银河系中央秒差距长期存在顶重IMF的证据
Evidence for a Long-Standing Top-Heavy IMF in the Central Parsec of the Galaxy
摘要：
利用VLT上的自适应光学积分场光谱仪SINFONI对距离Sgr A* 1秒差距以内的329颗晚型巨星进行了分类。这些观测结果代表了迄今为止获得的银河系中心最深的光谱数据集，达到了50%的完整性阈值，接近氦燃烧红团的大小（Ks ~ 15.5 mag.）。结合我们的光谱结果与NaCo H和Ks测光，我们构建了一个观察到的赫兹-罗素图，我们定量比较的理论分布的各种恒星形成历史的内星系，使用卡方分析。我们的最佳拟合模型对应于过去12 Gyr内连续的恒星形成，具有头重脚轻的初始质量函数（IMF）。这个IMF与最近恒星形成时期观察到的IMF的相似性是有趣的，也许暗示了最近恒星形成与银河系中心历史上形成的恒星之间的联系。
英文摘要：
We classify 329 late-type giants within 1 parsec of Sgr A*, using the adaptive optics integral field spectrometer SINFONI on the VLT. These observations represent the deepest spectroscopic data set so far obtained for the Galactic Center, reaching a 50% completeness threshold at the approximate magnitude of the helium-burning red clump (Ks ~ 15.5 mag.). Combining our spectroscopic results with NaCo H and Ks photometry, we construct an observed Hertzsprung-Russell diagram, which we quantitatively compare to theoretical distributions of various star formation histories of the inner Galaxy, using a chi-squared analysis. Our best-fit model corresponds to continuous star formation over the last 12 Gyr with a top-heavy initial mass function (IMF). The similarity of this IMF to the IMF observed for the most recent epoch of star formation is intriguing and perhaps suggests a connection between recent star formation and the stars formed throughout the history of the Galactic Center.
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