Azimuthally averaged profiles of the surface density perturbation Σ∕Σ_p (top), aspectratio h (middle), and midplane sound speed perturbation c_s∕c_s,0 (bottom) during the course of the fiducial simulation with irradiation. Solid curves corresponding to various simulation times are distinguished by colour. The vertical dashed line is the planet location, the grey vertical band marks the Hill sphere, and the hatched vertical band shows the extent of the gap width (following the definition of Kanagawa et al. 2016). The horizontal dotted line marks the gap depth according to Kanagawa et al. (2016). Dashed curves in the bottom panel are the least-squares fits of the Gaussian function of Hallam & Paardekooper (2018; magenta) and the skewed Gaussian (turquoise) given by Eq. (27). The peak of h and c_s can be directly related to the increased heating of the outer gap edge by stellar irradiation (see Fig. 2).