A Wide-Field WFC3 Imaging Survey in the COSMOS Field ("COSMOS-DASH")

COSMOS-Drift And SHift (COSMOS-DASH) is a Hubble Space Telescope WFC3 imaging survey of the COSMOS field in the F160W filter, comprising 456 WFC3 pointings covering an area of 0.49 deg^2, giving 0.66 deg^2 of total data in the archive. By taking advantage of the unique Drift And SHift (DASH) observing mode, COSMOS-DASH is the widest HST/WFC3 imaging survey in F160W, tripling the extragalactic survey area in the near-infrared at HST resolution. Generally, guide star acquisitions make it impractical to observe multiple pointings per orbit, so very wide near-IR surveys with HST are inefficient. However, this limitation can be overcome by guiding with gyros alone, which is possible when HST operates with three gyros. COSMOS-DASH observed eight independent WFC3-IR pointings per orbit, taking advantage of the fact that HST drifts by only a very small amount in the 25 seconds between non-destructive reads of unguided exposures. This dataset contains the drizzled mosaic products as well as derived morphological information for galaxies in the mosaic.

COSMOS-Drift And SHift（COSMOS-DASH）是一项针对COSMOS天区的哈勃空间望远镜（Hubble Space Telescope, HST）宽视场相机3（Wide Field Camera 3, WFC3）F160W滤光波段成像巡天项目，共包含456个WFC3观测指向，覆盖天区面积0.49平方度，存档总数据覆盖面积达0.66平方度。借助独特的漂移与移位（Drift And SHift, DASH）观测模式，COSMOS-DASH是目前F160W波段下视场最广的HST/WFC3成像巡天项目，将哈勃分辨率下近红外河外巡天面积扩充至原有三倍。常规情况下，导星采集会导致单次轨道内无法开展多指向观测，使得哈勃开展的大视场近红外巡天效率低下。但仅依靠陀螺仪（gyros）引导即可突破这一限制：当哈勃三台陀螺仪正常运行时，即可实现无导星引导的观测。COSMOS-DASH单次轨道内可完成8个独立的WFC3红外观测指向，利用了哈勃在非破坏性读取未导星曝光的25秒间隔内仅产生极小位移这一特性。本数据集包含基于drizzle算法的拼接产物，以及该拼接图像中星系的衍生形态学信息。