Planet mass vs. radial distance (panel a) and disk aspect ratio (panel b). The solid line represent the critical planet mass for rebound migration based on Eq. (8). The dashed blue, green, and orange lines give the fitting formulas of Crida et al. (2006), Fung et al. (2014), and Kanagawa et al. (2015), who define M_gap as the mass corresponding to 10% and 50% of the gas density at the center gap compared to the unperturbed values. The other parameters are α= 10⁻³ and Σ_PE = 20 × (r/10 au)⁻¹ g/cm⁻² at h = 0.05 in panel a and at r= 10 au in panel b.