WFC3/UVIS几何畸变--时间演化中的线性项相对于Gaia
WFC3/UVIS Geometric Distortion -- Time Evolution of Linear Terms w.r.t Gaia
AI总结：
研究WFC3/UVIS图像几何畸变线性项随时间变化，提出基于Gaia DR3的对齐方法，并推荐tweakreg程序用于高精度天体测量。
摘要：
我们对超过7400个WFC3/UVIS曝光数据与Gaia DR3目录进行对齐，以研究2009年至2022年间几何畸变解决方案中线性项（位移、旋转、尺度和扭曲）的时间演化。我们发现尺度和扭曲项存在微小的时间变化（13年内小于0.2像素），这些变化通常由内在散射主导（高达±0.3像素）。同时，观测到一个较大的滤光片依赖偏移在尺度项上，F275W和F814W图像在所有时期的最大差异为0.3像素。从2009年到2017年中期，测量到一个微小的旋转偏移至Gaia，为0.003±0.004度，之后偏移量达到0.01度，且具有较大的散射。MAST流水线处理包括一个额外的对齐步骤，当至少有10个匹配源时，该步骤会纠正UVIS图像相对于Gaia DR3的任何残余线性项。除了任何指向偏移外，该步骤还考虑了此处描述的畸变线性项的演变。对于需要高精度天体测量的观测者，我们建议使用tweakreg程序，根据匹配源的数量使用四参数拟合（x位移，y位移，旋转和尺度）或六参数拟合（x位移，y位移，x旋转，y旋转，x尺度和y尺度）重新对齐图像。我们提供了DrizzlePac教程的链接，以提高WFC3图像的绝对和相对天体测量。
英文摘要：
We align more than 7,400 WFC3/UVIS exposures to the Gaia DR3 catalog to examine the time evolution of the linear terms (shift, rotation, scale and skew) of the geometric distortion solution between 2009 and 2022. We find small linear temporal changes in the scale and skew terms (less than 0.2 pixels in 13 years) which are generally dominated by intrinsic scatter (up to $\pm$ 0.3 pixels). Concurrently, a larger filter-dependent offset in the scale term is observed, with a maximum difference of 0.3 pixels between F275W and F814W images at all epochs. A small rotation offset to Gaia of 0.003 $\pm$ 0.004 degrees is measured from 2009 to mid-2017, after which the offsets are as large as 0.01 degrees, with a large scatter. MAST pipeline processing includes an additional alignment step which corrects UVIS images for any residual linear terms with respect to Gaia DR3 when there are at least 10 matched sources. In addition to any pointing offsets, this step accounts for any evolution in the distortion linear terms described here. For observers requiring high-precision astrometry, we recommend using the tweakreg routine to realign images using a 4-parameter fit (x-shift, y-shift, rotation, and scale) or a 6-parameter fit (x-shift, y-shift, x-rotation, y-rotation, x-scale, and y-scale) depending on the number of matched sources. We provide links to DrizzlePac tutorials for improving both absolute and relative astrometry in WFC3 images.
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