Northern filament: comparison of the model with the observations. Left: contours are the surface density of molecular gas, predicted from the model. CO(2–1) beamwidths and positions are shown by black circles. Gas masses in each beam, predicted from the model, are in units of 10⁸   M_⊙. Middle: position-velocity diagram. Pink and blue isophotes in the colour map are the model predictions. Black crosses are CO(2–1) observations. Horizontal bars are the FWHM line widths. Red diamonds are Hα data (Hatch et al. 2006). Right: velocity distribution of the gas extracted from each region of the model. The predicted FWHM line widths of the distributions are in km s^-1.