Mass of the clumps as a function of distance. The black solid line indicates the typical mass sensitivity for the SEST images (see text). The sources with signs of active star formation are shown as red filled circles, those without as black open squares (see Sect. 5). Associated MSX emission is indicated as a black plus, and radio-continuum emission as a black cross. The white cross indicates 17195–3811c1 (see text).