Constraints on the distribution of gas and young stars in the Galactic
  Centre in the context of interpreting gamma ray emission features
  Gamma ray observations have found evidence of an extremely energetic outflow
emanating from the Galactic Centre, and an `excess' of emission at GeV energies
towards the Galactic Centre over that expected from current models. Determining
whether the outflow is AGN- or star formation-driven, and whether the `excess'
is astrophysical in origin or requires new physics (e.g. self-annihilation of
dark matter), requires the accurate modelling of the expected energy injection
from astrophysical sources and the subsequent interaction with the surrounding
environment. We briefly summarise current constraints on the distribution of
gas and young stars in the inner few hundred parsec of the Galaxy that can be
included in future 2D and 3D modelling of the astrophysical gamma ray emission.
The key points to highlight with respect to predominantly axisymmetric models
currently in use are: (i) the distribution of dense gas, young stars and
interstellar radiation field is highly asymmetric around the Galactic Centre;
(ii) star formation is almost exclusively constrained to a Galactocentric
radius of ~100pc; (iii) the star formation rate in this region has been
constant at <0.1Msun/yr to within a factor of 2 over the last ~5 Myr.
