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arXiv 0906.2006astro-ph.GA
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M82星团人口的光谱普查

A spectroscopic census of the M82 stellar cluster population

I. S. Konstantopoulos, N. Bastian, L. J. Smith, M. S. Westmoquette, G. Trancho, J. S. Gallagher

摘要:

我们提出了一个光谱研究的星团人口的M82,原型星暴星系,主要是基于新的双子座北多目标光谱的49个星团。这些观测结果构成了迄今为止最大的河外年轻星团光谱数据集,几乎连续覆盖整个星系;我们使用这些数据来推断有关星团以及M82后星爆盘和核星爆环境的信息。光谱测年法将星团的核和盘的年龄定位在(7,15)和(30,270)Myr之间,分布峰值分别在~10和~140 Myr。我们发现星系团的径向速度在(-160,220)km/s(wrt的星系中心)和视线Na I D星际吸收线速度在(-75,200)km/s,在许多情况下完全脱离了星系团。由于盘簇径向速度位于星系旋转曲线的平坦部分,我们得出结论,它们包括一个规则的轨道系统。我们的观察表明,大部分的人口是由于近距离接触M81 ~ 2.2亿年前。在棒上的固体旋转中发现了原子核中的团簇。可能检测到的WR功能在其光谱表明,团簇形成继续在中央星爆区。我们还报告了在M82晕中可能发现的两个年龄大于8 Gyr的古老星团。使用这些测量和简单的动力学考虑,我们得出了一个玩具模型的无形的物理结构的星系,并确认存在两个占主导地位的螺旋臂。

英文摘要:

We present a spectroscopic study of the stellar cluster population of M82, the archetype starburst galaxy, based primarily on new Gemini-North multi-object spectroscopy of 49 star clusters. These observations constitute the largest to date spectroscopic dataset of extragalactic young clusters, giving virtually continuous coverage across the galaxy; we use these data to deduce information about the clusters as well as the M82 post-starburst disk and nuclear starburst environments. Spectroscopic age-dating places clusters in the nucleus and disk between (7, 15) and (30, 270) Myr, with distribution peaks at ~10 and ~140 Myr respectively. We find cluster radial velocities in the range (-160, 220) km/s (wrt the galaxy centre) and line of sight Na I D interstellar absorption line velocities in (-75, 200) km/s, in many cases entirely decoupled from the clusters. As the disk cluster radial velocities lie on the flat part of the galaxy rotation curve, we conclude that they comprise a regularly orbiting system. Our observations suggest that the largest part of the population was created as a result of the close encounter with M81 ~220 Myr ago. Clusters in the nucleus are found in solid body rotation on the bar. The possible detection of WR features in their spectra indicates that cluster formation continues in the central starburst zone. We also report the potential discovery of two old populous clusters in the halo of M82, aged >8 Gyr. Using these measurements and simple dynamical considerations, we derive a toy model for the invisible physical structure of the galaxy, and confirm the existence of two dominant spiral arms.

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