Dynamics and Astrophysics of Galaxies

By Jo Bovy
(last changed June 06, 2025, rev. 9b46541; last built June 06, 2025)

This is an interactive, online graduate textbook on the astrophysics of galaxies. Starting out with the basics of gravitational dynamics on the scale of galaxies, the book contains an in-depth exploration of the dynamical and astrophysical processes that shape the formation and evolution of galaxies in the Universe and an exposition of the main theoretical and observational tools used to study galaxies. Embedded throughout the book are interactive examples and animations, and even Python code examples that you can run without leaving your browser, to explore the astrophysics of galaxies yourself.

This book is currently in press with Princeton University Press with an anticipated release in Spring 2026; check out the book’s page here: Dynamics and Astrophysics of Galaxies (Princeton University Press). The book can be cited as “Bovy J. Dynamics and Astrophysics of Galaxies. Princeton University Press, Princeton, NJ (2026; in press)”.

Front Matter

• Preface
• 1. Introduction

Preface

Introduction

Part I: Basics of galactic dynamics

• 2. Gravitation
• 3. Elements of classical mechanics
• 4. Orbits in spherical mass distributions
• 5. Equilibria of collisionless stellar systems
• 6. Masses of spherical stellar systems

Gravitation

Elements of classical mechanics

Orbits in spherical mass distributions

Equilibria of collisionless stellar systems

Masses of spherical stellar systems

Part II: Disk galaxies

• 7. Gravitation in galactic disks
• 8. The kinematics and dynamics of galactic rotation
• 9. Orbits in disks
• 10. Equilibria of galactic disks
• 11. Chemical evolution in galaxies

Gravitation in galactic disks

The kinematics and dynamics of galactic rotation

Orbits in disks

Equilibria of galactic disks

Chemical evolution in galaxies

Part III: Elliptical galaxies

• 12. Gravitation in elliptical galaxies and dark matter halos
• 13. Orbits in triaxial mass distributions and surfaces of section
• 14. Equilibria of elliptical galaxies and dark matter halos
• 15. Gravitational lensing
• 16. Mass modeling in elliptical galaxies

Gravitation in elliptical galaxies and dark matter halos

Orbits in triaxial mass distributions and surfaces of section

Equilibria of elliptical galaxies and dark matter halos

Gravitational lensing

Mass modeling in elliptical galaxies

Part IV: Galaxy formation and evolution

• 17. Formation of dark matter halos
• 18. Extragalactic astronomy
• 19. Hierarchical galaxy formation
• 20. Internal evolution in galaxies

Formation of dark matter halos

Extragalactic astronomy

Hierarchical galaxy formation

Internal evolution in galaxies

Appendices

• A. Coordinate systems
• B. Mathematical background
• C. The general theory of relativity and galaxies

Coordinate systems

Mathematical background

The general theory of relativity and galaxies

References

• References

References

Image credits: NGC 7773: ESA/Hubble & NASA, J. Walsh; NGC 5679 Galaxy Group / Arp 274: NASA, ESA, M. Livio and the Hubble Heritage Team (STScI/AURA); M100: NASA, ESA and Judy Schmidt.