arXiv 2108.058082021-08astro-ph.GA

不同的分子丝宽度作为吸积到丝上的示踪剂

Different molecular filament widths as tracers of accretion onto filaments

Gilberto C. Gómez, Catherine Walsh, Aina Palau

备注：: Accepted for publication in MNRAS
DOI：: 10.1093/mnras/stac912

摘要：

我们探讨如何密集的灯丝宽度，当使用不同的分子种类测量，可能会改变作为一个结果的气体吸积向灯丝。当一个气体团落入暗条时，它将经历不同的密度、温度和消光值。这种环境变化的速率会对不同分子的丰度产生不同的影响。因此，快速形成的分子将比缓慢形成的分子更好地反映气体包裹所经历的局部物理条件。由于这些差异取决于各自的时间尺度如何比较，不同的分子分布应该反映环境变化的速度，即，朝着细丝的增长率。我们发现，从C2 H，CO，CN，CS和C3 H2的随时间变化的丰度测量的细丝宽度，是最敏感的这种效果，是那些分子也呈现较宽的细丝宽度。相反，N_2H ~+、NH_3、H_2CO、HNC和CH_3OH等分子对吸积不太敏感，呈现最窄的丝条宽度。我们建议，不同示踪剂的细丝宽度的比率可能是一个有用的工具来估计到细丝上的吸积率。

英文摘要：

We explore how dense filament widths, when measured using different molecular species, may change as a consequence of gas accretion toward the filament. As a gas parcel falls into the filament, it will experience different density, temperature, and extinction values. The rate at which this environment changes will affect differently the abundance of different molecules. So, a molecule that forms quickly will better reflect the local physical conditions a gas parcel experiences than a slower-forming molecule. Since these differences depend on how the respective timescales compare, the different molecular distributions should reflect how rapidly the environment changes, i.e., the accretion rate toward the filament. We find that the filament widths measured from time-dependent abundances for C2H, CO, CN, CS, and C3H2, are sensitive the most to this effect, being those molecules the ones presenting also the wider filament widths. On the contrary, molecules such as N2H+, NH3, H2CO, HNC or CH3OH are not so sensitive to accretion and present the narrowest filament widths. We propose that ratios of filament widths for different tracers could be a useful tool to estimate the accretion rate onto the filament.

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