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

The course provides an overview of the physical processes governing the interstellar medium (ISM) and its fundamental role in the formation and evolution of galaxies/AGN. The course will provide tools needed to interpret current observations from major facilities such as ALMA and JWST.

Introduction

• Historical overview of the study of the interstellar medium.
• The different components of the interstellar medium (gas, dust, and cosmic rays). Major heating and cooling processes.

Spectroscopy

• Review of electronic, vibrational, and rotational transitions.
• Review of permitted, semi-forbidden, and forbidden transitions; fine-structure and hyperfine-structure lines.
• Detailed discussion of the key transitions used to probe the different phases of the ISM (e.g. Hα, [C II], and CO).

Level Populations and Line Formation

• Statistical equilibrium, level populations, Einstein coefficients, Local Thermodynamic Equilibrium (LTE), and the critical density
  
• Level population calculations coupled with radiative transfer. The escape probability formalism.
• Modelling the ISM: introduction to cosmological zoom-in simulations and the spectral synthesis code CLOUDY. Modelling of Photo-Dissociation Regions (PDRs) and X-ray-Dominated Regions (XDRs) to quantify the impact of star formation and black hole accretion on the ISM.

Interstellar Dust

• Absorption, scattering, and extinction cross sections. Composition of interstellar dust, polycyclic aromatic hydrocarbons (PAHs), Mie theory
• Chemical evolution of interstellar dust: formation, growth, and destruction processes.
• The dusty torus surrounding Active Galactic Nuclei (AGN).

The ISM in Galaxies from the Local Universe to the Epoch of Reionization

• Overview of recent results obtained with state-of-the-art ground-based and space facilities.
• The Schmidt–Kennicutt relation and its physical interpretation.
• Statistical methods for deriving the intrinsic evolutionary properties of galaxy populations while accounting for observational biases (i.e. luminosity functions)
• Cosmological evolution of the different gas phases and their connection to the evolution of the cosmic star formation rate density and black hole accretion rate density.
• The interstellar medium in primordial galaxies observed with ALMA and JWST.

Readings/Bibliography

The final examination can be prepared using the lecture slides and the review articles provided during the course. These materials will be made available on the Virtuale platform after each lecture.

The following textbooks are recommended for students who wish to explore the course topics in greater depth:

• Draine, B. T., Physics of the Interstellar and Intergalactic Medium, Princeton University Press.
• 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/theoretical 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.

 

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.

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.

The use of AI is forbidden during the examination.

 

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.

Office hours

See the website of Francesca Pozzi