We present mass models of the Milky Way created to fit observational constraints and to be consistent with expectations from theoretical modelling .
The method used to create these models is that demonstrated in [ ] , and we improve on those models by adding gas discs to the potential , considering the effects of allowing the inner slope of the halo density profile to vary , and including new observations of maser sources in the Milky Way amongst the new constraints .
We provide a best fitting model , as well as estimates of the properties of the Milky Way .
Under the assumptions in our main model , we find that the Sun is R _ { 0 } = ( 8.20 \pm 0.09 ) \mathrm { kpc } from the Galactic Centre , with the circular speed at the Sun being v _ { 0 } = ( 232.8 \pm 3.0 ) \mathrm { km s } ^ { -1 } ; that the Galaxy has a total stellar mass of ( 54.3 \pm 5.7 ) \times 10 ^ { 9 } { M } _ { \odot } , a total virial mass of ( 1.30 \pm 0.30 ) \times 10 ^ { 12 } { M } _ { \odot } and a local dark-matter density of 0.38 \pm 0.04 \mathrm { GeV cm } ^ { -3 } , where the quoted uncertainties are statistical .
These values are sensitive to our choice of priors and constraints .
We investigate systematic uncertainties , which in some cases may be larger .
For example , if we weaken our prior on R _ { 0 } , we find it to be ( 7.97 \pm 0.15 ) \mathrm { kpc } and that v _ { 0 } = ( 226.8 \pm 4.2 ) \mathrm { km s } ^ { -1 } .
We find that most of these properties , including the local dark-matter density , are remarkably insensitive to the assumed power-law density slope at the centre of the dark-matter halo .
We find that it is unlikely that the local standard of rest differs significantly from that found under assumptions of axisymmetry .
We have made code to compute the force from our potential , and to integrate orbits within it , publicly available .