Theory of cosmic structure formation outlines how stars, galaxies, clusters of galaxies, and large-scale structures formed out of primordial density fluctuations. It presents us a picture of cosmic mass assembly, and places strong constraints on cosmological model. Both observations and theories suggest that structures formation follows a "bottom up" process, in which small, low-mass component form first, and gradually develop into larger, more massive systems. This dissertation focuses on three crucial stages of cosmic structure formation: first generation stars, quasar host galaxies and the large-scale galaxy overdensities. In Chapter 1, I present an overview of structure formation, acquainting readers with a general picture from first object in the Universe to large-scale structures at later epochs. In Chapter 2 and Chapter 3, I derive strong constraints to the star formation rates (SFRs) of very massive Population III (Pop III) stars in two high redshift galaxies at z = 7. By probing the He II emission lines for both galaxies, I conclude that the contributions of very massive Pop III stars to total the SFRs are less than 3%. In Chapter 4, I move to more massive systems, quasar host galaxies at z ~ 3. Using damped Lyman alpha absorption systems as natural coronagraphs, I report that rest-frame far-UV emission of quasar host galaxy correlates strongly with quasar luminosity. This result suggests a co-evolution of supermassive black holes and their host galaxies. In Chapter 5, I develop a novel method for searching the most massive protoclusters at z = 2-3, by utilizing intergalactic Lyman alpha absorption. My investigations suggest that large intergalactic Lyman alpha absorption systems effectively trace the most overdense regions at large scale of ~ 15 h⁻¹ Mpc. In Chapter 6, I present our imaging observations of an extreme galaxy overdensity (protocluster) BOSS1441+4000, which is discovered using the techniques developed in Chapter 5. Furthermore, I report an intergalactic-scale Lyman alpha nebula detected at the density peak of BOSS1441+4000. This discovery, together with previously discovered Slug nebula, provide us a first look of intergalactic medium in emission in the early Universe. In the Chapter 7, I give a summary of this dissertation and discuss several future prospects.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/578387 |
| Date | January 2015 |
| Creators | Cai, Zheng |
| Contributors | Fan, Xiaohui, Fan, Xiaohui, Ozel, Feryal, Psaltis, Dimitrios, Rozo, Eduardo, Su, Shufang |
| Publisher | The University of Arizona. |
| Source Sets | University of Arizona |
| Language | en_US |
| Detected Language | English |
| Type | text, Electronic Dissertation |
| Rights | Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. |
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