Radio spectra of galaxies undergoing feedback by relativistic jets

The main aim of this project is to parallelise an existing Fortran program to take advantage of the parallel processing environment of the supercomputer raijin, located on the ANU campus.

The current program evaluates the radio spectrum of nonthermal jet plasma interacting with thermal gas in a clumpy inhomogeneous medium. The emissivity of the plasma is a power-law in frequency; the thermal gas is responsible for free-free absorption and this in turn produces a low frequency turnover in the spectrum. The location and spectral slope of the turnover are important diagnostics of the conditions in the thermal medium.

The existing program traces rays through the volume, perpendicular to the jet axis and evaluates the spectrum along each ray. It then sums up the contribution from each ray to produce a spectrum of the entire source.

The current program takes several hours to run in single processor mode. This could be shortened considerably by using OpenMP or MPI to make the time consuming part of the program work in parallel.

Other features to be pursued if there is enough time include

1. Spectra from specified regions
2. Other directions of rays (i.e. not perpendicular to jet axis)

For more information about this potential research topic or activity, or to discuss any related research area, please contact the supervisor.

Figure Caption: Mid-plane density slice of a 1045 erg s-1 jet (blue colour) powering its way through a clumpy medium populated with dense clouds (yellow and red). The colour bar indicates the value of log (number density). The clouds are responsible for the free-free absorption of the radio emission from the non-thermal jet plasma and this determines the resulting spectrum.

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