Cosmology with the cluster mass function: mass estimators and shape systematics in large weak lensing surveys
Cosmology with the cluster mass function: mass estimators and shape systematics in large weak lensing surveys
复制标题
具有簇质量函数的宇宙学：大型弱透镜巡天中的质量估计器和形状系统学
DOI：
10.1111/j.1365-2966.2009.14542.x
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发表时间：
2009
影响因子：
4.8
通讯作者：
L. King
中科院分区：
文献类型：
--
作者：
V. Corless;L. King
精确测量团簇质量函数是约束结构形成模型、物质功率谱和宇宙学物质密度的标准化以及暗能量的性质和演化的关键因素。对20 000个星系团和星系群的大型弱透镜巡天将是实现这一目标的关键观测工具;第一代巡天，如使用斯隆数字巡天（SDSS）的巡天，已经开始校准以前从X射线观测中获得的质量函数测量值，并将现有的限制扩展到星系群尺度。这些弱透镜效应的研究是通过叠加许多星系团和星系群的透镜效应信号来进行的，这些星系团和星系群是由质量相关的可观测量（如丰度和光度）划分的;通常这种分析忽略了暗物质晕的三轴结构，假设每个质量区间内的许多剪切信号的平均值使其影响可以忽略不计（在单个星系团的质量模型参数估计中，其影响可以忽略不计）。我们测试这一假设，利用人口的15 000分析三轴暗物质晕跨越2 dex的质量，并发现三轴性可以偏置三维维里质量估计相比，由几个百分点，如果使用次优质量估计的球形人口。这种偏见不仅影响直接透镜的质量函数的约束，但也可以影响来自透镜的质量可观测的关系，是如此重要的约束大样本的集群质量函数的分散和规范化。然而，我们证明，仔细选择的质量估计可以非常有效地消除偏差，如果从足够数量的三轴晕的透镜信号平均在一起，并进一步量化，足够的数量足够的形状平均。因此，我们表明，通过选择可观测的箱包含足够数量的晕，并通过利用精心选择的3D质量估计堆叠弱透镜分析可以给无偏约束的三轴质量函数。
Accurate measurement of the cluster mass function is a crucial element in efforts to constrain structure formation models, the normalization of the matter power spectrum and the cosmological matter density, and the nature and evolution of dark energy. Large weak lensing surveys of ∼20 000 galaxy clusters and groups will be key tools in the observational pursuit of that goal; first-generation surveys such as those using the Sloan Digital Sky Survey (SDSS) are already beginning to calibrate previous measurements of the mass function from X-ray observations and to extend existing constraints down to galaxy group scales. These weak lensing studies proceeded by stacking the lensing signals of many clusters and groups binned by mass-correlated observables such as richness and luminosity; typically such analyses ignore the triaxial structure of dark matter haloes on the assumption that the averaging of many shear signals within each mass bin makes its effects (as large as factors of two in mass model parameter estimates from individual clusters) negligible. We test this assumption utilizing a population of 15 000 analytic triaxial dark matter haloes spanning 2 dex in mass, and find that triaxiality can bias 3D virial mass estimates compared to those for a spherical population by a few per cent if suboptimal mass estimators are used. This bias affects not only direct lensing constraints on the mass function but can also affect the scatter and normalization of the mass-observable relations derived from lensing that are so crucial to constraining the cluster mass function with large samples. However, we demonstrate that a careful choice of mass estimator can remove the bias very effectively if the lensing signals from a sufficient number of triaxial haloes are averaged together, and further quantify that sufficient number for adequate shape averaging. We thus show that by choosing observable bins to contain an adequate number of haloes and by utilizing a carefully chosen 3D mass estimator stacked weak-lensing analyses can give unbiased constraints on the triaxial mass function.