标题： 来自双子邻近星系光谱巡天 I. 触须星系中的年轻大质量星团 显示英文标题

标题： Initial Mass Functions of Young Stellar Clusters from the Gemini Spectroscopic Survey of Nearby Galaxies I. Young Massive Clusters in the Antennae galaxies

摘要： 恒星初始质量函数（IMF）是理解恒星形成过程以及遥远星系中恒星群体综合性质的关键参数。我们对发生星暴现象的星系 NGC 4038/39 中的年轻大质量星团（YMCs）进行了光谱研究。使用安装在8.2米Gemini南望远镜上的GMOS-S获得的七个YMCs的积分光谱揭示了与恒星年龄和潜在IMF相关的光谱特征。我们利用沃尔夫-拉叶星的吸收线和强发射带来限制YMCs的年龄。内部消光也通过Na I D吸收线的强度估算得出。基于这些限制条件，观测光谱与从简单恒星群体模型生成的合成光谱相匹配。从光谱拟合中得到了集群的几个参数，包括年龄、消光、集群质量以及潜在的IMF。这些YMCs的年龄范围从2.5到6.5百万年，它们所含恒星质量从1.6 × 10⁵ M_sun到7.9 × 10⁷ M_sun不等。潜在的IMF似乎不同于Salpeter/Kroupa IMF的普遍形式。有趣的是，尽管由于拥挤效应导致某些集群的质量被高估，大质量集群往往具有底部较轻的IMF。因此，我们的结果显示当分析未分辨的恒星系统的综合光时，IMF的普遍形式并不总是有效的。然而，为了得出明确的结论，还需要更大样本量的进一步研究。 显示英文摘要

摘要： The stellar initial mass function (IMF) is a key parameter to understand the star formation process and the integrated properties of stellar populations in remote galaxies. We present a spectroscopic study of young massive clusters (YMCs) in the starburst galaxies NGC 4038/39. The integrated spectra of seven YMCs obtained with GMOS-S attached to the 8.2-m Gemini South telescope reveal the spectral features associated with stellar ages and the underlying IMFs. We constrain the ages of the YMCs using the absorption lines and strong emission bands from Wolf-Rayet stars. The internal reddening is also estimated from the strength of the Na I D absorption lines. Based on these constraints, the observed spectra are matched with the synthetic spectra generated from a simple stellar population model. Several parameters of the clusters including age, reddening, cluster mass, and the underlying IMF are derived from the spectral matching. The ages of the YMCs range from 2.5 to 6.5 Myr, and these clusters contain stellar masses ranging from 1.6 X 10^5 M_sun to 7.9 X 10^7 M_sun. The underlying IMFs appear to differ from the universal form of the Salpeter/Kroupa IMF. Interestingly, massive clusters tend to have the bottom-heavy IMFs, although the masses of some clusters are overestimated due to the crowding effect. Based on this, our results suggest that the universal form of the IMF is not always valid when analyzing integrated light from unresolved stellar systems. However, further study with a larger sample size is required to reach a definite conclusion.