Where are the Broad Absorption Line Outflows Situated and How Important are they to Active Galactic Nuclei Feedback?

宽吸收线流出位于哪里以及它们对活动星系核反馈有多重要？

• 批准号: 1413319
• 负责人: Nahum Arav
• 金额: $ 49.7万
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1413319&HistoricalAwards=false
• 关键词: Where; Broad; Absorption; Line; Outflows

Quasars are the most luminous objects in the universe. The active galactic nucleus (AGN) that is the quasar's powerhouse can outshine its entire host galaxy. In the more than fifty years since their discovery, a picture has emerged of a quasar as a supermassive black hole residing at or near the center of a large galaxy. Interstellar gas in the galaxy, perhaps the residue of stars disrupted by tidal forces as they orbit close to the black hole, falls into the black hole and in doing so is heated to very high temperatures and emits copious radiation over a wide range of wavelengths. Along with the gas inflow, it is also clear that quasars drive gas out of the nuclear region. This is evidenced by jets of material emitted by a minority of quasars but also by an outflow seen in absorption in the spectra of many quasars. These objects are called broad absorption line quasars or BAL quasars in reference to the broad spectral features due to mildly-ionized atomic species seen in their ultraviolet spectra. Long thought to be oddities, it is becoming clear that many or most quasars demonstrate such spectral features when viewed along certain lines of sight. An outstanding question is how the BAL outflow is generated. Is it gas that is launched from very near the black hole or is its genesis from somewhere outside of the nuclear region? The answer is important because, depending on its strength, the BAL wind can affect the properties of the host galaxy through so-called quasar feedback. This project will use detailed spectral analysis and imaging of a number of BAL quasars to better determine where the BAL gas originates and what its properties are. The project will engage a number of undergraduate researchers many of whom are women or underrepresented minorities.Arguably the most important parameter to be determined for broad absorption line outflows is their distance from the central source (R). A definitive answer will go a long way to: (a) determine whether these outflows are energetic enough to generate the sought after "quasar mode feedback," which is suggested by theorists to be a key mechanism for influencing the assembly history of galaxies and clusters; (b) establish the role of the outflows in the connection between the supermassive black hole and the host galaxy; (c) allow for realistic modeling of the outflow's origin and acceleration. Most AGN researchers and especially dynamical modelers, favor a picture where BAL outflows are launched from the AGN accretion disc and are observed in its vicinity (R~0.01-0.1 pc). However, in a recent series of papers the principal investigator's team measured R to more than 20 outflow components in 10 individual quasars and in every case found R to be between 100-10,000 parsecs. The large difference between the previously assumed and measured R has dramatic consequences since the outflow's mass flux and kinetic luminosity are linearly dependent on R. A prominent result was the team's finding of the most energetic quasar outflow measured to date, with ample kinetic luminosity to be a major contributor to AGN feedback. Therefore, if these large R flows are representative of most BAL outflows, they can supply the theoretically desired quasar mode feedback. This project will advance this unique observational and modeling program by observing a heterogeneous set of objects, to analyzing samples in well-designed surveys, acquiring direct imaging spectroscopy of these outflows, and extracting R from rich new data sets of BAL variability. The result should definitively assess whether BAL winds can be a dominant agent of AGN feedback.

类星体是宇宙中最明亮的物体。活动星系核（AGN）是类星体的发电站，它的亮度可以超过整个宿主星系。 在它们被发现后的50多年里，一幅关于类星体的图片已经出现，它是一个位于或靠近大星系中心的超大质量黑洞。 星系中的星际气体，可能是恒星在靠近黑洞的轨道上被潮汐力破坏的残余物，福尔斯落入黑洞，并在此过程中被加热到非常高的温度，并在很宽的波长范围内发出丰富的辐射。 沿着气体的流入，类星体将气体赶出核区域也是很清楚的。 少数类星体发射的物质喷流以及许多类星体光谱中吸收的外流都证明了这一点。 这些天体被称为宽吸收线类星体或BAL类星体，因为它们的紫外线光谱中存在轻度电离的原子物种。 长期以来被认为是怪异的，现在越来越清楚的是，许多或大多数类星体在沿着某些视线观察时，都表现出这样的光谱特征。 一个悬而未决的问题是如何产生的BAL流出。 它是从非常靠近黑洞的地方发射出来的气体，还是从核区域之外的某个地方产生的？ 答案很重要，因为根据其强度，BAL风可以通过所谓的类星体反馈影响宿主星系的属性。 该项目将对一些BAL类星体进行详细的光谱分析和成像，以更好地确定BAL气体的来源及其性质。 该项目将吸引一些本科研究人员，其中许多是妇女或代表性不足的少数民族。可以说，要确定的最重要的参数是广泛的吸收线流出是他们与中央源（R）的距离。一个明确的答案将有很长的路要走：（a）确定这些流出是否有足够的能量来产生所追求的“类星体模式反馈”，这是理论家建议的影响星系和星系团的组装历史的关键机制;（B）建立超大质量黑洞和宿主星系之间的连接流出的作用;（c）考虑到流出的起源和加速度的真实模拟。大多数活动星系核研究者，特别是动力学模型研究者，倾向于认为BAL流出物是从活动星系核吸积盘发射出来的，并在吸积盘附近被观测到（R~0.01-0.1 pc）。然而，在最近的一系列论文中，首席研究员团队测量了10个类星体中20多个流出分量的R，发现在每种情况下R都在100- 10，000秒差距之间。由于外流的质量通量和动力学光度与R呈线性关系，因此先前假设的R与测量的R之间的巨大差异具有戏剧性的后果。一个突出的结果是该团队发现了迄今为止测量到的最具活力的类星体外流，充足的动力学光度是AGN反馈的主要贡献者。因此，如果这些大的R流是大多数BAL流出的代表，它们可以提供理论上所需的类星体模式反馈。该项目将通过观察一组异质的对象来推进这一独特的观测和建模计划，以分析精心设计的调查中的样本，获取这些流出物的直接成像光谱，并从丰富的新BAL变异数据集中提取R。 结果应明确评估BAL风是否可以成为活动星系核反馈的主导因素。