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Massive 70μm quiet clumps – II. non-thermal motions driven by gravity in massive star formation?

Traficante, A., Fuller, G. A., Smith, R. J., Billot, N., Duarte Cabral, Ana ORCID:, Peretto, Nicolas ORCID:, Molinari, S. and Pineda, J. E. 2018. Massive 70μm quiet clumps – II. non-thermal motions driven by gravity in massive star formation? Monthly Notices of the Royal Astronomical Society 473 (4) , pp. 4975-4985. 10.1093/mnras/stx2672

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The dynamic activity in massive star-forming regions prior to the formation of bright protostars is still not fully investigated. In this work, we present observations of HCO+J = 1–0 and N2H+J = 1–0 made with the IRAM 30  m telescope towards a sample of 16 Herschel-identified massive 70 μm quiet clumps associated with infrared dark clouds. The clumps span a mass range from 300 to 2000 M⊙. The N2H+ data show that the regions have significant non-thermal motions with velocity dispersion between 0.28 and 1.5 km s−1, corresponding to Mach numbers between 2.6 and 11.5. The majority of the 70 μm quiet clumps have asymmetric HCO+ line profiles, indicative of significant dynamical activity. We show that there is a correlation between the degree of line asymmetry and the surface density Σ of the clumps, with clumps of Σ ≳ 0.1 g cm−2 having more asymmetric line profiles, and so are more dynamically active, than clumps with lower Σ. We explore the relationship between velocity dispersion, radius and Σ and show how it can be interpreted as a relationship between an acceleration generated by the gravitational field, aG, and the measured kinetic acceleration, ak, consistent with the majority of the non-thermal motions originating from self-gravity. Finally, we consider the role of external pressure and magnetic fields in the interplay of forces.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Publisher: Oxford University Press
ISSN: 0035-8711
Date of First Compliant Deposit: 20 December 2017
Date of Acceptance: 8 October 2017
Last Modified: 02 May 2023 23:19

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