THE IMPOSSIBLY EARLY GALAXY PROBLEM
THE IMPOSSIBLY EARLY GALAXY PROBLEM
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DOI：
10.3847/0004-637x/824/1/21
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发表时间：
2016-06-10
影响因子：
4.9
通讯作者：
Speagle, Josh S.
中科院分区：
文献类型：
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作者：
Steinhardt, Charles. L.;Capak, Peter;Speagle, Josh S.
目前的层次合并范式和Lambda CDM预测，z类似于4-8宇宙应该是最大质量的星系从最初的晕组装过渡到恒星形成星系和类星体中看到的重子演化的时间。然而，在许多高红移星系巡天中没有发现这种转变的证据，包括CFHTLS，宇宙组装近红外深河外巡天（CANDELS）和斯皮策大面积超超级凸轮巡天（SPLASH），这是第一个探测这些红移的高质量端的研究。事实上，如果在较低的红移下估计的晕质量与恒星质量之比继续保持在z类似于6-8，那么CANDELS和SPLASH报告的类似于10（12-13）M（圆点）晕的M比可能由这些红移形成的要多几个数量级，这意味着这些大质量星系不可能在早期形成。我们认为各种系统的恒星合成模型用来估计物理参数和可能的星系形成的情况下，努力调和观测与理论。虽然已知的不确定性可以大大减少最近的观测和冷暗物质合并模拟之间的差异，但即使采取最保守的观测观点，与当前理论仍然存在相当大的张力。
The current hierarchical merging paradigm and Lambda CDM predict that the z similar to 4-8 universe should be a time in which the most massive galaxies are transitioning from their initial halo assembly to the later baryonic evolution seen in star-forming galaxies and quasars. However, no evidence of this transition has been found in many high-redshift galaxy surveys including CFHTLS, Cosmic Assembly Near-infrared Deep Extragalactic Survey (CANDELS), and Spitzer Large Area Survey with Hyper-Suprime-Cam (SPLASH), which were the first studies to probe the high-mass end at these redshifts. Indeed, if halo mass to stellar mass ratios estimated at lower-redshift continue to z similar to 6-8, CANDELS and SPLASH report several orders of magnitude more M similar to 10(12-13)M(circle dot) halos than is possible to have been formed by those redshifts, implying that these massive galaxies formed impossibly early. We consider various systematics in the stellar synthesis models used to estimate physical parameters and possible galaxy formation scenarios in an effort to reconcile observation with theory. Although known uncertainties can greatly reduce the disparity between recent observations and cold dark matter merger simulations, there remains considerable tension with current theory even if taking the most conservative view of the observations.