L1544和IRAS 16293-2422中的碳链多样性：为SKAO的星化学路径开拓者研究
Carbon chain diversity in L1544 and IRAS 16293-2422: an astrochemical pathfinder study for the SKAO
AI总结：
研究通过观测L1544和IRAS 16293-2422发现长碳链物种，指出现有化学网络不完整，需补充离子-分子反应以解释观测结果。
摘要：
天体化学观测揭示了太阳类恒星形成早期阶段出乎意料的高化学复杂性，包括长碳链。这些物种的起源以及它们是否进一步生长，可能对行星系统的分子复杂性做出贡献，仍然是开放性问题。我们利用100米绿带望远镜对原星团L1544和原恒星系统IRAS 16293-2422进行了最近的观测。在L1544中，我们检测到几种复杂的碳bearing物种，包括C₂S、C₃S、C₃N、c-C₃H、C₄H和C₆H，补充了之前报告的氰基聚炔的发射。在IRAS 16293-2422中，我们检测到c-C₃H，并首次检测到HC₇N。得益于高光谱分辨率，我们细化了几个c-C₃H和C₆H过渡的静止频率。我们进行了辐射转移分析，突出两种来源之间的化学差异：IRAS 16293-2422的柱密度比L1544低10到100倍。我们进行了天体化学建模，使用最新的化学网络并修订了反应速率。模型再现了总体趋势，氰基聚炔和聚炔基团的丰度随着分子尺寸的增加而减少，但它们低估了比HC₅N更长的氰基聚炔的丰度，最多低估两个数量级。当前模型，包括主导的中性-中性形成途径，无法解释这一差异，表明化学网络不完整。我们提出，额外的离子-分子反应对于这些物种的形成至关重要。发展更全面的长碳链化学网络对于准确解释当前和未来的观测至关重要。
英文摘要：
Astrochemical observations have revealed a surprisingly high level of chemical complexity, including long carbon chains, in the earliest stages of Sun-like star formation. The origin of these species and whether they undergo further growth, possibly contributing to the molecular complexity of planetary systems, remain open questions. We present recent observations performed using the 100-m Green Bank Telescope of the prestellar core L1544 and the protostellar system IRAS 16293-2422. In L1544, we detected several complex carbon-bearing species, including $\mathrm{C_2S}$, $\mathrm{C_3S}$, $\mathrm{C_3N}$, $\mathrm{c\text{-}C_3H}$, $\mathrm{C_4H}$, and $\mathrm{C_6H}$, complementing previously reported emission of cyanopolyynes. In IRAS 16293-2422, we detected $\mathrm{c\text{-}C_3H}$ and, for the first time, $\mathrm{HC_7N}$. Thanks to the high spectral resolution, we refine the rest frequencies of several $\mathrm{c\text{-}C_3H}$ and $\mathrm{C_6H}$ transitions. We perform radiative transfer analysis, highlighting a chemical difference between the two sources: IRAS 16293-2422 shows column densities 10-100 times lower than L1544. We perform astrochemical modeling, employing an up-to-date chemical network with revised reaction rates. The models reproduce the general trends, with cyanopolyyne and polyynyl radical abundances decreasing as molecular size increases, but they underestimate the abundances of cyanopolyynes longer than $\mathrm{HC_5N}$ by up to two orders of magnitude. Current models, which include the dominant neutral-neutral formation routes, cannot account for this discrepancy, suggesting that the chemical network is incomplete. We propose that additional ion-molecule reactions are crucial for the formation of these species. Developing a more comprehensive chemical network for long carbon chains is essential for accurately interpreting present and future observations.
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