Study of the physical and chemical properties of dense clumps in several high-mass star-forming regions

Massive stars play an important role in the Universe. Unlike low-mass stars, the formation of these objects located at great distances is still unclear. It is expected to be governed by some combination of self-gravity, turbulence, and magnetic fields. Our aim is to study the chemical and physical conditions of dense clumps in several high-mass star-forming regions. We performed observations towards 5 high-mass star-forming regions (L1287, S187, S231, DR 21(OH), NGC 7538) with the IRAM 30-m telescope. We covered the 2-3 and 4 mm wavelength bands and analysed the lines of HCN, HNC, HCO$^+$, HC$_3$N, HNCO, OCS, CS, SiO, SO$_2$, and SO. Using the astrodendro algorithm on the 850 $\mu$m dust emission data from the SCUBA Legacy catalogue, we identified dense gas clumps and assessed their masses, H$_2$ column densities, and sizes. Furthermore, the kinetic temperatures, molecular abundances and dynamical state were obtained. The Red Midcourse Space Experiment Source survey (RMS) was utilized to identify the types of clumps. A total of 20 clumps were identified. We found no significant correlation between line width and size, but the linewidth-mass and mass-size relationships are strongly correlated. Virial analysis indicated that the clumps with H II regions and young stellar objects (YSOs) are gravitationally bound. Furthermore, it was suggested that significant magnetic fields provide additional support for clump stability. Molecular abundances show a decreasing trend from YSOs to submm and H II regions.