Distribution of bubble clumps (green contours), HDL clumps (red contours) and quiescent clumps (blue contours) classified according to their position distribution relative to the super bubble W4. The gray background image represents the integrated intensity map of ¹³CO. The yellow stars, black crosses, and small red and blue dots correspond to OB stars (Roman-Lopes et al. 2019), HMYSOs (Lumsden et al. 2013) and red and blue lobes identified as CO outflows by Li et al. (2019), respectively.