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arXiv 1106.5791astro-ph.CO
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检测到的SDSS LRG幅度波动:大流量特征还是系统性?

Detected fluctuations in SDSS LRG magnitudes: Bulk flow signature or systematic?

Alexandra Abate, Hume A. Feldman

摘要:

在本文中,我们寻找一个大规模的整体流动的签名,通过寻找遥远的LRG的幅度波动。我们从斯隆数字巡天中采集了一个连续天空区域红移z>0.08的LRG样本。相邻的LRG幅度被一起平均以找到幅度波动作为R.A.的函数。结果是在大约100度的范围内,通量有百分之几的波动。这种波动的来源可能来自大规模的整体流动,或者我们对数据集的处理中的系统性,或者数据集本身。用整体流模型拟合观测到的脉动,并对三个整体流参数α_b、δ_b、v_b的方向和大小进行了约束。我们发现,整体流动方向与其他作者发现的方向一致,α_b为180,δ_b为-50。但总体流量却非常大,v_b> 4000 km/s。LRG角选择函数不能充分考虑在我们的分析与可用的数据,可能是源的异常幅度的大流量信号,或可能的整个波动。然而,波动表明大规模流动方向非常接近使用其他数据集和分析发现的方向。需要对即将获得的数据进行进一步调查,以确认这一检测结果。

英文摘要:

In this paper we search for a signature of a large scale bulk flow by looking for fluctuations in the magnitudes of distant LRGs. We take a sample of LRGs from the Sloan Digital Sky Survey with redshifts of z>0.08 over a contiguous area of sky. Neighboring LRG magnitudes are averaged together to find the fluctuation in magnitudes as a function of R.A.. The result is a fluctuation of a few percent in flux across roughly 100 degrees. The source of this fluctuation could be from a large scale bulk flow or a systematic in our treatment of the data set, or the data set itself. A bulk flow model is fitted to the observed fluctuation, and the three bulk flow parameters, its direction and magnitude: alpha_b, delta_b, v_b are constrained. We find that the bulk flow direction is consistent with the direction found by other authors, with alpha_b 180, delta_b -50. The bulk flow magnitude however was found to be anomalously large with v_b>4000km/s. The LRG angular selection function cannot be sufficiently taken into account in our analysis with the available data, and may be the source of either the anomalous magnitude of the bulk flow signal, or possibly the entire fluctuation. However, the fluctuation indicates a bulk flow direction very close to those found using other data sets and analyses. Further investigation with upcoming data is required to confirm this detection.

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