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arXiv 1106.2801astro-ph.SRastro-ph.GA
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剑鱼座30的恒星形成

Star formation in 30 Doradus

Guido De Marchi, Francesco Paresce, Nino Panagia, Giacomo Beccari, Loredana Spezzi, Marco Sirianni, Morten Andersen, Max Mutchler, Bruce Balick, Michael A. Dopi… 展开作者

Guido De Marchi, Francesco Paresce, Nino Panagia, Giacomo Beccari, Loredana Spezzi, Marco Sirianni, Morten Andersen, Max Mutchler, Bruce Balick, Michael A. Dopita, Jay A. Frogel, Bradley C. Whitmore, Howard Bond, Daniela Clazetti, C. Marcella Carollo, Michael J. Disney, Donald N. B. Hall, Jon A. Holtzman, Randy A. Kimble, Patrick J. McCarthy, Robert W. O'Connell, Abhijit Saha, Joseph I. Silk, John T. Trauger, Alistair R. Walker, Rogier A. Windhorst, Erick T. Young

摘要:

利用哈勃空间望远镜(HST)上的WFC-3观测资料,研究了大麦云星云(30 Dor)中心区域的恒星星族性质。观测清楚地揭示了整个领域存在相当大的差异灭绝。我们使用年轻的大质量主序星来计算和量化这种效应,以获得该领域中大多数物体的统计红化校正。然后,我们通过寻找具有强(> 4 sigma)Halpha过量发射的天体来寻找前主序星(PMS),并在整个视场中找到了大约1150颗。将它们在赫罗图中的位置与理论上PMS演化轨迹相比较,发现这些天体中约有三分之一的年龄小于400万年,与中央电离星团R136中的大质量恒星的年龄一致,而其余的年龄可达3000万年,中位年龄约为1200万年。这表明恒星的形成已经持续了很长一段时间,尽管我们无法区分一个长时间的插曲和一系列短暂而频繁的爆发,这些爆发在时间上无法解决。虽然年轻的PMS人口优先占据集群的中心区域,但较老的PMS对象在整个领域中分布更均匀,并且在集群的中心非常少。我们把后一种效应归因于由R136的大量电离成员引起的较老的星周盘的光蒸发。

英文摘要:

Using observations obtained with the Wide Field Camera 3 (WFC3) on board the Hubble Space Telescope (HST), we have studied the properties of the stellar populations in the central regions of 30 Dor, in the Large Magellanic Cloud. The observations clearly reveal the presence of considerable differential extinction across the field. We characterise and quantify this effect using young massive main sequence stars to derive a statistical reddening correction for most objects in the field. We then search for pre-main sequence (PMS) stars by looking for objects with a strong (> 4 sigma) Halpha excess emission and find about 1150 of them over the entire field. Comparison of their location in the Hertzsprung-Russell diagram with theoretical PMS evolutionary tracks for the appropriate metallicity reveals that about one third of these objects are younger than ~4Myr, compatible with the age of the massive stars in the central ionising cluster R136, whereas the rest have ages up to ~30Myr, with a median age of ~12Myr. This indicates that star formation has proceeded over an extended period of time, although we cannot discriminate between an extended episode and a series of short and frequent bursts that are not resolved in time. While the younger PMS population preferentially occupies the central regions of the cluster, older PMS objects are more uniformly distributed across the field and are remarkably few at the very centre of the cluster. We attribute this latter effect to photoevaporation of the older circumstellar discs caused by the massive ionising members of R136.

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