A radiation transfer model for the Milky Way: II. The global properties and large-scale structure

We obtained an axisymmetric model for the large-scale distribution of stars and dust in the Milky Way (MW) using a radiative transfer code that can account for the existing near-infrared (NIR)/mid-infrared/submm all-sky emission maps of our Galaxy. We find that the MW has a star-formation rate of SFR = 1.25 +/- 0.2M(circle dot) yr(-1), a stellar mass M-* = (4.9 +/- 0.3) x 10(10) M-circle dot, and a specific SFR that is relatively constant with radius (except for the inner 1 kpc). We identified an inner radius R-in = 4.5 kpc beyond which the stellar emissivity and dust distribution fall exponentially. For R < R-in the emissivities fall linearly towards the centre. The old stellar populations in the disc have an exponential scale length that increases monotonically from h(s)(disc) (K) = 2.2 +/- 0.6 kpc in the NIR, to h(s)(disc) (B) = 3.2 +/- 0.9 kpc at the shorter optical bands, and a scale height that varies with radial distance, from z(s)(disc) (0) = 140 +/- 20 pc in the centre to z(s)(disc) (R-circle dot) = 300 +/- 20 pc at the solar radius. The young stellar populations have a scale length of h(s)(tdisc) = 3.2 +/- 0.9 kpc and a scale height that varies from z(s)(tdisc) (0) = 50 +/- 10 pc in the centre to z(s)(disc) (R-circle dot) = 90 +/- 10 pc at the solar radius. We discovered an inner stellar disc within the central 4.5 kpc, which we associate with the extended long bar of the MW. Most of the obscured star formation happens within this inner thin disc. The diffuse dust is mainly distributed in a disc with scale length h(d)(disc) = 5.2 +/- 0.8 kpc and scale height z(d)(disc) = 0.14 +/- 0.02 kpc. We give the first derivation of the MW attenuation curve and present it as a functional fit to the model data. We find the MW to lie in the Green Valley of the main sequence relation for spiral galaxies.