Issue |
A&A
Volume 685, May 2024
|
|
---|---|---|
Article Number | A101 | |
Number of page(s) | 34 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361/202348959 | |
Published online | 15 May 2024 |
Massive clumps in W43-main: Structure formation in an extensively shocked molecular cloud
1
Max-Planck-Institut für Extraterrestrische Physik,
Giessenbachstr. 1,
85748
Garching bei München,
Germany
e-mail: ylin@mpe.mpg.de
2
Max Planck Institute for Radio Astronomy,
Auf dem Hügel 69,
53121
Bonn,
Germany
3
Department of Physics, National Sun Yat-Sen University,
No. 70, Lien-Hai Road,
Kaohsiung City
80424,
Taiwan,
ROC
4
European Southern Observatory,
Karl-Schwarzschild-Str. 2,
85748
Garching bei München,
Germany
5
Leiden Observatory, Leiden University,
PO Box 9513,
2300 RA
Leiden,
The Netherlands
6
OASU/LAB-UMR5804, CNRS, Université Bordeaux,
allée Geoffroy Saint-Hilaire,
33615
Pessac,
France
7
Department of Astronomy, University of Florida,
PO Box 112055,
USA
8
South-Western Institute for Astronomy Research, Yunnan University,
Chenggong District,
Kunming
650091,
PR China
9
INAF – Osservatorio Astronomico di Cagliari,
Via della Scienza 5,
09047
Selargius
(CA),
Italy
Received:
14
December
2023
Accepted:
30
January
2024
Aims. W43-main is a massive molecular complex undergoing starburst activities, located at the interaction of the Scutum arm and the Galactic bar. We aim to investigate the gas dynamics, in particular, the prevailing shock signatures from cloud to clump scales. We also look to assess the impact of shocks on the formation of dense gas and early-stage cores in OB cluster formation processes.
Methods. We carried out NOEMA and IRAM-30 m observations at 3 mm towards five molecular gas clumps in W43 main located within large-scale interacting gas components. We used CH3CCH and H2CS lines to trace the extended gas temperature and CH3OH lines to probe the volume density of the dense gas components (≳105 cm−3). We adopted multiple tracers that are sensitive to different gas density regimes to reflect the global gas motions. The density enhancements constrained by CH3OH and a population of NH2D cores are correlated (in the spatial and velocity domains) with SiO emission, which is a prominent indicator of shock processing in molecular clouds.
Results. The emission of SiO (2–1) is extensive across the region (~4 pc) and it is contained within a low-velocity regime, hinting at a large-scale origin for the shocks. Position-velocity maps of multiple tracers show systematic spatio-kinematic offsets supporting the cloud-cloud collision-merging scenario. We identified an additional extended velocity component in the CCH emission, which coincides with one of the velocity components of the larger scale 13CO (2−1) emission, likely representing an outer, less-dense gas layer in the cloud merging process. We find that the ‘V-shaped’, asymmetric SiO wings are tightly correlated with localised gas density enhancements, which is direct evidence of dense gas formation and accumulation in shocks. The dense gas that is formed in this way may facilitate the accretion of the embedded, massive pre-stellar and protostellar cores. We resolved two categories of NH2D cores: those exhibiting only subsonic to transonic velocity dispersions and those with an additional supersonic velocity dispersion. The centroid velocities of the latter cores are correlated with the shock front seen via SiO. The kinematics of the ~0.1 pc NH2D cores are heavily imprinted by shock activities and may represent a population of early-stage cores forming around the shock interface.
Key words: ISM: clouds / ISM: kinematics and dynamics / ISM: molecules / ISM: structure
© The Authors 2024
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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Open Access funding provided by Max Planck Society.
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