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arXiv 2210.12980astro-ph.GA
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生活在中央分子带的边缘:G1是气体吸积到CMZ中的更可能的候选者

Living on the edge of the Central Molecular Zone: G1.3 is the more likely candidate for gas accretion into the CMZ

Laura A. Busch, Denise Riquelme, Rolf Güsten, Karl M. Menten, Thushara G. S. Pillai, Jens Kauffmann

摘要:

我们银河系中央分子带(CMZ)的1.3度(G1.3)和1.6度(G1.6)云复合体被认为可能位于X1和X2轨道的交叉区域,原因有几个。这包括探测同空间低速和高速云、高速色散、激波示踪分子的高分数分子丰度以及高于通常CMZ云的动力学温度。我们用IRAM 30 m和APEX 12 m望远镜在85 - 475 GHz频率范围内绘制了这两个云复合体的分子谱线。G1.3的运动学结构揭示了一个连接低速(~ 100 km/s)和高速(~ 180 km/s)气体的中等速度(~ 150 km/s)的“排放桥”和一个整体蓬松的壳状结构。这些可能代表了云-云相互作用的观测证据。G1.6中的低速和高速气体成分没有显示出这种相互作用的证据,这表明它们在空间上是分离的。我们在每个云复合体中选择了三个位置进行进一步分析。基于对CH_3CN系综的非LTE模型,我们推导出两种配合物的动力学温度为60- 100 K,H_2体积密度为10 $^4$ -10 $^5$ cm ~(-3)。相对于H2的分子丰度表明这两种云的化学性质相似,而且与其他GC云相似。我们的结论是,G1.3可能确实表现出云-云相互作用的迹象。我们提出了一个相互作用的气体是吸积从近侧尘埃带的CMZ,与气体预先存在于这个位置。G1.6中的低速和高速分量是相当巧合地沿着同一视线观察到的。它们可能与来自远侧尘埃线的过冲减速气体或实际的CMZ气体和在尘埃带上移动的高速气体有关。这些情景将与数值模拟相一致。

英文摘要:

The 1.3deg (G1.3) and 1.6deg (G1.6) cloud complexes in the Central Molecular Zone (CMZ) of our Galaxy have been proposed to possibly reside at the intersection region of the X1 and X2 orbits for several reasons. This includes the detection of co-spatial low- and high-velocity clouds, high velocity dispersion, high fractional molecular abundances of shock-tracing molecules, and kinetic temperatures that are higher than for usual CMZ clouds. We mapped both cloud complexes in molecular lines in the frequency range from 85 to 475GHz with the IRAM 30m and the APEX 12m telescopes. The kinematic structure of G1.3 reveals an `emission bridge' at intermediate velocities (~150km/s) connecting low-velocity (~100km/s) and high-velocity (~180km/s) gas and an overall fluffy shell-like structure. These may represent observational evidence of cloud-cloud interactions. Low- and high-velocity gas components in G1.6 do not show such evidence of interaction, suggesting that they are spatially separated. We selected three positions in each cloud complex for further analysis. Based on non-LTE modelling of an ensemble of CH3CN lines, we derived kinetic temperatures of 60-100K and H2 volume densities of 10$^4$-10$^5$cm-3 in both complexes. Molecular abundances relative to H2 suggest a similar chemistry of the two clouds, which is moreover similar to that of other GC clouds. We conclude that G1.3 may indeed exhibit signs of cloud-cloud interactions. We propose an interaction of gas that is accreted from the near-side dust lane to the CMZ, with gas pre-existing at this location. Low- and high-velocity components in G1.6 are rather coincidentally observed along the same line of sight. They may be associated with either overshot decelerated gas from the far-side dust line or actual CMZ gas and high-velocity gas moving on a dust lane. These scenarios would be in agreement with numerical simulations.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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