Introduction

Peest et al. 2017 describe a method for simulating the effects of scattering by spherical dust grains on the polarization of radiation in Monte Carlo codes such as SKIRT. Furthermore, they define a number of test cases to verify the simulation results by comparison with analytically calculated solutions.

References and downloads

Publication	Peest et al. 2017 [ADS]
Ski files	peest_tc1.ski peest_tc2.ski peest_tc3.ski

SKIRT results

The figures below show the SKIRT results (red) plotted over the analytical solutions (blue) for the first three test cases defined by Peest et al. 2017. The results for the fourth test case are not shown because SKIRT does not have a built-in material mix corresponding to the artificial, non-physical material used in that test case to produce circular polarization.

The panels below correspond to those of Figure 4 of Peest et al. 2017. They show relevant properties of the observed radiation as a function of the position along the horizontal axis of the detector ("x extent"). The top row shows the intensity (in arbitrary units), the middle row shows the linear polarization degree, and the bottom row shows the polarization direction or angle.

For test case 1, note that the polarization angle is undefined at the central horizontal position because the polarization degree becomes zero there. The resulting numerical instabilities at and near that position cause a spike in the otherwise essentially flat curve.

For test case 3, note that the polarization angle should be interpreted modulo 180 degrees, which maps the curve for this test case (bottom right panel) onto the one shown by Peest et al. 2017.

Test case 1	Test case 2	Test case 3

Performing this benchmark

To perform this benchmark, download the ski files provided above for each of the three test cases (References and downloads) and pass their names to SKIRT on the command line.