27218 - Extragalactic Astrophysics

Learning outcomes

Working knowledge (qualitative and quantitative) of extragalactic astrophysics. Subjects cover the structure, dynamics, formation and evolution of galaxies and their gaseous and dark matter components. Special attention is dedicated to central supermassive black holes, accretion theory and AGN physics. Some information about modern cosmology is also provided. The student will be able to understand research papers on extragalactic astrophysics.

Course contents

OBSERVATIONAL-MORPHOLOGICAL SECTION: General properties of stellar systems, from galactic to cluster scales; luminosity profiles, colors and stellar populations; kinematical properties:velocity dispersion, rotational velocity, ellipticity; Mbh-sigma, Lx-Lb, Faber-Jackson, Kormendy, Fundamental Plane, Tully-Fisher relations. Introduction to observational Cosmology.

THEORY (part 1): Basics of Stellar Dynamics: slingshot effect, collisionality and two-body relaxation time in impulsive approximation, dynamical friction, virial theorem, phase-space distribution functions, Jeans equations.Gravitational evaporation, gravothermal catastrophe and gravothermal oscillations. Dynamical evolution of open and globular clusters. [this part can be considered an introduction to the course of Dynamics of Stellar Systems]

THEORY (part 2): Elements of astrophysical fluido dynamics (material derivative, transport theorems, continuity, momentum and energy equations, viscosity and thermodynamics, Kelvin, Bernoulli, Poincare' theorems, barotropic and baroclinic equilibria, rotating flows, dispersion relations, sound velocity). Basics of accretion phenomena, Bondi accretion, Eddington luminosity, Jeans instability. Galaxy formation: monolithic, dissipationless and dissipative galaxy formation. Relations between QSO activity and galaxy formation. Cooling flows.

THEORY (part 3): introduction to modern Cosmology. Newtonian and relativistic cosmology. Evolutionary models: flat, open and closed models of the Universe. Introduction to LCDM cosmological model.

Readings/Bibliography

The reference text is 

"Introduction to Stellar Dynamics" (L. Ciotti, Cambridge University press)

Recommended additional readings: selected chapters from

"Dynamics of galaxies" (G. Bertin, Cambridge University Press)

"Galactic Dynamics" (J. Binney, S. Tremaine Princeton University Press)

"Galactic Astronomy" (J. Binney, M. Merrifield Princeton University Press)

"Supermassive Black Holes" (A. King, Cambridge University Press)

"Lecture Notes on Stellar Dynamics' (L. Ciotti - Scuola Normale Superiore Pisa, Springer-Verlag)

"Introduction to Cosmology" (B. Ryden, Addison Wesley)

Teaching methods

Class lectures with illustrative exercises. Discussion of the most relevant research papers published on international journals.

Assessment methods

Oral exam, on the blackboard, in the classroom. The exam has a maximum duration of 45 minutes and is divided into three parts (each lasting up to 15 minutes). Free-form topics are not permitted.

First part: Students are asked to present the general concepts of a topic from the syllabus (the purpose is to test their ability to present and analyze in depth, and their understanding of the topic in its astrophysical context).
Second part: Students are asked to solve and discuss a simple problem (the purpose is to test formal/numerical skills and the ability to make order-of-magnitude estimates of physical phenomena).
Third and final part: A question on a course topic unrelated to the first and second questions, requiring a simple answer (e.g., a given formula, a given result) without in-depth discussion (the purpose is to test overall preparation).

Each of the three questions is immediately scored numerically from 0 to 10:

1) Seriously incomplete/incorrect answer: less than 6
2) The knowledge demonstrated, even if incomplete, reveals sufficient preparation to allow the result to be used in other courses or, in any case, does not impede necessary in-depth study: between 6 and 8
3) Complete and comprehensive answer demonstrating full mastery of the topic and independent reflection on the discussion: between 8 and 10.

The final exam grade is the sum of the three grades. Please note that

• The order of presentation, clarity of language, and ability to formalize the mathematical aspects in a technically acceptable manner are all factors that influence the grade for each question.
• Pursuant to the CdS resolution of June 20, 2025, a successfully passed exam grade cannot be rejected more than twice; In case of retaking the exam, the final grade will be that of the last exam taken.
• Students with learning disabilities or temporary or permanent disabilities: contact the office https://site.unibo.it/studenti-con-disabilita-e-dsa/it

Teaching tools

Blackboard. Tools for online lectures. Lecture notes.

Office hours

See the website of Luca Ciotti