Modelling carbon chain and complex organic molecules in the DR21(OH) clump

Context . Star-forming regions host a large and evolving suite of molecular species. Molecular transition lines, particularly of complex molecules, can reveal the physical and dynamical environment of star formation. Aims . We aim to study the large-scale structure and environment of high-mass star formation through single-dish observations of CH 3 CCH, CH 3 OH, and H 2 CO. Methods . We conducted a wide-band spectral survey with the Institut de radioastronomie millimétrique 30 m telescope and the 100 m Green Bank Telescope towards the high-mass star-forming region DR21(OH)/N44. We used a multi-component local thermodynamic equilibrium (LTE) model to determine the large-scale physical environment near DR21(OH) and the surrounding dense clumps. We followed up with a radiative transfer code for CH 3 OH to look at non-LTE behaviour. We then used a gas-grain chemical model to understand the formation routes of these molecules in their observed environments. Results . We disentangled multiple components of DR21(OH) in each of the three molecules. We find both a warm and cold component towards both the dusty condensations MM1 and MM2, and a fifth broad, outflow component. We also find warm and cold components towards other dense clumps in our maps: N40, N36, N41, N38, and N48. We find that thermal mechanisms are adequate to produce the observed abundances of H 2 CO and CH 3 CCH while non-thermal mechanisms are needed to produce CH 3 OH. We determine that the production routes of these species are dominated by grain chemistry. Conclusions . Through a combination of wide-band mapping observations, LTE and non-LTE model analysis, and chemical modelling, the chemical and physical environments of star-forming regions are revealed. This method allows us to disentangle the different velocity and temperature components within our clump-scale beam, a scale that encompasses both the star-forming core and its parent cloud.