利用河外水超脉泽研究低质量星系的M-sigma关系和低光度活动星系核的反馈

The extragalactic water megamasers with a rest frequency of 22.235 GHz are often found in the nuclei of the Seyfert 2 galaxies and the LINERs with a distance less than 1pc from the central black hole. Thus, they are powerful tools to explore the central black holes and their vicinity. In this project, we will observe extragalactic water megamasers of all kinds of excitation mechanisms, using very long baseline interferometry (VLBI) with an extremely high angular resolution. On the one hand, we will measure the masses of central black holes accurately with masers associated with accretion disks, thus study the M-sigma relation at its low-mass end quantitatively and study the relation between black hole mass and spatial distribution of masers tentatively. The understanding of the co-evolution of the central black holes, the bulges and the accretion disks of the low-mass galaxies (and also the low-luminosity AGNs) will be intensified with our studies. On the other hand, we will also use masers associated with jets and outflows, or with multiple excitation mechanisms to study the interaction between jet / outflow and interstellar media in the nuclear region of the host galaxies. The understanding of the feedback of low-luminosity AGNs to the host galaxies and the intrinsic properties of low-luminosity AGNs will be enriched with our studies. With a reliable source of data, effective and feasible methods, and necessary international cooperation, our project will be completed successfully.

静止频率为22.235GHz的河外水超脉泽通常分布于赛弗特2型星系和低电离发射区，距离中心黑洞1pc左右的区域，是探测其中心黑洞及邻近区域性质的有力工具。本项目旨在利用超高角分辨率的甚长基线干涉技术对各类河外水超脉泽进行观测研究：一方面，利用与吸积盘成协的脉泽精确测定中心黑洞质量，从而定量深入研究M-sigma等关系在低质量端的性质，并探索性研究中心黑洞质量与脉泽空间分布的关系，从而深化对以脉泽星系为代表的低质量星系（同时也是低光度活动星系核）的中心黑洞与核球，吸积盘共同演化过程的认识；另一方面，利用过去被关注较少的与喷流/外流成协的脉泽和包含多种激发机制的复杂脉泽，定量研究喷流/外流与星系核区星际介质的相互作用，深化对“低光度活动星系核对寄主星系反馈过程”的认识，丰富对低光度活动星系核本身性质的认识。本项目具备可靠的观测数据来源，有效可行的分析方法，必要的国际合作，并已经取得阶段性成果。

在项目执行期间，项目负责人将研究重点放在利用脉泽定量研究喷流/外流与核区 ISM 的相互作用和低光度活动星系核对寄主星系的反馈上，并取得了相当的进展：精确测得了NGC3079中心由黑洞吸积活动而产生的射电成分的自行速度和光变，验证了该星系中的低光度活动星系核与介质存在激烈的相互作用；首次测到由星爆活动所激发的射电成分相对星系中心（以及整个水脉泽系统）的亚相对论运动，证实了星系核心的星爆活动与外流的激发存在直接关系。相关论文已经写作完成，目前在与合作者讨论阶段，有待发表。其他低光度活动星系核喷流激发区域的形态与物理性质，及其与介质的相互作用的论文已发表。这些成果可广泛应用于以塞弗特星系为代表的低光度活动星系核中，对于活动星系核性质与演化的研究具有相当的学术价值。