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最大熵方法在活动星系核反响映射研究中的应用
其他题名APPLICATION OF MAXIMUM ENTROPY METHOD IN REVERBERATION MAPPING OF ACTIVE GALACTIC NUCLEI
肖铭
学位类型博士
导师白金明
2019
学位授予单位中国科学院大学
学位授予地点北京
学位专业天体物理
关键词活动星系核 宽线区 黑洞质量 最大熵方法
摘要活动星系核(以下简称AGN)中心的黑洞及其周围环境的物理一直是人们感兴趣的课题,从十九世纪六十年代第一颗AGN被首次发现开始,人们对AGN进行了密集的监测。同时,探测AGN物质结构及变化规律的方法和模型不断被提出,新的结果不断刷新着人们对于AGN的认知。作为AGN的子类,超爱丁顿吸积的大质量黑洞(以下简称SEAMBH)由于具有成为新的宇宙学烛光的潜力而成为我们最为感兴趣的目标。从2012年以来,我们使用丽江2.4m光学望远镜对一批高吸积率的AGN的样本进行了持续监测,目的是更清楚地了解吸积率在宽线区和黑洞吸积物理中扮演的角色。目前我们已经成功认证并测量了24个源的宽线区平均半径以及黑洞质量。结果显示,SEAMBH的吸积盘由于超爱丁顿吸积产生的光子囚禁效应,其光度达到饱和,坚实了其作为新的宇宙学烛光的理论依据。同时,通过速度分解方法的应用,我们已经初步揭示了SEAMBH宽线区的几何和动力学特征。本文进一步将最大熵方法应用于第一批观测的9个SEAMBH的样本,并成功重建了其中6个源的速度延迟图。Mrk~335 \hb 和\hr 发射线的速度延迟图显示出其宽线区具有内流的结构。Mrk~142 \hb 和\hr 发射线显示出外流的结构。Mrk~1044显示出相对较为复杂的形态 -- 一个维里化运动的特征伴随着外流的迹象。IRAS~F12397的速度延迟图显示出对称结构,说明其宽线区具有盘状或球壳状结构,同时,Mrk~486和MCG~+06-26-012 \hb 发射线分别显示了盘状和球壳状的结构。这些速度延迟图揭示出SEAMBH的宽线区具有丰富多样的几何和形态结构。由于SEAMBH的发射线展宽较窄,目前数据质量下重建的速度延迟图在速度方向的分辨率还不是很高,我们在接下来的工作中选取了历史上有过多次成功反响映射监测的NGC~5548作为目标源进行了一次高质量的监测,并重建了一个目前最高质量之一的速度延迟图。该图显示出总体对称的结构,在时间延迟$\tau \lesssim 15$处有着很强的红蓝两翼的响应和在$\tau \gtrsim 15$处较窄的速度分布,并且在中心存在响应的缺失。这些响应与理论计算的简单盘状宽线区结构吻合的很好,同时其红端长时延处较弱的响应揭示了NGC~5548宽线区的外区存在辐射的各向异性。我们收集了AGN Watch项目对NGC~5548长达13年的连续监测数据,并分别重建了每年的速度延迟图。结果显示,NGC~5548的宽线区在内流和盘状结构间相互转化。这一结果为我们理解宽线区长时标的演化提供了依据。
其他摘要The central black hole in active galactic nuclei (AGNs) and their surrounding structures are of interest to astronomers. AGNs have been intensively monitored since the first time they been identified at the 1960s. Many methods and models have been raised in the past years, which are continuing to detect the intrinsic nature of AGNs. Super-Eddington accreting massive black holes (SEAMBHs) are a special subclass of AGNs, as they can serve as a new type of cosmological candles, and are also the objects we are interested in.Since the fall of 2012, we have monitored a large sample of high accretion rate AGNs, aiming at better understanding the role of accretion rates on BLRs and the physics of accretion onto black holes. Our results reveal that SEAMBHs reach saturated luminosities due to the photon trapping caused by Super-Eddington accretion. These results build a solid foundation for the cosmological candle theory. We have used the velocity-resolved analysis to offer a glimpse into the geometry and kinematics of the BLRs. This paper focuses on applying the maximum entropy method (MEM) to our SEAMBH sample for the velocity-delay maps of \hb and \hr emission lines. The maps of six objects are reliably reconstructed using MEM. The maps of H$\beta$ and H$\gamma$ emission lines of Mrk 335 indicate that the gas of its broad-line region (BLR) is infalling. For Mrk 142, its H$\beta$ and H$\gamma$ lines show signatures of outflow. The H$\beta$ and H$\gamma$ maps of Mrk 1044 demonstrate complex kinematics -- a virialized motion accompanied by an outflow signature, and the H$\beta$ map of IRAS F12397+3333 is consistent with a disk or a spherical shell. The \hb\ maps of Mrk~486 and MCG~+06-26-012 suggest the presence of an inflow and outflow, respectively. These super-Eddington accretors show diverse geometry and kinematics.NGC 5548 has been well spectroscopically monitored for reverberation mapping of the central kinematics by 19 campaigns. Using the maximum entropy method in this Letter, we build up a high-quality velocity-delay map of the \hb\ emission line in the light curves of the continuum and the line variations observed between 2015-2016. The map shows the response strength and lags of the velocity fields of the \hb\ emitting regions. The velocity-delay structure of the map is generally symmetric, with strong red and blue wings at time lag $\tau \lesssim 15$ days, a narrower velocity distribution at $\tau \gtrsim 15$ days, and a deficit of response in the core. This is suggestive of a disk geometry of the broad-line region (BLR).The relatively weaker \hb\ response at the longer lags in the red side indicates anisotropic emission from the outer part of the BLR. We also recover the velocity-delay maps of NGC~5548 from the historical data of 13 years to investigate the long-term variability of its BLR. In general, the BLR of NGC 5548 was switching between the inflow and virialized phases in the past years. The resultant maps of seven years reveal inflow signatures and show decreasing lags, indicating that the changes in the BLR size are related to the infalling BLR gas. The other four maps show potential disk signatures which are similar to our map.
学科领域天文学 ; 星系与宇宙学
学科门类理学 ; 理学::天文学
页数100
语种中文
文献类型学位论文
条目标识符http://ir.ynao.ac.cn/handle/114a53/25392
专题南方基地
作者单位中国科学院云南天文台
第一作者单位中国科学院云南天文台
推荐引用方式
GB/T 7714
肖铭. 最大熵方法在活动星系核反响映射研究中的应用[D]. 北京. 中国科学院大学,2019.
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