用WFIRST日冕仪进行外太阳辐射观测的潜力
The Potential of Exozodiacal Disks Observations with the WFIRST Coronagraph Instrument
摘要：
宽视场红外巡天望远镜（WFIRST）日冕仪（CGI）将是第一个使用主动波前控制的高性能恒星日冕仪，用于太空中的深层星光抑制，为光学天文观测提供前所未有的对比度，空间分辨率和灵敏度。CGI的一个科学案例将是拍摄附近类日恒星的宜居带（~10 pc）和更远恒星的雪线（~ 20 pc）中存在的微弱行星际尘埃结构的图像和（R~50）光谱，直到尘埃密度水平与太阳系黄道云相当。对比度首次低于~10-7，CGI将跨越碎片盘物理学的一个重要门槛，访问光学深度足够低的盘，其结构由传输现象而不是碰撞主导。因此，CGI结果对于确定外黄带尘埃颗粒如何在成熟恒星周围的低密度盘中产生和运输至关重要。此外，CGI将能够测量亮度水平，并在光学上限制单个附近类日恒星周围的外黄道光云的不对称程度，在~ 10倍太阳黄道光发射水平。这一信息对于优化未来可能的地外直接成像飞行任务的观测战略，特别是那些计划在光学波长上运行的飞行任务，如可居住系外行星观测站和大型紫外线/光学/红外探测器，将是极其宝贵的。
英文摘要：
The Wide Field Infrared Survey Telescope (WFIRST) Coronagraph Instrument (CGI) will be the first high-performance stellar coronagraph using active wavefront control for deep starlight suppression in space, providing unprecedented levels of contrast, spatial resolution, and sensitivity for astronomical observations in the optical. One science case enabled by the CGI will be taking images and(R~50)spectra of faint interplanetary dust structures present in the habitable zone of nearby sunlike stars (~10 pc) and within the snow-line of more distant ones(~20pc), down to dust density levels commensurate with that of the solar system zodiacal cloud. Reaching contrast levels below~10-7 for the first time, CGI will cross an important threshold in debris disks physics, accessing disks with low enough optical depths that their structure is dominated by transport phenomena than collisions. Hence, CGI results will be crucial for determining how exozodiacal dust grains are produced and transported in low-density disks around mature stars. Additionally, CGI will be able to measure the brightness level and constrain the degree of asymmetry of exozodiacal clouds around individual nearby sunlike stars in the optical, at the ~10x solar zodiacal emission level. This information will be extremely valuable for optimizing the observational strategy of possible future exo-Earth direct imaging missions, especially those planning to operate at optical wavelengths, such as Habitable Exoplanet Observatory (HabEx) and the Large Ultraviolet/Optical/Infrared Surveyor (LUVOIR).
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