Abstract We estimated the ortho-H2O abundances of G267.9–1.1, G268.4–0.9, G333.1–0.4 and G336.5– 1.5, four of the brightest ortho-H2O sources in the southern sky observed by the Submillimeter Wave Astronomy Satellite (ortho-H2O 110–101 line, 556.936 GHz). The typical molecular clumps in our sample have H2 column densities of 1022 to 1023 cm−2 and ortho-H2O abundances of 10−10. Compared with previous studies, the ortho-H2O abundances are at a low level, which can be caused by the low temperatures of these clumps. To estimate the ortho-H2O abundances, we used the CS J = 2 → 1 line (97.98095 GHz) and CS J = 5 → 4 (244.93556 GHz) line observed by the Swedish-ESO 15 m Submillimeter Telescope (SEST) to calculate the temperatures of the clumps and the 350 μm dust continuum observed by the Caltech Submillimeter Observatory (CSO) telescope to estimate the H2 column densities. The observations of N2H+ (J = 1 → 0) for these clumps were also acquired by SEST and the corresponding abundances were estimated. The N2H+ abundance in each clump shows a common decreasing trend toward the center and a typical abundance range from 10−11 to 10−9.

Keywords ISM: abundances — (ISM:) HII regions — ISM: molecules — stars: formation

https://doi.org/10.1088/1674–4527/16/3/039