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.