RADIOASTRONOMY

The course will address the fundamental questions of current Astrophysics, providing students with an overview of the potential of the radio frequency range, which allows us to probe the universe from its initial moments. The student will acquire a detailed knowledge of Radio Astronomy, current and future instruments, fundamental know-how to access the world of international research in the near future. These topics are widely addressed by the INAF radio group - Catania Astrophysical Observatory.

Aims of the course are topics of Astrophysics not fully understood: supernovae explosions, radio-bursts, pulsars, quasars, galaxy and cosmological evolution up to the reionization era (z~15) and more.,Knowledge of emission processes such as Bremsstrahlung and synchrotron radiation is very important. The student will be directed towards a multiwavelength and/or multimessenger approach, of great importance for a correct interpretation of astrophysical data, but also for a critical approach in all areas of work.

In order to stimulate the ability to apply previous knowledge and to test understanding of the topics that are gradually addressed, during the lessons students will be encouraged to take a first approach to problem solving. We will move on to rigorous treatment, always trying to relate it to the students' original approaches. This stimulates the ability to apply previous knowledge and understanding of the topics already covered.

Personal interpretations of the phenomena studied and comparison with others are encouraged in order to evaluate one's own judgment.

Ability to deal with topics in the field of radio astronomy and astrophysics in general in both Italian and English.

Learning skills: Ability to learn the topics both by attending the course and studying the handouts and recommended books, and by reading scientific and research articles on accredited sites (NASA ESO, ESA, INAF, various Italian and foreign universities and research institutions...).

Attending the lectures is highly recommended; Interaction with students is of fundamental importance for the education of students.

1. Introduction to Radioastronomy. Historic overview, the radio window.
2. The EM radiation– Intensity, Brightness, Flux density, Planck law, Brightess temperature, Approximations at radio wavelengths, Brightness Temperature, Radiative transfer, EM waves in vacuum, Energy of EM field, Propagation of EM waves in a plasma, Plasma frequency, Ionosphere, Dispersion measure, Dispersion measure with Pulsars, Polarisation of EM waves, Faraday rotation, Galactic magnetic field, the radiation spectrum, Electromagnetic potentials, Retarded potentials, Radiation from a single charge, non-relativistic case, Dipole radiation, Dipole approximation
3. Bremsstrahlung radiation (free-free), emission and absorption coefficients, Spectra, Example of Bremsstrahlung radio source: NGC7027
4. Synchrotron radiation, emission and absorption coefficients, Spectra, Energy requirements for synchrotron radio sources, Example of Synchrotron radiosources: Cyg-A, Cas-A – Thomson scattering, Inverse Compton– Sunyaev Zeldovich (SZ) effect
5. Radiotelescopes, Antenna beam, Antenna configurations and mounts, Antenna temperature and brightness temperature, aperture efficiency, telescope gain, effects of Earth’s atmosphere, The receiver system, super-heterodyne receiver, system temperature and sensitivity
6. Interferometry – Basic Theory and theorem of Van Cittert Zernike – Visibility function and sky brightness – Linear Interferometers (WSRT, ATCA)- Angular Resolution of an interferometer– Aperture Synthesis – The mapping process- Interferometers in the world (VLA, VLBI, VLBA, ALMA, SKA)
7. Example of radio sources: Supernovae and Supernovae remnants (SNR) – Shock waves – Fermi Acceleration (first order), Microquasars, superluminal motions, Doppler boosting, Star Forming Regions (HII) –Fast Radio Bursts

The course is based mainly on the first two books. The others are useful for further information.

1. Rybicki and Lightman, Radiative Processes in Astrophysics, John Wiley & Sons, Inc (1979)
2. Rohlfs, Tools of Radio Astronomy, A&A library, Springer-Verlag
3. Burke and Graham-Smith: An Introduction to Radio Astronomy, Cambridge University Press, (1977, 2002)
4. Longair: High Energy Astrophysics, Vol. 1, Cambridge University Press
5. Verschuur and Kellermann eds, Galactic and Extragalactic Radio Astronomy, A&A library, Springer-Verlag

The final grade is based on knowledge of the radioastronomy, the ability of the student to discuss, the clarity of the arguments, the capability to relate different part of the program with other Astrophysical subjects. The active participation of the student to the lesson is also taken into account.

First topic chosen by the student.

Other possible topics:

Radio source spectra and deducible parameters.

Emission processes.

Propagation effects of radio waves in plasmas.

Angular resolution of radio telescopes or interferometers.

Radiotelescopes, receivers, antenna temperature, system temperature, brightness.