论文标题
在近似LightCone模拟中解决小规模的聚类问题
Solving small-scale clustering problems in approximate lightcone mocks
论文作者
论文摘要
逼真的灯酮模拟在大型星系调查的聚类分析中很重要。对于仅可用快照的模拟，通常可以通过将快照将球形壳中的快照连接在一起。我们评估了由千年-XXL模拟构建的近似灯光中心星系的两点聚类测量，这些测量是使用不同数量的快照构建的。由于某些星系在LightCone的快照之间重复，因此在低于1 mpc/h的小尺度上，实际空间相关函数的单极和四极杆在1 mpc/h以下的小尺度上得到了强烈的增强。当使用更多快照时，重复的星系的总数大约是恒定的，但它们被推到较小的分离。只要快照被切成真实空间中的壳，它在红移空间中的效果很小。随机去除重复的星系能够减少多余的聚类信号。包括卫星星系在内，将减少重复项的影响，因为许多小规模对来自同一光环中的卫星。边界处的LightCone缺少的星系可以通过在每个外壳之间有一个小的重叠来添加到LightCone中。这种效果将影响使用非常小规模的聚类测量以及使用模拟测试纤维碰撞影响时的分析。
Realistic lightcone mocks are important in the clustering analyses of large galaxy surveys. For simulations where only the snapshots are available, it is common to create approximate lightcones by joining together the snapshots in spherical shells. We assess the two-point clustering measurements of central galaxies in approximate lightcones built from the Millennium-XXL simulation, which are constructed using different numbers of snapshots. The monopole and quadrupole of the real-space correlation function is strongly boosted on small scales below 1 Mpc/h, due to some galaxies being duplicated at the boundaries between snapshots in the lightcone. When more snapshots are used, the total number of duplicated galaxies is approximately constant, but they are pushed to smaller separations. The effect of this in redshift space is small, as long as the snapshots are cut into shells in real space. Randomly removing duplicated galaxies is able to reduce the excess clustering signal. Including satellite galaxies will reduce the impact of the duplicates, since many small-scale pairs come from satellites in the same halo. Galaxies that are missing from the lightcone at the boundaries can be added to the lightcone by having a small overlap between each shell. This effect will impact analyses that use very small-scale clustering measurements, and when using mocks to test the impact of fibre collisions.
