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arXiv 1311.2736astro-ph.GA
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关于Hi-GAL场中稠密团簇的质量函数的形状。II。用贝叶斯推断研究团块质量函数

On the shape of the mass-function of dense clumps in the Hi-GAL fields. II. Using Bayesian inference to study the clump mass function

L. Olmi, D. Angles-Alcazar, D. Elia, S. Molinari, M. Pestalozzi, S. Pezzuto, E. Schisano, L. Testi, M. Thompson

摘要:

上下文恒星形成于密集的尘埃分子云中,但人们对它们的起源、演化和详细的物理性质知之甚少。特别是,这些团块的质量分布(也称为“团块质量函数”或CMF)和恒星初始质量函数(IMF)之间的关系仍然知之甚少。目标。为了更好地了解CMF如何向IMF演化,并辨别CMF的“真实”形状,需要大量真实的前恒星和原恒星团块样本。本文介绍了赫歇尔红外银道面巡天(Hi-GAL)中获得的两个这样的数据集。需要稳健的统计方法来推断描述用于拟合CMF的模型的参数,并比较竞争模型本身。方法.在本文中,我们应用贝叶斯推断的分析CMF的两个地区讨论的文件I。首先,我们确定每个拟合参数的贝叶斯后验概率分布。然后,我们进行了定量比较的模型来拟合CMF。结果我们比较了几种实现贝叶斯推断的方法的结果,我们还分析了先验的选择和各种约束条件对参数优选值的统计结论的影响。我们发现,参数估计和模型比较依赖于参数先验的选择。结论.我们的研究结果证实了我们先前的结论,即这里研究的两个Hi-GAL区域的CMF具有非常相似的形状,但质量尺度不同。此外,对数正态模型似乎可以更好地描述在这里研究的两个Hi-GAL区域测量的CMF。然而,这一初步结论依赖于参数先验的选择。

英文摘要:

Context. Stars form in dense, dusty clumps of molecular clouds, but little is known about their origin, their evolution and their detailed physical properties. In particular, the relationship between the mass distribution of these clumps (also known as the "clump mass function", or CMF) and the stellar initial mass function (IMF), is still poorly understood. Aims. In order to better understand how the CMF evolve toward the IMF, and to discern the "true" shape of the CMF, large samples of bona-fide pre- and proto-stellar clumps are required. Two such datasets obtained from the Herschel infrared GALactic Plane Survey (Hi-GAL) have been described in paper I. Robust statistical methods are needed in order to infer the parameters describing the models used to fit the CMF, and to compare the competing models themselves. Methods. In this paper we apply Bayesian inference to the analysis of the CMF of the two regions discussed in Paper I. First, we determine the Bayesian posterior probability distribution for each of the fitted parameters. Then, we carry out a quantitative comparison of the models used to fit the CMF. Results. We have compared the results from several methods implementing Bayesian inference, and we have also analyzed the impact of the choice of priors and the influence of various constraints on the statistical conclusions for the preferred values of the parameters. We find that both parameter estimation and model comparison depend on the choice of parameter priors. Conclusions. Our results confirm our earlier conclusion that the CMFs of the two Hi-GAL regions studied here have very similar shapes but different mass scales. Furthermore, the lognormal model appears to better describe the CMF measured in the two Hi-GAL regions studied here. However, this preliminary conclusion is dependent on the choice of parameters priors.

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