合并/相互作用星系中年轻星团的双子光谱巡天。III。天线
Gemini Spectroscopic Survey of Young Star Clusters in Merging/Interacting Galaxies. III. The Antennae
摘要：
我们提出了合并星系NGC 4038/39（“银河系”）中16个星团的光谱学，并补充了HST成像的数据集。每个星团的年龄和金属丰度是通过简单的恒星星族模型观测到的巴耳末线和金属线的强度之间的比较得出的。然后我们用光度法估算出折射率和质量。我们发现，除了三个星团外，所有星团的年龄都在3- 2亿年之间，这与合并后恒星形成率的预期增加一致。大多数星团的速度与附近的分子和HI气体一致，这些气体先前已被证明在祖星系内旋转，因此恒星/团簇形成仍在星系盘内发生。然而，有三个星团的径向速度与旋转气体盘的一部分不一致，这是令人惊讶的年轻（200- 500 Myr）年龄。有趣的是，我们在这三个星团中的一个附近发现了一个具有相同颜色（V-I）的恒星协会，这表明星团和协会是同时形成的，并且在空间上保持相关。我们发现证据的空间分布的团簇形成整个合并的持续时间。探讨了各种假设的恒星/团簇形成率对解释团簇年龄分布的影响，我们没有发现长期的“婴儿死亡率”的证据，如先前所建议的。星系合并的模型，包括恒星形成的处方，可以提供一个整体良好的拟合所观察到的星系团年龄分布。
英文摘要：
We present optical spectroscopy of 16 star clusters in the merging galaxies NGC 4038/39 ("The Antennae") and supplement this dataset with HST imaging. The age and metallicity of each cluster is derived through a comparison between the observed Balmer and metal line strengths with simple stellar population models. We then estimate extinctions and masses using the photometry. We find that all but three clusters have ages between ~3-200 Myr, consistent with the expected increase in the star-formation rate due to the merger. Most of the clusters have velocities in agreement with nearby molecular and HI gas that has been previously shown to be rotating within the progenitor galaxies, hence star/cluster formation is still taking place within the galactic disks. However, three clusters have radial velocities that are inconsistent with being part of the rotating gas disks, which is surprising given their young (200-500Myr) ages. Interestingly, we find a stellar association with the same colors (V-I) near one of these three clusters, suggesting that the cluster and association were formed concurrently and have remained spatially correlated. We find evidence for spatially distributed cluster formation throughout the duration of the merger. The impact of various assumptions about the star/cluster formation rate on the interpretation of the cluster age distribution are explored, and we do not find evidence for long term "infant mortality" as has been previously suggested. Models of galaxy mergers that include a prescription for star formation can provide an overall good fit to the observed cluster age distribution.
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