Linear version of Fig. 2b, left panel, including the region of the disk within which the growing planet will accrete its gas (the feeding zone) for a given disk radius. The small dashed lines show the disk scale height and three times the disk scale hight. When the planet opens a gap (i.e. the feeding zone exceeds the gas scale height), the planet begins feeding on gas accreted between the gas scale height and three times the gas scale height. Shown is the extent of the feeding zone for the 600 M_⊕ planet (black hatches). Once a planet opens a gap it changes the region of the disk from which the planet feeds.