Application of a clumpy core model to NGC 2071

The multi-transitional observations of CS molecules towards the NGC 2071 core have been re-analysed by using a tri-dimensional Monte Carlo radiative transfer code. Better agreement with the observations is made by an introduction of clumpiness to this model than by smoothly varying density to the 1D microturbulent one. The best-fitting model shows that, when a unique density is assumed for clumps, the volume filling factor of the clumps varies as r^-2 with an average of ~5 per cent over the entire core, and that the H_2 number density and the CS abundance of the clump relative to H_2 are ~2x10^6cm^-3 and ~6x10^-10, respectively. The radial density gradient ~r^-2 obtained from our clumpy core model is steeper than that (~r^-1.3) obtained from the microturbulent model. Since all clumps are subject to random bulk motions in this 3D clumpy macroturbulent model, synthesized line profiles do not show self-absorption dips even for opaque transitions and the resulting linewidth is in good accordance with the observations.