一种识别爱因斯坦环和圆弧的计算机视觉方法
A Computer Vision Approach To Identify Einstein Rings And Arcs
摘要：
爱因斯坦环是强透镜现象中罕见的瑰宝。与双重或四重透镜系统不同，环图像可以用来探测每个位置角的潜在透镜引力势，对透镜质量分布施加更严格的约束。此外，放大的背景源也使我们能够探测高z星系，提高空间分辨率和更高的S/N，这是不可能的非透镜星系的研究。尽管它们很有用，但到目前为止，只有少数爱因斯坦环被报道过，主要是偶然发现或对数十万大质量星系或星系团进行目视检查。随着正在进行和即将到来的大面积调查，如大型综合巡天望远镜，目视检查发现爱因斯坦环是非常困难的，并且需要一种自动方法来识别大数据中的环模式。本文提出了一种基于计算机视觉技术的爱因斯坦环识别方法。该算法的核心是圆Hough变换，它可以识别图像中任意位置、任意半径的圆形图案或圆弧。我们设计了一种两层方法：首先预先选择与多个蓝色物体相关的LRG作为可能的透镜星系，然后将这些可能的透镜送入霍夫变换。作为概念验证，我们使用斯隆数字巡天调查我们的方法。我们的结果显示了高的完整性，虽然纯度低。我们还将我们的方法应用于三个新发现的爱因斯坦环/弧，在DES，HSC-SSP和UltraVISTA调查，说明了我们的方法的通用性，以进行中的和即将到来的大型巡天一般。我们的方法的美妙之处在于它完全基于JPEG图像，可以通过SDSS查找图表工具以批处理模式轻松获取，而无需对图像进行任何预处理。（节录）
英文摘要：
Einstein rings are rare gem of the strong lensing phenomena. Unlike doubly or quadruply lensed systems, the ring images can be used to probe the underlying lens gravitational potential at every position angle, putting much tighter constraints on the lens mass profile. In addition, the magnified background source also enable us to probe high-z galaxies with enhanced spatial resolution and higher S/N, which is otherwise not possible for un-lensed galaxy studies. Despite their usefulness, only a handful of Einstein rings have been reported so far, mainly by serendipitous discoveries or visual inspections of hundred thousands of massive galaxies or galaxy clusters. With the on-going and forth-coming large area surveys such as Large Synoptic Survey Telescope, visual inspection to discover Einstein rings is very difficult, and an automated approach to identify ring pattern in the big data to come is in high demand. Here we present an Einstein ring recognition approach based on computer vision techniques. The workhorse is the circle Hough transform, which can recognize circular patterns or arcs at any position with any radius in the images. We devise a two-tier approach: first pre-select LRGs associated with multiple blue objects as possible lens galaxies, then feed these possible lenses to Hough transform. As a proof-of-concept, we investigate our approach using the Sloan Digital Sky Surveys. Our results show high completeness, albeit low purity. We also apply our approach to three newly discovered Einstein rings/arcs, in the DES, HSC-SSP, and UltraVISTA survey, illustrating the versatility of our approach to on-going and up-coming large sky surveys in general. The beauty of our approach is that it is solely based on JPEG images, which can be easily obtained in batch mode from SDSS finding chart tools, without any pre-processing of the image. (Abridged)
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