Title: Discovery of the 7-ring PAH Cyanocoronene (C$_{24}$H$_{11}$CN) in GOTHAM Observations of TMC-1 Show Chinese title

Title: GOTHAM对TMC-1观测中发现7环多环芳烃氰基冠烯（C$_{24}$H$_{11}$CN）

Abstract: We present the synthesis and laboratory rotational spectroscopy of the 7-ring polycyclic aromatic hydrocarbon (PAH) cyanocoronene (C$_{24}$H$_{11}$CN) using a laser-ablation assisted cavity-enhanced Fourier transform microwave spectrometer. A total of 71 transitions were measured and assigned between 6.8--10.6\,GHz. Using these assignments, we searched for emission from cyanocoronene in the GBT Observations of TMC-1: Hunting Aromatic Molecules (GOTHAM) project observations of the cold dark molecular cloud TMC-1 using the 100\,m Green Bank Telescope (GBT). We detect a number of individually resolved transitions in ultrasensitive X-band observations and perform a Markov Chain Monte Carlo analysis to derive best-fit parameters, including a total column density of $N(\mathrm{C}_{24}\mathrm{H}_{11}\mathrm{CN}) = 2.69^{+0.26}_{-0.23} \times 10^{12}\,\mathrm{cm}^{-2}$ at a temperature of $6.05^{+0.38}_{-0.37}\,$K. A spectral stacking and matched filtering analysis provides a robust 17.3$\,\sigma$ significance to the overall detection. The derived column density is comparable to that of cyano-substituted naphthalene, acenaphthylene, and pyrene, defying the trend of decreasing abundance with increasing molecular size and complexity found for carbon chains. We discuss the implications of the detection for our understanding of interstellar PAH chemistry and highlight major open questions and next steps. Show Chinese abstract

Abstract: 我们使用激光烧蚀辅助腔增强傅里叶变换微波光谱仪，合成了七环多环芳烃（PAH）氰基冠烯（C$_{24}$H$_{11}$CN）并进行了实验室旋转光谱学研究。 在6.8--10.6 GHz范围内测量并指认了71条跃迁。 利用这些指认，我们使用100米格林班克望远镜（GBT）对冷暗分子云TMC-1的GOTHAM项目观测数据进行了搜索，以寻找氰基冠烯的发射。 我们在超灵敏的X波段观测中检测到了若干个单独分辨的跃迁，并进行了马尔可夫链蒙特卡罗分析，以推导最佳拟合参数，包括温度为$6.05^{+0.38}_{-0.37}\,$K时的总柱密度为$N(\mathrm{C}_{24}\mathrm{H}_{11}\mathrm{CN}) = 2.69^{+0.26}_{-0.23} \times 10^{12}\,\mathrm{cm}^{-2}$。光谱叠加和匹配滤波分析为整体检测提供了17.3$\,\sigma$的显著性。 推导出的柱密度与氰基取代的萘、苊烯和芘相当，这与碳链中分子大小和复杂性增加导致丰度减少的趋势相悖。 我们讨论了该检测对星际PAH化学理解的影响，并强调了主要的开放问题和下一步工作。