Research in Astronomy and Astrophysics Water Abundance in Four of the Brightest Water Sources in the

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 ob-served by the SubmillimeterWave Astronomy Satellite (ortho-H2O 110- 101 line, 556.936 GHz). The typical molecular clumps in our sample have H2 column densities of 10 22 to 1023cm−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 Swedish-ESO 15 m Submillimeter Telescope (SEST) to calculate the temperatures of the clumps and the 350 µm dust continuum observed by Caltech Submillimeter Observatory (CSO) tele-scope 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 esti-mated. The N2H + abundance in each clump shows a common decreasing trend toward the center and the typical abundance ranges from 10−11 to 10−9