Size (FWHM) of the outflow plotted as a function of the critical density of the corresponding molecular transition used as a wind tracer. Our CO(1 − 0) and CO(2 − 1) IRAM PdBI data are represented by filled circles, while the HCN(1 − 0) observations by Aalto et al. (2012) are denoted by filled triangles. Critical densities were calculated for a molecular medium at T = 100 K. Note that the same conversion factor of 0.828 kpc arcsec^-1 has been applied to all data in order to allow comparisons.