[论文解读] AGN-driven winds on all scales in Markarian 231: from hot nuclear ultra-fast up to kpc-extended molecular outflow

C. Feruglio, F. Fiore+10 more|arXiv (Cornell University)|Mar 4, 2015

Astrophysics and Star Formation Studies参考文献 3被引用 6

一句话总结

本研究展示了Mrk 231中分子盘和喷流的高分辨率图谱，揭示了一道kpc尺度的双锥形分子喷流，其动能速率约为~7–10×10⁴³ erg/s，以及一处位于~-20,000 km/s的核区超快喷流（UFO）。UFO的动能速率与大尺度喷流相匹配，强烈支持活动星系核吸积能量通过能量守恒膨胀驱动大规模喷流的机制。

ABSTRACT

We present the best sensitivity and angular resolution maps of the molecular disk and outflow of Mrk231, obtained with IRAM/PdBI, and an analysis of archival Chandra and NuSTAR data. We constrain the physical properties of both the molecular disk and outflow, the presence of a highly-ionized ultra-fast nuclear wind, and their connection. The CO(2-1) outflow has a size of ~1 kpc, and extends in all directions around the nucleus, being more prominent along the south-west to north-east direction, suggesting a wide-angle biconical geometry. Its maximum projected velocity is nearly constant out to ~1 kpc, thus implying that the density of the outflowing material must decrease from the nucleus outwards as ~ r^-2. This suggests that either a large part of the gas leaves the flow during its expansion, or that the bulk of the outflow has not yet reached ~1 kpc, implying a limit on its age of ~ 1 Myr. The mass and energy rates of the molecular outflow are dM/dt(OF)=[500-1000] Msun/yr and dE(kin,OF)/dt=[7-10] 10^43 erg/s, its total kinetic energy is E(kin,OF)>~E(disk). Remarkably, our analysis reveals a nuclear ultra-fast outflow (UFO) with velocity ~-20000 km/s, dM(UFO)/dt=0.3-1.6 MSun/yr, and momentum load dP(UFO)/dt/(Lbol/c)=0.25-1.2. We find dE(kin,UFO)/dt~dE(kin,OF)/dt as predicted for outflows undergoing an energy conserving expansion. This suggests that most of the UFO kinetic energy is transferred to mechanical energy of the kpc-scale outflow, strongly supporting that the energy released during accretion of matter onto super-massive black holes is the ultimate driver of giant massive outflows.The momentum flux dP(OF)/dt derived for the large scale outflows in Mrk 231 enables us to estimate a momentum boost dP(OF)/dP(UFO)~ 30-50. The ratios dE(kin, UFO)/dt/L(bol,AGN) = 0.8-4% and dE(kin,OF)/dt/L(bol,AGN) = 1-3% agree with the requirements of the most popular models of AGN feedback.

研究动机与目标

• 利用高灵敏度、高角分辨率观测，约束Mrk 231中分子盘和喷流的物理特性。
• 调查活动星系核中心区域是否存在高度电离的超快核区风（UFO）及其性质。
• 确定核区UFO与kpc尺度分子喷流之间的关联，特别是能量与动量传递机制。
• 评估观测到的能量与动量速率是否与活动星系核反馈模型预测一致。
• 基于其空间与运动学结构，估算喷流的年龄与质量损失历史。

提出的方法

• 利用IRAM/PdBI干涉仪获取Mrk 231中分子盘和喷流的高灵敏度、高角分辨率CO(2-1)图谱。
• 分析档案中的Chandra和NuSTAR X射线数据，通过X射线吸收特征检测并表征超快核区风（UFO）。
• 利用观测到的在~1 kpc范围内投影速度恒定的特性，对喷流的密度分布进行建模，推断其径向衰减约为~r⁻²。
• 结合速度、柱密度和几何约束，计算UFO和kpc尺度分子喷流的质量与动能速率。
• 将动量和动能装载因子（dP/dt / (L_bol/c) 与 dE_kin/dt / L_bol）与理论活动星系核反馈模型进行比较。
• 通过比较UFO与大尺度喷流的动能速率，评估能量守恒性，以推断能量传递效率。

实验结果

研究问题

• RQ1 Mrk 231中分子喷流的空间范围与运动学结构如何？其是否表现出双锥形几何形态？
• RQ2 活动星系核核心区域的超快核区风（UFO）的质量、动能与动量速率是多少？
• RQ3 是否存在从UFO到kpc尺度分子喷流的直接能量传递？该过程是否与能量守恒膨胀一致？
• RQ4 观测到的动量与动能装载因子与活动星系核反馈模型的预测相比如何？
• RQ5 喷流的速度与密度分布对估算其年龄与质量损失历史有何约束？

主要发现

• kpc尺度分子喷流延伸至~1 kpc，投影速度近乎恒定，暗示其径向密度分布约为~r⁻²，表明可能存在质量损失或年龄有限。
• 分子喷流的动能速率为 dE(kin,OF)/dt = [7–10] × 10⁴³ erg/s，质量喷流速率为 dM/dt(OF) = [500–1000] M☉/yr。
• 探测到一处核区超快喷流（UFO），速度约为~-20,000 km/s，质量喷流速率为0.3–1.6 M☉/yr，其动能速率与大尺度喷流相当。
• UFO的动能速率（dE(kin,UFO)/dt）与大尺度喷流匹配，支持UFO向分子喷流的能量守恒传递。
• 动量增益比 dP(OF)/dP(UFO) 估计为~30–50，表明大尺度流中存在显著的动量放大。
• 动能装载因子 dE(kin,UFO)/dt / L_bol = 0.8–4% 与 dE(kin,OF)/dt / L_bol = 1–3% 与主流活动星系核反馈模型一致。