We present our calibration of spectroscopic measures of luminosity and metallicity for halo giant candidates and give metallicities and distances for our first sample of spectroscopically confirmed giants. These giants have distances ranging from 15 to 83 kpc. As surveys reach farther into the Galaxy's halo with K giant samples, identification of giants becomes more difficult. This is because the numbers of foreground halo K dwarfs rise for V magnitudes of 19–20, typical for halo giants at ~100 kpc. Our photometric survey uses the strength of the Mg b/H feature near 5170 ? to weed K dwarfs out of the disk and thick disk, but we need spectroscopic measures of the strength of the Ca II K, Ca I λ4227, and Mg b/H features to distinguish between the very metal-poor dwarfs and halo giants. Using a full error analysis of our spectroscopic measures, we show why a signal-to-noise ratio of ~15 pixel-1 at Ca I λ4227 and ~10 at Ca II K is needed for reliable luminosity discrimination. We use the Ca II K and Mg b features to measure metallicity in our halo giants, with typical errors (random plus systematic) of 0.3 dex for [Fe/H] values from -0.8 to -3.0.
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机译：我们介绍了针对光晕巨星候选者的光谱度和金属度的光谱测量标定，并给出了我们经光谱确认的巨星的第一个样本的金属度和距离。这些巨人的距离从15到83 kpc。随着对K个巨型样本的调查深入到银河系的光环，识别巨人变得更加困难。这是因为前景光晕K矮子的数量在19-20的V量级上增加，这是光晕巨人在100 kpc时的典型值。我们的光度测量使用的Mb b / H功能强度接近5170？从盘和厚盘中除掉K矮星，但是我们需要用光谱学方法测量Ca II K，Ca Iλ4227和Mg b / H特征的强度，以区分金属贫乏的矮星和晕环巨人。使用我们对光谱测量的完整误差分析，我们证明了为什么需要可靠的光度判别在Ca Iλ4227处的信噪比为〜15 pixel-1，在Ca II K处的信噪比为〜10。我们使用Ca II K和Mg b特征来测量我们晕轮中的金属度，对于[Fe / H]值从-0.8到-3.0的典型误差（随机加上系统误差）为0.3 dex。
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