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

Using new continuum and molecular line data from the Atacama Large Millimeter/submillimeter Array Three-millimeter Observations of Massive Star-forming Regions (ATOMS) survey and archival Very Large Array, 4.86 GHz data, we present direct observational evidence of hierarchical triggering relating th...

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Bibliographic Details
Published in:Astrophysical journal. Letters 2024-08, Vol.970 (2), p.L40
Main Authors: Saha, Anindya, Tej, Anandmayee, Liu, Hong-Li, Liu, Tie, Garay, Guido, Goldsmith, Paul F., Lee, Chang Won, He, Jinhua, Juvela, Mika, Bronfman, Leonardo, Baug, Tapas, Vázquez-Semadeni, Enrique, Sanhueza, Patricio, Li, Shanghuo, Chibueze, James O., Bhadari, N. K., Dewangan, Lokesh K., Das, Swagat Ranjan, Xu, Feng-Wei, Issac, Namitha, Hwang, Jihye, Tóth, L. Viktor
Format: Article
Language:English
Subjects:
Arrays
Atomic properties
Collapse
Excitation spectra
Gravitational collapse
Interstellar medium
Line spectra
Massive stars
Molecular gases
Radio telescopes
Ring structures
Star & galaxy formation
Star formation
Star forming regions
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Summary:Using new continuum and molecular line data from the Atacama Large Millimeter/submillimeter Array Three-millimeter Observations of Massive Star-forming Regions (ATOMS) survey and archival Very Large Array, 4.86 GHz data, we present direct observational evidence of hierarchical triggering relating three epochs of massive star formation in a ringlike H ii region, G24.47+0.49. We find from radio flux analysis that it is excited by a massive star(s) of spectral type O8.5V–O8V from the first epoch of star formation. The swept-up ionized ring structure shows evidence of secondary collapse, and within this ring, a burst of massive star formation is observed in different evolutionary phases, which constitutes the second epoch. ATOMS spectral line (e.g., HCO + (1–0)) observations reveal an outer concentric molecular gas ring expanding at a velocity of ∼9 km s −1 , constituting the direct and unambiguous detection of an expanding molecular ring. It harbors twelve dense molecular cores with surface mass density greater than 0.05 g cm −2 , a threshold typical of massive star formation. Half of them are found to be subvirial and thus in gravitational collapse making them the third epoch of potential massive star-forming sites.
ISSN:2041-8205
2041-8213
DOI:10.3847/2041-8213/ad6144