(CO)-C-13 mapping study for massive molecular cloud cores

Using the newly installed SIS receiving system on the 13.7 m telescope at Q inghai Station of PMO, United Radio Astronomy of CAS, CO isotope (CO)-C-13 J = 1-0 and (CO)-O-18 J = 1-0 lines were observed for three sources S241, S 39 and ON3. Results show that the three sources have massive cores, of whic h the size is similar to 2-5 pc, masses are similar to 10(3)-10(4) M-circle dot. The widths of lines are also larger than those in low mass cores. And high velocity characteristics were observed for all the sources. The V-LSR distribution presents rotation of the core in ON3. And all the three cores contain deeply embedded forming massive stars. The young stellar objects i n S241 and ON3 seem to be moving away from their birth sites.