χ² variations with the source parameters. The upper panels show the variations of χ²-24755 for the line maps and the lower panels show χ²-22188 for the continuum maps. From left to right the abscissae are the source size (FWHM), ρ, assuming a circular Gaussian source; the offset in RA, x_off; the offset in Dec, y_off; the position angle θ assuming an elliptical Gaussian source; the source major axis, ρ_maj, and the source axis ratio r = ρ_min/ρ_maj. The horizontal line shows the 68% confidence level (1 × σ) taking into account the number of free parameters.