96398 - THE INTERSTELLAR MEDIUM

Learning outcomes

At the end of the course, the student has a detailed knowledge of the observational and physical properties of the interstellar medium (ISM). In particular, the student acquires knowledge of the main constituents of the ISM (ionized, atomic, and molecular gas; dust; magnetic fields; cosmic rays; EM radiation), the different environments in which these are encountered (the 2- and 3-phase models of the ISM) and the physical processes that govern them. In addition, the student will acquire some knowledge about the central role played by the ISM in the evolution of galaxies and AGN across the cosmic time.

Course contents

Introduction to the Interstellar Medium

- History of the study of the Interstellar Medium

- The different components of the interstellar medium (i.e. gas, dust, cosmic rays); how the are excited/heated, how they cool, and how can be observed.

Spettroscopy

- Recap of electronic, vibrational and molecular transitions.

- Recap of allowed, semi-forbidden and forbidden lines; fine and hyperfine structure lines

- Detailed focus on key transition to study the different gas phases in the ISM (i.e. Halpha; [CII], CO)

Level population and line formation

- Statistical equilibrium equation, level populations, and line formation. Einstein coefficients, Local Thermal Equilibrium (LTE) condition, and critical density of various transitions.

- Line ratios as diagnostics for density, temperature and abundance.

- Line formation coupled with the radiative transfer equation. Escape probability Formalism.

- Modelling the ISM: introduction to cosmological zoom-in simulations and the spectral synthesis code CLOUDY code. Modelling the Photo Dominated and the X-ray dominated Regions (PDRs/XDRs) to quantify the impact of the star-formation and the black hole accretion on the ISM

Interstellar dust

- Extinction curves and reddening. Definitions of absorption, scattering and extinction cross sections. Constituents of the interstellar dust. PAHs. Mie theory. Radiative heating and cooling of dust grains.

- Dust chemical models: dust formation, evolution and destruction.

- The dusty 'torus' around Active Galactic Nuclei (AGN)

The ISM in local galaxies

- Overview of recent results obtained with state-of-the art telescopes and satellites

- Spatial distribution of the different ISM components. ISM kinematics and presence of outflows.

- Schimdt-Kennicutt law (SK) and its interpretation

The ISM in galaxies from the local Universe up the reionization epoch

-Overview of recent results obtained with state-of-the art telescopes/satellites.

- Methods to construct the luminosity function and derive intrinsic evolutionary properties

-Cosmological evolution of the different gas phases and their with the evolution of the star-formation density and of the Black Hole accretion density. Methods to derive the cosmological evolution of key galaxies properties, corrected for observational biases.

-The ISM content of primordial galaxies discovered by ALMA and JWST

Readings/Bibliography

The final exam can be prepared using the lecture slides and review articles given during the lessons. Both will be available in the web site 'Virtuale' at the end of each lecture.

Additional text books useful for further detailed study are:

Draine B., 'Physics of the interstellar and intergalactic medium', Princeton Series in Astrophysics

Tielens A. ,The physics and chemistry of the interstellar medium', Cambridge

Teaching methods

The course is made of 6 CFU, corresponding to 48 hours of front lectures. These are made with the support of power-point presentations and at the blackboard for specific demonstrations and clarifications.

Key and updated observational aspects of the ISM will be presented with the use of articles/reviews and thanks to few lessons given by colleagues of INAF-OAS on specific topics.

There will be room for questions and discussion.

Assessment methods

The final examination aims to verify and evaluate the achievement of the learning objectives. It consists of an oral assessment, usually lasting 45 minutes. The blackboard will be used.

The exam begins with a topic chosen by the student. The topic will be part of the course program, but students are expected to explore it in greater depth using additional articles and reviews. A couple of questions will be asked to assess the student’s understanding of the chosen topic. Afterwards, there will be another couple of questions on different subjects. The aim of the exam is to evaluate the student’s overall knowledge, as well as their ability to reproduce the mathematical demonstrations presented during the lectures.

Grade of the marks:

The grade scale is 18/30-30/30.

Preparation on a very limited number of topics covered in the course and analytical ability that emerges only with the help of the teacher, expression in generally correct language → 18-21;

preparation on a large number of topics covered in the course but analytical ability autonomous only in a limited way, and/or only on purely executive questions, expression in correct language → 22-25;

Preparation on a large number of topics covered in the course, ability to make autonomous choices of critical analysis, mastery of specific terminology → 26-29;

Preparation complete and excellent ability to independently carry out critical analysis and connection between the various topics covered in the course, with full mastery of the terminology and argumentation ability, → 30 or 30L

 

The grade can be rejected up to two times, in accordance with the decision of the Degree Program Committee.

Teaching tools

Lectures are supported by power-point presentations, which are updated and made available to the students every year on the dedicates web site "Virtuale UniBo" of the Bologna University.

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.

Office hours

See the website of Francesca Pozzi