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arXiv 1612.00697astro-ph.SRastro-ph.GA
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年轻星系团Stock 8中的低质量星族：恒星性质和初始质量函数

The low-mass population in the young cluster Stock 8: Stellar properties and Initial Mass Function

Jessy Jose, Gregory J. Herczeg, Manash R. Samal, Qiliang Fang, Neelam Panwar

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Accepted for publication in ApJ
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摘要：

HII区域/超壳层的演化可以在其外围触发新一代的恒星/星团，环境条件可能会影响初始质量函数，盘演化和恒星形成效率。在本文中，我们研究了年轻星团Stock 8中的恒星含量和恒星形成过程，该星团本身被认为是在超壳层膨胀过程中形成的。我们介绍了深光学测光以及UKIDSS和Spitzer-IRAC的JHK和3.6，4.5 μm测光。我们使用多色标准来识别该地区的候选年轻恒星对象。使用进化模型，我们得到一个中位数日志（年龄）的~6.5（~3.0百万年）与观察到的年龄分布的~0.25德克斯集群。根据对光度不确定性、微分红化、二值性和变异性的估计，对种群8的蒙特卡罗模拟表明，这些不确定性引入了约0.15 dex的年龄分布。集群中的固有年龄分布约为0.2 dex。年轻的恒星天体被盘包围的比例约为35%。Stock 8的K波段光度函数类似于梯形星团。库存8的IMF在>0.5 Msun处具有类似萨尔彼得的斜率，并且IMF在~0.4 Msun处具有峰值，低于该峰值下降到亚恒星区域。虽然Stock 8被几颗大质量恒星包围，但由于星团周围的大质量恒星非常接近，因此似乎没有严重的IMF环境效应。

英文摘要：

The evolution of HII regions/supershells can trigger a new generation of stars/clusters at their peripheries, with environmental conditions that may affect the initial mass function, disk evolution and star formation efficiency. In this paper we study the stellar content and star formation processes in the young cluster Stock 8, which itself is thought to be formed during the expansion of a supershell. We present deep optical photometry along with JHK and 3.6, 4.5 μm photometry from UKIDSS and Spitzer-IRAC. We use multi-color criteria to identify the candidate young stellar objects in the region. Using evolutionary models, we obtain a median log(age) of ~6.5 (~3.0 Myr) with an observed age spread of ~0.25 dex for the cluster. Monte Carlo simulations of the population of Stock 8, based on estimates for the photometric uncertainty, differential reddening, binarity, and variability, indicate that these uncertainties introduce an age spread of ~0.15 dex. The intrinsic age spread in the cluster is ~0.2 dex. The fraction of young stellar objects surrounded by disk is ~35%. The K-band luminosity function of Stock 8 is similar to that of the Trapezium cluster. The IMF of Stock 8 has a Salpeter- like slope at >0.5 Msun and the IMF flattens and peaks at ~0.4 Msun, below which declines into the substellar regime. Although Stock 8 is surrounded by several massive stars, there seems to be no severe environmental effect in the form of IMF due to the proximity of massive stars around the cluster.

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