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The earliest phases of high-mass star formation in entire molecular complexes
We have started complete studies of several high-mass star-forming regions using submillimeter continuum imagings and follow-up surveys. We here present the results we recently obtained for the Cygnus X molecular cloud complex and compare them with other preliminar studies.
Indeed, we have used the MAMBO-2 camera at the IRAM 30 m telescope to make an extensive 1.2 mm continuum mosaicing study of Cygnus X. Our complete study of with ~0.09 pc resolution provides, for the first time, an unbiased census of massive young stellar objects.
Since our sample is derived for a single molecular complex and covers every embedded phases of high-mass star formation, it gives the first statistical estimates of their lifetime. In contrast to what is found for low-mass class 0 and class I phases, the infrared-quiet protostellar phase of high-mass stars may last as long as their better-known high-luminosity infrared phase. Moreover, the statistical lifetimes of Cygnus X high-mass protostars and pre-stellar cores (~10^4 yr and < 10^3 yr) are one (resp. more than two) order(s) of magnitude smaller than that found in nearby, low-mass star-forming regions.
We propose that high-mass pre-stellar and protostellar cores are free-falling in a molecular cloud where highly turbulent processes dominate.
We anticipate to measure lifetimes variations, if they exist, from the SIMBA or MAMBO-2 imaging we are currently analyzing for a couple of massive molecular cloud complexes.
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