EPoS Contribution
EPoS Contribution
Properties of high-mass protostars and massive pre-stellar cores at the dawn of Herschel and ALMA

Frederique Motte
AIM/SAp, CEA Saclay, Gif-sur-Yvette, France
We have started searching, in an unbiased way and in the 6 closest (<3 kpc) high-mass star-forming complexes, for the high-mass analogs of low-mass pre-stellar cores and class 0 protostars. We will here present the extensive millimeter continuum mappings of the Cygnus X and NGC 6334-6357 complexes that have already revealed 40 new, cold (or IR-quiet) dense cores that should correspond to the earliest phases of high-mass star formation: FWHM size ~0.1 pc, gas mass ~100 Msun, volume averaged density ~2 105 cm-3, mass averaged temperature ~20 K, undetected by MSX. We will also show that the Herschel imaging planned for the closest high-mass star-forming complexes (Key Program HOBYS by Motte, Zavagno, Bontemps et al., see http://starformation-herschel.iap.fr/hobys/) and the forthcoming ALMA studies of further-away regions will undoubtedly find many more of these massive and extremely dense, cold dense cores. Furthermore, thanks to several complementary surveys done by us in Cygnus X, we have started to statistically characterize high-mass protostars and massive pre-stellar cores. We will detail our first fundamental result, which is, that the statistical lifetimes of high-mass protostars and pre-stellar cores could be one and two order(s) of magnitude smaller, respectively, than what is found in nearby, low-mass star-forming regions.

We will also present the recent Spitzer/MIPS imagings (at 24 and 70 micron, from a Spitzer Legacy program and CSO/Sharc II maps (at 350 micron) that nicely complement the IRAM 30m/MAMBO-2 mosaicking. We will derive the first luminosity estimates of the cold (or IR-quiet) dense cores that are the precursors of high-mass stars in Cygnus X, estimates which are expected to be refined by future Herschel far-infrared to submillimeter (75-500 micron) flux measurements. We will also give some evidences that high-mass stars may form in free-falling clumps where highly turbulent processes dominate: their short lifetimes and some global infall traced on parsec scales by HCO+ or CS imagings. Finally, we will assess the effect of subfragmentation on the above results, using the very recent interferometric survey of 12 Cygnus X dense cores at the IRAM Plateau de Bure.