Overview

Numerical astrophysics aims to model and understand the physical processes that are responsible for astrophysical phenomena. As a convienient by-product, these numerical simulations can produce stunning visualisations. This page lists several images and movies that can be downloaded, as well as some astrophysical codes that I have written.

Images

Movies

Structure formation in a LCDM Universe

This simulation shows how strucutres form in the Universe. The dark matter first collapses into sheets and filaments. At the intersection of these filaments the dark matter then falls into gravitationally bound objects, called haloes. Each such a halo acts as a potential well into which gas can fall and galaxies form. They are therefore the cradles of galaxy formation.

Galaxy minor merger

This movie shows the interaction of a Milky Way-like galaxy with a satellite galaxy that has a tenth of its halo mass. The interaction triggers the formation of spiral arms, and thickens the disc considerably. For more information on this simulation, have a look at out paper: Moster et al. (2010).

Merger tree simulation

This simulation follows the merger tree of a galaxy. The galaxy is initialised as a disc surrounded by a gaseous halo at z = 1, and simulated until z = 0. When a satellite galaxy enters the virial radius, a particle realisation is added to the simulation. The multiple mergers then have a different impact on the evolution of the galaxy compared to a series of binary mergers. See our paper Moster et al. (2014) for more details.

Driving turbulance in the ISM

In this simulation supernova explosions drive turbulence in the interstellar medium. The size of the periodic box is 256 parsecs, and after each 1.5 million years, a supernova is triggered, releasing 1051erg into the ISM. The interaction of these blast waves leads to the formation of a turbulant filametary structure and a multi-phase ISM.

Driving turbulance in the ISM

This simulation shows how the meshless finite mass algorithm for hydrodynamics performs in a Kelvin-Helmholtz-instability test. Two fluids with different densities in pressure equilibrium are moving with respect to each other along the discontinuity. This drives an instability between the fluids, which causes them to mix. This standard test is generally used to test the performance of hydrodynamic codes.

Codes

I have written several codes for astrophysics. You can download and use some of them freely. Please do not forget to include a reference in your work, should you find any of these codes useful.


Cosmic Variance Cookbook

This is a publicly available IDL code which computes cosmic variance (sample variance) for galaxies in given stellar mass bins as a function of mean redshift and redshift bin size. It is based on work in Moster et al. (2011).

Cosmic Variance IDL Code

The empirical galaxy formation model Emerge

Emerge, an Empirical ModEl for the foRmation of GalaxiEs, is a freely available code that populates simulated dark matter halo merger trees with galaxies using simple empirical relations between galaxy and halo properties. For each model represented by a set of parameters, it computes a mock universe, which it then compares to observed statistical data to obtain a likelihood. Parameter space can be explored with several advanced stochastic algorithms such as MCMC to find the models that are in agreement with the observations. For any model, Emerge can generate mock galaxy catalogues and main branch histories.

Emerge Website