The Galactic Centre - A Laboratory for Starburst Galaxies (?)
  The Galactic centre - as the closest galactic nucleus - holds both intrinsic
interest and possibly represents a useful analogue to star-burst nuclei which
we can observe with orders of magnitude finer detail than these external
systems. The environmental conditions in the GC - here taken to mean the inner
200 pc in diameter of the Milky Way - are extreme with respect to those
typically encountered in the Galactic disk. The energy densities of the various
GC ISM components are typically ~two orders of magnitude larger than those
found locally and the star-formation rate density ~three orders of magnitude
larger. Unusually within the Galaxy, the Galactic centre exhibits
hard-spectrum, diffuse TeV (=10^12 eV) gamma-ray emission spatially coincident
with the region's molecular gas. Recently the nuclei of local star-burst
galaxies NGC 253 and M82 have also been detected in gamma-rays of such
energies. We have embarked on an extended campaign of modelling the broadband
(radio continuum to TeV gamma-ray), non- thermal signals received from the
inner 200 pc of the Galaxy. On the basis of this modelling we find that
star-formation and associated supernova activity is the ultimate driver of the
region's non-thermal activity. This activity drives a large-scale wind of hot
plasma and cosmic rays out of the GC. The wind advects the locally-accelerated
cosmic rays quickly, before they can lose much energy in situ or penetrate into
the densest molecular gas cores where star-formation occurs. The cosmic rays
can, however, heat/ionize the lower density/warm H2 phase enveloping the cores.
On very large scales (~10 kpc) the non-thermal signature of the escaping GC
cosmic rays has probably been detected recently as the spectacular 'Fermi
bubbles' and corresponding 'WMAP haze'.
