Article Dans Une Revue Monthly Notices of the Royal Astronomical Society Année : 2024

ATOMS: ALMA three-millimeter observations of massive star-forming regions - XVIII. On the origin and evolution of dense gas fragments in molecular shells of compact H II regions

Tie Liu
Archana Soam
Yong Zhang

Résumé

Fragmentation and evolution for the molecular shells of the compact H II regions are less explored compared to their evolved counterparts. We map nine compact H II regions with a typical diameter of 0.4 pc that are surrounded by molecular shells traced by CCH. Several to a dozen dense gas fragments probed by H$^{13}$CO$^+$ are embedded in these molecular shells. These gas fragments, strongly affected by the H II region, have a higher surface density, mass, and turbulence than those outside the shells but within the same pc-scale natal clump. These features suggest that the shells swept up by the early H II regions can enhance the formation of massive dense structures that may host the birth of higher mass stars. We examine the formation of fragments and find that fragmentation of the swept-up shell is unlikely to occur in these early H II regions, by comparing the expected time scale of shell fragmentation with the age of H II region. We propose that the appearance of gas fragments in these shells is probably the result of sweeping up pre-existing fragments into the molecular shell that has not yet fragmented. Taken together, this work provides a basis for understanding the interplay of star-forming sites with an intricate environment containing ionization feedback such as those observed in starburst regions.

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insu-04846473 , version 1 (18-12-2024)

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Siju Zhang, Tie Liu, Ke Wang, Annie Zavagno, Guido Garay, et al.. ATOMS: ALMA three-millimeter observations of massive star-forming regions - XVIII. On the origin and evolution of dense gas fragments in molecular shells of compact H II regions. Monthly Notices of the Royal Astronomical Society, 2024, 535 (2), pp.1364-1386. ⟨10.1093/mnras/stae2415⟩. ⟨insu-04846473⟩
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