Imprint of DESI fiber assignment on the anisotropic power spectrum of emission line galaxies
Imprint of DESI fiber assignment on the anisotropic power spectrum of emission line galaxies
复制标题
DOI：
10.1088/1475-7516/2017/04/008
复制
发表时间：
2016-11
影响因子：
6.4
通讯作者：
L. Pinol;R. Cahn;N. Hand;U. Seljak;M. White
中科院分区：
文献类型：
--
作者：
L. Pinol;R. Cahn;N. Hand;U. Seljak;M. White
暗能量光谱仪（DESI）是一个多路光纤馈送光谱仪，是一个第四阶段的地面暗能量实验，旨在测量2900万个发射在线星系（ELG）， 400万个发光红星系（LRG）和200万个准恒星物体（QSO）的红移。调查设计包括天空上的平铺图案，望远镜焦平面上光纤定位器的位置，以及由光纤分配算法确定的观测策略，该算法优化了光纤到目标的分配。这种策略允许在五年的调查中平均覆盖给定区域五次，平均变化约为1.5，这在星系集群上留下了空间依赖的模式。我们研究了光纤分配覆盖对elg各向异性星系群集的系统影响，并表明，在没有任何修正的情况下，它会导致功率谱多极在大尺度上的10%的差异。我们引入了一种方法，其中随机目录中的对象被分配一个覆盖范围，并且为每个覆盖因素单独计算平均密度。我们表明，这种方法减少了，但没有消除影响。我们接下来研究了污染信号的角依赖性，认为它主要局限于纯横向模式。我们证明了去除污染信号的最干净的方法是对各向异性功率谱P（k,μ）进行分析并去除最低的μ bin，使μ > 0模式精确到百分之几的水平。在这里，μ是视线与k / l方向之间夹角的余弦。我们还研究了随机目录的两种替代定义，并表明它们是可比较的，但不如覆盖随机方法有效。
The Dark Energy Spectroscopic Instrument (DESI), a multiplexed fiber-fed spectrograph, is a Stage-IV ground-based dark energy experiment aiming to measure redshifts for 29 million Emission-Line Galaxies (ELG), 4 million Luminous Red Galaxies (LRG), and 2 million Quasi-Stellar Objects (QSO). The survey design includes a pattern of tiling on the sky, the locations of the fiber positioners in the focal plane of the telescope, and an observation strategy determined by a fiber assignment algorithm that optimizes the allocation of fibers to targets. This strategy allows a given region to be covered on average five times for a five-year survey, with a typical variation of about 1.5 about the mean, which imprints a spatially-dependent pattern on the galaxy clustering. We investigate the systematic effects of the fiber assignment coverage on the anisotropic galaxy clustering of ELGs and show that, in the absence of any corrections, it leads to discrepancies of order ten percent on large scales for the power spectrum multipoles. We introduce a method where objects in a random catalog are assigned a coverage, and the mean density is separately computed for each coverage factor. We show that this method reduces, but does not eliminate the effect. We next investigate the angular dependence of the contaminated signal, arguing that it is mostly localized to purely transverse modes. We demonstrate that the cleanest way to remove the contaminating signal is to perform an analysis of the anisotropic power spectrum P(k,μ) and remove the lowest μ bin, leaving μ > 0 modes accurate at the few-percent level. Here, μ is the cosine of the angle between the line-of-sight and the direction of k⃗. We also investigate two alternative definitions of the random catalog and show that they are comparable but less effective than the coverage randoms method.