University of Waterloo
200 University Avenue West
Waterloo, Ontario, Canada N2L 3G1
Phone: (519) 888-4567 ext 32215
Fax: (519) 746-8115
One of the most important outstanding problems in astrophysics is determining the magnitude of the transport coefficients, that is the viscosity and thermal conduction, of all phases of galactic and extragalactic plasma. This problem is particularly acute in the study of the intracluster medium (ICM) of cluster of galaxies, and the presence or absence of viscosity plays a key role in the thermodynamic evolution of the gas and the relative importance of sources and sinks of energy. In a terrestrial setting, the viscosity of a fluid can be directly measured by studying the wake of flow behind a solid obstruction. In an astrophysical context, the closest analogy is the infall of an early-type galaxy into a cluster of galaxies. As the galaxy falls into the potential, the outer layers of gas are stripped off and form a long tail. If the ICM viscosity is low (i.e. the Reynolds number is high), Kelvin-Helmholtz instabilities (KHIs) will efficiently mix the ICM gas with the stripped galaxy gas. If the ICM viscosity is low, KHIs will be suppressed, the galaxy gas will not mix efficiently with the ICM, and a long, cold tail will will formed. The presence or absence of this cold tail then is, in principle, a direct measurement of the viscosity of the ICM. In this talk I will present results from a combined analysis of deep Chandra observations of the stripped tails of two nearby early-type galaxies, NGC 4552 and NGC 1404, with specially tailored hydrodynamic simulations to characterize the flow patterns and efficiency of mixing to measure the viscosity of the ICM.
The University of Waterloo acknowledges that much of our work takes place on the traditional territory of the Neutral, Anishinaabeg and Haudenosaunee peoples. Our main campus is situated on the Haldimand Tract, the land granted to the Six Nations that includes six miles on each side of the Grand River. Our active work toward reconciliation takes place across our campuses through research, learning, teaching, and community building, and is centralized within our Indigenous Initiatives Office.