MILLIMETER STUDY OF STAR-FORMATION IN SOUTHERN GLOBULES

The paper presents the results of a dedicated millimetre continuum and molecular line (CO and CS) search for cold and dense (protostellar) c ores and molecular outflows in 35 southern Bok globules (Dec. less tha n or equal to -30 degrees). Only globules which are associated with co ld IRAS point sources (FIR colour temperatures below 35 K) were select ed for this study. We could demonstrate that globules are often loosel y associated with molecular cloud complexes from which they probably f ormed. Based on such associations, we determined reliable distances fo r most of the globules of our sample. It turned out that half of the s elected globules are located in the local spiral arm at distances betw een 170 and 400 pc. The most prominent features in the spatial distrib ution of these globules are the Lindblad ring and the Vela-Gum complex . A group of 14 globules is located at larger distances (0.7-4 kpc) in the Carina arm. The objects in the far Carina arm (d > 2 kpc) are cle arly different from ''classical'' Bok globules being more massive and more luminous. Out of the 35 globules observed, all globules were dete cted in the (CO)-C-12(2-1) line (detection rate 100%, 3 sigma detectio n limit T-mb = 0.3 K), 24 globules were detected in the CS(2-1) line ( 69%, detection limit 0.2 K), and 18 globules were detected in the 1.3 mm continuum emission (51%, detection limit 40 mJy/beam). In 12 globul es (34%), CO line wings indicating the presence of molecular outflows have been found, of which 8 outflows were previously unknown. The colo urs of the embedded IRAS point sources, the strength of the millimetre dust continuum emission, the CS line temperatures as well as the pres ence of molecular outflows are all well correlated with each other. Ba sed on these results and on the IRAS colour-colour diagram, we can cle arly distinguish two groups of sources: Objects with active protostell ar cores (''Class 0'' and ''I'') and globules with less dense and less centrally peaked cores (pre-protostellar cores and globules which may not form stars at all). The objects with active protostellar cores ar e characterized by centrally condensed cores (typical beam-averaged de nsity of approximate to 10(6) cm(-3)) and molecular outflows. The mass spectrum dN/dM of the circum-protostellar envelopes can be fitted wit h a single slope of -1.8 between 0.15 and 2 M. and a mean mass of 0.6 M.. Two objects in our sample clearly resemble the properties of ''Cla ss 0'' protostars while the majority of the star-forming cores probabl y already passed the main accretion phase. Five of the colder and less -condensed objects are proposed to be pre-protostellar cores.