HIGH ENERGY ASTROPHYSICS

Second cycle degree in ASTRONOMY

Campus: PADOVA

Language: English

Teaching period: First Semester

Lecturer: ALBERTO FRANCESCHINI

Number of ECTS credits allocated: 6


Syllabus
Prerequisites: The mandatory courses of 1st year of Laurea Magistrale in Astronomia
Examination methods: Oral discussion
Course unit contents: FUNDAMENTALS OF CLASSICAL ELECTRODYNAMICS. Basic formulae of electro-magnetism in the classical limit.Electromagnetic waves. The relationship of electric charges and the radiation fields (radiations from moving charges, Lienard-Wiekert potentials, fundamental equation,Larmor,dipole emission,multi-polar contributions,the radiation spectrum.
BREHMSSTRALUNG RADIATION. The classical limit,electric dipole contribution.The Gaunt factor.Thermal Bremsstrahlung.Plasma cooling by free-free emission.Radiative transfer and Bremsstrahlung self-absorption.Relativistic and non-thermal Bremsstrahlung. Applications of thermal free-free emissions by astrophysical plasmas.
GAS DYNAMICS AND PLASMA EFFECTS. Fundamentals of hydrodynamics. General equations and conservation laws.Adiabatic and isothermal stationary flows.Sound waves.Particle collisions in plasmas. Momentum transfer among particles:viscosity.Energy transfer and heat conduction.Shock waves. Effects of magnetic field.
HOT PLASMAS IN GALAXIES AND CLUSTERS OF GALAXIES.Fundamental physical parameters.Thermalization timescales.Heat conduction. Magnetic field effects.Ionization mechanisms.Collisional ionization.Line emissions.Metal abundances in the plasma.Models of plasma distribution.Cooling and heating mechanisms.Origin, astrophysical and cosmological significance of the IC plasma.
SYNCHROTRON RADIATION.Charges in magnetic fields.Total synchrotron emitted power.Aberration, beaming, angular distribution of radiation.Synchrotron spectrum of a single pulse and its spectrum.The transition from the cyclotron to the synchrotron spectrum.Emission by a non-thermal electron distribution.The full treatment. Synchrotron self-absorption and spectral cutoffs.Synchrotron polarization. Limits of validity of our treatment.Electron energy losses and synchrotron spectral evolution.Radio-galaxies and their synchrotron emission. Energetics of the synchrotron emission by radio galaxies. Radio-Quiet Active Nuclei:Quasars and Seyfert galaxies.
COSMIC RAYS AND ACCELERATION MECHANISMS. Observational properties of cosmic rays.Fermi first-order and second order acceleration mechanisms.
INVERSE COMPTON EMISSION.COMPTONIZATION OF RADIATION.Electron scattering.Quantum effects:the Klein-Nishina cross-section. Compton scattering and Inverse Compton.Emitted power from single scattering.Emission by many particles.Effects of multiple IC scatterings (Compton parameter, spectral distortions, Bose-Einstein distributions, thermal and kinetic Sunyaev–Zeldovich effect).X-ray emission of radio-quiet (and radio-loud) AGNs by thermal Comptonization.Compton reflection. AGN Unification Scheme and the X-ray Background. The BLAZAR phenomenon. Inverse Compton production of very high-energy photons: Synchrotron-Self Compton and External Compton emissions. Doppler boosting. Super-luminal motions.
ACCRETION POWER IN ASTROPHYSICS. The compactness parameter. The Eddington limit. Critical accretion regimes. Bondi and spherically-symmetric accretion. The analogue: accretion in binary systems. Plasma viscosity in disks. Thin accretion discs. Observational tests. Accretion in AGNs.
PROPAGATION OF RADIATION THROUGH PLASMAS. Propagation of electromagnetic waves through plasmas. Propagation along magnetic fields: the Faraday rotation. Cherenkov radiation. Electron-Positron Pair Production (in thermal and non-thermal plasmas).
CHERENKOV ASTRONOMY. Detection technique. Atmospheric showers. Imaging the shower. Existing and future facilities. The VHE extragalactic sky.
THE COSMIC PHOTON-PHOTON AND PARTICLE-PHOTON OPACITIES. Extragalactic background radiations, background energy density. The photon opacity, applications to current and future observations.