Estimate of dark halo ellipticity by lensing flexion
Estimate of dark halo ellipticity by lensing flexion
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DOI：
10.1051/0004-6361/201015766
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发表时间：
2010-09
影响因子：
6.5
通讯作者：
X. Er;P. Schneider
中科院分区：
文献类型：
--
作者：
X. Er;P. Schneider
目标。众所周知，根据结构形成模型对暗物质晕椭圆率的预测很难通过观察来检验。直接测量将对星系的形成及其对晕中暗物质分布的影响产生重要的约束。在这里，我们表明，星系星系弯曲提供了一个直接的和潜在的强大的方法来确定椭圆透镜（合奏）的椭圆率。方法.我们将自旋1屈曲分解为径向和切向分量。使用切线与径向弯曲的比率，这是独立的径向质量分布，质量椭圆度可以估计。结果的质量分布的椭圆率的估计，推导和模拟测试。我们表明，估计是略有偏置。我们量化了这种偏差，并提供了一种方法来减少它。此外，弯曲比和方向的参数拟合提供了另一种估计的暗晕椭圆率，这是更准确的个别镜头。总的来说，星系-星系弯曲似乎是限制质量分布椭圆率的有力工具。
Aims. The predictions of the ellipticity of dark matter halos from models of structure formation are notoriously difficult to test with observations. A direct measurement would give important constraints on the formation of galaxies, and its effect on the dark matter distribution in their halos. Here we show that galaxy-galaxy flexion provides a direct and potentially powerful method for determining the ellipticity of (an ensemble of) elliptical lenses. Methods. We decompose the spin-1 flexion into a radial and a tangential component. Using the ratio of tangential-to-radial flexion, which is independent of the radial mass profile, the mass ellipticity can be estimated. Results. An estimator for the ellipticity of the mass distribution is derived and tested with simulations. We show that the estimator is slightly biased. We quantify this bias, and provide a method to reduce it. Furthermore, a parametric fitting of the flexion ratio and orientation provides another estimate for the dark halo ellipticity, which is more accurate for individual lenses. Overall, galaxy-galaxy flexion appears as a powerful tool for constraining the ellipticity of mass distributions.