ANIR：用于1.0米miniTAO望远镜的阿塔卡马近红外相机
ANIR : Atacama Near-Infrared Camera for the 1.0-m miniTAO Telescope
摘要：
我们为安装在智利北部Cerro Chajnantor山顶（海拔5640米）的东京大学阿塔卡马天文台1.0米望远镜（miniTAO）开发了一台名为ANIR（阿塔卡马近红外相机）的近红外相机。该照相机在0.95至2.4 $μ$ m的波长范围内提供5“.1 $\times$ 5”.1的视场，空间分辨率为0”.298 /像素。利用干燥的场地，相机能够进行氢帕申- $α$（Pa $α$，空气中的$λ=$ 1.8751 $μ$ m）窄带成像观测，由于主要来自水蒸气的深层大气吸收，在该波长下进行地面观测相当困难。自2009年ANIR首次观测以来，我们已经成功地获得了银河系天体和附近星系的Pa $α$图像。窄带滤波器（$N1875$，$N191$）的吞吐量（包括大气吸收）显示出比宽带滤波器（几个百分点）更大的色散（~10%），这表明它们受到站点上方可吸入水汽（PWV）的时间波动的影响。我们通过窄带滤光片处的大气透射率来评估PWV含量，并推导出PWV分布的中值和色散对于$N1875$为0.40+/-0.30 mm，对于$N191$为0.37+/-0.21 mm，这比Cerro Chajnantor（海拔5100米）基地的辐射测量值小得多（$N1875$为49+/-38%，$N191$为59+/-26%）。当我们假设水汽的垂直分布近似为指数分布，尺度高度在0.3-1.9 km（以前在夜间观测到的值）时，PWV的降低可以通过站点的海拔高度来解释。因此，我们得出结论，在Cerro Chajnantor峰会的miniTAO/ANIR确实为我们提供了一个“地基”Pa $α$观测的优秀能力。
英文摘要：
We have developed a near-infrared camera called ANIR (Atacama Near-InfraRed camera) for the University of Tokyo Atacama Observatory 1.0m telescope (miniTAO) installed at the summit of Cerro Chajnantor (5640 m above sea level) in northern Chile. The camera provides a field of view of 5'.1 $\times$ 5'.1 with a spatial resolution of 0".298 /pixel in the wavelength range of 0.95 to 2.4 $μ$m. Taking advantage of the dry site, the camera is capable of hydrogen Paschen-$α$ (Pa$α$, $λ=$1.8751 $μ$m in air) narrow-band imaging observations, at which wavelength ground-based observations have been quite difficult due to deep atmospheric absorption mainly from water vapor. We have been successfully obtaining Pa$α$ images of Galactic objects and nearby galaxies since the first-light observation in 2009 with ANIR. The throughputs at the narrow-band filters ($N1875$, $N191$) including the atmospheric absorption show larger dispersion (~10%) than those at broad-band filters (a few %), indicating that they are affected by temporal fluctuations in Precipitable Water Vapor (PWV) above the site. We evaluate the PWV content via the atmospheric transmittance at the narrow-band filters, and derive that the median and the dispersion of the distribution of the PWV are 0.40+/-0.30 mm for $N1875$ and 0.37+/-0.21 mm for $N191$, which are remarkably smaller (49+/-38% for $N1875$ and 59+/-26% for $N191$) than radiometry measurements at the base of Cerro Chajnantor (5100 m alt.). The decrease in PWV can be explained by the altitude of the site when we assume that the vertical distribution of the water vapor is approximated at an exponential profile with scale heights within 0.3-1.9 km (previously observed values at night). We thus conclude that miniTAO/ANIR at the summit of Cerro Chajnantor indeed provides us an excellent capability for a "ground-based" Pa$α$ observation.
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