Dr Voit and his team will explore the conditions under which the hot diffuse gas of a galaxy cluster can make a transition to inhomogeneous cooling and star formation. The results may explain why galaxies do not grow indefinitely large. Analytic calculations will explore how the thermal stability of the hot gas depends on the entropy gradient. These linear calculations will be used to test a hydrodynamic code that has been modified to include thermal conduction. That code will then be used to explore the nonlinear growth of instabilities, producing models that can be compared with X-ray observations of real clusters. Simulations will test how long cool gas stripped from galaxies can survive as such in the hot cluster medium, and compute the expected optical spectra from those wisps of dense gas. Simulations will be run from both spherically-symmetric and cosmologically-generated initial conditions. Dr Voit and his team will then investigate how including thermal conduction, magnetohydrodynamic effects, and energy fed back into the cluster gas by active galactic nuclei in the calculation would affect the results. The team will also obtain optical images of the central regions in a sample of nearby galaxy clusters that have been studied in X-rays, to explore how star formation in and around the central galaxy is related to the state of the hot cluster gas.
A graduate student will be trained by participation in the research. Dr Voit and collaborator Dr Donahue have a strong record of both graduate and undergraduate student training. They are also co-authors of a major text for introductory astronomy, and will incorporate insights from this research into future editions. Both will continue to be active in public outreach.
