The OverWhelmingly Large Simulations Project
The project for my PhD is part of the OverWhelmingly Large Simulations project. OWLS consists of a large suite of cosmological N-body/SPH simulations, using a modified version of Volker Springel's Gadget code. The power of the projects lies in the large variation of subgrid models for the unresolved physics. For the non-experts: simulations have a limited mass resolution (and a limited spatial resolution). Therefore, many processes that are important in the formation of galaxies (e.g. forming stars, growing a supermassive black hole in the center, exploding supernovae, ...) can not be followed explicitly. Therefore one makes assumptions about how these processes work out on the larger scales that can be resolved. These models are called subgrid models, and the most important aspect of OWLS is the large variation in these models.
In particular, the following parameters are varied:
A list of OWLS related papers with more (technical) information can be found in the links section.
My Project: The Galaxies
My project focuses mainly on the galaxies that form inside a the simulation box, a beautiful example of which you see depicted here (click on it to see it from three sides). Selecting these galaxies automatically is not as trivial as it may seem, as a computer cannot look at such images as we can.
A part of my topic is to select groups of particles that make up something together that an observer might call a galaxy. A comparison of several of these methods, from very easy (by linking particles that are close enough together), along physically motivated (group together gravitationally bound structures) all the way to creating mock observations of the simulation (and selecting galaxies with the tools observers would use for the same purpose) is an important part of my project.
Once the galaxies are identified I try to explain their physical properties (total mass, mass in stars, ages, metallicity, star formation rate, luminosity, etc...) and relate them to the input physics of the specific run. Example questions are "How is the star formation rate of a galaxy related to the wind velocity due to supernova explosions?" and "What kind of processes do we need to explain the observed, red and dead (no star formation) elliptical galaxies?"
Getting observables (magnitude, color, reddening due to dust) for galaxies is also something of my concern. I implemented an adapted version of the Bruzual and Charlot (2003) population synthesis code to determine the luminosity of the stellar component of the simulated universe. This light then travels towards us and encounters gas and dust. What this gas and dust do to the light is vaguely known and I am now trying to consistently model effects, in order to come up with realistic luminosities and colors of the galaxies.
Other OWLS Projects
There is quite a big list of people working with the OWLS simulations. Some of them may be found in my links section. If they alread published a paper, that can probably be found in the list of papers about OWLS on the links section.