Gas velocity structure as a function of the distance to the center clump (l = 323.459°, b = −0.079°). The data points from the top to the bottom panels of the diagram are from the whole junction, the left half of the junction (l > 323.46^°) and the right half of the junction (l < 323.46°), respectively. For all panels different fitted lines describe the expected velocity profile for a free-falling particle in a series of potential wells with different masses M observed at different angles α following Eq. (4). The parameters are showed at the lower right corner of each panel, the masses are in M_⊙ and angles are in degrees. The blue contours are the density-plot of the cross points.