The Central Molecular Zone in H13CO+ and thermal SiO emission lines

We present results from a high-resolution wide-field imaging observation of the Central Molecular Zone (CMZ) in (HCO)-C-13+ J = 1-0 and SiO v = 0, J = 2-1 emission lines using the 45-m telescope at the Nobeyama Radio Observatory in order to depict the high-density molecular gas mass distribution and explore molecular gas affected by interstellar shocks. By using the clumpfind algorithm we identify 114 molecular clumps in the H13CO+ data cube. The clump mass function (CMF) can be described by a power law (dN/dM proportional to M-gamma, with gamma similar or equal to 2) in the range of 5 x 10(3) < M-clump < 2 x 10(4)M(circle dot). The brightness temperature ratio R-T = T(SiO)/T((HCO+)-C-13) indicates the strength of the shock. The Sgr B2 complex has several expanding shell-like structures with a large velocitywidth (Delta V > 50 km s(-1)). They correspond to the high brightness temperature ratio area (RT less than or similar to 8). A Large Velocity Gradient model analysis with the RADEX program confirms the enhancement of SiO molecules in the shells. On the other hand, there is no such large shell with a high ratio in the SgrA complex. A hollow hemispherical structure is found in the l-b-v data cube of the Sgr B2 complex. The central part of the structure has a high ratio (R-T less than or similar to 8). The ratio decreases with proximity to the outer area. The properties are consistent with those expected from simulations of cloud-cloud collisions. The structure is probably a site of ongoing cloud-cloud collision.