2000ApJ...535..857S

We present maps of a ∼14 pcx20 pc region covering the Sgr B2 molecular cloud complex in the ¹³CO (1-0) and CS (1-0) lines with high angular resolution. A more restricted central area was also mapped in the C¹⁸O (1-0) line. The ¹³CO cloud consists of two components: a compact core of ∼3 pc in diameter roughly centered on Sgr B2(M) and an extended plateau of ∼17 pcx7.5 pc area containing the maser sources and most of the H II regions. Compact, massive (∼3x10⁵ M_☉) C¹⁸O cores are associated with Sgr B2(M) and Sgr B2(N). The obtained intensity distributions are compared with those of molecular masers and compact H II regions reported in the literature. Low-velocity (40-65 km.s^–1) masers, with positions roughly aligned in the north-south line connecting the three major compact H II region complexes, are located near the eastern margin of a large hole in the low-velocity molecular cloud. In contrast, most of the high-velocity (65-80 km.s^–1) masers are distributed near the center of a compact molecular cloud at higher velocity, where a shock seems to have occurred. These results provide further evidence supporting the cloud-cloud collision hypothesis based on limited ¹³CO (1-0) data. In addition, this hypothesis appears to be consistent with a wide range of new observations that have appeared in the literature.