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arXiv 1507.05095astro-ph.GA
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三毫米终极Mopra Milky Way调查。I.调查概述、初始数据发布和初步结果

The Three-mm Ultimate Mopra Milky Way Survey. I. Survey Overview, Initial Data Releases, and First Results

Peter J. Barnes, Erik Muller, Balthasar Indermuehle, Stefan N. O'Dougherty, Vicki Lowe, Maria R. Cunningham, Audra K. Hernandez, Gary A. Fuller

摘要:

我们描述了一个新的毫米波分子线测绘调查的南银道面和它的第一个数据发布。3毫米终极莫普拉银河系巡天(ThrUMMS)使用快速测绘技术与莫普拉射电望远镜的组合,同时在112 GHz附近的$^{12}$ CO,$^{13}$ CO,C $^{18}$ O和CN的J = 1 - 0线上以~角分和~0.3 km s $^{-1}$分辨率绘制了我们银河系第四象限的60 ° x2 °扇区,对于$^{12}$ CO具有~2 K通道$^{-1}$灵敏度,对于其它跃迁具有~1 K通道$^{-1}$。从这些观测中获得的校准数据立方体在通过我们的管道处理后可供社区使用。在这里,我们描述了ThrUMMS的动机,新的观测技术的发展Mopra,以及如何优化这些技术的调查目标。我们展示了一些样本数据产品,并描述了第一个科学结果的CO同位素线比。这些在银河平面上变化很大,表明光学深度和激发条件的范围很广,从温暖和半透明到寒冷和不透明。特别是冷云的总体具有$^{12}$ CO容易超过100的光学深度。我们从$^{12}$ CO积分强度到柱密度推导出一个新的非线性转换定律,这表明在银河系盘中CO追踪的分子质量可能被大大低估了。这进一步表明,盘星系中的一些全球关系,如恒星形成定律,可能需要重新校准。大型ThrUMMS团队正在进行其他几项科学调查。

英文摘要:

We describe a new mm-wave molecular-line mapping survey of the southern Galactic Plane and its first data releases. The Three-mm Ultimate Mopra Milky Way Survey (ThrUMMS) maps a 60°x2° sector of our Galaxy's fourth quadrant, using a combination of fast mapping techniques with the Mopra radio telescope, simultaneously in the J=1-0 lines of $^{12}$CO, $^{13}$CO, C$^{18}$O, and CN near 112 GHz at ~arcminute and ~0.3 km s$^{-1}$ resolution, with ~2 K channel$^{-1}$ sensitivity for $^{12}$CO and ~1 K channel$^{-1}$ for the other transitions. The calibrated data cubes from these observations are made available to the community after processing through our pipeline. Here, we describe the motivation for ThrUMMS, the development of new observing techniques for Mopra, and how these techniques were optimised to the objectives of the survey. We showcase some sample data products and describe the first science results on CO-isotopologue line ratios. These vary dramatically across the Galactic Plane, indicating a very wide range of optical depth and excitation conditions, from warm and translucent to cold and opaque. The population of cold clouds in particular have optical depths for $^{12}$CO easily exceeding 100. We derive a new, nonlinear conversion law from $^{12}$CO integrated intensity to column density, which suggests that the molecular mass traced by CO in the Galactic disk may have been substantially underestimated. This further suggests that some global relationships in disk galaxies, such as star formation laws, may need to be recalibrated. The large ThrUMMS team is proceeding with several other science investigations.

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