Published online by Cambridge University Press: 14 August 2015
I will define the central region of the Galaxy as being the inner four kiloparsecs. The distinguishing characteristics of this region are:
1) The dominance of a central spheroidal component in the mass distribution – a bulge.
2) An apparent deficiency of gas, at least between radii of 500 pc and 4000 pc.
3) High non-circular gas velocities. Now let us consider these characteristics in some detail.