Author(s): , ,
Institution(s): 1. AIM Paris-Saclay, 2. NAOJ, 3. UMI France-Chili
Herschel revealed high-density cloud filaments of several pc^3, which are forming clusters of OB-type stars. Counting Herschel protostars gives a direct measure of the mass of stars forming in a period of ~10^5 yrs, the ``instantaneous'' star formation activity. Given their activity, these so-called mini-starburst cloud ridges could be seen as "miniature and instant models" of starburst galaxies. Their characteristics could shed light on the origin of massive clusters.