Qualifying Exam

Analyzing Stellar Velocity Dispersion in Non-relaxed Stellar Systems


As requested by my advisor, I will give a roughly 45-minute presentation describing my summer research and then I’ll describe my proposed Ph.D. project. Questions will follow.


The project that I worked on this summer examined how velocity dispersion changes during mergers of stellar systems. My goal was to determine how much scatter can be expected in the observed line-of-sight velocity dispersion, $$\sigma_*$$ of a stellar system if the system is observed from random viewing angles during a non-quiescent phase of its evolution. In addition to measuring the velocity dispersion in the way typically done by simulation researchers, I measured velocity dispersion using methods which are somewhat more consistent with observational methods. The methods of determining $$\sigma_*$$ yield significantly different results in some cases. This discrepancy is one of several issues which provides the motivation for performing a more careful and detailed study of velocity dispersion measurements in a future project.

Rough outline:

I will begin by defining a few quantities and reviewing a few important concepts.  The definitions will be followed by an introduction to the $$M-\sigma_*$$ relation and the scientifically important questions that motivated my project. I will then describe the code that I wrote, discuss the output of the simulations that I have performed thus far, and explain why more rigorous work needs to be done in order to answer the questions quantitatively.  I will finish by describing the Ph.D. thesis project that I have designed to answer the questions in a more satisfactory manner.


Before coming to UCR, I earned a B.S. and an M.S. in physics from schools which put special emphasis on theoretical and computational physics. I formally studied numerical analysis, computational physics, and computational fluid dynamics. When I came to UCR, I planned to apply and expand my skill set and knowledge base.  Over the course of last 18 months, I have…
  • independently studied galaxy dynamics and N-body simulation techniques
  • learned C++ and OpenMP (I was previously mostly familiar with Fortran and Matlab)
  • started learning MPI and Python
  • reviewed the galaxy simulation literature and several popular existing simulation codes
  • reviewed much of the observation-based literature regarding galaxy evolution
  • given a short series of introductory lectures explaining the basic principles involved in N-body simulations
  • attended the UC-HIPACC summer school for galaxy simulations
  • written a simple simulation code in C/C++ and OpenMP
  • run several small simulations using my own code
  • analyzed the simulation output
  • Obtained and compiled  source code for the most popular research code in the field: GADGET-2
  • designed a Ph.D. thesis project
  • written proposals to obtain funding for computing time and hardware

I would like to finish the qualifying exam before the end of this quarter. I am available at any time on Mondays, Tuesdays after 1:00 PM, and Wednesdays after 12:00 noon. Please let me know (1) which day of the week is most suitable for you and (2) which specific dates this quarter are off-limits because of prior commitments. Thank you!