Surface temperature (for Z = Z_⊙) for different values of mechanical heating. Each panel shows the surface temperature contours for a different value of Γ_mech mentioned at the top of each panel. In probing the effect of mechanical heating, each panel should be compared to the middle panel of Fig. 1 which is also for Z = Z_⊙. Different parts of the parameter space in n and G₀ are affected differently, depending mainly on the gas density. For Γ_mech < 10^-21 erg cm^-3 s^-1, regions in density with n < 10³ cm^-3 have their temperatures increase significantly. The vertical dashed red lines mark densities n = n_c where Γ_mech = Γ_{total,surface}. The location of these lines moves from very low densities (n ~ 10⁰.5 cm^-3) to very high densities (n > 10⁵ cm^-3) as Γ_mech increases from 10^-24 to 10^-16 erg cm^-3 s^-1, sweeping the parameter space in density (for a certain grid) from left to right. In general the contour lines at n = n_c become vertical, indicating that the surface temperature becomes independent of G₀. In subsequent plot, those lines are plotted only for Z = Z_⊙ grids, since the fits from which n = n_c were derived were done only for solar metallicity.