96454 - Galaxy Clusters

Learning outcomes

The aim of this course is to provide a broad-band knowledge of the physical properties of galaxy clusters ecosystem (dark matter, gas, galaxies and non thermal components). At the end of the class the student will be familiar with the current astrophysical research on the evolution of gas and galaxies in clusters. The student will acquire a deep understanding of several important processes, like AGN feedback, chemical enrichment, galaxy ram pressure stripping, relativistic particles physics, and more. The course will provide the necessary astronomical background and will dive deep into several key research topics, always comparing theory and observations. At the end of the course the student will be able to comprehend research papers on these subjects.

Course contents

This course is arranged in two modules: module 1 by Fabrizio Brighenti deals with theoretical subjects related to gas and galaxy astrophysics in Clusters. Module 2 by Myriam Gitti mainly concerns with the non-thermal components of Galaxy Clusters, such as magnetic fields and relativistic particles. Both modules include some (guided) lab sessions to allow the students to work on real astro-problems, through analysis of simulations (module 1) and real observational data (module 2).

Module 1 content:

Physical components of Galaxy Clusters: dark matter, intracluster gas, galaxies, relativistic particles and magnetic field.

Intracluster medium: basics of plasma physics. Equilibrium configurations of the gas. Thermal and dynamical evolution of the gas: theory of cooling flow. Cooling flow problems. AGN feedback. Chemical enrichment of the intracluster medium. Use of clusters in Cosmology.

Galaxies: morphology-density relation. Dynamical interactions between galaxies: mergings and harassment. Interaction between galaxies and the intracluster medium: ram pressure stripping and evaporation. Formation of the central galaxy: dynamical friction.

Module 2 content:

Frontal lectures (~4 hours):
Radio-mode AGN feedback: AGN/ICM interaction; cavity energy, age and power; shock detectability; proxy of AGN power; energy equipartition (minimum energy of a radio source); radio lobe composition; presentation of the practical activity on RBS 797.
Diffuse radio emission: observational properties of radio halos, relics and mini-halos; X-ray and radio connection; basic theory: estimate of radio source age, slow diffusion problem, hadronic and leptonic models, turbulent and shock re-acceleration.

Practical activity (~4 hours): tutorial on X-ray Chandra data analysis with the software ds9; individual work: estimate of cavity power from the Chandra image of the cluster RBS 797.
The students are requested to provide a short report (2-3 pages) of the activity before the oral exam.

Readings/Bibliography

Slides of the lectures (provided before the lectures)

Specific chapters of several books and several scientific papers, quoted during the lectures and in the slides, for example:

Gitti, Brighenti & McNamara, 2012, "Evidence for AGN Feedback in Galaxy Clusters and Groups", Advances in Astronomy, vol. 2012, ID 950641 (link: https://onlinelibrary.wiley.com/doi/10.1155/2012/950641 )

McNamara & Nulsen, 2007, ARAA, Vol 45, 117. Link: https://arxiv.org/pdf/0709.2152

Brunetti & Jones, 2014, "Cosmic Rays in Galaxy Clusters and Their Nonthermal Emission", International Journal of Modern Physics D, Volume 23, Issue 4, id. 1430007-98 (Preprint: arXiv:1401.7519; Link: https://arxiv.org/pdf/1401.7519 )

Teaching methods

Teaching makes use of powerpoint presentations (always available before the lectures on the Virtuale website) and blackboard.

Practical activity: visualization and simple analysis of X-ray (Chandra) data with the software ds9 (module 2). During the Lab sessions the students will be guided by the professor and a tutor. Students can use both the PC in the Lab or her/his own laptop (some help with the software installation will be provided).

Note: to attend this class it is required by the University policy that all students take the on-line courses (modules 1 and 2) on the Safety in University Computing Lab (see: https://elearning-sicurezza.unibo.it/).

Assessment methods

The students must take an oral exam and submit (at least two days in advance of the oral exam) a very brief (2-3 pages) written report on the Lab projects.

The oral exam includes a discussion on a few topics covered in the class. The first part is about a subject chosen by the student. The second part concerns questions on other topics covered in the class.

The grade scale, 0-30, can be (roughly) described as:

1) limited (though sufficient) preparation and capability to discuss and explain theoretical and observational topics: 18-22;

2) satisfactory though not complete preparation in technical, observational and theoretical issues: 23-25;

3) good/very good capability to explain and provide almost complete answers to theoretical questions: 26-28;

4) excellent/outstanding ability to discuss the topics covered in the course, including unsolved problems currently studied by the scientific community: 29-30. Honors are awarded by the professor to students who have shown exceptional mastery.

By policy of the LM in Astrophysics and Cosmology Course, students may not decline a grade more than twice.

Students with learning disabilities or temporary or permanent disabilities: please contact the relevant University office promptly (https://site.unibo.it/studenti-con-disabilita-e-dsa/it). The office will advise students of possible adjustments, that will be submitted to the professor for approval 15 days in advance. He/she will evaluate their suitability also in relation to the academic objectives of the course.

Teaching tools

Powerpoints presentations (always available before the class), blackboard writing, guided laboratory sessions.

Office hours

See the website of Fabrizio Brighenti

See the website of Myriam Gitti