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arXiv 1609.06540astro-ph.GA
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银河系高纬度分子中速云的全天普查

All-sky census of Galactic high-latitude molecular intermediate-velocity clouds

T. Röhser, J. Kerp, D. Lenz, B. Winkel

摘要:

银河系的HI晕云,特别是中速云(IVC),被认为与银河系的喷泉过程有关。观测喷泉云对于理解物质循环和吸积到银河系盘上的作用以及随后的恒星形成非常重要。在这里,我们量化了星系晕中分子气体的数量。我们专注于罕见的一类分子IVC(MIVC)和寻找新的对象。HI-FIR相关性在银河系纬度$|b|>20^\circ$的整个银河系南北半球进行了研究,以确定IVC中分子气体的数量和分布。我们使用了最新的大规模HI和FIR数据,Effelsberg Bonn-HI巡天,Parkes银河系全天巡天和Planck FIR巡天。我们提出了一个目录的239个MIVC候选人在银河系的南北半球。在这些候选者中,除了一个单一的源之外,所有先前已知的MIVC都被恢复。候选者的频率在银河系南北半球之间以及负LSR速度和正LSR速度之间存在显着差异。在我们的方法中,我们分析了当地的银河系环境。将我们的结果外推到整个银河系,原子和分子IVC气体到银河系的全球流入可能占维持当前银河系恒星形成速率所需的气体质量的主要部分。

英文摘要:

The HI halo clouds of the Milky Way, and in particular the intermediate-velocity clouds (IVCs), are thought to be connected to Galactic fountain processes. Observations of fountain clouds are important for understanding the role of matter recycling and accretion onto the Galactic disk and subsequent star formation. Here, we quantify the amount of molecular gas in the Galactic halo. We focus on the rare class of molecular IVCs (MIVCs) and search for new objects. The HI-FIR correlation was studied across the entire northern and southern Galactic hemispheres at Galactic latitudes $|b|>20^\circ$ to determine the amount and distribution of molecular gas in IVCs. We used the most recent large-scale HI and FIR data, the Effelsberg Bonn-HI Survey, the Parkes Galactic All-Sky Survey, and the Planck FIR surveys. We present a catalogue of 239 MIVC candidates on the northern and southern Galactic hemispheres. Among these candidates, all previously known MIVCs are recovered except for one single source. The frequency of candidates differs significantly between the northern and southern Galactic hemispheres and between negative and positive LSR velocities as well. In our approach we analyse the local Galactic environment. Extrapolating our results to the entire Galaxy, the global inflow of atomic and molecular IVC gas onto the Milky Way may account for the major fraction of the gaseous mass that is required to sustain the current Galactic star formation rate.

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