Horizontal (along RA, left) and vertical (along Dec, right) position-velocity diagrams through the position of one of the exciting sources IRS5 (marked in each panel) derived from the [CII] line emission. corresponding roughly to the estimated center of bubble B. The contour levels are in 3σ steps. The black dotted lines outline the elliptical shape a spherical shell would have in the pv diagram – given a radius of 100″ and expansion velocities of 10 and 3 km s⁻¹ at negative and positive relative velocities, respectively.