薛艳杰
论文题目：X射线星系团动力学性质及其宇宙学应用
作者简介：薛艳杰，女，1975年12月出生，1998年09月师从于中科院国家天文台武向平教授，于2002年06月获博士学位。
摘
要
星系团是宇宙中最大的维里化引力束缚体系，是检验宇宙学模型和结构形成理论的理想实验室，其物质组成、结构及分布、动力学特性及丰度与演化揭示出丰富的宇宙起源与演化的信息。观测上多波段的结合、理论上解析与数值模拟的结合成为当今研究星系团的新手段。
本文联合光学、X射线、引力透镜效应和S-Z效应等多种探测手段，以光学和X射线统计样本为基础，利用解析和半解析的分析方法，对星系团(群)的动力学性质及其宇宙学应用进行全面和深入的研究，并取得了一些重要的研究结果。主要研究内容有：
(1) 建立迄今最大的光学和X射线联合星系团(群)样本，以此研究了星系团(群)X射线光度、温度、星系速度弥散和动力学质量之间的相关性质，这些统计特性证实并加强了在星系团(群)中存在非引力加热机制的观点，为研究星系团何星系群内热气体的演化提供了可靠的观测依据，这方面的工作被相关的研究广泛地采纳。另外，大样本统计可以精确地给出描述气体分布的b模型以及大半径处气体分布的斜率－－b参数，我们的结果研究解决了争执数年的b不一致性问题。
(2) 利用气体分布作为星系团引力势的标度，对现有暗物质晕物质分布的解析模型做了详尽的检验。在星系团尺度上排除了暗物质晕具有较大核半径的可能性(如Burkert模型)，并第一次从观测上对数值模拟给出的暗物质晕结构关系(c-Mvir)做出了检验。
(3) 结合X射线观测，深入研究了恒星形成导致的气体分布自调整模型[星系团(群)中恒星形成与气体演化的统一模型]，提出了区分这一模型与预加热模型的判据。我们的研究发现二者在大半径的行为有着很大的区别，前者的气体分布在大半径处遵循暗物质的分布，而后者则非常延展。利用Chandra卫星进行长时间的曝光观测可以给出最终的判据。
(4) 利用星系团(群)X射线光度与温度的相关关系及X射线光度函数代替描述暗物质晕分布和演化的PS质量函数，把可能存在的非引力加热效应自然地纳入了S-Z星系团计数，我们的研究结果显示非引力加热效应对SZ星系团计数有一定的影响，这会给未来的SZ巡天结果带来不确定性，进而影响宇宙学参数的确定。另外，我们还考虑了这种非引力加热机制对来自星系团何星系群内热气体的宇宙X射线背景的影响，我们的模型所预测的来自星系团何星系群的宇宙X射线背景与目前X射线背景的观测限完全一致，这不仅说明非引力加热效应对X射线背景有非常大的影响，而且对寻找宇宙中失踪的重子物质有重要价值。
(5) 探讨了利用现有引力透镜观测数据限制暗物质晕的物质分布模型及利用未来的小尺度引力透镜多重像统计限制暗物质粒子属性的可能性。我们的研究结果表明，未来高分辨率的引力透镜巡天观测可以对冷暗物质宇宙学模型何温暗物质宇宙学模型给出限制。
Abstract
Clusters of galaxies are the largest coherent and gravitationally bound structures in the Universe. Their study is significant for our understanding of distribution and organization of cosmic matter on scales of 1-100 Mpc, for cosmological test of theories of formation and evolution of structures in the universe, and for determination of cosmological parameters such as the density parameter WM, the cosmological constant WL, and the normalization parameter s8. Considerable progress in high-sensitivity multi-wavelength observations, (semi)analytical approaches and numerical simulations in recent years has opened a new era of exploring clusters as a cosmological laboratory.
This work concentrates on the dynamical properties of clusters and their cosmological applications, based on a jointly observational and theoretical studies of optical and X-ray measurements, gravitational lensing and Sunyaev-Zel'dovich effects. The main contribution of this work includes: (1) Compilation of the hitherto largest optical and X-ray sample of groups and clusters. This permits a statistical study of correlations between the dynamical properties of dark matter, optical galaxies and X-ray emitting gas such as gravitating mass, X-ray luminosity, X-ray temperature, velocity dispersion of galaxies, etc. The newly established relationships confirm and reinforce the existence and significance of nongravitational heating in groups and clusters. Meanwhile, the large data set of optical/X-ray clusters provides a reliable estimate of the b parameters, which eliminates the long standing puzzle of the so-called b discrepancy.
(2) Test of the mass profiles of dark halos. Assuming that the hot gas is a good tracer of the underlying gravitational potential of groups and clusters, we have made an attempt to distinguish various density profiles of dark halos suggested numerically or empirically. A comparison of the predicted and observed X-ray surface brightness of clusters sets robust constraints on the inner cores of dark halos. Consequently, the Burkert profile with a finite core has been ruled out on cluster scales. Moreover, we have conducted the first observational test of the c-Mvir relation motivated by numerical simulations.
(3) Observational constraints on the galaxy-formation regulated gas evolution model. Such a model provides a simple, unified scenario for formation of stars and evolution of hot gas in groups and clusters without additional heating, and has proved very successful at explaining current X-ray observations. We have given an observational criterion to disentangle the model from preheating mechanism.
(4) We have adopted the observationally determined X-ray luminosity function instead of the Press-Schechter mass function in the predictions of S-Z cluster counts and X-ray background produced by groups and clusters, which allows us to include naturally non-gravitational heating effect without the detailed knowledge of the essential physics. We have found a good agreement between the theoretically expected X-ray background and the upper limit set by current X-ray observations such as ROSAT, Chandra and XMM. This may have significant impacts on future search for the missing baryons.
(5) Gravitational lensing of dark halos. The matter distributions of clusters revealed by both strong and weak gravitational lensing provide an effective and independent test of dark matter models. We have explored the possibility of whether current available lensing data are sufficient to distinguish various proposed density profiles of dark halos on cluster scales. On (sub)galactic scales we have shown how the probability of the multiply-lensed images of distant quasars depends upon the rest mass of dark matter particles. This may be used as a powerful method for weighing dark matter particles when combined with future statistical surveys of the lensed images of quasars below sub-arcsecond scales.
