Galaxy Formation and Evolution; How Did the First Stars and Galaxies Form?
DOI: 10.1063/PT.3.1169
Galaxies are the fundamental building blocks of the universe. They come in many varieties, including giant spheroids, magnificent spiral disks of grand design, and irregulars that look like galactic-scale train wrecks. Once, long ago, there was a first generation of galaxies—progenitors and infant precursors of today’s galaxies. We determine how they formed by studying star formation in nearby mature galaxies and applying known physical principles to extrapolate back in time to the galaxies’ infancy and adolescence. Though incomplete, our models, along with detailed observations using the world’s largest telescopes, help us to predict what we might see at very early epochs in the universe.
According to the standard concordance model, quantum fluctuations generated during the inflationary epoch provide the density irregularities that grow via gravitational instabilities to eventually form galaxies. Bottom-up galaxy formation commences once dark-matter clumps are sufficiently massive for the baryons to be able to cool and condense. (For additional details, see the article by Tom Abel in PHYSICS TODAY, April 2011, page 51 .) Under the assumptions that cold, weakly interacting dark matter predominates and that luminous baryonic mass traces that dark matter, numerical simulations of large-scale structure have produced realistic maps of the galaxy distribution. On smaller scales, however, detailed baryon physics is essential, and current simulations have thus far failed to account for all of the observed properties of individual galaxies.
Our incomplete knowledge makes galaxy formation and evolution an exciting area of research whose progress is driven by observations of the distant universe. Indeed, the field is at the forefront of current astrophysics research. It teems with big questions that will potentially spawn a host of future PhD theses. The largest ground- and space-based telescopes are gearing up to probe the earliest phases of galaxy evolution and address those questions by gazing far away and, hence, back in time.
Galaxy Formation and Evolution by Houjun Mo, Frank van den Bosch, and Simon White is an ideal introduction for anyone with a minimal background in astrophysics who wishes to enter the field of large-scale structure formation. It is well suited for use in a general astrophysics course for senior-undergraduate and graduate students and is also an excellent reference source for more advanced courses on specific topics in astrophysics. The authors are leading theoretical astrophysicists who have made major contributions to galaxy formation theory. Their text provides a comprehensive review of relevant topics, ranging from the growth of the first density fluctuations to the evolution of the stellar populations in galaxies. It is a timely update of similar but now more dated texts, such as John Peacock’s Cosmological Physics (Cambridge University Press, 1999) and Jim Peebles’s Principles of Physical Cosmology (Princeton University Press, 1993).
The monograph How Did the First Stars and Galaxies Form? by Abraham Loeb covers all the usual ground, but it is succinct to the point of losing all but the most avid readers. It has enough equations to deter the nontechnical audience but too few to provide any in-depth explanations. The book is what the publisher calls a “primer,” though just who or what it is intended to prime is anybody’s guess. Perhaps it is aimed at the reader who doesn’t want a demanding academic challenge but who would be tempted by a book-length exploration of a subject at the forefront of current cosmology. That is where it could well succeed. However, for a deeper and more academic immersion, I recommend the more versatile Galaxy Formation and Evolution.
More about the Authors
Joseph Silk. University of Oxford Oxford, UK.
