ANDROMEDA (M31) OPTICAL AND INFRARED DISK SURVEY. I. INSIGHTS IN WIDE-FIELD NEAR-IR SURFACE PHOTOMETRY
ANDROMEDA (M31) OPTICAL AND INFRARED DISK SURVEY. I. INSIGHTS IN WIDE-FIELD NEAR-IR SURFACE PHOTOMETRY
复制标题
DOI：
10.1088/0004-6256/147/5/109
复制
发表时间：
2013-03
期刊：
影响因子：
--
通讯作者：
J. Sick;S. Courteau;J. Cuillandre;M. McDonald;R. D. de Jong;R. Tully
中科院分区：
文献类型：
--
作者：
J. Sick;S. Courteau;J. Cuillandre;M. McDonald;R. D. de Jong;R. Tully
我们目前的仙女座星系（M31）的宽视场近红外J和Ks图像与WIRCam在加拿大-法国-夏威夷望远镜的仙女座星系光学和红外磁盘调查的一部分。这个数据集允许同时观测M31整个凸起和盘（R = 22 kpc内）的解析恒星和近红外（NIR）表面亮度，从而可以直接测试附近星系中近红外光的恒星组成。在这里，我们开发了近红外观测和还原方法，以恢复M31的3° × 1°圆盘上的均匀表面亮度图，其中有27个WIRCam场。两个天空目标点头策略进行了测试，我们发现，严格减少天空采样延迟不能提高背景减除精度优于2%的背景水平，由于时空变化的近红外天空辉光。我们充分描述了我们的WIRCam减少管道，并主张使用在一个晚上从夜空图像构建的单位，而不是不捕获WIRCam照明场的圆顶单位。与天空和星系盘场之间背景形状的随机差异相比，来自天区散射光和热背景的污染对表面亮度形状的影响可以忽略不计，其为背景水平的1.03%。最引人注目的校准步骤是对每个图像引入标量天空偏移，以优化表面亮度连续性。天空偏移将观测区块之间的平均表面亮度差异从背景水平的1%降低到<0.1%，尽管绝对背景水平在统计上仍然不确定到背景水平的0.15%。我们介绍了WIRCam缩减管道和性能分析，为改进近红外宽视场成像方法提供具体建议。
We present wide-field near-infrared J and Ks images of the Andromeda Galaxy (M31) taken with WIRCam at the Canada–France–Hawaii Telescope as part of the Andromeda Optical and Infrared Disk Survey. This data set allows simultaneous observations of resolved stars and near-infrared (NIR) surface brightness across M31's entire bulge and disk (within R = 22 kpc), permitting a direct test of the stellar composition of near-infrared light in a nearby galaxy. Here we develop NIR observation and reduction methods to recover a uniform surface brightness map across the 3° × 1° disk of M31 with 27 WIRCam fields. Two sky-target nodding strategies are tested, and we find that strictly minimizing sky sampling latency cannot improve background subtraction accuracy to better than 2% of the background level due to spatio-temporal variations in the NIR skyglow. We fully describe our WIRCam reduction pipeline and advocate using flats built from night-sky images over a single night, rather than dome flats that do not capture the WIRCam illumination field. Contamination from scattered light and thermal background in sky flats has a negligible effect on the surface brightness shape compared to the stochastic differences in background shape between sky and galaxy disk fields, which are ∼0.3% of the background level. The most dramatic calibration step is the introduction of scalar sky offsets to each image that optimizes surface brightness continuity. Sky offsets reduce the mean surface brightness difference between observation blocks from 1% to <0.1% of the background level, though the absolute background level remains statistically uncertain to 0.15% of the background level. We present our WIRCam reduction pipeline and performance analysis to give specific recommendations for the improvement of NIR wide-field imaging methods.