Comparison of p_ext/A_V and p_em vs. A_V from our model and the data of Pipe-109. In the optical (first row) and near-IR (second row) wavelengths, we plot p_ext/A_V (alignment efficiency) against A_V, while for the submm wavelength (third row), we use p_em versus A_V. The fourth row combines all datasets above, with a shaded region indicating the range of a_max that covers the data shown in the above panels. The grain axial ratio at 870 μm is set to 2 because the value of 1.4 used at other wavelengths (as shown in Figure A.1) is too low. Polarisation data are adapted from Alves et al. (2014) and references therein.