Radiative Transfer on Voronoi Meshes

Feb 14, 2019

An increasing amount of astrophysical and cosmological simulations are carried out on a moving unstructed mesh defined by the Voronoi tessellation.

Photons are spawned in a Monte Carlo fashion from emitting gas cells. At each scattering the contribution reaching the observer along specified lines of sight is computed.

Lately, we expanded the priorly used code in Behrens et al., 2019 ( public version here) to work on such meshless structure. This will ensure the code’s relevance in the future and application to new simulations that would not have been able to be processed with prior code due to the larger memory requirement due to an intermediate interpolation step. First applications of the new code include IGM transmission and simulating individual LAEs.

Voronoi Geometry

Below are two impressions of the implemented Voronoi geometry: A video visualizing the geometry itself as seen by a simple raytracing and a projection of the Lyman-$\alpha$ photon contributions moving within such geometry.

Zoom of edge-on view onto galaxy in IllustrisTNG100 at z=3. On shown scales, the Voronoi gas cells have a maximal resolution of 0.3 kpc. Outside of star-forming regions the resolution can be in the order of kpcs. Those Voronoi cells become visible on zoom-ins in the radiative transfer simulations. Yellow regions are well traced out by photons, indicating high HI densities, whereas the cell shapes are not traced in blue regions due to lower densities.

Radiative Transfer

Next, we show the application of the new radiative transfer code with the voronoi data structure applied on different scales. For each scale, one representation without radiative transfer is given, followed by another one with radiative transfer. In this presentation, only emission from star-forming regions is considered. All simulations were carried out at a redshift of 3.0.

Individual Galaxy

Individual Halo

Cosmic Web

Chris Byrohl

Postdoc

My research interests include cosmoslogical galaxy formation simulations, Lyman-$\alpha$ radiation to study galaxies and the large-scale structure, supernovae type Ia and high-performance computing.