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arXiv 1004.0221astro-ph.CO
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具有紧密QSO群的三维宇宙网的高分辨光谱

High resolution spectroscopy of the three dimensional cosmic web with close QSO groups

M. Cappetta, V. D'Odorico, S. Cristiani, F. Saitta, M. Viel

摘要:

我们利用类星体对的高分辨光谱和宇宙学流体动力学模拟得到的模拟光谱研究了z~2处物质的三维分布。我们提出了一个样本的15个类星体,对应于21个基线的角间距均匀分布在1和14弧分之间,观察到的紫外和视觉中阶梯光谱仪(UVES)在欧洲南方天文台甚大望远镜(ESO-VLT)。在HI Lya森林中观测到的横向和沿视线的透射通量的关联函数是一致的,这意味着由于特殊速度引起的红移空间的扭曲相对较小,并且在相对较大的误差范围内不显著。聚类信号在速度分离达到~300 km/s时是显著的,对应于大约5 h^{-1} Mpc的同向运动。自相关函数和互关联函数以及互相关系数集在2 sigma水平上的兼容性已被发现。分析特别侧重于样本中的两组类星体。通过在红移空间中寻找不同视线的Lya吸收线之间的排列,发现了在同动空间中存在着一个宽的HI结构,并给出了星系际介质中两个宇宙低密度区的大小限制。

英文摘要:

We study the three-dimensional distribution of matter at z~2 using high resolution spectra of QSO pairs and simulated spectra drawn from cosmological hydro-dynamical simulations. We present a sample of 15 QSOs, corresponding to 21 baselines of angular separations evenly distributed between ~1 and 14 arcmin, observed with the Ultraviolet and Visual Echelle Spectrograph (UVES) at the European Southern Observatory-Very Large Telescope (ESO-VLT). The observed correlation functions of the transmitted flux in the HI Lya forest transverse to and along the line of sight are in agreement, implying that the distortions in redshift space due to peculiar velocities are relatively small and - within the relatively large error bars - not significant. The clustering signal is significant up to velocity separations of ~300 km/s, corresponding to about 5 h^{-1} comoving Mpc. Compatibility at the 2 sigma level has been found both for the Auto- and Cross-correlation functions and for the set of the Cross correlation coefficients. The analysis focuses in particular on two QSO groups of the sample. Searching for alignments in the redshift space between Lya absorption lines belonging to different lines of sight, it has been possible to discover the presence of a wide HI structures extending over about ten Mpc in comoving space, and give constraints on the sizes of two cosmic under-dense regions in the intergalactic medium.

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