Cold streams in early massive hot haloes as the main mode of galaxy formation
Cold streams in early massive hot haloes as the main mode of galaxy formation
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DOI：
10.1038/nature07648
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发表时间：
2008-08
期刊：
影响因子：
64.8
通讯作者：
A. Dekel;Y. Birnboim;G. Engel;J. Freundlich;T. Goerdt;M. Mumcuoglu;E. Neistein;C. Pichon;R. Tey
中科院分区：
文献类型：
--
作者：
A. Dekel;Y. Birnboim;G. Engel;J. Freundlich;T. Goerdt;M. Mumcuoglu;E. Neistein;C. Pichon;R. Tey
100亿年前，年轻宇宙中的大质量星系以惊人的强度形成了恒星。[1，2]虽然这通常被归因于剧烈的合并，但这些星系中的许多似乎是与合并不相容的扩展旋转盘。3，2，4为了揭示这种现象的起源，我们使用最先进的宇宙学模拟5和聚类理论6，7来探索这些星系是如何获得它们的气体的。我们发现，这些是“流美联储星系”，通过稳定，狭窄，冷气流，有效地穿透暗物质晕的冲击加热介质作为银河系的质量增长。这证实了早先的一个猜想。[8]一半的水流质量是成团的，导致质量比为1：10或更高的合并，另一半是更平稳的水流。由于合并的占空比是0.1，因此在以给定速率形成恒星的星系中，有四分之三是由平滑的流供给的。与破坏性的大合并不同，平滑的流动可以保持圆盘的完整性，虽然厚和扰动。观测到的大量恒星形成星系意味着流入的气体以最高效率转化为恒星。相比之下，形成恒星的亚毫米星系甚至更密集1，9，10主要是紧凑的合并引起的恒星爆发，其晕是质量的两倍。
The massive galaxies in the young universe, ten billion years ago, formed stars at surprising intensities. 1, 2 While this was commonly attributed to violent mergers, many of these galaxies seem to be extended rotating discs incompatible with mergers. 3, 2, 4 In order to uncover the origin of this phenomenon, we use a state-of-the-art cosmological simulation5 and clustering theory6, 7 to explore how these galaxies acquired their gas. We find that these are “Stream-Fed Galaxies”, growing via steady, narrow, cold gas streams, which penetrate effectively through the shock-heated media of dark-matter haloes as massive as the Milky Way’s. This confirms an earlier conjecture. 8 Half the stream mass is in clumps leading to mergers of mass ratio 1: 10 or higher, and half is in smoother flows. Since the merger duty cycle is 0.1, three-quarters of the galaxies forming stars at a given rate are fed by smooth streams. Unlike destructive major mergers, the smoother flows can keep the discs intact, though thick and perturbed. The observed abundance of star-forming galaxies implies that the inflowing gas turns into stars at maximum efficiency. In contrast, the sub-millimeter galaxies that form stars even more intensely1, 9, 10 are largely compact merger-induced starbursts in haloes twice as massive.