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The First Galaxies in the Universe

The First Galaxies in the Universe

Abraham Loeb
Steven R. Furlanetto
Copyright Date: 2013
Edition: STU - Student edition
Pages: 520
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  • Book Info
    The First Galaxies in the Universe
    Book Description:

    This book provides a comprehensive, self-contained introduction to one of the most exciting frontiers in astrophysics today: the quest to understand how the oldest and most distant galaxies in our universe first formed. Until now, most research on this question has been theoretical, but the next few years will bring about a new generation of large telescopes that promise to supply a flood of data about the infant universe during its first billion years after the big bang. This book bridges the gap between theory and observation. It is an invaluable reference for students and researchers on early galaxies.

    The First Galaxies in the Universestarts from basic physical principles before moving on to more advanced material. Topics include the gravitational growth of structure, the intergalactic medium, the formation and evolution of the first stars and black holes, feedback and galaxy evolution, reionization, 21-cm cosmology, and more.

    Provides a comprehensive introduction to this exciting frontier in astrophysicsBegins from first principlesCovers advanced topics such as the first stars and 21-cm cosmologyPrepares students for research using the next generation of large telescopesDiscusses many open questions to be explored in the coming decade

    eISBN: 978-1-4008-4560-6
    Subjects: Physics, Astronomy, General Science

Table of Contents

  1. Front Matter
    (pp. i-vi)
  2. Table of Contents
    (pp. vii-x)
  3. Preface
    (pp. xi-xiv)
    A. L. and S. F.

    • Chapter One Introduction and Cosmological Background
      (pp. 3-24)

      On large scales, the Universe is observed to be expanding. As it expands, galaxies separate from one another, and the density of matter (averaged over a large volume of space) decreases. If we imagine playing the cosmic movie in reverse and tracing this evolution backward in time, we would infer that there must have been an instant when the density of matter was infinite. This moment in time is the Big Bang, before which we cannot reliably extrapolate our history. But even before we get all the way back to the Big Bang, there must have been a time when...

    • Chapter Two Linear Growth of Cosmological Perturbations
      (pp. 25-40)

      After cosmological recombination, the Universe entered the “dark ages,” during which the relic CMB light from the Big Bang gradually faded away. During this “pregnancy” period (which lasted hundreds of millions of years), the seeds of small density fluctuations planted by inflation in the matter distribution grew until they eventually collapsed to make the first galaxies. Here we describe the first stages of that process and introduce the methods conventionally used to describe these fluctuations.

      As discussed earlier, small perturbations in density grow owing to the unstable nature of gravity. Overdense regions behave as if they reside in a closed...

    • Chapter Three Nonlinear Structure and Halo Formation
      (pp. 41-91)

      In the last chapter, we followed the evolution of structure in the linear regime, when the perturbations are small. Of course, most of the objects we study with telescopes are far outside this regime, with typical densities many thousands of times the cosmic mean. In this chapter, we take the next steps toward understanding these objects by studying the evolution of perturbations in the nonlinear regime. We focus for the most part on analytic models that shed light on the physical processes involved.

      The advent of computer technology has made numerical studies of nonlinear evolution almost routine, and many of...

    • Chapter Four The Intergalactic Medium
      (pp. 92-130)

      Although much of astronomy focuses on the luminous material inside galaxies, the majority of matter today—and the vast majority at z > 6—actually lies outside these structures, in theintergalactic medium(IGM). This material ultimately provides the fuel for galaxy and cluster formation and—because it is much less affected by the complex physics of galaxies—offers a cleaner view of the underlying physical processes of structure formation and of fundamental cosmology. It is therefore of great interest to study the properties of the IGM, especially during the era of the first galaxies (when the IGM underwent major...


    • Chapter Five The First Stars
      (pp. 133-173)

      The formation of the first stars tens or hundreds of millions of years after the Big Bang marked a crucial transition in the early Universe. Before this point, the Universe was elegantly described by a small number of parameters. But as soon as the first stars formed, complex chemical and radiative processes entered the scene. Today, 13.7 billion years later, we find very complicated structures around us. Even though the present structures inside galaxies are a direct consequence of the simple initial conditions in the early Universe, the relationships among them were irreversibly blurred by complex processes over many decades...

    • Chapter Six Stellar Feedback and Galaxy Formation
      (pp. 174-216)

      Chapter 5 described star formation in gas with a primordial composition, assuming that the star-forming region is completely isolated from its surroundings. However, as also discussed in the introduction to that chapter, such isolation cannot last long: those very same stars generate radiation fields that travel vast distances through the IGM. These photons can ionize the surrounding gas, drive winds or shocks through it, heat it, or photodissociate the H₂ or HD that is crucial for subsequent star formation. Moreover, supernovae or winds produced by these stars can also enrich the ambient gas with heavy elements. The second generation of...

    • Chapter Seven Supermassive Black Holes
      (pp. 217-250)

      A black hole is the end product of the complete gravitational collapse of a material object, such as a massive star. It is surrounded by a horizon from which even light cannot escape. Black holes have the dual virtues of being extraordinarily simple solutions to Einstein’s equations of gravity (as they are characterized only by their mass, charge, and spin) but also the most disparate from their Newtonian analogs. In Einstein’s theory of gravity, black holes represent the ultimate prisons: you can check in, but you can never check out.

      Ironically, black hole environments are the brightest objects in the...

    • Chapter Eight Physics of Galaxy Evolution
      (pp. 251-282)

      Let us summarize briefly what we have learned in the previous chapters. According to the popular cold dark matter cosmological model, dwarf galaxies started to form when the Universe was only 100 million years old. Lacking heavy elements to cool the warm primordial gas left over from the Big Bang to lower temperatures, the gas could have fragmented only into relatively massive clumps that condensed to make the first stars. Computer simulations indicate that these first stars were much more massive than the Sun. These stars were efficient factories of ionizing radiation. Once they exhausted their nuclear fuel, some of...

    • [Plates]
      (pp. None)
    • Chapter Nine The Reionization of Intergalactic Hydrogen
      (pp. 283-334)

      The CMB indicates that hydrogen atoms formed 400,000 years after the Big Bang, as soon as the cosmological expansion cooled the gas below 3,000 K. However, observations of the CMB as well as the spectra of early galaxies, quasars, and gamma-ray bursts indicate that less than a billion years later the same gas underwent a wrenching transition from its atomic state back to its constituent protons and electrons in a process known asreionization. More specifically, the z ~ 6 Lyman-α forest shows that the IGM was highly ionized at that time (see §4.7), though there are possible hints from...


    • Chapter Ten Surveys of High-Redshift Galaxies
      (pp. 337-366)

      The study of the first galaxies has so far been mostly theoretical, but it is soon to become an observational frontier. How the primordial cosmic gas was reionized is one of the most exciting questions in cosmology today. As discussed in the previous chapter, most theorists associate reionization with the first generations of stars, whose UV radiation streamed into intergalactic space and broke hydrogen atoms apart in H II bubbles that grew in size and eventually overlapped. Others conjecture that accretion of gas onto low-mass black holes gave off sufficient X-ray radiation to ionize the bulk of the IGM nearly...

    • Chapter Eleven The Lyman-α Line as a Probe of the Early Universe
      (pp. 367-407)

      Early in the book, we explored the physics behind structure formation, which led to the first sources of light in the Universe. In chapter 10, we began applying this framework to observable systems: galaxies. We have now arrived at the point where we can study a number of specific observational probes of the high-redshift Universe. We begin that endeavor in this chapter by examining the Lyman-α line, an extraordinarily rich and useful—albeit complex—probe of both galaxies and the IGM. In the next two chapters, we will describe a variety of other observables.

      We saw in §10.2.1 that young...

    • Chapter Twelve The 21-cm Line
      (pp. 408-458)

      As powerful as it is for studying the high-zUniverse, the Lyman-α transition has the following major disadvantages:

      Most important, the Gunn-Peterson optical depth is enormous. Even a very small neutral fraction, of the order of ~10-3, suffices to render the IGM opaque in this line. Thus, we are not able to use it to study the early, or even middle, phases of reionization except in special circumstances.

      Because the Lyman-α transition lies in the UV band, observing it requires bright UV sources that are very rare at high redshifts, limiting forest studies to only a modest number of lines...

    • Chapter Thirteen Other Probes of the First Galaxies
      (pp. 459-494)

      So far we have discussed four classes of observational probes of the first galaxies: direct observations of individual galaxies (over a variety of wavelengths), the Lyman-a line (both as a test of the galaxy populations and the IGM), the spin-flip line from intergalactic gas, and gravitational waves from black holemergers (see §7.7). However, there are many other, less direct, ways to probe structures during the cosmic dawn. In this chapter, we discuss several of these:

      Secondary anisotropiesof the CMB were generated as those photons passed through gas during the cosmic dawn. CMB photons did not interact with the IGM...

  7. Appendix A Useful Numbers
    (pp. 495-496)
  8. Appendix B Cosmological Parameters
    (pp. 497-498)
  9. Notes
    (pp. 499-508)
  10. Further Reading
    (pp. 509-512)
  11. Index
    (pp. 513-540)