2021ApJ...913...14L

We presented a multiwavelength study of the AFGL 333-Ridge. The molecular line data reveals that the AFGL 333-Ridge has two independent velocity components at -50.5 and -48.0 km s^–1. In the position-velocity diagram, the bridge feature connects with two parts that are spatially correlated but separated in velocity. This observational evidence supports the scenario that the two velocity components have collided and merged into one molecular cloud. The majority of Class I young stellar objects (YSOs) are distributed within the collision region, suggesting that the cloud-cloud collision has induced the YSOs' formation in the ridge. Using the radio recombination line (RRL) data obtained by the Five-hundred-meter Aperture Spherical radio Telescope, the RRL velocities of three H II regions are consistent with that of the AFGL 333-Ridge. By comparing the three H II regions' dynamical ages with the collision timescale of the two components, we conclude that the influence of the three H II regions may not drive the two clouds to merge. The formation of the AFGL 333-Ridge is probably due to the expansion of the giant H II region W4.