大视场巡天望远镜探测器响应与滤光片优化分析  

A Study of Detector Response and Filter Optimization for the Wide Field Survey Telescope

作　　者：师冬冬 郑宪忠[1] 赵海斌[1] 娄铮[1] 王海仁[1] 钱元[1] 刘伟[1] 姚大志[1] SHI Dong-dong;ZHENG Xian-zhong;ZHAO Hal-bin;LOU Zheng;WANG Hai-ren;QIAN Yuan;LIU Wei;YAO Da-zhi(Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008;School of Astronomy and Space Science, University of Science and Technology of China Hefei 230026)

机构地区：[1]中国科学院紫金山天文台,南京210008 [2]中国科学技术大学天文与空间科学学院,合肥230026

出　　处：《天文学报》2018年第3期1-16,共16页Acta Astronomica Sinica

基　　金：国家重点研发计划(2017YFA0402703);国家自然科学基金项目(11773076)资助

摘　　要：大视场巡天望远镜(Wide Field Survey Telescope,WFST)是采用主焦式光学设计、2.5 m口径、具备强大巡天能力的望远镜,可以开展大规模图像巡天,用于刻画银河系和近邻宇宙的组成和结构、普查太阳系天体和外部构成、开展时域天文监测等科学研究工作.结合大视场巡天望远镜光学系统的透过率、西藏阿里站址的大气透过率和冒纳凯阿台址的天光发射谱,比较不同电荷耦合器件(Charge Coupled Device,CCD)量子响应曲线、读出噪声和不同曝光时间情况下,不同类型天体在u、g、r、i、z和w波段的能谱响应,分析各个波段测光信噪比,优化确定CCD响应曲线和用于太阳系天体巡天的白光滤光片(w)设计.分析结果显示:蓝敏CCD对探测超新星等高能爆发暂现源有优势,但在r、i、z波段效率降低,从而降低这些波段的巡天探测灵敏度.光学宽带CCD响应曲线兼顾蓝端和红端能谱响应,在相同观测时间内,可以实现比蓝敏CCD更高的巡天灵敏度.采用宽带CCD响应曲线,结合估算的WFST系统光学成像效率及站址的天光和消光,计算给出了巡天观测对太阳系天体(G2V恒星光谱)、椭圆星系(E)、漩涡星系(Sbc/Scd)、不规则星系(Im)、类星体、I型和II型超新星的探测灵敏度.通过调节w波段的带宽和中心波长,可以实现对不同类型天体的能谱响应信噪比最大化.综合比较,确定w滤光片的优化设计波长范围为367–795 nm.最后,计算给出了各波段长期巡天图像数据叠加的探测灵敏度随曝光时间的变化曲线.The Wide Field Survey Telescope （WFST） is designed to be a powerful survey machine with prime-focus optics, 2.5 m diameter primary mirror, and 3 degree field of view. It is dedicated to a northern sky imaging survey over 20000 square degrees area. The main science goals include： （i） characterizing the compositions and structures of the Milky Way and local universe; （2） mapping the solar system objects; and （3） exploring variable universe. We combine the optical throughput, charge coupled device （CCD） quantum response, and filter transmission with atmospheric transmission of a 5130 m-altitude site and sky emission from the site of Mauna Kea to analyze the sensitivities of the telescope with different types of CCD response curves. Our results denote that a typical blue-sensitive CCD provides a higher sensitivity in observing blue-color objects like supernova and quasar than a typical broadband CCD, but a lower sensitivity in the r, i, and z bands, leading to a lower survey efficiency to the same u, g, r, i, and z depths. We show that the wavelength range of the w filter （-g ＋ r ＋ i） can be optimized in terms of the energy distribution of survey targets, and give the optimal wavelength range of 367-795 nm for the w filter. Finally, we present the u, g, r, i, z, and w sensitivities as a function of integration time to demonstrate the capability of WFST.

关 键 词：大视场巡天 滤光片 电荷耦合器件 信噪比 灵敏度 

分 类 号：P111[天文地球—天文学]