[论文解读] The Galaxy Activity, Torus and Outflow Survey (GATOS) I. ALMA images of dusty molecular tori in Seyfert galaxies

S. García‐Burillo, A. Alonso‐Herrero+33 more|arXiv (Cornell University)|Apr 20, 2021

Astrophysics and Star Formation Studies参考文献 237被引用 5

一句话总结

本研究首次对10个邻近赛弗特星系中的尘埃分子环进行了高分辨率ALMA观测，结果表明这些环的取向与活动星系核喷流轴垂直，中位尺寸约为42 pc，质量约为6×10⁵ M☉。结果揭示了X射线吸收柱密度与分子气体柱密度之间存在强烈相关性，表明环是X射线遮蔽的主要来源，并提供了AGN反馈与高光度赛弗特星系中核区气体缺失及喷流之间关联的证据。

ABSTRACT

We present the first results of the Galaxy Activity, Torus and Outflow Survey (GATOS), a project aimed at understanding the properties of the dusty molecular tori and their connection to the host galaxy in nearby Seyfert galaxies. Our project expands the range of AGN luminosities and Eddington ratios covered by previous surveys of Seyferts conducted by ALMA and allows us to study the gas feeding and feedback cycle in a combined sample of 19 Seyferts. We used ALMA to obtain new images of the emission of molecular gas and dust using the CO(3-2) and HCO+(4-3) lines as well as their underlying continuum emission at 870 microns with high spatial resolutions (0.1'' ~ 7 - 13 pc) in the CND of 10 nearby (D < 28 Mpc) Seyfert galaxies. Our new ALMA observations detect 870 micron continuum and CO line emission from spatially resolved disks located around the AGN in all the sources. The bulk of the continuum flux can be accounted for by thermal emission from dust in the majority of the targets. For most of the sources the disks show a preponderant orientation perpendicular to the AGN wind axes, as expected for dusty molecular tori. The median diameters and molecular gas masses of the tori are ~ 42 pc, and ~ 6 x 10**5 Msun, respectively. We find a positive correlation between the line-of-sight gas column densities responsible for the absorption of X-rays and the molecular gas column densities derived from CO towards the AGN in our sources. The radial distributions of molecular gas in the CND of our combined sample show signs of nuclear-scale molecular gas deficits. We also detect molecular outflows in the sources that show the most extreme nuclear-scale gas deficits in our sample. These observations find for the first time supporting evidence that the imprint of AGN feedback is more extreme in higher luminosity and/or higher Eddington ratio Seyfert galaxies.

研究动机与目标

• 利用高分辨率ALMA观测研究邻近赛弗特星系中尘埃分子环的结构与取向。
• 确定环中分子气体柱密度与X射线吸收柱密度之间的关联，检验环在AGN遮蔽中的作用。
• 探讨赛弗特星系吸积盘中AGN反馈、核区气体缺失与分子喷流之间的关系。
• 扩展先前ALMA对分子环观测中所覆盖的AGN光度与爱丁顿比的动态范围。
• 评估环与大尺度星系盘之间存在错位时，对AGN反馈在核区效率的影响。

提出的方法

• 对10个邻近赛弗特星系（D < 28 Mpc）进行了870 μm连续谱及CO(3–2)、HCO⁺(4–3)谱线的高空间分辨率ALMA观测。
• 利用数据绘制了环核盘中分子气体与尘埃的空间分布、质量与运动学特征。
• 将尘埃连续谱发射建模为冷尘埃的热辐射，以估算环的质量与尺寸。
• 将X射线吸收柱密度与由CO谱线发射反演得到的分子气体柱密度进行比较，以评估遮蔽机制。
• 分析径向气体面密度分布以检测核尺度分子气体缺失。
• 通过CO与HCO⁺谱线的线型不对称性及高速发射特征识别喷流信号。

实验结果

研究问题

• RQ1 邻近赛弗特星系中尘埃分子环的空间结构与取向如何？它们与AGN喷流轴的对齐关系如何？
• RQ2 环中分子气体柱密度在赛弗特星系观测到的X射线遮蔽中贡献程度如何？
• RQ3 核区气体缺失程度与环核区域分子喷流的存在之间是否存在相关性？
• RQ4 环的物理特性（如尺寸、质量与密度分层）在不同AGN光度与爱丁顿比下如何变化？
• RQ5 环与大尺度星系盘之间存在错位时，其在增强核区AGN反馈效率方面发挥何种作用？

主要发现

• 所有10个观测的赛弗特星系均显示出空间分辨的870 μm连续谱发射与CO谱线发射，证实了尘埃分子环的存在。
• 环的中位直径约为42 pc，中位分子气体质量约为6×10⁵ M☉，空间分辨率极高（约0.1弧秒，即7–13 pc）。
• 环主要与AGN喷流轴垂直取向，与AGN遮蔽的标准统一模型一致。
• 发现X射线吸收柱密度与由CO反演得到的分子气体柱密度之间存在强烈正相关性，且两者的中位值相近，表明环是X射线遮蔽的主要来源。
• 在气体动力学最极端的源中检测到核尺度分子气体缺失，且在这些系统中也观测到分子喷流，表明反馈与气体耗竭存在关联。
• CO/HCO⁺谱线强度比在样本中变化达数个数量级，表明环内存在显著的径向密度分层，内区密度更高。