STREGA：银河系的结构和进化。I.调查概述和初步结果
STREGA: STRucture and Evolution of the GAlaxy. I. Survey Overview and First Results
摘要：
STREGA（银河系的结构和演化）是在VST（ESO VLT巡天望远镜）上进行的一项保证时间的巡天，用于绘制星系晕中约150平方度的地图，以限制星系形成和演化的机制。该调查是一个为期五年的项目，分为两部分：一个核心计划，探索选定恒星系统的周围区域，第二个补充部分，绘制天炉座轨道的南部部分，并扩展核心计划的观测。所采用的恒星示踪剂主要是变星（天琴座RR变星和长周期变星）和主序星，并获得了g、r、i波段的观测结果。我们提出了一个概述的调查和一些初步结果，已经完成了三个观测运行。对于以$ω$ ~Cen（37 deg^2）为中心，覆盖约3个潮汐半径的区域，我们还讨论了所探测到的恒星密度径向剖面和角分布，从而鉴别出潮外星团星。我们还得出结论，集群潮汐半径约为1.2度，与文献中基于威尔逊模型的值一致。
英文摘要：
STREGA (STRucture and Evolution of the GAlaxy) is a Guaranteed Time survey being performed at the VST (the ESO VLT Survey Telescope) to map about 150 square degrees in the Galactic halo, in order to constrain the mechanisms of galactic formation and evolution. The survey is built as a five-year project, organized in two parts: a core program to explore the surrounding regions of selected stellar systems and a second complementary part to map the southern portion of the Fornax orbit and extend the observations of the core program. The adopted stellar tracers are mainly variable stars (RR~Lyraes and Long Period Variables) and Main Sequence Turn-off stars for which observations in the g,r,i bands are obtained. We present an overview of the survey and some preliminary results for three observing runs that have been completed. For the region centered on $ω$~Cen (37 deg^2), covering about three tidal radii, we also discuss the detected stellar density radial profile and angular distribution, leading to the identification of extratidal cluster stars. We also conclude that the cluster tidal radius is about 1.2 deg, in agreement with values in the literature based on the Wilson model.
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