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arXiv 0905.0723astro-ph.GA
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银河系环巡天中确定的分子云运动学距离

Kinematic Distances to Molecular Clouds identified in the Galactic Ring Survey

Julia Roman-Duval, James M. Jackson, Mark Heyer, Alexis Johnson, Jill Rathborne, Ronak Shah, Robert Simon

摘要:

假设银河系的克莱门斯自转曲线,推导了13 CO J=1-0波士顿大学-五学院射电天文台银河系环巡天(BU-FCRAO GRS)中发现的750个分子云的运动学距离。运动学距离的模糊性是通过检查HI自吸收的存在下,对每个云的13 CO发射峰使用甚大阵银河平面调查(VGPS)解决。我们还确定了21厘米的连续源嵌入在GRS云,以使用HI 21厘米连续吸收功能,以区分近和远的运动距离。银河系中GRS云的分布与银河系的四臂模型一致。由GRS云追踪到的盾牌-十字架和英仙座臂的位置与银河遗产红外线中面巡天(GLIMPSE)的恒星计数数据相匹配。我们的结论是,分子云必须形成在旋臂中,并且是短暂的(寿命<1000万年),以解释在旋臂间空间中没有大质量的13 CO明亮分子云。

英文摘要:

Kinematic distances to 750 molecular clouds identified in the 13CO J=1-0 Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey (BU-FCRAO GRS) are derived assuming the Clemens rotation curve of the Galaxy. The kinematic distance ambiguity is resolved by examining the presence of HI self-absorption toward the 13CO emission peak of each cloud using the Very Large Array Galactic Plane Survey (VGPS). We also identify 21 cm continuum sources embedded in the GRS clouds in order to use absorption features in the HI 21 cm continuum to distinguish between near and far kinematic distances. The Galactic distribution of GRS clouds is consistent with a four-arm model of the Milky Way. The locations of the Scutum-Crux and Perseus arms traced by GRS clouds match star count data from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) star-count data. We conclude that molecular clouds must form in spiral arms and be short-lived (lifetimes < 10 Myr) in order to explain the absence of massive, 13CO bright molecular clouds in the inter-arm space.

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