Samuel Skillman

  • Academic Institution: University of Colorado at Boulder
  • Program Year: 4
  • Practicum(s):
    Oak Ridge National Laboratory (2011)
  • Degree(s):
    B.S. Physics, Harvey Mudd College, 2007
  • Field of Study: Astrophysics
  • Academic Advisor: Jack Burns

Summary of Research:

The use of analytical techniques in astrophysical problems is nearing its end. Most of the problems that can be solved analytically have been done, which leaves us with the difficult, non-linear, multidimensional problems that require the use of computational techniques. One of the biggest problems that makes computational approaches difficult in astrophysics is the underlying dynamic range of the physical system. This is especially true in the field of cosmology. One has to couple cosmic structure formation with metal and ionizing feedback from stars and galaxies.

In order to tackle such a large dynamic range, I use Enzo, an Adaptive Mesh Refinement (AMR) N-Body + Hydrodynamics code. Enzo allows one to adaptively change the resolution based on criteria such as density, shock discontinuities, or many other requirements. By doing so, large cosmological simulations, run on thousands of processors, are capable of covering unprecedented scales.

My research deals with identifying shock structures in these simulations. Shocks are capable of accelerating cosmic ray electrons and protons that may play a role in the hydrodynamic feedback onto the surrounding medium. By constructing synthetic observational signatures of these cosmic rays we are able to test our understanding of their origin and behavior. My thesis work focuses on including the back-reaction of these cosmic rays onto the hydrodynamics within the Enzo framework.

In addition to the scientific goals of studying cosmic structure formation, I actively develop tools for analyzing and visualizing complex datasets such as those found in AMR simulations. In particular, I am involved in the “yt” project (http://yt-project.org) that aims at providing a uniform API capable of addressing many different types of simulation data. Recently I have been involved in developing different methods of volume-rendering AMR simulations using an MPI+OpenMP hybrid parallelism framework.

Publications:

Skillman, Samuel W.; Xu, Hao; Hallman, Eric J.; O’Shea, Brian W.; Burns, Jack O.; Li, Hui; Collins, David C.; Norman, Michael L. Cosmological Magnetohydrodynamic Simulations of Galaxy Cluster Radio Relics: Insights and Warnings for Observations. 2013. ApJ. 765. 21.

Skory, Stephen; Hallman, Eric; Burns, Jack O.; Skillman, Samuel W.; O’Shea, Brian W.; Smith, Britton D. On the Road to More Realistic Galaxy Cluster Simulations: The Effects of Radiative Cooling and Thermal Feedback Prescriptions on the Observational Properties of Simulated Galaxy Clusters. 2013. ApJ. 763. 38.

Skillman, Samuel W.; Hallman, Eric J.; O’Shea, Brian W.; Burns, Jack O.; Smith, Britton D.; Turk, Matthew J. Galaxy Cluster Radio Relics in Adaptive Mesh Refinement Cosmological Simulations: Relic Properties and Scaling Relationships. 2011. ApJ. 735. 96.

Turk, Matthew J.; Smith, Britton D.; Oishi, Jeffrey S.; Skory, Stephen; Skillman, Samuel W.; Abel, Tom; Norman, Michael L. yt: A Multi-code Analysis Toolkit for Astrophysical Simulation Data. 2011. ApJS. 192. 9.

Hallman, Eric J.; Skillman, Samuel W.; Jeltema, Tesla E.; Smith, Britton D.; O’Shea, Brian W.; Burns, Jack O.; Norman, Michael L. The Properties of X-ray Cold Fronts in a Statistical Sample of Simulated Galaxy Clusters. 2010. ApJ, 725. 1053

Burns & Skillman. Cosmological numerical simulations of radio relics in galaxy clusters: Insights for future observations. MmSAI..82..615B 2011, 82, 615 “Non-thermal phenomena in colliding galaxy clusters” (Nice, France, Nov 2010).

Burns, Jack O.; Skillman, Samuel W.; O’Shea, Brian W. Galaxy Clusters at the Edge: Temperature, Entropy, and Gas Dynamics Near the Virial Radius. 2010. ApJ. 721. 1105.

Trenti, Michele; Smith, Britton D.; Hallman, Eric J.; Skillman, Samuel W.; Shull, J. Michael. How Well do Cosmological Simulations Reproduce Individual Halo Properties? 2010. ApJ. 711. 1198

Skillman, S. W., O’Shea, B. W., Hallman, E. J., Burns, J. O., & Norman, M. L. Cosmological Shocks in Adaptive Mesh Refinement Simulations and the Acceleration of Cosmic Rays. 2008. ApJ. 689. 1063

Skillman, S. W., O’Shea, B. W., Hallman, E. J., Burns, J. O., & Norman, M. L. Shock-Accelerated Cosmic Rays in AMR Cosmological Simulations. To appear in the Course on the “Astrophysics of Galaxy Clusters” of the International School of Physics “Enrico Fermi” (Varenna, July 2008) proceedings.

Skillman, S., O’Shea, B. W., Hallman, E. J., Burns, J. O., & Norman, M. L. Shock-Generated Cosmic Rays within 3D AMR Cosmological Simulations. 211th Meeting of the AAS. January 7-11. Poster.

Talks with no proceedings:
“Shock-Accelerated Cosmic Rays in AMR Cosmological Simulations” (Talk) Skillman, Samuel W; O’Shea, Brian W.; Hallman, Eric J.; Burns, Jack O.; Norman, Michael L., Santa Fe Cosmology Workshop 2008, June 30th, 2008.

“Shock-Accelerated Cosmic Rays in AMR Cosmological Simulations” (Talk) Skillman, Samuel W; O’Shea, Brian W.; Hallman, Eric J.; Burns, Jack O.; Norman, Michael L., The Dark Universe Group Meeting, Los Alamos National Laboratory, June 26th, 2008.

“Shock-Generated Cosmic Rays in AMR Hydro/N-body Cosmological Simulations.” (Talk) Skillman, Samuel W; O’Shea, Brian W.; Hallman, Eric J.; Burns, Jack O.; Norman, Michael L., JILA Astrophysics Lunch Seminar, April 25th, 2008.

Awards:

Harvey Mudd College Departmental Honors in Physics 2007
Harvey Mudd College Graduation with Distinction 2007
Harvey Mudd College Dean’s List, 2004, 2005, 2006, 2007
Chosen to attend 2008 Enrico Fermi Summer School on the “Astrophysics of Galaxy Clusters”