AI 中文总结
针对升级后的凯克NIRC2红外成像仪，研究人员构建穆勒矩阵模型完成J、H波段偏振校准，得到M3二向色性值并建立初始校准框架，为后续优化提供方向。
AI 中文摘要
凯克望远镜的NIRC2红外成像仪于2025年完成升级，新增了覆盖约1.1至4.1微米（J、H、K、L'波段）的双光束偏振观测模式。我们利用凯克 tertiary 镜（M3）、半波片（HWP）、图像旋转器（IMR）、下游光学元件及沃拉斯顿棱镜的波长相关穆勒矩阵模型，对NIRC2偏振测量进行了初步的J、H波段校准。我们通过每个波段内包含10个HWP角度和9个IMR角度的穹顶平场序列，对M3下游的模型进行约束。尽管该模型能重现主要调制效应，但残差呈现出依赖HWP和IMR角度的结构。对非偏振标准星观测数据进行测量矩阵反演，得到M3在J、H、Kp波段的二向色性分别为0.0119±0.0009、0.0098±0.0004和0.0068±0.0005，这一结果与铝的菲涅尔预测值更为接近，相比之下，从穹顶平场推导的数值偏差更大。穹顶平场产生的较大调制可能源于入射穹顶照明的偏振特性或穆勒矩阵模型的不准确性。这些结果建立了初始校准框架，同时为后续研究提供了方向：改进输入偏振约束、采用前期实验室测量确定的HWP固定参数、利用偏振标准星验证模型，以及将校准扩展至L'波段。
英文摘要
The Keck/NIRC2 infrared imager was upgraded in 2025 with dual-beam polarimetric observing modes spanning approximately 1.1--4.1 microns (JHKL' bands). We present a preliminary JHK calibration of NIRC2 Polarimetry using a wavelength-dependent Mueller matrix model of the Keck tertiary mirror (M3), half-wave plate (HWP), image rotator (IMR), downstream optics, and Wollaston prism. We constrain the model downstream of M3 using dome flat sequences spanning ten HWP and nine IMR angles in each band. Although the model reproduces the dominant modulation, the residuals show structure dependent on HWP and IMR angle. Measurement matrix inversion of unpolarized standard star observations gives M3 diattenuations of 0.0119+/-0.0009, 0.0098+/-0.0004, and 0.0068+/-0.0005 in J, H, and Kp, substantially closer to Fresnel predictions for aluminum than the values derived from dome flats. The larger dome flat modulation may indicate polarization in the incident dome illumination or Mueller matrix model inaccuracies. These results establish an initial calibration framework while motivating improved input polarization constraints, fixed HWP parameters from previous laboratory measurements, model validation with polarized standard stars, and extension to L'.
CommentsSubmitted to SPIE Astronomical Telescopes + Instrumentation 2026
