Searching for massive clusters in weak lensing surveys
Searching for massive clusters in weak lensing surveys
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DOI：
10.1111/j.1365-2966.2004.07691.x
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发表时间：
2003-10
影响因子：
4.8
通讯作者：
T. Hamana;M. Takada;N. Yoshida
中科院分区：
文献类型：
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作者：
T. Hamana;M. Takada;N. Yoshida
我们探索了弱透镜探测定位大质量星系团的能力。我们使用暗物质晕的分析模型和从大型宇宙N体模拟产生的模拟弱透镜调查。分析模型描述了弱透镜晕的平均性质，并预测了数量，使我们能够计算出有效的调查选择函数。我们认为，大质量晕的可探测性不仅取决于晕的质量，而且强烈地取决于晕所在的红移。我们用模拟数值数据检验了对弱透镜质量图中峰值数目的模型预测，发现由星系固有椭圆性产生的噪声引起了增加峰值数目的系统效应。我们以经验的方式提出了系统效应的修正方案，并表明修正后的模型预测与模拟数据吻合得很好。用模拟数据检验了弱透镜晕搜索的完备性和效率，充分考虑了噪声和大尺度结构的投影效应。结果表明，S/N=4∼5的检测门限在完备性和效率之间取得了最佳的平衡。我们的结果表明，对于星系数密度为ng=30arcmin-2，平均红移为1的弱透镜探测，期望产生S/N=4以上透镜信号的晕的平均数目为N balo(S/N>；4)=37/10°2，而其中23个晕实际被S/N>；4探测到，有效完备性高达63%。或者，在S/N=4的探测阈值下，同一区域的平均峰数为N峰=62。在62个峰中，23个峰是由预期峰高为S/N>；4的晕引起的，13个峰是由3<；S/N<；4的晕引起的，其余26个峰是由噪声引起的假峰或具有较低预期峰高的晕。因此，污染率为44%(这可能是高估了)。因此，弱透镜探测为寻找大质量星系团提供了一种相当有效的方法。
We explore the ability of weak lensing surveys to locate massive clusters. We use both analytic models of dark matter haloes and mock weak lensing surveys generated from a large cosmological N-body simulation. The analytic models describe the average properties of weak lensing haloes and predict the number counts, enabling us to compute an effective survey selection function. We argue that the detectability of massive haloes depends not only on the halo mass but also strongly on the redshift where the halo is located. We test the model prediction for the peak number counts in weak lensing mass maps against mock numerical data, and find that the noise resulting from intrinsic galaxy ellipticities causes a systematic effect which increases the peak counts. We develop a correction scheme for the systematic effect in an empirical manner, and show that, after correction, the model prediction agrees well with the mock data. The mock data is also used to examine the completeness and efficiency of the weak lensing halo search by fully taking into account the noise and the projection effect by large-scale structures. We show that the detection threshold of S/N = 4 ∼ 5 gives an optimal balance between completeness and efficiency. Our results suggest that, for a weak lensing survey with a galaxy number density of n g = 30 arcmin -2 with a mean redshift of z = 1, the mean number of haloes which are expected to cause lensing signals above S/N = 4 is N balo (S/N > 4) = 37 per 10 deg 2 , whereas 23 of the haloes are actually detected with S/N > 4, giving the effective completeness as good as 63 per cent. Alternatively, the mean number of peaks in the same area is N peak = 62 for a detection threshold of S/N = 4. Among the 62 peaks, 23 are caused by haloes with the expected peak height S/N >4, 13 result from haloes with 3 < S/N < 4 and the remaining 26 peaks are either the false peaks caused by the noise or haloes with a lower expected peak height. Therefore the contamination rate is 44 per cent (this could be an overestimation). Weak lensing surveys thus provide a reasonably efficient way to search for massive clusters.