Our group at UMD and beyond

Our group’s motto is “turtles all the way down,” a saying that applies to both the (approximately self-similar) structure of dark matter in the Universe and to the University of Maryland’s mascot, the terrapin. Most of us are based here at UMD, but we also have collaborators in a number of other places.

While we obviously try hard to do excellent science, we put humans first! This means that we strive to create an inclusive, supportive, and fun environment in all of our group meetings and interactions. Below you can get an impression of the faces in our group (in chronological order of when they joined).

If you are interested in joining our group, please read the F.A.Q. section below. You can browse the research pages to get an idea of the kind of questions and techniques we are interested in.

Benedikt DiemerBenedikt Diemer (he/him)
Assistant Professor
website, twitter
Katya LeidigKatya Leidig (they/them)
Graduate student
Calvin OsingaCalvin Osinga (he/him)
Graduate student
personZe'ev Vladimir (he/him)
personErik Chou (he/him)
personWenxi Wu (she/her)
personShazali Audu (he/him)


Spencer ScottSpencer Scott (he/him)
Undergraduate, Harvard U.
Now in industry
personShmuel Bialy (he/him)
CTC postdoc fellow, 2021-23
Now faculty at Technion, Israel
website, twitter

F.A.Q. for prospective students

This section is intended to give potentially interested students a brief overview of the sort of work we do. It is less focused on exact projects (which tend to evolve over time) and more focused on the kinds of interests and qualifications that would be a good match. Of course, this page is not meant to replace in-person conversations! If you have questions, please just email me or find me in my office at UMD. Let me try to answer a few common questions.

Q: Are you looking for students?
Always! Please note that, in general, it is much easier to take on students who are at UMD. If you would like to do a PhD, you need to apply to the UMD Astronomy Graduate Program.

Q: What kind of research do you do?
Our research focuses on structure formation, the process by which matter in the universe collapses into the objects we observe (such as galaxies) and those that are hidden (such as dark matter halos). This evolution is extremely complex and non-linear, meaning that it cannot easily be understood with pen-and-paper math. Instead, we use supercomputer simulations of two different types: dark matter only “N-body” simulations, where we neglect the normal matter and study dark matter halos and the cosmic web; and hydrodynamical simulations where we include normal matter and study galaxies.

Q: What is your day-to-day work like, and is it for me?
Basically, we run and analyze simulations, and try to connect the results to the galaxies we observe in the real Universe. One particular focus is on analyses that include the full dynamics of billions of virtual particles. The common theme to virtually all our work is that it is numerical in nature, as in, based on computer programming and large datasets. Some of the skills that you would develop are:

  • Programming in a scripting language (ideally python)
  • Analyzing data sets and creating scientific plots
  • Working with small, medium, and very large computers (shell commands, parallel computing, etc.)
  • Communicating your research: giving presentations, writing papers, etc.
  • If you’re really into coding: C/C++ and MPI parallelization
  • Visualizing data

This is not a list of pre-requisites! If you already have some of these skills, great; if not, you will learn them. But as you probably guessed by now, you should be interested in working with computers in some form.

Q: What student projects do you have on offer?
There are way too many possible projects to list here, and choosing a research topic is something that we should do in conversation, not from a website! Nevertheless, here is an incomplete list of some research directions that we are pursuing or intend to pursue in the future:

  • What is the real shape of halos? The splashback radius is a recently proposed definition of the boundary of dark matter halos: how can we measure it in simulations? How does our understanding of structure change when we use it? How can we best observe the edge of halos in the real Universe? What will we be able to achieve with future instruments?
  • Atomic and molecular gas in the IllustrisTNG simulations: how does it compare to observations? How can the simulations become more realistic?
  • Running better N-body simulations: how can we build reliable simulations and understand their limitations?
  • The density structure of dark matter halos and how it is connected to their evolution
  • Understanding the detailed dynamics of billions of dark matter particles with the SPARTA code
  • Applications of machine learning to dark matter simulations
  • Hydrodynamics and magnetic fields in galaxies
  • Three-dimensional visualization and 3D printing

Again, this is intended as a list of general topics; if any of them pique your interest, let’s talk.