arXiv 0706.39412007-06-27astro-ph

星系的内禀排列及其对质量浓度弱透镜探测的影响

Intrinsic alignments of galaxies and their effects on weak lensing detections of mass concentrations

Z. H. Fan

备注：: ApJ in press
DOI：: 10.1086/521182

摘要：

在本文中，我们研究背景星系的内在排列对质量浓度的弱透镜探测的影响。具体来说，我们分析了透镜收敛映射中固有椭圆性导致的假峰的数量计数。包括源星系的排列，收敛$κ$-图中来自内禀椭圆星系的全部噪声方差可以写成$σ^2_0=σ^2_{0ran}+σ^2_{0corr}$，其中$σ^2_{0ran}$是随机取向的源星系贡献的噪声，$σ^2_{0corr}$表示来自内禀排列的附加噪声。然而，在观测上很难测量$σ^2_{0corr}$，并且在弱透镜观测中通常只能估计$σ^2_{0ran}$。因此，观测信噪比通常是相对于$σ_{0ran}$来定义的，本文将其表示为$ν_{ran}$。则根据$σ_0$的真实信噪比$ν$为$ν=ν_{ran}/(1+σ^2_{0corr}/σ^2_{0ran})^{1/2}$。给定$ν_{ran}$上的检测阈值，$σ^2_{0corr}/σ^2_{0ran}$的较大值导致$ν$上的较低阈值，并因此导致较大的假峰的预期数量。使用$σ^2_{0corr}/σ^2_{0ran}\sim 10%$时，使用$ν_{ran}\ge 3.5$时的平均假峰数几乎是不考虑比对时的两倍，而对于$ν_{ran}\ge 5$，假峰数是三倍。结果，弱透镜簇检测的效率显著降低。（节录）

英文摘要：

In this paper we investigate the influence of the intrinsic alignment of background galaxies on weak lensing detections of mass concentrations. Specifically, we analyze the number counts of false peaks resulting from intrinsic ellipticities in lensing convergence maps. Including the alignment of source galaxies, the full noise variance from intrinsic ellipticites in convergence $κ$-maps can be written as $σ^2_0=σ^2_{0ran}+σ^2_{0corr}$, where $σ^2_{0ran}$ is the noise contributed from randomly oriented source galaxies and $σ^2_{0corr}$ denotes the additional noise from intrinsic alignments. However, it is observationally difficult to measure $σ^2_{0corr}$ and usually only $σ^2_{0ran}$ can be estimated in weak lensing observations. Thus the observational signal-to-noise ratio is often defined with respect to $σ_{0ran}$, which is denoted as $ν_{ran}$ in this paper. The true signal-to-noise ratio $ν$ in terms of $σ_0$ is then $ν=ν_{ran}/(1+σ^2_{0corr}/σ^2_{0ran})^{1/2}$. Given a detection threshold on $ν_{ran}$, a larger value of $σ^2_{0corr}/σ^2_{0ran}$ leads to a lower threshold on $ν$ and therefore a larger expected number of false peaks. With $σ^2_{0corr}/σ^2_{0ran}\sim 10%$, the average number of false peaks with $ν_{ran}\ge 3.5$ nearly doubles compared to that without considering the alignment, and for $ν_{ran}\ge 5$, the number is tripled. As a result, the efficiency of weak lensing cluster detection degrades significantly. (Abridged)

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英文摘要：

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