WUNA Lunch Talk:

Brian Lacki


Supernova-Driven Turbulence and the Chaotic Starburst

April 24

12:10PM, Room 230, NRAO, Edgemont Road


I explain my investigation into how supernovae power turbulence in the ISMs of starburst regions, and the implications for magnetic fields and cosmic rays. In weaker starbursts, supernovae blast open a hot (~40 MK) phase that escapes as a superwind. I calculate that supernovae can drive Mach ~ 1 turbulence in the hot wind. In the densest starbursts, like Arp 220, the volume is instead filled by cold molecular gas. Supernovae alone can drive turbulence in this gas to ~20 - 30 km/s, despite strong radiative losses. I predict magnetic field strengths of 70 microGauss in the Galactic Center starburst, 200 microGauss in NGC 253 and M82, and 2 milliGauss in Arp 220's nuclei. I show how supernova driving of turbulence naturally results in equipartition between several ISM phases in starbursts. I also discuss why CR diffusion may be very slow in these regions. Instead, turbulent mixing by the ISM may transport CRs, a very different process. Finally, time permitting, I consider what happens when the starburst winds leave the starbursts. In most cases, the starburst wind reaches the intergalactic medium, injecting a substantial cosmic ray energy density. For the Galactic Center starburst, the termination shock is instead just a few kpc above the Galactic plane -- suggesting its power appears to us as the Fermi Bubbles.