Title: Hydrodynamic simulations of the Disc of Gas Around Supermassive black holes (HDGAS) -II; The transition from neutral atomic to molecular gas phases Show Chinese title

Title: 超大质量黑洞周围气体盘 (HDGAS) 的流体动力学模拟 - II；从中性原子到分子气体相的转变

Abstract: We use HDGAS hydrodynamic simulations to study the impact of active galactic nucleus (AGN) feedback on the conversion of atomic-gas to molecular-gas within the circumnuclear-disc (CND) of a typical AGN-dominated galaxy. The comparison of CI, CII, and CO line intensities and their ratios in the HDGAS post-processing radiative-transfer analysis reveals the complex interplay between AGN-activity, cold molecular gas properties, and the physical processes governing the evolution of star-formation in galaxies. Our results demonstrate that the CI/CO intensity ratio serves as a reliable indicator of the atomic-to-molecular gas transition. We present the probability distribution function (PDF) and abundance trends of various metal species related to molecular H$2$ gas, highlighting differences in clumpiness and intensity maps between AGN feedback and NoAGN models. The profile of the integrated intensity (moment-0) maps shows that the AGN-feedback model exhibits a lower CI/CO intensity ratio in the vicinity of the supermassive black hole (< 50 pc), indicating a smaller atomic-gas abundance and the presence of positive AGN-feedback. Our simulations have successfully predicted the presence of faint-CO emissions extending to larger radii from the galactic center. We also explore the relationships between CII/CO and CI/CII intensity ratios, as well as the ratios versus CO intensity, which provides insights into the "CO-dark" issues. One notable feature in the later time-scale of the AGN model is the presence of a "CO-dark" region, where the intensity of CO emission ($\rm I_{CO}$) is depleted relative to the H$_2$ column density ($N_{\rm H_2}$) compared to the NoAGN model. Show Chinese abstract

Abstract: 我们利用HDGAS流体动力学模拟研究了活动星系核（AGN）反馈对典型AGN主导星系核区盘（CND）中原子气体向分子气体转化的影响。 通过HDGAS后处理辐射转移分析比较CI、CII和CO线的强度及其比值，揭示了AGN活动、冷分子气体属性以及决定星系恒星形成演化的物理过程之间的复杂相互作用。 我们的结果显示CI/CO强度比是一个可靠的原子气体向分子气体转变的指示器。 我们展示了与分子H$2$气体相关的各种金属元素的概率分布函数（PDF）和丰度趋势，突出了AGN反馈模型与无AGN模型在团块性和强度图谱上的差异。 积分强度（零阶矩）图的轮廓显示，在超大质量黑洞附近（< 50 pc），AGN反馈模型具有较低的CI/CO强度比，表明较小的原子气体丰度以及正AGN反馈的存在。 我们的模拟成功预测了从星系中心延伸到更大半径的微弱CO发射的存在。 我们还探讨了CII/CO和CI/CII强度比以及这些比值与CO强度的关系，这为我们提供了关于“CO暗区”问题的见解。 AGN模型后期时间尺度的一个显著特征是存在一个“CO暗区”，与无AGN模型相比，该区域的CO发射强度（$\rm I_{CO}$）相对于H$_2$柱密度（$N_{\rm H_2}$）有所减少。