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arXiv 1901.07779astro-ph.GA
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中央分子带大质量分子云的恒星形成速率

Star Formation Rates of Massive Molecular Clouds in the Central Molecular Zone

Xing Lu, Qizhou Zhang, Jens Kauffmann, Thushara Pillai, Adam Ginsburg, Elisabeth A. C. Mills, J. M. Diederik Kruijssen, Steven N. Longmore, Cara Battersby, Hauy… 展开作者

Xing Lu, Qizhou Zhang, Jens Kauffmann, Thushara Pillai, Adam Ginsburg, Elisabeth A. C. Mills, J. M. Diederik Kruijssen, Steven N. Longmore, Cara Battersby, Hauyu Baobab Liu, Qiusheng Gu

摘要:

我们调查恒星形成在非常早期的演化阶段,在5个大规模的云内500 pc的银河系,中央分子区。利用干涉仪观测的H $_2$ O脉泽和超紧凑的H II区域,我们发现了正在进行的恒星形成的证据,嵌入在0.2 pc尺度和$\gtrsim$ 10 $^5$ cm $^{-3}$密度的核心。在这五个星云中,Sgr C在引力束缚和/或原恒星核心中拥有很高(9%)的气体质量,并且遵循从附近星云外推的致密($\gtrsim$ 10 $^4$ cm $^{-3}$)气体星形成关系。其他四个星云在引力束缚和/或原恒星核心中的质量不到1%,恒星形成率比致密气体恒星形成关系预测的低10倍。在这些核心的空间尺度上,恒星形成效率与银河系盘源相当。我们认为,在这些中央分子区云的整体不活跃的恒星形成可能是因为有少得多的气体被限制在引力约束的核心,这可能是由于在这个地区的强烈湍流和/或非常早期的演化阶段的云时,崩溃才刚刚开始。

英文摘要:

We investigate star formation at very early evolutionary phases in five massive clouds in the inner 500 pc of the Galaxy, the Central Molecular Zone. Using interferometer observations of H$_2$O masers and ultra-compact H II regions, we find evidence of ongoing star formation embedded in cores of 0.2 pc scales and $\gtrsim$10$^5$ cm$^{-3}$ densities. Among the five clouds, Sgr C possesses a high (9%) fraction of gas mass in gravitationally bound and/or protostellar cores, and follows the dense ($\gtrsim$10$^4$ cm$^{-3}$) gas star formation relation that is extrapolated from nearby clouds. The other four clouds have less than 1% of their cloud masses in gravitationally bound and/or protostellar cores, and star formation rates 10 times lower than predicted by the dense gas star formation relation. At the spatial scale of these cores, the star formation efficiency is comparable to that in Galactic disk sources. We suggest that the overall inactive star formation in these Central Molecular Zone clouds could be because there is much less gas confined in gravitationally bound cores, which may be a result of the strong turbulence in this region and/or the very early evolutionary stage of the clouds when collapse has only recently started.

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