Orion as seen by Herschel and Planck

We present high-resolution, high dynamic range column-density and color-temperature maps of the Orion complex using a combination of Planck dust-emission maps, Herschel dust-emission maps, and 2MASS NIR dust-extinction 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 0.01 mag < A_K < 30 mag, or 2×10²⁰ cm⁻² < N < 5×10²³ cm⁻². We determined the ratio of the 2.2 microns extinction coefficient to the 850 microns 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 pdf, over a large range of column densities, can be well fitted by a simple power law. Moreover, we considered the local Schmidt-law for star formation, and confirm earlier results, showing that the protostar surface density Σ∗ follows a simple law Σ∗∝Σ_gas^β, with β~2.

Combined optical-depth and temperature map of Orion A and B. The image is based on high-resolution Herschel data, where available, and on Planck data, elsewhere.