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红外背景辐射的宇宙学意义
吴建新
学位类型博士
导师张柏荣
1990-06-30
学位授予单位中国科学院云南天文台
学位授予地点昆明
摘要迄今为止,人类所能观测到最早期的宇宙中的天体是类星体,它的红移最大约为4,但是,按照大爆炸宇宙理论,1965年Penzias和Wilson所发现的宇宙微波背景辐射产生于红移Z≈1000的退耦时期。在红移4 approx= Z approx= 1000的漫长的宇宙演化阶段是观测上的“空白”。在这个“黑暗”的时代,并非宇宙是沉寂的,一定有许多辐射源存在。在这个时期,恰恰有许多宇宙演化过程中重要的宇宙活动。例如,星系的形成,第一代星,类星体中央大质量黑洞的形成等。由于我们今天所观测到的背景辐射或者是产生于这个时代,或者要受到辐射传播过程中这个时期所途经的物质的影响,所以背景辐射的观测也必然带来复合之后,特别是Z~4~1000时期的物质成因才以及星际物质再热过程等有关信息。所以,近20年来,对背景辐射从各种角度的研究一直是天体物理,特别是宇宙学领域的活跃课题之一。它是最近被称为“复合后宇宙学”(The Post-Recombination Cosomology)的重要组成部分。基于下面的两个原因,搜寻起源于红移4<Z<1000范围的辐射应该在远红外(100μm-1000μm):(1)被宇宙尘埃吸收的能量可能以灰体辐射的形式再辐射。然后红移到远红外波段;(2)在远红外波段,宇宙是光学薄的。至少能观测到更早期的辐射。它的重要性促使本文作者详细地讨论了红外背景辐射的宇宙学意义。在论文的第二部分,我们回顾了近年来在这个领域所进行的一些有意义的观测。自从微波背景辐射被发现以来。对它的探测一直没有间断过,随着实验技术的改进,使得探测的灵敏度不断提高。在射电波段已经取得了一致的结论。尤其,近年空间技术的发展使对亚毫米波估背景辐射的探测取得了辉煌的发展,尽管得到的结论还有待于进一步确证。接着,我们在理论上讨论了星系前可能的辐射,而不管辐射现在是否被观测到了。如果那时的辐射没有阻碍地传播到地球上,那么它们将形成背景辐射。各种不同的辐射源都能给我们留下它们的背景谱,对于红移Z在10-1000的星系前期间内有如下几种可能的红外背景辐射源存在,它们分别是:(1)原星系;(2)星系前恒星(星族III);(3)星系前爆发;(4)吸积的黑洞;(5)大爆炸遗迹粒子的衰变。此外,红外星系辐射作为一种背景存在时,也可能出现在远红外区。贡献到Matsumoto所探测到的微波背景过量如去。论文的第四部分,从观测事实出发,给出了星际尘埃,星系际尘埃和河外星系内尘埃的丰度,成份和光学性质。宇宙尘埃主要是硅酸盐微粒。其次还有一部分石墨粒子,其余如冰(H_2O),铁粒子等含量很少。它们的光学性质归结为各种不同半径(假设尘粒是球状的)的粒子的辐射吸收效率因子与波长λ的关系。论文的第五部分、论述了宇宙尘埃怎样产生远红外背景辐射,而使宇宙微波背景辐射产生畸变。首先,我们给出了一般宇宙空间的辐射条件下,早期星系际宇宙尘粒对辐射的转移方程。我们得到如下结论:(1)在宇宙早期没有中性氢吸收的情况下,硅酸盐尘粒再辐射能产生相应于3K背景峰值强度10%的畸变谱;(2)宇宙早期中性氢很丰富时,硅酸盐尘粒只能导致微波背景辐射峰值附近的畸变约为1%;(3)即使在没有中性氢吸收的情况下,仅由石墨构成的尘埃也只能使3K背景辐射峰值附近的畸变小于1‰。其次,当河外星系内星际尘埃的热辐射作为一种背景存在时。也能产生一定的远红外背景,甚至导致3K背景谱的畸变。最后,也讨论了尘埃分布的不均匀性与红外背景辐射的各向异性性的关系。文章的最后一部分,作者讨论了其它物理过程对红外背景谱可能产生的影响。内容包括(1)VMOC电离宇宙热电子的compton效应;(2)富星系因中高温电子对背景光子的Sunyaev-Zel'devich效应以及引力透镜效应可能产生的影响。在这部分每个问题的前面均附有提要。
其他摘要So far, the earliest objects in the universe which have been observed are Quasi-Stellar Objects and the corresponding largest redshift is about 4. According to the Big Bang cosmic model, the cosmic microwave background radiation Penzias and Wilson discovered in 1965 was produced during the decoupling epoch which redshift is Z ~ 1000. No objects have been observed during the long cosmic evolution 4 < Z < 1000. During this "dark" epoch, the universe was not quiet and there must been many radiative sources. And also some important cosomological activities happened in this epoch, e.g., the formation of galaxies; the first stars; the formation of the massive black holes which lie in the center of QSOs and so on. Because either the background radiation we observe today is produced during this epoch or it is affected by the matter of this epoch on the radiative propagation way, observations on the cosmic background radiation must bring us the information of the matter clustering and the re-heated process of interstella medium after the cosmic recombination, particular during the epoch 4 < Z < 1000. Since over 20 years, the researches from various angels have been one of the most active directions of astrophysics and particularly cosmology. and it is an important part of the recently so-called The Post-Recombination Cosomology". Based on the following two reasons, the radiation origining from redshift range 4 approx= Z approx= 1000 should be searched for in the far infrared waveband(100μm-1000μm): 1. the energy absorbed by cosmic dust may re-radiate in the form of greybody radiation and then redshifted to the far infrared waveband; 2. in the far infrared range, the universe is optioally thin, and at least we can observe much earlier radiation in the far infrared waveband than in the optical and ultravie range. So its importance makes me discuss cosmological implications of the infrared background radiation in detail as my Ph.D thesis. In the second part of the thesis, I review some significant observations in the cosmic background radiation field in recent years. Since the microwave background radiation was discovered, it has been detect constantly and as experimental technology is improved on, the detecting sensitivity is becoming higher and higher. The almost identical result is already gotten in the radio waveband. Particularly, the development of space science makes great progress of the detection the sub-millimeter background radiation, although the results have to be confirmed further. And then, I discuss the possible theoretical radial sources in the early universe, and no matter whether their radiation is already collected. If the radiation from that time spread unblockedly to the observers, the may form background radiation. Various radiative sources leave us their background spectrum. The follow radiative sources possibly exist in the so-called pregalactic range 10 < Z < 1000: 1.Protogalaxies; 2.Pregalactic Stars(Pop.III); 3.Formation of Large-Scale Structure; 4.Accreting Black holes; 5.Decaying Particles. Besides those, the radiation from "infrared galaxies" may appear in the far infrared waveband, and could make contribution to the excessive background radiation Matsumoto detected in 1988. At the angle of observations, the fourth part gives out the abundance, composition and optical proper of interstellar dust, intergalactic dust and dust in extragalaxies. Cosmic dust is cosmposed of mainly silicate grains and secondly graphite grains, and others such as ice grains(H_2O) and iron grains and so on are very few. The ralationship of absorption efficiency on radiation with wavelength expresses their optical properties. I discuss how cosmic dust make the far infrared background radiation in the fifth part of my thesis, and also produce the distortion of the cosmic microwave background radiation. Firstly, I express the radiative transfer equations of early intergalactic cosmic dust under the ordinary radiative condition of early cosmic space. The following results are arrived: 1.if there exists no abundant medium hydrogen in the early universe silicate grains can produce the distortion background spectrum which corresponds to 10% of the peak intensity of the 2.74 K blackbody background; 2.much hydrogen absorption in the early universe makes silicate grains result in only 1% of peak spectrum of the 2.74 K blackbody intensity; 3.even if no significant medium hydrogen exists in the early universe, cosmic dust which is only composed of graphite produces the distortion less than 1% of the 2.74 K blackbody peak intensity. Secondly, if it forms background spectrum, the re-radiation from the interstellar grains existing in extragalaxies should make some far infrared background intensity and even result in the distortion of the 2.74 K microwave background spectrum. Lastly, I discuss the relationship of the inhomogeneity of grain distribution and anistropy of the infrared background radiation. In the last part, how other physical process possibly affect the infrared background spectrum is discussed. Its content includes: 1.The Compton effect of the thermal electrons existing in the universe ionized by VMOs; 2.the Sunyaev-Zel'dovich effect of the thermal electrons existing in rich galactic clusters scattering off the background photons and possible effect from micro-gravitational lenses. The results are shown in Fig.3 and List 10.
学科领域天文学
页数142
语种中文
文献类型学位论文
条目标识符http://ir.ynao.ac.cn/handle/114a53/6577
专题太阳物理研究组
推荐引用方式
GB/T 7714
吴建新. 红外背景辐射的宇宙学意义[D]. 昆明. 中国科学院云南天文台,1990.
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