巨大星の誕生：宇宙の謎

タイトル: Study of the physical and chemical properties of dense clumps at different evolutionary stages in several regions of massive star and stellar cluster formation

概要: 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. In this work, we aim to study the chemical and physical conditions of dense clumps at different evolutionary stages. We performed observations towards 5 regions of massive star and stellar cluster formation (L1287, S187, S231, DR 21(OH), NGC 7538) with the IRAM-30m telescope. We covered the 2 and 3$-$4 mm wavelength bands and analysed the lines of HCN, HNC, HCO$^+$, HC$_3$N, HNCO, OCS, CS, SiO, SO$_2$, and SO. Using astrodendro algorithm on the 850 $\mu$m dust emission data from the SCUBA Legacy catalogue, we determined the masses, H$_2$ column densities, and sizes of the clumps. Furthermore, the kinetic temperatures, molecular abundances, and dynamical state were obtained. The Red Midcourse Space Experiment Source survey (RMS) was used to determine the clump types. A total of 20 clumps were identified. Three clumps were found to be associated with the Hii regions, 10 with young stellar objects (YSOs), and 7 with submillimetre emission. The clumps have typical sizes of about 0.2 pc and masses ranging from 1 to $10^{2}\,M_\odot$, kinetic temperatures ranging from 20 to 40 K and line widths of $\rm H^{13}CO^{+} (1-0)$ approximately 2 $\rm km\,s^{-1}$. We found no significant correlation in the line width$-$size and the line width$-$mass relationships. However, a strong correlation is observed in mass$-$size relationships. The virial analysis indicated that three clumps are gravitationally bound. Furthermore, we suggested that magnetic fields of about 1 mG provide additional support for clump stability. The molecular abundances relative to H$_2$ are approximately $10^{-10}-10^{-8}$.