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Published online by Cambridge University Press: 30 March 2016
This paper deals with the interpretation of molecular line emission from class I OH/H2O emission centers associated with compact HII regions and with the OH 18 cm emission from dark clouds in T-Tauri star associations. Observational evidence is presented, that class IOH/H2O emission centers represent a particular stage in the evolution of a massive star (or a group of massive stars) whereas protostars of lower mass apparently do not go through such a stage.
It appears that in associations the low-mass stars are formed first and the massive O-stars are formed last. T-Tauri star associations may represent an early evolutionary stage of a star association where low-mass stars are formed. Evidence is presented that the physical conditions in some parts of the Taurus complex of dust clouds and T-Tauri stars are appropriate for the formation of single stars of about a solar mass.