Steps to build an asymmetrical model from 1D spherical models. Based on a single density profile (eq. 1), we compute two models with different temperature profiles in the outer parts (either 12 or 20 K, top row, see Fig. 4). We apply two different abundance profiles (central row) for each ion for the east and west parts, the west part is computed for both temperature profiles. We extract the parts corresponding to each region of interest (sampled with a 1″ resolution) and we assemble them in a cube (RA, Dec, Frequency, bottom row left). Finally, we convolve the cube with a 14″ half-power beamwidth Gaussian beam to compare to the observations (bottom row right). We extract the spectra along the dash-dot line and compare them to the observations (see Fig. 3).