Deviation from the equilibrium sub-Keplerian velocity of the gas in the protoplanetary disc (v_θ,gas/v_K) due to the presence of a planetary core located at a normalized radius of r = 1 (here corresponding to an orbital radius of a = 5 AU). For cores with masses above 20M_E (blue curve) and higher (red and black curves) the gas orbits faster than the Keplerian velocity (horizontal dashed line) in a region outside the orbit of the planet. This ring acts as a trap for pebbles drifting inwards and halts the accretion of pebbles onto the core.