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Chemical composition of the massive cores forming high-mass stars can put some constrains on the time scale of the massive star formation: sulphur chemistry is of specific interest due to its rapid evolution in warm gas and because the abundance of sulphur bearing species increases significantly with the temperature. Two mid-infrared quiet and two brighter massive cores are observed in various transitions (E_up up to 289K) of CS, OCS, H2S, SO, SO2 and of their isotopologues at mm wavelengths with the IRAM 30m and CSO telescopes. 1D modeling of the dust continuum is used to derive the density and temperature laws, which are then applied in the RATRAN code to model the observed line emission, and to derive the relative abundances of the molecules. All lines, except the highest energy SO2 transition, are detected. Infall (up to 2.9km/s) may be detected towards the core W43MM1. The inferred mass rate is 5.8-9.4 10^{-2} M_{odot}/yr. We propose an evolutionary sequence of our sources (W43MM1-IRAS18264-1152-IRAS05358+3543-IRAS18162-2048), based on the SED analysis. The analysis of the variations in abundance ratios from source to source reveals that the SO and SO2 relative abundances increase with time, while CS and OCS decrease. Molecular ratios, such as [OCS/H2S], [CS/H2S], [SO/OCS], [SO2/OCS], [CS/SO] and [SO2/SO] may be good indicators of evolution depending on layers probed by the observed molecular transitions. Observations of molecular emission from warmer layers, hence involving higher upper energy levels are mandatory to include.
We present an observational study of the sulfur (S)-bearing species towards Orion KL at 1.3 mm by combining ALMA and IRAM-30,m single-dish data. At a linear resolution of $sim$800 au and a velocity resolution of 1 $mathrm{km, s^{-1}, }$, we have iden
We surveyed 81 dense molecular cores associated with regions of massive star formation and Sgr A in the 5_{05}-4_{04} and 10_{010}-9_{09} lines of HNCO. Line emission was detected towards 57 objects. Selected subsamples were also observed in other HN
Young massive stars are usually found embedded in dense massive molecular clumps and are known for being highly obscured and distant. During their formation process, deuteration is regarded as a potentially good indicator of the very early formation
We have observed several emission lines of two Nitrogen-bearing (C2H5CN and C2H3CN) and two Oxygen-bearing (CH3OCH3 and HCOOCH3) molecules towards a sample of well-known hot molecular cores (HMCs) in order to check whether the chemical differentiatio
Theoretical and numerical works indicate that a strong magnetic field should suppress fragmentation in dense cores. However, this has never been tested observationally in a relatively large sample of fragmenting massive dense cores. Here we use the p