Orion optical-depth and column-density maps

The column-density maps combine the robustness of the 2MASS NIR extinction maps with the resolution and coverage of the Herschel and Planck dust-emission maps and constitute the highest dynamic range column-density maps ever constructed for the entire Orion complex, covering 0.01mag<A_K_<30mag, or 2x10^20^cm^-2^<N<5x10^23^cm^-2^.

We determined the ratio of the 2.2{mu}m extinction coefficient to the 850{mu}m opacity and found that the values obtained for both Orion A and B are significantly lower than the predictions of standard dust models, but agree with newer models that incorporate icy silicate-graphite conglomerates for the grain population. We show that the cloud projected probability distribution function, over a large range of column densities, can be well fitted by a simple power law.