A Multi-wavelength Study on the Formation of AFGL 333-Ridge

TL;DR

This study uses multi-wavelength observations to show that the AFGL 333-Ridge was formed by cloud-cloud collision possibly triggered by the expansion of the W4 HII region, leading to star formation.

Contribution

It provides observational evidence linking cloud collision and HII region expansion to the formation of AFGL 333-Ridge and associated star formation.

Findings

Two velocity components indicate cloud collision

YSOs are concentrated in the collision region

HII region expansion likely triggered ridge formation

Abstract

We presented a multi-wavelength study of AFGL 333-Ridge. The molecular line data reveals that the AFGL 333-Ridge has two independent velocity components at -50.5 km/s and -48.0 km/s. In the Position-Velocity diagram, the bridge feature connects with two parts that are spatially correlated but separated in velocity. These observational evidences support the scenario that the two velocity components have collided and merged into one molecular cloud. The majority of Class I 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 (FAST), the RRL velocities of three HII regions are consistent with that of the AFGL 333-Ridge. By comparing the three HII regions' dynamical ages with the collision timescale of the two components, we conclude that the influence of the three HII 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 HII region W4.