Book review: "Extragalactic astronomy and cosmology—an introduction"
Frontiers in Astronomy and Space Sciences
This is the second edition of a textbook conceived to be used in an introductory course on extragalactic astronomy and cosmology (the author is professor at Bonn University and a wellknown specialist in gravitational lensing). A new edition is fully justified because, as Schneider (2015) explains in the preface, the field has been evolving rapidly during the years which have passed since the first edition (published in 2006), with the advent of new observational facilities and new surveys. The
... d new surveys. The first characteristic of the book is apparent from its title: it covers both extragalactic astronomy and cosmology. It is not the only textbook to deal with both subjects; there have been other examples, such as Combes et al. (2002) or Jones et al. (2015) with a new edition published this year; however, most introductory textbooks focus either on galaxies (e.g., Spark and Gallagher, 2006) or on cosmology (e.g., Liddle, 2015; Roos, 2015) , or give a general introduction to astronomy at a very simple technical level (e.g., Unsöld and Baschek, 2005) . The treatment of both subjects at the same level is a very good choice, as a lot of research in extragalactic astronomy, such as structure formation, weak lensing or galaxy evolution, has implications for cosmology and vice-versa. Obviously the price to be paid is the size of the book, which in this case is about 600 pages long, and a teacher will have to carefully select parts of the text depending on the length of his or her course. On the other hand I have to stress that part of the large size of this book is due to one of its qualities, i.e., the large number of illustrations. There are many graphs but also nice color images, which undoubtedly have an aesthetic value and should help to kindle the interest of students. The mathematical level of the book is accessible to readers who have a basic knowledge of calculus. Formulae and mathematical derivations are frequent (more advanced or detailed subsections are printed in smaller characters), allowing the student to go beyond pure notions and to grasp the nature of astrophysical phenomena and processes in a quantitative way. Moreover, every important sub-field of research in extragalactic astronomy and cosmology is introduced and discussed, with a good balance between theory and observations, and the text is fully uptodate. Not surprisingly, the first chapter is a general introduction to the subject, but for its length (more than 40 pages) and content it could stand by itself as an accessible review. It is divided into two main parts: the first one gives a synthesis of the scientific theme of the book, while the second one describes the present main observational facilities on Earth and in space at different wavelengths.