DR21(OH) is the most massive protocluster within 3 kpc and therefore serves as a perfect laboratory to study the onset of high-mass star-formation. Recent high-angular resolution observations identified flows of cold dense gas from parsec to sub-parsec scales associated with the sites of high-mass protostars similarly as it is predicted by the dynamical, fast star-formation scenario. It is however observationally challenging to find direct evidence and proof for the converging flow model. Our group has identified the most promising potential sites in the Cygnus-X complex where the shocks associated with these converging flows could be found. Here we aim for a detailed study of typical shock tracers (i.e.OI, OH and H2O lines using PACS and SPIRE spectroscopy) to reveal the signatures of the shocks as well as to study the CO ladder to constrain the excitation conditions at these sites. We also target a water line with HIFI to obtain velocity resolved spectra of the proposed shocks. This will provide a comprehensive view on these shocks and test the converging flow scenario. Herschel is the only opportunity to extensively study these molecular tracers and could provide the first direct evidence for dynamical star-formation models.
Herschel was launched on 14 May 2009! It is the fourth 'cornerstone' mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 µm range, bridging the gap between earlier infrared space missions and groundbased facilities.