Ph.D. in Physics from Dartmouth College, 2011
B.S. in Astrophysics from The University of New Mexico, 2001
I have come to Denison because of my desire to educate young minds in the methods of science. As part of a liberal education, I believe that students must have a clear understanding of what science is, and what it is not. I try to teach my students that science is not the answer, rather it is a methodical approach for finding your own answers.
I am an observational astrophysicist specializing in extragalactic studies and cosmology. The overriding question guiding my research is how gravity behaves on very large scales. Currently, I am studying the gravitational interactions of merging galaxy clusters. One of several methods I use is examining the asymmetric distribution of cluster gas which results from cluster mergers, called gas sloshing because, in effect, the gas sloshes around in the cluster’s gravitational field, much like wine sloshing in a glass. This sloshing gas often appears as a spiral pattern or concentric shells around the cluster center. By examining the properties of the gas within and around merging clusters, constraints can be placed on the characteristics of the merger which initiated the sloshing. Although cluster mergers occur over periods of billions of years, studying the cluster gas allows us to constrain the merger history of the cluster.
My research requires analysis of X-ray, radio and optical observations of galaxy clusters. Potential student involvement ranges from introductory and intermediate programming/scripting, reduction and analysis of astronomical images using standard packages, and proposal and implementation of observing programs on world class telescopes.
I am also interested in astronomy education and public outreach. I host several open houses throughout the year at Denison’s Swasey Observatory. I also host public shows at Denison’s planetarium. If your group would like to inquire about a show, please call the department office.
- “Sloshing Gas in the Core of the Most Luminous Galaxy Cluster RXJ1347.5-1145”, Johnson, Ryan E., ZuHone, John, Jones, Christine, Forman, William R., Markevitch, Maxim, The Astrophysical Journal, Vol 751, 95 (2012)
- “Core Gas Sloshing in a Sample of Chandra Clusters”, Johnson, Ryan E., Markevitch, Maxim, Wegner, Gary A., Jones, Christine, Forman, William R., Bulletins of the American Astronomical Society, 42, 387 (2011)
- “Core Gas Sloshing in Abell 1644”, Johnson, Ryan E., Markevitch, Maxim, Wegner, Gary A., Jones, Christine, Forman, William R., The Astrophysical Journal, Volume 710, Issue 2, pp. 1776-1785 (2010)
- “Stirring Up the Pot: Can Cooling Flows in Galaxy Clusters be Quenched by Gas Sloshing?”, Zuhone, John, Markevitch, Maxim, Johnson, Ryan E., The Astrophysical Journal, Volume 717, Issue 2, pp. 908-928 (2010)
For complete list of publications, projects, funding, and other information, see Dr. Johnson's full CV [pdf].