Integrated velocity contours of HNC (top panel) and HCO⁺ (bottom panel) emission superimposed on the GLIMPSE 8.0 μm grayscale. The contours are at multiples of 11%, 11%, 12%, and 12% level of the blue lobe of HNC, the red lobe of HNC, the blue lobe of HCO⁺, and the red lobe of HCO⁺ emission peaks, which are 9.539, 8.618, 12.861, and 10.800 K km s^-1, respectively. Source C is indicated with “C” in the image. The symbols “▴”, “■” and “★” indicate the positions of the water maser, the methanol maser, and IRAS 16158-5055, respectively.