2D maps showing the column densities of C II. Panel 3a shows the projections for R32-AL simulation along the y-axis for down-the-barrel images (top) and along the x-axis for edge-on (bottom). The same for the model R32-TR in panel 3b. From left to right, the plots display C II column densities at t = 0.2, 1.2, 2.2 and 3.2 Myr (or t/t_cc = 0.2, 0.9, 1.7, 2.5) respectively. We note how C II, tracer of the cold and dense gas, in the down-the-barrel projections of model R32-TR, survives up to t/t_cc ∼ 2.5 via magnetic shielding.