POLARIMETRIC CALIBRATION OF MIMIR AND THE GALACTIC PLANE INFRARED POLARIZATION SURVEY (GPIPS)
POLARIMETRIC CALIBRATION OF MIMIR AND THE GALACTIC PLANE INFRARED POLARIZATION SURVEY (GPIPS)
复制标题
MIMIR 的偏振校准和银河平面红外偏振测量 (GPIPS)
DOI：
10.1088/0067-0049/200/2/20
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
M. Pavel
中科院分区：
文献类型：
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作者：
D. Clemens;A. Pinnick;M. Pavel
本文介绍了用于支持银河平面红外偏振巡天和其他应用的Mimir近红外成像偏振计全视场偏振校准的方法和观测结果。旋光校准包括三个步骤：（1）利用复合零阶半波片（HWP）在偏振观测中使用的16个位置角获得的圆顶图像进行平场化，（2）通过对球状星团恒星的观测映射和去除剩余的仪器偏振，（3）利用偏振标准星将仪器偏振位置角转换为赤道角，确定线偏振效率。对于Mimir，偏振平坦场化将整个FOV上的偏振效率的系统变化减少了20倍。对8个球状星团的151次观测产生了40，000颗恒星，测量了剩余的0.05%-0.45%的仪器偏振，不确定度为0.02%-0.04%。经过这些校正后，对23颗偏振星的444次观测使赤道偏振位置角的确定达到了0.5 °的典型不确定度，并确定了轴上（校正到全视场）偏振效率为91.1% ± 0.4%。完全校正的标准星星观测结果表明，与公布的偏振百分比和位置角的值非常一致。此外，对包含Whittet等人的“初级”偏振标准星的四个天区的观测进行了分析，产生了30个新的“次级”标准星。它们比原色更暗，允许使用更大的望远镜孔径。二级标准的偏振位置角不确定度小于5°，偏振度范围为0.4%至8.5%。
Methods and observations are described for the full field of view (FOV) polarimetric calibration of the Mimir near-infrared imaging polarimeter in support of the Galactic Plane Infrared Polarization Survey and other applications. Polarimetric calibration consisted of three steps: (1) flat fielding using in-dome images obtained with the compound zero-order half-wave-plate (HWP) in the 16 position angles employed in polarimetric observations, (2) mapping and removing the remaining instrumental polarization via observations of globular cluster stars, and (3) using polarization standard stars to convert instrument-based polarization position angles to equatorial and to determine the linear polarimetric efficiency. For Mimir, the polarization flat fielding reduced systematic variations of the polarization efficiency across the FOV by a factor of 20. The 151 observations of eight globular clusters yielded 40,000 stars for measuring the remaining 0.05%–0.45% instrumental polarization to uncertainties of 0.02%–0.04%. After these corrections, the 444 observations of 23 polarized stars enabled equatorial polarization position angles to be determined to typical uncertainties of 0.°5, and the on-axis (corrected to full FOV) polarization efficiency of 91.1% ± 0.4% to be determined. Fully corrected standard star observations showed excellent agreement with published values of polarization percentage and position angle. Additionally, the observations of four sky fields containing Whittet et al. “primary” polarization standard stars were analyzed to yield 30 new “secondary” standards. These are fainter than the primaries, allowing use with larger telescope apertures. The secondary standards have polarization position angle uncertainties under 5° and range in degree of polarization from 0.4% to 8.5%.