Tracing gas accretion in the Galactic center using isotopic ratios
Tracing gas accretion in the Galactic center using isotopic ratios
复制标题
使用同位素比率追踪银河系中心的气体吸积
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
L. Bronfman
中科院分区：
文献类型：
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作者：
D. Riquelme;M. A. Amo;J. Martín;R. Mauersberger;S. Martín;L. Bronfman
目标。我们研究了中心分子带盘和晕中的12 C/ 13 C同位素比值，以追踪银河系中心区域的气体吸积。方法.使用IRAM 30 m望远镜，我们观测到HCO +、H CN、HNC的J = 1−0转动跃迁及其13 C同位素取代，以测量12 C/ 13 C同位素比。我们观察了整个银河系中心区域的9个位置，包括高纬度的云，与禁止势相关的X1和X2轨道预计相交的位置，以及典型的银河系中心分子云。结果我们发现，在星系晕和X1轨道上，12 C/ 13 C同位素比率（>40）比银河系中心分子云（20-25）更高。我们的研究结果指出，分子气体已经经历了不同程度的核处理比观察到的气体朝向银河系内部中心区域。结论.高同位素比率与来自晕和银河系盘外围的气体吸积相一致。
Aims. We study the 12 C/ 13 C isotopic ratio in the disk of the central molecular zone and in the halo to trace gas accretion toward the Galactic center region in the Milky Way. Methods. Using the IRAM 30m telescope, we observed the J = 1−0 rotational transition of HCO + ,H CN, HNC, and their 13 C isotopic substitutions in order to measure the 12 C/ 13 C isotopic ratio. We observed 9 positions selected throughout the Galactic center region, including clouds at high latitude, locations where the X1 and X2 orbits associated with the barred potential are expected to intersect, and typical Galactic center molecular clouds. Results. We find a systematically higher 12 C/ 13 C isotopic ratio (>40) toward the halo and the X1 orbits than for the Galactic center molecular clouds (20–25). Our results point to molecular gas that has undergone a different degree of nuclear processing than observed in the gas towards the inner Galactic center region. Conclusions. The high isotopic ratios are consistent with the accretion of the gas from the halo and from the outskirts of the Galactic disk.