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首页> 外文期刊>The astronomical journal >Optimal Stellar Photometry for Multi-conjugate Adaptive Optics Systems Using Science-based Metrics
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Optimal Stellar Photometry for Multi-conjugate Adaptive Optics Systems Using Science-based Metrics

机译：基于科学指标的多共轭自适应光学系统的最佳恒星测光

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We present a detailed discussion of how to obtain precise stellar photometry in crowded fields using images from multi-conjugate adaptive optics (MCAO) systems, with the intent of informing the scientific development of this key technology for the Extremely Large Telescopes. We use deep J and K s exposures of NGC 1851 taken with the Gemini Multi-Conjugate Adaptive Optics System (GeMS) on Gemini South to quantify the performance of the instrument and to develop an optimal strategy for stellar photometry using point-spread function (PSF)-fitting techniques. We judge the success of the various methods we employ by using science-based metrics, particularly the width of the main sequence turnoff region. We also compare the GeMS photometry with the exquisite HST data in the visible of the same target. We show that the PSF produced by GeMS possesses significant spatial and temporal variability that must be accounted for during the analysis. We show that the majority of the variation of the PSF occurs within the "control radius" of the MCAO system and that the best photometry is obtained when the PSF radius is chosen to closely match this spatial scale. We identify photometric calibration as a critical issue for next-generation MCAO systems such as those on the Thirty Meter Telescope and European Extremely Large Telescope. Our final CMDs reach K s?~?22—below the main sequence knee—making it one of the deepest for a globular cluster available from the ground. Theoretical isochrones are in remarkable agreement with the stellar locus in our data from below the main sequence knee to the upper red giant branch.
机译：我们将详细讨论如何使用来自多共轭自适应光学（MCAO）系统的图像在拥挤的田野中获得精确的恒星光度法，以期为超大型望远镜提供这项关键技术的科学发展信息。我们使用Gemini South上的Gemini多共轭自适应光学系统（GeMS）对NGC 1851进行的J和K深度曝光来量化仪器的性能，并使用点扩展函数（PSF）制定最佳的恒星光度测量策略）拟合技术。我们通过使用基于科学的度量标准来判断所采用的各种方法是否成功，尤其是主序列关闭区域的宽度。我们还将GeMS光度法与相同目标可见光下的精美HST数据进行比较。我们表明，GeMS产生的PSF具有显着的时空变异性，必须在分析过程中加以考虑。我们表明，大多数的PSF的变化的MCAO系统的“控制范围”内，并且在选择了PSF半径这个空间尺度密切配合，得到最好的测光发生。我们将光度校准确定为下一代MCAO系统（如三十米望远镜和欧洲超大型望远镜上的系统）的关键问题。我们的最终CMD达到K s？〜？22（在主序列拐点以下），使其成为可从地面获得的球状星团中最深的球之一。从我们的主要序列膝盖以下到上部红色巨型分支，理论等时线与我们数据中的恒星轨迹非常吻合。

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