Star cluster progenitors are dynamically decoupled from their parent molecular clouds

Peretto, Nicolas ORCID: https://orcid.org/0000-0002-6893-602X, Rigby, Andrew J., Louvet, Fabien, Fuller, Gary A., Traficante, Alessio and Gaudel, Mathilde 2023. Star cluster progenitors are dynamically decoupled from their parent molecular clouds. Monthly Notices of the Royal Astronomical Society 525 (2) 10.1093/mnras/stad2453

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Abstract

The formation of stellar clusters dictates the pace at which galaxies evolve, and solving the question of their formation will undoubtedly lead to a better understanding of the Universe as a whole. While it is well known that star clusters form within parsec-scale overdensities of interstellar molecular gas called clumps, it is, however, unclear whether these clumps represent the high-density tip of a continuous gaseous flow that gradually leads towards the formation of stars, or a transition within the gas physical properties. Here, we present a unique analysis of a sample of 27 infrared dark clouds embedded within 24 individual molecular clouds that combine a large set of observations, allowing us to compute the mass and velocity dispersion profiles of each, from the scale of tens of parsecs down to the scale of tenths of a parsec. These profiles reveal that the vast majority of the clouds, if not all, are consistent with being self-gravitating on all scales, and that the clumps, on parsec-scale, are often dynamically decoupled from their surrounding molecular clouds, exhibiting steeper density profiles (ρ∝r−2) and flat velocity dispersion profiles (σ∝r0), clearly departing from Larson’s relations. These findings suggest that the formation of star clusters correspond to a transition regime within the properties of the self-gravitating molecular gas. We propose that this transition regime is one that corresponds to the gravitational collapse of parsec-scale clumps within otherwise stable molecular clouds.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Physics and Astronomy
Publisher:	Oxford University Press
ISSN:	0035-8711
Funders:	STFC
Date of First Compliant Deposit:	24 October 2023
Date of Acceptance:	5 August 2023
Last Modified:	21 Aug 2024 10:32
URI:	https://orca.cardiff.ac.uk/id/eprint/163470

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