论文标题
为什么弱透镜簇形状对自我互动的暗物质不敏感
Why weak lensing cluster shapes are insensitive to self-interacting dark matter
论文作者
论文摘要
我们研究了是否可以用弱重力透镜推断出的星系簇的形状可以用作暗物质本质的测试。我们分析了模拟弱透镜数据，从宇宙学模拟中提取的重力镜片具有两个不同的暗物质模型（CDM和SIDM）。我们将椭圆形NFW曲线拟合到模拟簇的剪切场。尽管CDM和SIDM之间的3D形状分布有很大差异，但我们发现弱透明的簇簇形状的分布几乎是无法区分的。我们将这些信息丢失追溯到两个原因。首先，弱透镜测量了投影质量分布的形状，而不是基本的3D形状，而投影效果消除了一些差异。其次，弱透镜对簇的投影形状最敏感，在接近病毒半径（〜1.5 MPC）的尺度上，而SIDM形状与内晕中的CDM不同。我们介绍了一个模型，用于星系簇的质量分布，其中质量分布的椭圆度可以随距离群集中心的距离而变化。尽管这种质量分布并不能使弱透镜数据与簇形状区分CDM和SIDM（小半径的椭圆形受到弱透镜的约束），但是当建模结合了簇的强和弱的重力透镜时，这可能是有用的。
We investigate whether the shapes of galaxy clusters inferred from weak gravitational lensing can be used as a test of the nature of dark matter. We analyse mock weak lensing data, with gravitational lenses extracted from cosmological simulations run with two different dark matter models (CDM and SIDM). We fit elliptical NFW profiles to the shear fields of the simulated clusters. Despite large differences in the distribution of 3D shapes between CDM and SIDM, we find that the distributions of weak-lensing-inferred cluster shapes are almost indistinguishable. We trace this information loss to two causes. Firstly, weak lensing measures the shape of the projected mass distribution, not the underlying 3D shape, and projection effects wash out some of the difference. Secondly, weak lensing is most sensitive to the projected shape of clusters, on a scale approaching the virial radius (~ 1.5 Mpc), whereas SIDM shapes differ most from CDM in the inner halo. We introduce a model for the mass distribution of galaxy clusters where the ellipticity of the mass distribution can vary with distance to the centre of the cluster. While this mass distribution does not enable weak lensing data to distinguish between CDM and SIDM with cluster shapes (the ellipticity at small radii is poorly constrained by weak lensing), it could be useful when modelling combined strong and weak gravitational lensing of clusters.
