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

Abstract

Whether ionization feedback triggers the formation of massive stars is highly debated. Using ALMA 3 mm observations with a spatial resolution of ∼0.05 pc and a mass sensitivity of 1.1 $\rm M_\odot$ beam−1 at 20 K, we investigate the star formation and gas flow structures within the ionizing feedback-driven structure, a clump-scale massive (≳ 1500 $\rm M_\odot$) 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 (≲ 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 center, indicating that these filaments are fueling mass towards cores. The local core-scale mass infall rate derived from H13CO+ J = 1 − 0 blue profile is of the same order of magnitude as the filamentary mass inflow rate, approximately 1 $\rm M_\odot$ 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 ∼2 km s−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.

The ALMA-QUARKS Survey. I. Survey Description and Data Reduction

“…How stellar feedback from outflows, H II regions and stellar winds from formed OB protostars influences the formation of new generation of stars and reshapes gas distribution in clouds is highly debated (e.g., Krumholz et al 2014;Peters et al 2017;Schneider et al 2020;Zhang et al 2023b;Herrington et al 2023;Pouteau et al 2023). The ATOMS survey studied the impact of UC H II regions (S. Zhang et al 2023, in preparation) on their surrounding molecular gas, but detailed investigation was limited by sensitivity, and resolution.…”

Direct Observational Evidence of Multi-epoch Massive Star Formation in G24.47+0.49

“…Over the last decade or so, there has been a plethora of observational evidence linking the expansion of H II regions to triggered star formation (e.g., Zavagno et al 2006Zavagno et al , 2007Figueira et al 2017, and references therein). The peripheries of infrared dust bubbles (Churchwell et al 2006;Kendrew et al 2012) have served as ideal sites to investigate triggered star formation through various competing mechanisms (e.g., Deharveng et al 2010;Kendrew et al 2012;Thompson et al 2012;Liu et al 2016;Das et al 2017;Bhadari et al 2021;Zhang et al 2023b). However, theoretically (e.g., Dale et al 2015; González-Samaniego & Vazquez-Semadeni 2020) and observationally (e.g., Cambrésy et al 2013), it is also seen that commonly used signposts of triggered star formation do not always lead to definite conclusions on positive feedback.…”