ATOMS: ALMA three-millimeter observations of massive star-forming regions - XIII. Ongoing triggered star formation within clump-fed scenario found in the massive (∼1500 M⊙) clump

Whether ionization feedback triggers the formation of massive stars is highly debated. Using ALMA 3-mm observations with a spatial resolution of similar to 0.05 pc and a mass sensitivity of 1.1 per beam at 20 K, we investigate the star formation and gas flow structures within the ionizing feedback-driven structure, a clump-scale massive (greater than or similar to 1500 ) bright-rimmed cloud (BRC) associated with IRAS 18290-0924. This BRC is bound only if external compression from ionized gas is considered. A small-scale (less than or similar to 1 pc) age sequence along the direction of ionizing radiation is revealed for the embedded cores and protostars, which suggests triggered star formation via radiation-driven implosion (RDI). Furthermore, filamentary gas structures converge towards the cores located in the BRC's centre, indicating that these filaments are fueling mass towards cores. The local core-scale mass infall rate derived from (HCO+)-C-13 J = 1 - 0 blue profile is of the same order of magnitude as the filamentary mass inflow rate, approximately 1 M-circle dot kyr(-1). A photodissociation region (PDR) covering the irradiated clump surface is detected in several molecules, such as CCH, HCO+, and CS whereas the spatial distribution stratification of these molecules is indistinct. CCH spectra of the PDR possibly indicate a photoevaporation flow leaving the clump surface with a projected velocity of similar to 2 kms(-1). Our new observations show that RDI accompanied by a clump-fed process is operating in this massive BRC. Whether this combined process works in other massive BRCs is worth exploring with dedicated surveys.

Automated summary

This study uses ALMA observations to investigate the formation of massive stars triggered by ionization feedback. The results suggest that radiation-driven implosion is responsible for the formation of embedded cores and protostars within the ionizing feedback-driven structure. Additionally, filamentary gas structures fuel mass towards the cores in the bright-rimmed cloud. These findings reveal the operation of the combined process of radiation-driven implosion and clump-fed process in this massive bright-rimmed cloud.