Strong orientation dependence of surface mass density profiles of dark haloes at large scales
Strong orientation dependence of surface mass density profiles of dark haloes at large scales
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DOI：
10.1093/mnras/sty762
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发表时间：
2017-11
影响因子：
4.8
通讯作者：
K. Osato;T. Nishimichi;M. Oguri;M. Takada;T. Okumura
中科院分区：
文献类型：
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作者：
K. Osato;T. Nishimichi;M. Oguri;M. Takada;T. Okumura
我们研究的依赖性表面质量密度分布，这可以直接测量弱引力透镜，晕相对于视线方向的方向，使用一套$N$体模拟。我们发现，当晕的主轴与视线方向对齐时，表面质量密度分布具有比所有晕方向上的平均值更高的振幅，在我们研究的从0.1 $到100 $，\mathrm {Mpc}/h$的所有尺度上。虽然在小尺度的取向依赖性归因于晕三轴性，我们的研究结果表明，在所谓的两晕制度，甚至更强的取向依赖性，高达$100\，\mathrm {Mpc}/h$。两个晕项的取向依赖性很好地近似于振幅的乘法移位，因此近似于晕偏置参数值的移位。从两个光环项的光环偏差可以被高估或低估高达$\sim 30 \%$取决于视角，这转化为估计的光环质量的偏差高达2倍，从光环偏差测量。在大尺度上的取向依赖性源于各向异性晕物质相关函数，它具有椭圆形状的轴比$\sim 0.55$到$100\，\mathrm{Mpc}/h$。我们讨论了晕取向偏差对其他观测量的潜在影响，如光学选择的集群样本和大规模结构示踪剂，如类星体的聚类分析。
We study the dependence of surface mass density profiles, which can be directly measured by weak gravitational lensing, on the orientation of haloes with respect to the line-of-sight direction, using a suite of $N$-body simulations. We find that, when major axes of haloes are aligned with the line-of-sight direction, surface mass density profiles have higher amplitudes than those averaged over all halo orientations, over all scales from $0.1$ to $100\,\mathrm{Mpc}/h$ we studied. While the orientation dependence at small scales is ascribed to the halo triaxiality, our results indicate even stronger orientation dependence in the so-called two-halo regime, up to $100\,\mathrm{Mpc}/h$. The orientation dependence for the two-halo term is well approximated by a multiplicative shift of the amplitude and therefore a shift in the halo bias parameter value. The halo bias from the two-halo term can be overestimated or underestimated by up to $\sim 30 \%$ depending on the viewing angle, which translates into the bias in estimated halo masses by up to a factor of two from halo bias measurements. The orientation dependence at large scales originates from the anisotropic halo-matter correlation function, which has an elliptical shape with the axis ratio of $\sim 0.55$ up to $100\, \mathrm{Mpc}/h$. We discuss potential impacts of halo orientation bias on other observables such as optically selected cluster samples and a clustering analysis of large-scale structure tracers such as quasars.