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arXiv 1609.08693astro-ph.IM
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双子座行星成像仪观测校准XIII:波长校准改进、稳定性和非线性

Gemini Planet Imager Observational Calibration XIII: Wavelength Calibration Improvements, Stability, and Nonlinearity

Schuyler G. Wolff, Kimberly Ward-Duong, Joe Zalesky, Alex Z. Greenbaum, Marshall D. Perrin, James Graham

摘要:

我们提出了改进的波长校准的小透镜为基础的积分场光谱仪(IFS),作为科学仪器的双子座行星成像仪(GPI)。GPI IFS具有2.7”$\times$ 2.7”视场和190 $\times$ 190小透镜阵列(14.1 mas/小透镜),光谱分辨率范围为R $\sim$ 35至78。一个独特的波长的解决方案是确定每个小透镜的特征在于一个二维的位置,一个n维多项式描述的光谱色散,和旋转的光谱相对于检测器轴。我们研究了所有Y,J,H和K波段的光谱色散的非线性,通过两个天空弧光灯图像和模拟IFS图像使用的光路模型。此外,10孔非冗余掩模模式GPI提供了一个替代措施的波长色散内的数据立方体通过互相关的参考PSF与科学图像。这种方法可以用来确认从线性分散的减少数据立方体的偏差。我们发现,包括一个二次项提供了一个因素的10改善波长的解决方案的精度在线性解决方案,是必要的,以实现在J波段的像素的百分之几的不确定性在K波段的像素的几千。这对应于所有滤波器的波长不确定度为$\sim$ 0.2 nm。

英文摘要:

We present improvements to the wavelength calibration for the lenslet-based Integral Field Spectrograph (IFS), that serves as the science instrument for the Gemini Planet Imager (GPI). The GPI IFS features a 2.7" $\times$ 2.7" field of view and a 190 $\times$ 190 lenslet array (14.1 mas/lenslet) with spectral resolving power ranging from R $\sim$ 35 to 78. A unique wavelength solution is determined for each lenslet characterized by a two-dimensional position, an n-dimensional polynomial describing the spectral dispersion, and the rotation of the spectrum with respect to the detector axis. We investigate the non-linearity of the spectral dispersion across all Y, J, H, and K bands through both on-sky arc lamp images and simulated IFS images using a model of the optical path. Additionally, the 10-hole non-redundant masking mode on GPI provides an alternative measure of wavelength dispersion within a datacube by cross-correlating reference PSFs with science images. This approach can be used to confirm deviations from linear dispersion in the reduced datacubes. We find that the inclusion of a quadratic term provides a factor of 10 improvement in wavelength solution accuracy over the linear solution and is necessary to achieve uncertainties of a few hundredths of a pixel in J band to a few thousands of a pixel in the K bands. This corresponds to a wavelength uncertainty of $\sim$0.2 nm across all filters.

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