Development of a new calibration method for ground-based Paschen-alpha imaging data
Development of a new calibration method for ground-based Paschen-alpha imaging data
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开发一种新的地基帕邢-α成像数据校准方法
DOI：
10.1117/12.924263
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
S. Koshid
中科院分区：
文献类型：
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作者：
Tateuchi;K.;K. Motohara;M. Konishi;H. Takahashi;N. Kato;R. Ohsawa;K. Yutaro;Y. Yoshii;M. Doi;T. Handa;K. Kohno;K. Kawara;M. Tanaka;T. Miyata;T. Minezaki;S. Sako;T. Tanabe;T. Morokuma;Y. Tamura;T. Aoki;T. Soyano;K. Tarusawa;S. Koshid
阿塔卡马近红外相机（英语：Atacama Near Infrared camera）是东京大学阿塔卡马1.0米望远镜的近红外相机，安装在智利北方的Chajnantor山顶（海拔5640米）。该地点海拔高，水汽含量极低（可降水量：PWV=0.5mm），使我们能够在1.8751 μm处观测到氢帕邢α（Paα）发射线。自2009年6月首次观测以来，我们成功地获得了银河系天体和近星系的Paα窄带图像。然而，由于在窄带滤光片的波长范围内存在许多随时间变化的大气吸收特征，因此很难准确地校准发射线通量。因此，我们发展了一种新的方法来恢复Paα发射线通量从地基窄带滤波成像观测。首先，平均大气透过率内的窄带滤波器推导出使用2 MASS星的图像。其次，通过与大气透过率模型软件ATRAN计算的透过率进行比较，估算出PWV。最后，根据所得到的PWV对应的模式大气，计算了Paα发射线波长处的大气透过率。将此方法应用于ANIR观测的近地亮红外星系数据，估算出的发射线强度相对于HST/NICMOS观测值的精度在10%以内。在本文中，我们描述的校准方法及其精度的细节。
ANIR (Atacama Near InfraRed camera) is a near infrared camera for the University of Tokyo Atacama 1.0m telescope installed at the summit of Co. Chajnantor (5640m altitude) in northern Chile. The high altitude and the extremely low water vapor (precipitable water vapor:PWV=0.5mm) of the site enables us to perform observation of hydrogen Paschen alpha (Paα) emission line at 1.8751 μm. Since the first light observation in June 2009, we have succesfully obtained Paα narrow-band images of Galactic objects and near-by Galaxies. However, as there are many atmospheric absorption features within the wavelength range of the narrow-band filters which vary temporally due to change of PWV, it is difficult to calibrate the emission line flux accurately. Therefore, we have developed a new method to restore Paα emission-line flux from ground-based narrow-band filter imaging observations. First, average atmospheric transmittance within the narrow-band filter is derived using 2MASS stars in a image. Second, PWV is then estimated by comparing the transmittance with that calculated by atmospheric transmittance model software, ATRAN. Finally, the atmospheric transmittance at the wavelength of Paα emission-line is obtained from the model atmosphere corresponding to the obtained PWV. By applying this method to the data of nearby Luminous Infrared Galaxies obtained by ANIR, the emission line strength is estimated within the accuracy of 10% relative to that observed by HST/NICMOS. In this paper, we describe details of the calibration method and its accuracy.