Oxygen isotope ratio studies in the Galactic center region

Using the Delingha 13.7 m telescope with a 9-beam SIS superconducting receiver installed, we carried out mapping of C18O and C17O J = (1 − 0) toward molecular clouds in the central molecular zone (CMZ) and in the halo of our galaxy. From the integrated intensity ratio of C18O to C17O, the isotope ratio 18O/17O ratio can be estimated, which is considered to be one of the most useful tracers of nuclear processing and metal enrichment. Here preliminary results are presented toward Sgr A, Sgr B2, Sgr C, Sgr D, and the 1.°3 complex in the CMZ and M+5.3–0.3 in the halo.