Metal enrichment of the intracluster medium: SN-driven galactic winds
  We investigate the role of supernova (SN)-driven galactic winds in the
chemical enrichment of the intracluster medium (ICM). Such outflows on galactic
scales have their origin in huge star forming regions and expel metal enriched
material out of the galaxies into their surroundings as observed, for example,
in the nearby starburst galaxy NGC 253. As massive stars in OB-associations
explode sequentially, shock waves are driven into the interstellar medium (ISM)
of a galaxy and merge, forming a superbubble (SB). These SBs expand in a
direction perpendicular to the disk plane following the density gradient of the
ISM. We use the 2D analytical approximation by Kompaneets (1960) to model the
expansion of SBs in an exponentially stratified ISM. This is modified in order
to describe the sequence of SN-explosions as a time-dependent process taking
into account the main-sequence life-time of the SN-progenitors and using an
initial mass function to get the number of massive stars per mass interval. The
evolution of the bubble in space and time is calculated analytically, from
which the onset of Rayleigh-Taylor instabilities in the shell can be
determined. In its further evolution, the shell will break up and
high-metallicity gas will be ejected into the halo of the galaxy and even into
the ICM. We derive the number of stars needed for blow-out depending on the
scale height and density of the ambient medium, as well as the fraction of
alpha- and iron peak elements contained in the hot gas. Finally, the amount of
metals injected by Milky Way-type galaxies to the ICM is calculated confirming
the importance of this enrichment process.
