Wik, Daniel (University of Utah)
Faculty Advisor: Wik, Daniel (Science, Physics and Astronomy)
Mergers between galaxy clusters are some of the most energetic events in the universe, driving shock fronts in the intracluster medium (ICM), an X-ray hot plasma permeating the cluster. Shock fronts heat thermal electrons, causing an increase in their temperature. The mechanism by which this occurs is undetermined, with two models being proposed to explain the phenomenon. The first proposes direct shock-heating and the second suggests indirect adiabatic compression, with the electrons subsequently equilibrating with ions heated by the shock. We utilize NuSTAR observations, advantaging its effective area at higher energies, of a shock in the merging cluster Abell 665 in order to discriminate between the models. To do so, a temperature profile was constructed across the shock, utilizing spectral fitting, and compared against the models' predictions. In addition, temperature maps across the cluster were generated to better understand the merger event as a whole. We find that the temperature profile is suggestive of the shock model but is not yet statistically significant, due to NuSTAR's comparatively worse spatial resolution. As a result, we apply a novel joint fitting technique to NuSTAR data and Chandra observations in order to statistically distinguish between the models for the first time, accounting for the scattering of photons due to the PSF. Understanding these processes increases our understanding of the magnetic field of the ICM, allowing for mass determination, permitting galaxy clusters to be used to constrain cosmological studies.