Physics Department and Michigan Center for Theoretical Physics, University of Michigan, Ann Arbor, Michigan 48109-1040, USA.
Nature. 2012 Jul 12;487(7406):202-4. doi: 10.1038/nature11224.
It is a firm prediction of the concordance cold-dark-matter cosmological model that galaxy clusters occur at the intersection of large-scale structure filaments. The thread-like structure of this 'cosmic web' has been traced by galaxy redshift surveys for decades. More recently, the warm–hot intergalactic medium (a sparse plasma with temperatures of 10(5) kelvin to 10(7) kelvin) residing in low-redshift filaments has been observed in emission and absorption. However, a reliable direct detection of the underlying dark-matter skeleton, which should contain more than half of all matter, has remained elusive, because earlier candidates for such detections were either falsified or suffered from low signal-to-noise ratios and unphysical misalignments of dark and luminous matter. Here we report the detection of a dark-matter filament connecting the two main components of the Abell 222/223 supercluster system from its weak gravitational lensing signal, both in a non-parametric mass reconstruction and in parametric model fits. This filament is coincident with an overdensity of galaxies and diffuse, soft-X-ray emission, and contributes a mass comparable to that of an additional galaxy cluster to the total mass of the supercluster. By combining this result with X-ray observations, we can place an upper limit of 0.09 on the hot gas fraction (the mass of X-ray-emitting gas divided by the total mass) in the filament.
一致性冷暗物质宇宙学模型明确预测，星系团出现在大尺度结构纤维的交叉点处。几十年来，星系红移调查一直追踪着这种“宇宙网”的线状结构。最近，在发射和吸收中观测到了低红移纤维中存在的温暖-热星系际介质（温度为 10(5)开尔文至 10(7)开尔文的稀疏等离子体）。然而，由于早期暗物质骨架的可靠直接探测仍然难以捉摸，暗物质骨架应该包含超过一半的物质，因为早期对这种探测的候选者要么被伪造，要么受到信噪比低和暗物质与发光物质物理错位的影响。在这里，我们报告了从弱引力透镜信号中检测到连接 Abell 222/223 超星系团系统两个主要组件的暗物质纤维，无论是在非参数质量重建还是参数模型拟合中都是如此。这条纤维与星系和弥散的软 X 射线发射的过密度重合，并为超星系团的总质量贡献了与额外星系团相当的质量。通过将这一结果与 X 射线观测相结合，我们可以对纤维中热气体的比例（发射 X 射线的气体质量与总质量之比）施加 0.09 的上限。
