【作者】 胡剑；

【导师】 李惕碚；

【作者基本信息】 清华大学 ， 物理学， 2007， 博士

【摘要】 本论文研究了星系团和超大质量黑洞中的若干重要的高能天体过程。星系团中维里化的高温电离气体中的电子与宇宙微波背景辐射(CMB)光子发生Compton散射,从而改变CMB的能谱,这种被称为Sunyaev-Zel’dovich(SZ)效应的物理过程是研究宇宙学和星系团结构与演化的独特工具。我们研究了星系团中的磁场对于SZ效应的一种修正机制,称之为磁SZ效应。与经典SZ效应相比,磁SZ效应信号更强,空间分布更陡。结合X射线辐射和SZ谱观测,磁SZ效应可以限制星系团中的磁场强度,如A2163团中心磁场为～30μG。我们分析了WMAP卫星三年数据,对一个星系团样本找到了10σ显著性的SZ效应信号。SZ信号与X射线观测的共同数据拟合显示星系团内热气体(ICM)的分布在维里半径处存在外边界,这可能是星系团外缘存在维里化激波的证据。我们还确认了星系团中重子占总物质的比例低于宇宙均值。磁SZ效应和星系团ICM外部边界的存在将影响利用SZ效应测量宇宙学参数的系统误差。星系团是研究暗物质性质的天然实验室。我们分析了暗物质-重子粒子碰撞解释“冷流”星系团中心缺乏过冷气体的加热机制。星系团的观测数据给出单位质量暗物质粒子-质子碰撞截面上限为σxp/mx<～2×10?25 cm2 GeV?1。ICM能量平衡方程的稳定性分析证明了暗物质-重子粒子碰撞不是“冷流”星系团中心的主要加热机制。我们计算了21个有X射线图像和能谱高分辨率观测数据的星系团中暗物质的等效“温度”(速度弥散)分布,发现部分星系团的暗物质“温度”低于团内气体的温度,证明星系团中存在对气体的非引力加热机制。星系中心超大质量黑洞的形成问题对于研究星系形成与演化和宇宙再电离具有重要意义。我们首次提出了宇宙早期超大质量黑洞通过对自相互作用暗物质和重子物质的两阶段吸积快速形成的机制,从而解释了类星体SDSS1148+5251的形成,并预言了中心有大质量黑洞的暗星系的存在。我们建立了类星体HE0450-2958的动力学模型,解释了其中心黑洞与伴星系星爆活动的形成过程,证明这是一个由星系高速交会触发的类星体。更多还原

【Abstract】 The thesis studies several important high energy astrophysical processes in galaxyclusters and super-massive black holes (SMBHs).Electrons in the fully ionized intracluster medium (ICM) hot gas will change theenergy spectrum of cosmic microwave background by Compton scattering. This so-called Sunyaev-Zel’dovich effect (SZE) is a unique tool for the study of cosmologyand structure and evolution of galaxy clusters. We explore the modification mech-anism of intracluster magnetic fields on the classical SZE. Such magnetic SZ effect(MSZE) tends to enhance the SZE signal with a steeper radial profile. By applyingthe MSZE model to spectral observations of SZE signals and X-ray emissions fromthe galaxy clusters, the intracluster magnetic field can be constrained, i.e., a～30μGcentral magnetic field is predicted for the galaxy cluster A2163. We analyze the three-year data of WMAP satellite, find SZE signal of 10σsignificance in a sample of galaxyclusters. Combined SZ and X-ray data fitting require the outer edge of ICM distribu-tion at cluster virial radius, which could be the evidence of virilization shock aroundthe clusters. We confirm the previous results that the baryons fraction in clusters islower than the cosmic mean value. The existence of the MSZE and an outer edge ofICM distribution bear important systematic uncertainty for cluster-based estimation ofcosmological parameters.Galaxy clusters are the astrophysical laboratory for the study of dark mat-ter. The collision between dark matter particles (DMPs) and baryons is a possi-ble heating source accounting for the absence of over-cooling gas in the central re-gions of“cooling ?ow”clusters. We examine this mechanism in a sample of clus-ters and derive the upper limit for the collisional cross section per DMP mass asσxp/mx～< 2×10?25 cm2 GeV?1. The stability analysis on the energy equilibriumequation of ICM demonstrates that the DMPs-baryons collision cannot be the domi-nant heating source in the center of“cooling ?ow”clusters. We calculate the equiva- lent“temperature”(velocity dispersion) profiles of dark matter in a sample of 21 galaxyclusters with X-ray observations of high spatial and spectral resolution. The dark mat-ter is found to be cooler than the ICM in part of clusters, indicating the existence ofnon-gravitational heating mechanism for ICM.The formation problem of SMBHs in the center of galaxies are crucial for thestudy of galaxy formation and evolution, and cosmic reionization. We proposed theSMBHs quick formation mechanism by two-phase accretion of self-interacting darkmatter and baryons in the early universe, thus explain the formation of quasar SDSS1148+5251, and predict the existence of massive black holes dwelling in the centerof dark galaxies. We also model the dynamics of quasar system HE 0450-2958 andexplain the processes of its SMBH formation and star-burst in the companion galaxy,show that the quasar is triggered by the strong interaction in the high-speed encounterwith the companion galaxy.更多还原