Authors: D.J. Marshall, G. Joncas & A. Jones

Genetic forward modelling is used along with the 2MASS dataset and the Besancon Galactic model to deduce the three dimensional distribution of interstellar extinction. This derived dust distribution can then be used to determine the distance and mass of Infrared Dark Clouds, independently of kinematic models of the Milky Way. Their mass spectrum along with their physical size suggest that this population of clouds is intermediate between star forming clumps and giant molecular clouds. The IRDCs are seen to lie preferentially along the spiral arms and in the molecular ring of the Milky Way, reinforcing the idea that they are the birthplace of massive stars.

This technique can be used on any stellar dataset from the UV to the near-infrared. Together with the stellar predictions from the Besancon model, constraints can be placed on structures in high extinction regions of the Milky Way such as the bar, the spiral arms and the warp.