Project Advisor: Prof. Tereasa Brainerd

Weak lensing by galaxy clusters is a well-known and well-understood phenomenon in the universe. Here we will explore the theory of weak lensing to determine the degree to which observations of lensing clusters can provide information about two distinct quantities: [1] the mass density profile of the cluster lens and [2] the redshift distribution of the lensed galaxies.

Time per week needed to carry out the project:
5 to 10 hours

Number of semesters required to complete the project:
2 or more, depending on the student's level of interest

What the student will learn during the project:
The student will learn the basics of weak lensing theory, ray-tracing, and the analysis of high-resolution computer simulations. In the case of the investigation of the redshift distribution of the lensed galaxies, the student will also learn about the intrinsic clustering of galaxies in the universe and how it can be affected by weak lensing. These projects require fairly strong analytical skills and at least basic computational skills (i.e., computer programming). We will likely make use of BU's parallel supercomputers in order to carry out the projects, but no previous experience with parallel environments is necessary.

Anticipated results:
In the first study we will determine whether or not the standard theoretical dark matter density profiles can simultaneously reproduce both the observed weak shear fields of cluster lenses (as obtained from HST imaging) and the details of their velocity fields. In the second study we will determine whether or not weak lensing by clusters will provide useful constraints on the shape of the redshift distribution of galaxies with redshifts between z=1 and z=2.5. The majority of the 80 billion galaxies in the universe are expected to exist at such redshifts, but their redshifts are inaccessible to optical spectroscopy. Therefore, the development of statistical methods which can constrain the shape of their redshift distribution are needed, and it is expected that weak lensing will be able to provide such constraints.