Course Unit Page
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Teacher Filippo Fraternali
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Credits 6
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SSD FIS/05
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Teaching Mode Traditional lectures
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Language Italian
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Campus of Bologna
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Degree Programme Second cycle degree programme (LM) in Astrophysics and cosmology (cod. 8018)
Academic Year 2016/2017
Learning outcomes
The student will get acquainted with the theory of ideal and viscous gases and its application to the study of the interstellar medium in galaxies. In particular, they will be able to describe the processes of star formation and stellar feedback. They will also acquire a broad knowledge of the main observational techniques (e.g. of optical and radio emission lines) that allow the study of gas kinematics in galaxies.
Course contents
1. Overview on ISM: Composition and spatial distribution in
galaxies, phases and equilibria, cooling and heating, Maxwellian
distribution.
2. Ideal gas dynamics: Equation of continuity and Euler eq.;
Pressure; Equation of state: Barotropic, adiabatic and isothermal
flows; Energy equation; Heat sources: conduction and radiation;
Entropy and the heat equation; Propagation of sound waves, sound
speed; Hydrostatics: isothermal slab, z-distribution with
stars; Shock waves and instabilities: Jump conditions;
Adiabatic shocks; Entropy jump in adiabatic shocks; Radiative
shocks; Convection; Instabilities: Rayleigh-Taylor,
Kelvin-Helmholtz, Gravitational, Rotational, and Thermal.
3. Viscous fluids and turbulence: Momentum flux and stress tensor;
Viscous stress tensor; Navier-Stokes equation; Vorticity in ideal
and viscous fluids; Energy dissipation in viscous flows; General
heat equation; Reynolds number; Transition to turbulence in a
Poiseuille flow; Fully developed turbulence, Kolmogorov law;
Compressible turbulence, sources of turbulence in the ISM.
4. Molecular clouds: composition and properties. Plasmas: Charge
neutrality, infinite conductivity; Field freezing; Euler equation
with magnetic force; Magnetic Pressure and tension; Magnetic virial
theorem; Shocks with magnetic field. Stability of
clouds: Isothermal sphere, Lane-Emden equation; Bonnor-Ebert
sphere and mass; Analysis of stability; Effect of rotation; Effect
of magnetic field; Hydromagnetic waves; The role of turbulence.
Collapse of clouds: Free-fall time; Self-similar collapse;
Ambipolar diffusion, magnetic braking.
5. Effect of massive stars on the ISM (feedback): Evolution of
SNRs - adiabatic phase; Sedov -Taylor solutions for shell interior;
Pressure driven and Snowplow phases; Energy budget; Stellar wind
bubbles: structure and self similar solution; Temperature, pressure
& evolutionary phases; Energy budget; Superbubbles: evolution,
blowout, SNR inside superbubbles; Galactic fountain and winds.
Readings/Bibliography
Principles of Astrophysical Fluid Dynamics, C.
J. Clarke & R. F. Carswell, Cambridge University Press
The Physics of Astrophysics II: Gas dynamics, F. H. Shu, University Science Books
The Formation of Stars, S. W. Stahler & F. Palla, Wiley-VCH
Physical Processes in the Interstellar Medium, L. Spitzer, Wiley-VCH
Teaching methods
Lectures can be in ENGLISH if there are non-italian speaking students
Assessment methods
Oral exam
Teaching tools
Blackboard and powerpoint presentations.
Links to further information
http://www.filippofraternali.com/filippofraternali/Teaching/Teaching.html
Office hours
See the website of Filippo Fraternali