Using the Submillimeter Array (SMA), we identified two bright hot subcores, MM1a and MM1b (size ~ 1" and mass ~ 0.5 M⊙) separated by about 1.600, in the 230 GHz continuum emission toward the massive star-forming region DR21(OH). Both display typical hot core characteristics but have slightly different chemical properties. For example, highly saturated species show stronger emission toward MM1a and seem to be evaporating directly from the grain mantles. In contrast, simple sulfur-bearing species have brighter emission at MM1b. These features indicate that MM1a is at an earlier stage than MM1b, and the small-scale chemical differences between these two cores may result from the age difference of the order of 104 104 years.

• Y. C. MINH(Korea Astronomy and Space Science Institute) Corresponding Author
• H. R. CHEN(Institute of Astronomy & Department of Physics, National sing Hua University)
• Y. N. SU(Academia Sinica, Institute of Astronomy and Astrophysics)
• S. Y. LIU(Academia Sinica, Institute of Astronomy and Astrophysics)