An Efficient Targeting Strategy for Multiobject Spectrograph Surveys: the Sloan Digital Sky Survey “Tiling” Algorithm
An Efficient Targeting Strategy for Multiobject Spectrograph Surveys: the Sloan Digital Sky Survey “Tiling” Algorithm
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DOI：
10.1086/344761
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发表时间：
2001-05
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影响因子：
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通讯作者：
M. Blanton;Huan Lin;R. Lupton;F. M. Maley;N. Young;I. Zehavi;J. Loveday
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作者：
M. Blanton;Huan Lin;R. Lupton;F. M. Maley;N. Young;I. Zehavi;J. Loveday
使用多目标摄谱仪的大型调查需要自动化的方法来决定如何有效地点观测和如何分配目标到每个指向。斯隆数字巡天（SDSS）将使用多目标光纤摄谱仪观测分布在约10，000平方度区域内的目标的约106个光谱，该摄谱仪可以同时观测半径为1.49 °的圆形视场（称为“瓦片”）中的640个物体。在同一次观测中，两个光纤的距离不能超过55英寸;多个目标的距离如果超过这个距离，就被称为“碰撞”。“我们在这里提出了一种将纤维分配到所需目标的方法，给定一组瓷砖中心，其中包括碰撞的影响，并且几乎是最佳效率和均匀的。由于星系分布中的大尺度结构（形成SDSS目标的大部分），用等间隔的瓦片覆盖天空并不能产生均匀的采样。因此，我们提出了一个启发式扰动中心的瓷砖从等距分布，提供更均匀的完整性。对于SDSS样本，我们可以获得大于92%的所有目标的采样率，以及大于99%的不相互碰撞的目标组的采样率，效率大于90%（定义为分配给目标的可用光纤的分数）。这里使用的方法可能对那些计划其他大型调查的人有用。
Large surveys using multiobject spectrographs require automated methods for deciding how to efficiently point observations and how to assign targets to each pointing. The Sloan Digital Sky Survey (SDSS) will observe around 106 spectra from targets distributed over an area of about 10,000 deg2, using a multiobject fiber spectrograph that can simultaneously observe 640 objects in a circular field of view (referred to as a "tile") 1.°49 in radius. No two fibers can be placed closer than 55″ during the same observation; multiple targets closer than this distance are said to "collide." We present here a method of allocating fibers to desired targets given a set of tile centers that includes the effects of collisions and that is nearly optimally efficient and uniform. Because of large-scale structure in the galaxy distribution (which form the bulk of the SDSS targets), a naive covering of the sky with equally spaced tiles does not yield uniform sampling. Thus, we present a heuristic for perturbing the centers of the tiles from the equally spaced distribution that provides more uniform completeness. For the SDSS sample, we can attain a sampling rate of greater than 92% for all targets, and greater than 99% for the set of targets that do not collide with each other, with an efficiency greater than 90% (defined as the fraction of available fibers assigned to targets). The methods used here may prove useful to those planning other large surveys.