PH700
Professor Michael Smith
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Project: Shock waves in molecular clouds
Shock waves are observed in many locations in the Universe: they are almost
ubiquitous. http://www.phy.duke.edu/~kolena/shockwave.html
http://www.astro.uiuc.edu/~pmricker/research/numhydro/
They represent the impact of gas moving at supersonic speeds. When one of the
components is molecular, strong infrared emission may result. In particular,
strong emission lines of molecular hydrogen in the near infrared are found.
Although the emission lines can be modeled, it is not clear how robust the
interpretations are. This will be of great importance in the coming years, with the
next generation (James Webb) Space Telescope planning to carry several narrow
filters at the wavelengths of molecular hydrogen lines.
The object of this project is to write a code for shock waves which can be used to
predict their physical and observable properties. The first aim is to take an existing
FORTRAN code for shock waves and generate a MATLAB version. A step-by-step
process will be undertaken which can be terminated at any stage according to time
constraints. First, the code for a hydrodynamic one dimensional adiabatic shock
wave will be written, and the nature of a shock wave understood. Then, cooling
and heating functions can be added to produce a radiative shock. Finally, the
strengths of molecular lines can be predicted by adding appropriate formula.
Predictions for near infrared and mid infrared wave bands observed from ground
and space based telescopes may then be employed to construct infrared colourcolour diagrams. These can be used by observers to help distinguish shock waves
from faint stars.
A further goal may be to construct the shock wave equivalent of the ‘Cloudy’
astrophysical photoionisation code, adding more complex physical processes,
magnetohydrodynamics and chemistry.
Learning outcomes: ability to understand and review scientific literature. Ability
to manipulate and exploit astronomical computer codes. An understanding of
astrophysical hydrodynamics and supersonic flow. An understanding of infrared
astronomy.
To begin
1.
2.
3.
4.
Literature review of numerical methods for astrophysics
Literature review of shock waves: types, physics, stability.
Simple methods for steady state flows
Build a shock wave model in terms of the shock speed, shock area, and the
upstream conditions: calculate shock profiles….working from equations
and fortran code, construct adiabatic shock, radiative shock, …..
5. Put in modules for cooling and H2 chemistry
6. Calculate shock properties: e.g. ‘the breakdown speed’; the speed for which
H2 gets destroyed.
References: The stability of radiative shocks
http://ukads.nottingham.ac.uk/abs/1989MNRAS.238..235S
Jump Shocks in Molecular Clouds - Speed Limits and Excitation Levels
http://ukads.nottingham.ac.uk/abs/1994MNRAS.266..238S
PH700
Professor Michael Smith
SHOCK WAVES IN ASTROPHYSICS
http://www.physics.hku.hk/~phys3031/Chapter_4_08.doc
Herbig-Haro Flows: Probes of Early Stellar Evolution
http://ukads.nottingham.ac.uk/abs/2001ARA%26A..39..403R
Theory of interstellar shocks
http://ukads.nottingham.ac.uk/abs/1993ARA%26A..31..373D
More on equations:
http://msowww.anu.edu.au/~geoff/HEA/Shocks_4.pdf
http://ukads.nottingham.ac.uk/abs/2005M%26PS...40.1283T
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