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arXiv 1208.0599astro-ph.GA
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G305恒星形成复合体:Herschel Hi-GAL发现的嵌入式大质量恒星形成

The G305 star-forming complex: Embedded Massive Star Formation Discovered by Herschel Hi-GAL

A. Faimali, M. A. Thompson, L. Hindson, J. S. Urquhart, M. Pestalozzi, S. Carey, S. Shenoy, M. Veneziani, S. Molinari, J. S. Clark

摘要:

我们利用银河平面的Hi-GAL巡天的PACS 70、160 μm和SPIRE 250、350和500 μm观测数据,对丰富的大质量恒星形成复合体G305进行了赫歇尔远红外研究。本研究的重点是确定嵌入在G305的大质量恒星形成人口,结合远红外数据与无线电连续谱,H2O脉泽,甲醇脉泽,MIPS,和红色MSX源调查数据从以前的研究。通过应用频率论技术,我们能够在我们的多波长数据集中识别最可能的关联的样本,然后可以从拟合的光谱能量分布(SED)获得的衍生属性中识别。SED建模使用一个简单的修改黑体和拟合到一个全面的网格模型SED,约16个候选协会被确定为嵌入式大规模恒星形成区域。我们从log(F70/F500)\geq 1和log(F160/F350)\geq 1.6的样本中推导出一个二选色准则,以识别另外31个没有相关恒星形成示踪物的嵌入式大质量恒星候选者。利用这一结果,我们可以绘制出该复合体现今恒星形成的图像,并通过外推初始质量函数,得出当前存在的年轻恒星天体(YSO)数量为\approx 2 \times 10^4,对应的恒星形成速率(SFR)为0.01-0.02 M \odot yr^-1。比较这个解决的恒星形成率,河外恒星形成率示踪剂(基于肯尼库特-施密特关系),我们发现恒星形成活动被低估的一个因素相比,来自YSO人口的SFR的\geq 2。

英文摘要:

We present a Herschel far-infrared study towards the rich massive star- forming complex G305, utilising PACS 70, 160 μm and SPIRE 250, 350, and 500 μm observations from the Hi-GAL survey of the Galactic plane. The focus of this study is to identify the embedded massive star-forming population within G305, by combining far-infrared data with radio continuum, H2O maser, methanol maser, MIPS, and Red MSX Source survey data available from previous studies. By applying a frequentist technique we are able to identify a sample of the most likely associations within our multi-wavelength dataset, that can then be identified from the derived properties obtained from fitted spectral energy distributions (SEDs). By SED modelling using both a simple modified blackbody and fitting to a comprehensive grid of model SEDs, some 16 candidate associations are identified as embedded massive star-forming regions. We derive a two-selection colour criterion from this sample of log(F70/F500)\geq 1 and log(F160/F350)\geq 1.6 to identify an additional 31 embedded massive star candidates with no associated star-formation tracers. Using this result we can build a picture of the present day star-formation of the complex, and by extrapolating an initial mass function, suggest a current population of \approx 2 \times 10^4 young stellar objects (YSOs) present, corresponding to a star formation rate (SFR) of 0.01-0.02 M\odot yr^-1. Comparing this resolved star formation rate, to extragalactic star formation rate tracers (based on the Kennicutt-Schmidt relation), we find the star formation activity is underestimated by a factor of \geq 2 in comparison to the SFR derived from the YSO population.

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