η-ν (see text) plot for the cores associated with the PDRs around the HII regions G353.2+0.9 (filled red squares) and G353.1+0.6 (open blue squares). The dash dotted lines mark the critical densities for turbulent cores for different values of the non-thermal to thermal pressure ratio (α) and the magnetic to thermal pressure ratio (β), and a frozen magnetic field. The solid lines mark the evolution of the column density ratio η against the parameter ν (which increases with increasing G₀) for pre-existing cores embedded in an interclump medium. The dotted lines indicate the fraction of mass lost by such cores due to photoevaporation when exposed to a steadily increasing G₀. The dashed line marks the critical density for such cores, i. e. the column density of a core that would be completely photoevaporated by a FUV field ν.