TAPIR Seminar

In person: 370 Cahill. To Join via Zoom: 864 8902 5566

ABSTRACT: High velocity outflows are ubiquitous in astrophysics. Since they often expand over several orders of magnitude in size and time, high resolutions or high dynamic ranges are required to model them numerically. A jet from an active galactic nucleus (AGN) is a prominent example. I will begin with a description of its morphological properties, investigated using the moving mesh code Jet. I provide an explanation for the Fanaroff-Riley (edge brightened vs center brightened) morphological dichotomy and bright "knots" observed in AGN jets. The predictions for the jet energetics are found to be consistent with the jets in M87 and Cygnus A. I will also describe my novel moving mesh hydro code Sprout, which solves the equations of hydrodynamics on an expanding Cartesian mesh. This provides high dynamic range for many orders of magnitude of expansion with little numerical diffusion, capturing shocks and fine structures accurately. Finally, we will discuss the application of Sprout in modeling hydrodynamic instabilities in a young supernova remnant, which is another example of a high velocity outflow. These instabilities provide an observable that is a direct diagnostic of the density profile of the progenitor and may be related to the cauliflower-like structures in Tycho's SNR. It is also found that inhomogeneities in the ejecta or the surrounding medium do not influence structure formation in the remnant, unless they have a very large amplitude and form large-scale coherent structures.