Wide-angle effects on galaxy ellipticity correlations
Wide-angle effects on galaxy ellipticity correlations
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DOI：
10.1093/mnrasl/slab009
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发表时间：
2020-12
影响因子：
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通讯作者：
M. Shiraishi;A. Taruya;T. Okumura;Kazuyuki Akitsu
中科院分区：
文献类型：
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作者：
M. Shiraishi;A. Taruya;T. Okumura;Kazuyuki Akitsu
我们提出了一种有效的方法来计算三维配置空间中星系固有排列的广角或全天空统计数据。为此，我们使用一个新引入的自旋相关的三极球谐基展开两点关联函数。因此，指向每对对象的两个视线（LOS）方向上的角度依赖性，在小角度或平面平行（PP）近似下的常规分析中，这是相互退化的，被明确地分解。利用这一方法，我们首次计算了星系的内禀椭圆率、数密度和速度之间的广角自相关和广角互相关，并与PP极限的结果进行了比较。对于椭圆度-椭圆度和密度-椭圆度的相关性，如果两个视线方向之间的张角超过30 - 50，我们发现与PP极限结果的偏差超过10。它还表明，即使PP-极限的结果是严格为零，非零相关性得到了各种尺度上，纯粹从弯曲的天空效应。我们的研究结果表明，为了更精确地确定宇宙学参数和/或通过正在进行的和即将进行的广角星系巡天发现新的物理，数据分析不依赖于PP近似的重要性。
We show an efficient way to compute wide-angle or all-sky statistics of galaxy intrinsic alignment in three-dimensional configuration space. For this purpose, we expand the two-point correlation function using a newly introduced spin-dependent tripolar spherical harmonic basis. Therefore, the angular dependences on the two line-of-sight (LOS) directions pointing to each pair of objects, which are degenerate with each other in the conventional analysis under the small-angle or plane-parallel (PP) approximation, are unambiguously decomposed. By means of this, we, for the first time, compute the wide-angle auto and cross correlations between intrinsic ellipticities, number densities and velocities of galaxies, and compare them with the PP-limit results. For the ellipticity-ellipticity and density-ellipticity correlations, we find more than $10\%$ deviation from the PP-limit results if the opening angle between two LOS directions exceeds $30^\circ - 50^\circ$. It is also shown that even if the PP-limit result is strictly zero, the non-vanishing correlation is obtained over the various scales, arising purely from the curved-sky effects. Our results indicate the importance of the data analysis not relying on the PP approximation in order to determine the cosmological parameters more precisely and/or find new physics via ongoing and forthcoming wide-angle galaxy surveys.