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arXiv 1407.2614astro-ph.GA
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过密环境中高红移Galerkin的温和增长

The Gentle Growth of Galaxies at High Redshifts in Overdense Environments

Emilio Romano-Diaz, Isaac Shlosman, Jun-Hwan Choi, Raphael Sadoun

摘要:

我们已经探索了红移z ~ 6-14的星系生长的主要模式,比较了宇宙的过度密集和正常区域,使用高分辨率的放大宇宙学模拟。这种罕见的过密区域被认为是高z类星体的宿主。我们表明,在这样的环境中的星系增长主要是由一个平稳的吸积从宇宙细丝占主导地位的质量输入主要,中间和次要的合并。我们发现,到z ~6时,在过密区,合并产生的星系累积质量分数是星系累积吸积质量的1/10,而在正常环境中,则是1/5。此外,合并的恒星质量输入率也低于原位恒星形成(SF)率。在这些红移下,星系中恒星质量中由合并贡献的比例在过密区域为~ 12%,在正常区域为~33%。我们对~几个X 10^9 Mo星系的SF率中值与斯皮策SURF-UP巡天中最近估计的z ~ 7星系的SF率非常一致。最后,我们发现正常区和过密区的主要区别在于大质量星系在大质量暗物质晕中的放大生长。这导致了>= 10^{10} Mo星系的形成,因为在上述时间段内质量增加了约100倍。这样的星系在这些红移的正常区域基本上是不存在的。

英文摘要:

We have explored prevailing modes of galaxy growth for redshifts z ~ 6-14, comparing substantially overdense and normal regions of the universe, using high-resolution zoom-in cosmological simulations. Such rare overdense regions have been projected to host high-z quasars. We demonstrate that galaxies in such environments grow predominantly by a smooth accretion from cosmological filaments which dominates the mass input from major, intermediate and minor mergers. We find that by z ~6, the accumulated galaxy mass fraction from mergers falls short by a factor of 10 of the cumulative accretion mass for galaxies in the overdense regions, and by a factor of 5 in the normal environments. Moreover, the rate of the stellar mass input from mergers also lies below that of an in-situ star formation (SF) rate. The fraction of stellar masses in galaxies contributed by mergers in overdense regions is ~12%, and ~33% in the normal regions, at these redshifts. Our median SF rates for ~few X 10^9 Mo galaxies agrees well with the recently estimated rates for z ~ 7 galaxies from Spitzer's SURF-UP survey. Finally, we find that the main difference between the normal and overdense regions lies in the amplified growth of massive galaxies in massive dark matter halos. This leads to the formation of >= 10^{10} Mo galaxies due to the ~100-fold increase in mass during the above time period. Such galaxies are basically absent in the normal regions at these redshifts.

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