H₂CO (3₀₃ → 2₀₂) integrated intensity map (left) and the noise map (right) observed with the APEX in the GC. Left: black contour levels for the molecular line emission (on a scale) are −3, 3, 6, 9, 12, 15, 20, 30, 40, 50 σ (1σ=0.72 K km s^-1). The black rectangle shows a smaller region where most of the molecular line emission is detected. The molecular cloud labels with M followed by the galactic coordinates are adopted from Güsten et al. (1981). The wedge at the side shows the intensity range of the line emission on a scale. The beam size of 30″ is shown in the bottom-left corner. Right: noise map across the region. The wedge at the side shows the range of noise on a scale at a velocity resolution of 2 km s^-1. The spectra presented in Fig. B.1 are shown as the plus symbols with numbers. Sgr A^∗ is the reference position and shown as a white cross symbol. The dashed line marks the Galactic plane through Sgr A^∗.