Infrared Survey of the Galactic Center with the 1.4-m IRSF telescope at SAAO

在J、H和K波段对银河系中心进行了高分辨率0.45“/像素的红外巡天。观测区域覆盖银河系纬度±1度（±150pc）和银河系经度±10度（±1.5 kpc）。我们使用同时红外无偏巡天成像仪（SIRIUS），将3个1024x1024的HgCdTe阵列连接到位于名古屋大学南非天文台的IRSF 1.4 m望远镜上。阵列读出得到了改进，观察的效率现在非常高。首先，利用探测到的处于核心He燃烧阶段的中心度红团星，确定了星际变红规律；这与文献中的颜色过剩法不同，而且更加准确。星际消光偏离Rieke-Lebofsky定律（与波长的-1.6阶成正比），而是遵循波长的-2阶。有时有人认为，红外消光在各种视线中是“普遍的”，但这一结果提供了明确的证据。测定的折射率本身对于消除观测光谱的误差也很重要。然后，我们推导出了银河系中心周围±1.5 kpc区域内红团星分布的峰值。视星等峰值沿银道面连续变化，从K=13.4等到去震源后的12.2等。这种变化可以用先前研究中发现的棒状结构来解释，但我们在直径1.2 kpc的区域内发现了一个额外的内部结构，其中视星等峰值仅变化0.1等。

Infrared survey of the Galactic center has been performed in the J, H, and K bands with the high resolution of 0.45"/pix. The observed area covers ±1 deg (±150 pc) in the Galactic latitude and ±10 deg (±1.5 kpc) in the Galactic longitude. We used Simultaneous Infrared Imager for Unbiased Survey (SIRIUS) with three 1024x1024 HgCdTe arrays, which were attached to the IRSF 1.4-m telescope placed at South African Astronomical Observatory by Nagoya University. The array read-out has been improved and the efficiency of the observation is now extremely high.First, using the detected red clump stars in the central degree, which are in the core He burning phase, we determined the interstellar reddening law ; this is different from the color-excess method in the literature, and much more accurate. The interstellar extinction is deviated from the Rieke-Lebofsky law (proportional to the -1.6th order of the wavelength), and rather follows to the -2nd order of the wavelength. It has been sometimes argued that the infrared extinction is "universal" in the various lines of sight, but this result has presented clear evidence against it. The determined index itself is also important in dereddening the observed spectra.Then, we derived the peak of distribution of red clump stars in the ±1.5 kpc region around the Galactic center. The apparent magnitude peak changes continuously along the Galactic plane, from K=13.4 mag to 12.2 mag after dereddening. This variation is explained by the bar-like structure found in previous studies, but we find an additional inner structure within the region of 1.2 kpc in diameter, where the apparent magnitude peak changes by only 0.1 mag.