Description:

We have known for decades that magnetic fields and relativistic particles (cosmic rays) can play a key role in some astrophysical environments. But it has only recently become possible to model these directly including other key physics (like radiative cooling, self-gravity, star formation, etc.) in models of galaxies and super-massive black hole growth and “feedback.” Moreover those simulations have historically been limited to a very narrow dynamic range of scales being probed. I’ll discuss how a combination of new physics and new numerical methods has led to breakthroughs that now allow us to simulate problems like supermassive black hole growth, star and galaxy formation with truly unprecedented dynamic range reaching from the horizon to the intergalactic medium. These have revealed some major surprises. In particular, non-thermal physics may be vastly more important on both the smallest and largest scales, compared to previous assumptions. I’ll show how these simulations predict qualitatively new forms of strongly-magnetized accretion disks around supermassive black holes, that can resolve many decades-old observational puzzles and make new unique observational predictions. At the same time, the feedback from supernovae and black holes could be, on the largest (circum and intergalactic medium) scales dominated by cosmic rays. I’ll show how recent new observations of X-rays and the Sunyaev-Zeldovich effect, in particular, appear to be clearly indicating that most of the pressure on these scales is not — as assumed in almost all models for decades — primarily thermal, but appears to be coming from cosmic rays. And I’ll show how new observations can probe this further over a range of galaxy mass scales.

Philip F. Hopkins, Professor, Caltech

Host: Claude-André Faucher-Giguére