Understanding Dark Matter Halo Formation in Numerical Simulations
(MSc or PhD)
Galaxies and clusters of galaxies form within surrounding dark matter halos, large, roughly spherical distributions of dark matter bound together by gravity. Since dark matter halos are invisible to normal telescopes, most of what we know about them comes from computer simulations. We know they have a range of shapes and a characteristic density profile, but we still can’t explain how these properties arise from fundamental theory.
This project would involve running “n-body” simulations of cosmological structure formation, finding halos in these simulations, and studying how their properties change over the history of the Universe. In particular, it would look at how mergers between halos rearrange their internal structure. Good theoretical models of this process are essential to understand current observations in gravitational lensing surveys, as well as searches for galaxy clusters using their x-ray or microwave emission.
In massive clusters, we can use the galaxies themselves to trace out the details of a dark matter halo’s mass distribution, and possibly even find partially-digested debris from previous mergers. In recent work with my students Anson Wong and Uzair Hussain, we have shown that the relative amount of debris, substructure or inhomogeneity in a halo provides a good measure of its age (or formation time), and that cluster ages in turn provide a useful test of cosmological models. Deriving and calibrating age estimates for clusters is an important goal for LoCuSS, one of the surveys I am participating in.
This project would compare gravitational lensing data from the LoCuSS and other surveys with n-body or semi-analytic models of dark matter halos, in order to develop this important cosmological test. Depending on the student’s interest, it might also include other related work on gravitational lensing at higher redshift, or lensing tests of dark energy.
Galaxy Cluster Age as a Test of Cosmology
(MSc or PhD) Searching for the Smallest Galaxies
(MSc or PhD)
One of the most surprising predictions of cold dark matter simulations is that dark matter structure should form over a very wide range of scales, from the scale of massive clusters down to scales much smaller than our galaxy. This is surprising because we observe relatively few small galaxies. Where then is all the predicted small scale structure?
In recent work, my M.Sc. student Ryan Speller was able to identify one population of faint dwarfs using a clustering analysis of the Sloan Digital Sky Survey. There are several deeper data sets now available that might yield even more of these “missing satellites”.
This project would involve a combination of theoretical modelling with data analysis, searching through several recent data sets for signs of very faint galaxies, and trying to understand their spatial and kinematic distribution. It is a good project for a student who has some interest in or experience with observations, or for a M.Sc. student who is considering an observational Ph.D..
For information about these or other projects, please contact me at taylor@uwaterloo.ca.
I have a number of possible research projects for students who are considering graduate studies in Astronomy and Astrophysics. These projects are mainly theoretical, but may involve some analysis of observational data as well. All of them require very strong programming skills, and would be much easier for a student with several years of programming experience. Please contact me or check my website for more details.
Graduate Research Projects