Cloud collision-induced star formation in Sagittarius B2. I. Large-scale kinematics

We present maps of a similar to 14 pc x 20 pc region covering the Sgr B2 molecular cloud complex in the (CO)-C-13 (1-0) and CS (1-0) lines with high angular resolution. A more restricted central area was also mapped in the (CO)-O-18 (1-0) line. The 13CO cloud consists of two components: a compact core of similar to 3 pc in diameter roughly centered on Sgr B2(M) and an extended plateau of similar to 17 pc x 7.5 pc area containing the maser sources and most of the H II regions. Compact, massive (similar to 3 x 10(5) M.) (CO)-O-18 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 (CO)-C-13 (1-0) data. In addition, this hypothesis appears to be consistent with a wide range of new observations that have appeared in the literature.