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We found that in regions of high mass star formation the CS emission correlates well with the dust continuum emission and is therefore a good tracer of the total mass while the N$_2$H$^+$ distribution is frequently very different. This is opposite to their typical behavior in low-mass cores where freeze-out plays a crucial role in the chemistry. The behavior of other high density tracers varies from source to source but most of them are closer to CS. Radial density profiles in massive cores are fitted by power laws with indices about -1.6, as derived from the dust continuum emission. The radial temperature dependence on intermediate scales is close to the theoretically expected one for a centrally heated optically thin cloud. The velocity dispersion either remains constant or decreases from the core center to the edge. Several cores including those without known embedded IR sources show signs of infall motions. They can represent the earliest phases of massive protostars. There are implicit arguments in favor of small-scale clumpiness in the cores.
We investigate at a high angular resolution the spatial and kinematic structure of the S255IR high mass star-forming region, which demonstrated recently the first disk-mediated accretion burst in the massive young stellar object. The observations wer
We use sub-arcsecond resolution ($sim$0.4$$) observations with NOEMA at 1.37 mm to study the dust emission and molecular gas of 18 high-mass star-forming regions. We combine the derived physical and chemical properties of individual cores in these re
Low-mass dense cores represent the state of molecular gas associated with the earliest phases of low-mass star formation. Such cores are called protostellar or starless, depending on whether they do or do not contain compact sources of luminosity. In
In our SCUBA survey of Perseus, we find that the fraction of protostellar cores increases towards higher masses and the most massive cores are all protostellar. In this paper we consider the possible explanations of this apparent mass dependence in t
As Pr. Th. Henning said at the conference, cold precursors of high-mass stars are now hot topics. We here propose some observational criteria to identify massive infrared-quiet dense cores which can host the high-mass analogs of Class 0 protostars an