1] Department of Astronomy and Astrophysics, University of California, 1156 High Street, Santa Cruz, California 95064, USA [2] University of California Observatories, Lick Observatory, 1156 High Street, Santa Cruz, California 95064, USA.
Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany.
Nature. 2014 Feb 6;506(7486):63-6. doi: 10.1038/nature12898. Epub 2014 Jan 19.
Simulations of structure formation in the Universe predict that galaxies are embedded in a 'cosmic web', where most baryons reside as rarefied and highly ionized gas. This material has been studied for decades in absorption against background sources, but the sparseness of these inherently one-dimensional probes preclude direct constraints on the three-dimensional morphology of the underlying web. Here we report observations of a cosmic web filament in Lyman-α emission, discovered during a survey for cosmic gas fluorescently illuminated by bright quasars at redshift z ≈ 2.3. With a linear projected size of approximately 460 physical kiloparsecs, the Lyman-α emission surrounding the radio-quiet quasar UM 287 extends well beyond the virial radius of any plausible associated dark-matter halo and therefore traces intergalactic gas. The estimated cold gas mass of the filament from the observed emission-about 10(12.0 ± 0.5)/C(1/2) solar masses, where C is the gas clumping factor-is more than ten times larger than what is typically found in cosmological simulations, suggesting that a population of intergalactic gas clumps with subkiloparsec sizes may be missing in current numerical models.
宇宙结构形成的模拟预测，星系嵌入在一个“宇宙网”中，大部分重子以稀薄的高度电离气体形式存在。几十年来，人们一直在吸收背景光源来研究这些物质，但这些本质上是一维的探针过于稀疏，无法直接限制潜在的宇宙网的三维形态。在这里，我们报告了在红移 z ≈ 2.3 处，在对被明亮类星体荧光照亮的宇宙气体的调查中，发现了莱曼-α发射的宇宙网纤维的观测结果。具有大约 460 个物理千秒差距的线性投影大小，在无线电安静类星体 UM 287 周围的莱曼-α发射远远超出了任何合理关联的暗物质晕的引力半径，因此它可以追踪星系际气体。从观察到的发射中估计的纤维冷气体质量 - 约 10(12.0 ± 0.5)/C(1/2)太阳质量，其中 C 是气体聚集因子 - 比宇宙学模拟中通常发现的要大十倍以上，这表明在当前的数值模型中可能缺少具有亚千秒差距大小的星系际气体团块。
