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arXiv 2202.02157astro-ph.GA
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银河系冷核的化学探测

Chemical exploration of Galactic cold cores

Chenlin Zhou, Charlotte Vastel, Julien Montillaud, Cecilia Ceccarelli, Karine Demyk, Jorma Harju, Mika Juvela, Isabelle Ristorcelli, Tie Liu

备注：
26 pages, 13 figures, accepted in A&A in January 2022
发表信息：
A&A 658, A131 (2022)
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摘要：

一个太阳型系统从一个初始的分子核心开始，随着它的进化，它获得了有机的复杂性。可以研究的所谓星前核非常罕见，这阻碍了我们对有机化学如何形成和发展的理解。目标。我们从冷核目录中选择了最好的星前核心目标，这些目标代表了其环境的多样性，以探索其化学复杂性：1390（在Lambda Ori的压缩壳层中），869（在MBM 12云中）和4149（在加利福尼亚星云中）。我们获得了光谱调查的IRAM 30米望远镜，以探索分子的复杂性的核心。我们进行了辐射转移分析检测到的过渡，以放置一些约束的物理条件的核心和分子柱密度。我们还使用了分子离子的调查，估计宇宙射线电离率和S/H初始元素丰度使用气相化学模型，以重现其丰度。我们发现在分子的复杂性（氘，复杂的有机分子，硫，碳链和离子），并比较它们的化学性质与一个冷的核心和两个星前的核心有很大的差异。我们在三个核心中发现的化学多样性似乎与它们的化学演化有关：其中两个是星前（1390和4149），一个是早期（869）。环境的影响可能是有限的，因为冷核与周围环境有很强的屏蔽。高消光防止星际紫外线辐射深入核心。因此，需要对核心进行更高空间分辨率的观测，以限制核心的物理结构，以及更大规模的分子离子分布，以了解环境对其分子复杂性的影响。

英文摘要：

A solar-type system starts from an initial molecular core that acquires organic complexity as it evolves. The so-called prestellar cores that can be studied are rare, which has hampered our understanding of how organic chemistry sets in and grows. Aims. We selected the best prestellar core targets from the cold core catalogue that represent a diversity in terms of their environment to explore their chemical complexity: 1390 (in the compressed shell of Lambda Ori), 869 (in the MBM12 cloud), and 4149 (in the California nebula). We obtained a spectral survey with the IRAM 30 m telescope in order to explore the molecular complexity of the cores. We carried out a radiative transfer analysis of the detected transitions in order to place some constraints on the physical conditions of the cores and on the molecular column densities. We also used the molecular ions in the survey to estimate the cosmic-ray ionisation rate and the S/H initial elemental abundance using a gas-phase chemical model to reproduce their abundances. We found large differences in the molecular complexity (deuteration, complex organic molecules, sulphur, carbon chains, and ions) and compared their chemical properties with a cold core and two prestellar cores. The chemical diversity we found in the three cores seems to be correlated with their chemical evolution: two of them are prestellar (1390 and 4149), and one is in an earlier stage (869). The influence of the environment is likely limited because cold cores are strongly shielded from their surroundings. The high extinction prevents interstellar UV radiation from penetrating deeply into the cores. Higher spatial resolution observations of the cores are therefore needed to constrain the physical structure of the cores, as well as a larger-scale distribution of molecular ions to understand the influence of the environment on their molecular complexity.

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