银河系中心星团的组成：来自自适应光学窄带光谱能量分布的星族分析
Composition of the galactic center star cluster: Population analysis from adaptive optics narrow band spectral energy distributions
摘要：
本工作的目标是发展一种基于窄带滤波器的分离致密星团早、晚型恒星成分的新方法，并将其应用于GC中心秒差距区，对该区域进行星族分析。我们使用AO辅助观测在ESO VLT在近红外H波段和7个中间波段覆盖近红外K波段。比较由此产生的SEDs与一个黑体的变量消光，然后让我们来确定的存在和强度的CO吸收功能，以区分早期和晚期类型的恒星。新的方法适用于K巨星（和更晚的）以及B2主序星（和更早的），这些恒星在中央秒差距的K波段亮度超过15.5等。与以前仅限于13-14等的光谱研究相比，这代表了观测深度的重大改进，并减少了所需的观测时间。我们将312颗恒星归类为早期类型的候选者，样本为5914个来源。早型星的分布可用陡幂律拟合（beta（R> 1 ''）= -1.49 +/- 0.12，或者违反幂律，beta（R=1- 10“）= -1.08 +/-0.12，beta（R=10- 20”）= -3.46 +/-0.58，因为我们发现早型密度在~ 10“处下降）。我们还首次检测到0.5 pc以外的早期类型候选人。晚型密度函数在内部6“中显示出反转，具有β（R<6”）= 0.17 +/- 0.09的幂律斜率。晚型KLF的幂律斜率为0.30 $\pm$ 0.01，非常类似于银河系凸起的KLF。早期类型KLF具有0.14 +/- 0.02的更平坦的斜率。我们的结果最符合原位恒星形成的情况。
英文摘要：
The goals of this work are to develop a new method to separate early and late type stellar components of a dense stellar cluster based on narrow band filters, to apply it to the central parsec of the GC, and to conduct a population analysis of this area. We use AO assisted observations obtained at the ESO VLT in the NIR H-band and 7 intermediate bands covering the NIR K-band. A comparison of the resulting SEDs with a blackbody of variable extinction then allows us to determine the presence and strength of a CO absorption feature to distinguish between early and late type stars. The new method is suitable to classify K giants (and later) as well as B2 main sequence (and earlier) stars which are brighter than 15.5 mag in the K band in the central parsec. Compared to previous spectroscopic investigations that are limited to 13-14 mag, this represents a major improvement in the depth of the observations as well as reducing the needed observation time. We classify 312 stars as early type candidates out of a sample of 5914 sources. The distribution of the early type stars can be fitted with a steep power law (beta(R>1'') = -1.49 +/- 0.12, alternatively with a broken power law, beta(R=1-10'') = -1.08 +/- 0.12, beta(R=10-20'') = -3.46 +/- 0.58, since we find a drop of the early type density at ~10''). We also detect early type candidates outside of 0.5 pc in significant numbers for the first time. The late type density function shows an inversion in the inner 6'', with a power law slope of beta(R<6'') = 0.17 +/- 0.09. The late type KLF has a power law slope of 0.30$\pm$0.01, closely resembling the KLF obtained for the bulge of the Milky Way. The early type KLF has a much flatter slope of 0.14 +/- 0.02. Our results agree best with an in-situ star formation scenario.
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