Galactic Winds from Starburst Galaxies
Abstract
From observational facts it is evident that cosmic rays leave a galaxy and this additional energy flux can be used to drive an outflow if the thermal gas is coupled to these streaming particles, e.g. momentum transfer provided by the resonant excitation of MHD waves. Since the bulk of cosmic rays is accelerated by shock waves generated in SNRs and since the hot thermal plasma is also produced by SN-explosion we examine the consequence of both effects occurring over about 108 years in a starburst region. During this time scale the mean physical properties of the interstellar medium within the starburst region are changing which results in a different evolution of the SNRs. In particular, the amount of the SN-energy transferred into cosmic rays as well as the amount of radiative cooling of the remnant depend through the sweep-up time and the cooling time on the external density. The ongoing mass loss as well as the energy input from the ongoing starburst activity introduce time-dependent effects which will show up in the galactic wind since the interaction of cosmic rays and thermal gas drives a large scale outflow from the starburst region. To include the various effects like acceleration and diffusive transport of cosmic rays, radiative cooling and dissipation of Alfvén-waves we have performed time-dependent numerical calculations in a flux-tube geometry. We show how the galactic wind solutions are coupled to the changing inner boundary conditions determined by the starburst activity. The results are discussed in the context of observations of nearby starburst galaxies, e.g. M82 or NGC 251.
- Publication:
-
Astronomische Gesellschaft Meeting Abstracts
- Pub Date:
- 2001
- Bibcode:
- 2001AGM....18S0115D