Time-evolution of υ_c in the simulation from Laporte et al. (2018). Top and middle: the difference between the Jeans equation derived υ_c and the true υ_c,true. The top panel shows the result for x < 0 and the middle panel shows the opposite side of the disc (x > 0). Bottom: the RMS of υ_ctrue with azimuth. Green (white) horizontal lines show the pericentres of the satellite. The start of the simulation is at t = 0.