对DESI亮星系巡天中纤维分配不完全性的修正
Correcting for Fibre Assignment Incompleteness in the DESI Bright Galaxy Survey
摘要：
暗能量光谱仪（DESI）亮星系巡天（BGS）将是一个明亮的，低红移星系的巡天，计划在3次通过中覆盖约14，000平方度的区域。每个通道将覆盖约2000个点的测量区域，每个点的面积约为8平方度。目前提出的BGS包括一个明亮的高优先级样本到r波段幅度限制r ~ 19.5，一个较暗的低优先级样本到r ~ 20。望远镜焦平面中DESI光纤定位器的几何形状会影响调查的完整性，并对聚类测量产生重要影响。使用BGS模拟目录，我们表明，由于纤维分配的完整性主要取决于星系的表面密度。在低密度区域，完整性很高（>95%），但在大质量星团的中心，完整性很低（<10%）。我们应用对逆概率（PIP）加权校正的聚类测量从BGS模拟已通过纤维分配算法。这种方法只有在可以观测到每一对星系的情况下才是无偏的。为了促进这一点，我们随机地将较暗样本的一小部分提升为高优先级，并以小角度抖动瓦片位置集。我们发现，逆对加权结合角度upweighting提供了一个公正的校正星系聚类测量完整的3通调查，也经过1通，这是非常不完整的。
英文摘要：
The Dark Energy Spectroscopic Instrument (DESI) Bright Galaxy Survey (BGS) will be a survey of bright, low redshift galaxies, which is planned to cover an area of ~14,000 sq deg in 3 passes. Each pass will cover the survey area with ~2000 pointings, each of area ~8 sq deg. The BGS is currently proposed to consist of a bright high priority sample to an r-band magnitude limit r ~ 19.5, with a fainter low priority sample to r ~ 20. The geometry of the DESI fibre positioners in the focal plane of the telescope affects the completeness of the survey, and has a non-trivial impact on clustering measurements. Using a BGS mock catalogue, we show that completeness due to fibre assignment primarily depends on the surface density of galaxies. Completeness is high (>95%) in low density regions, but very low (<10%) in the centre of massive clusters. We apply the pair inverse probability (PIP) weighting correction to clustering measurements from a BGS mock which has been through the fibre assignment algorithm. This method is only unbiased if it is possible to observe every galaxy pair. To facilitate this, we randomly promote a small fraction of the fainter sample to be high priority, and dither the set of tile positions by a small angle. We show that inverse pair weighting combined with angular upweighting provides an unbiased correction to galaxy clustering measurements for the complete 3 pass survey, and also after 1 pass, which is highly incomplete.
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