星体过量分布不可能仅由星系团物质产生。即使考虑遵循空间两点关联函数的所有星系团，情况也没有改变，同时发现尺度为$>20$兆秒差距的物质团块也无法提供所需的面质量密度，因为它们的密度对比度受到宇宙微波背景辐射各向异性测量值的严格限制。此外，我们指出，非零宇宙常数对类星体-星系团关联的影响非常微小。我们得出结论，要么观测到的类星体数目被宇宙物质不均匀性的放大偏差严重污染，要么存在某种小于$\sim20$兆秒差距的星系团间物质，例如来自星系团-星系关联，其平均宇宙密度比星系团的平均密度高出约一个数量级。 显示英文摘要

摘要： Motivated by the significant overdensity of background bright quasars recently detected behind the foreground clusters of galaxies on scale of $10$ arcminutes, we have investigated the possibility of attributing the quasar-cluster associations to gravitational lensing by large-scale matter inhomogeneities. Based on the conventional lensing models, we have shown that the reported quasar overdensity is unlikely to be generated by cluster matter alone. The situation does not change even if all the clusters of galaxies which follow their spatial two-point correlation function are taken into account, while matter clumps on scale of $>20$ Mpc are also found to be unable to provide the required mass surface density since their density contrast is strictly limited by the anisotropy measurements of the cosmic background radiation. Moreover, we have pointed out that the influence of a nonzero cosmological constant on the quasar-cluster associations is very minor. We conclude that either the observed quasar number counts have been seriously contaminated by the magnification bias of matter inhomogeneities of the universe or there should exists some intercluster matter on scale of less than $\sim20$ Mpc, e.g. from cluster-galaxy correlation, whose mean cosmic density is about an order of magnitude higher than that of clusters of galaxies.