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On fragmentation of turbulent self-gravitating discs in the long cooling time regime

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journal contribution
posted on 2018-08-14, 15:51 authored by Ken Rice, Sergei Nayakshin
It has recently been suggested that in the presence of driven turbulence discs may be much less stable against gravitational collapse than their non-turbulent analogues, due to stochastic density fluctuations in turbulent flows. This mode of fragmentation would be especially important for gas giant planet formation. Here, we argue, however, that stochastic density fluctuations due to turbulence do not enhance gravitational instability and disc fragmentation in the long cooling time limit appropriate for planet forming discs. These fluctuations evolve adiabatically and dissipate away by decompression faster than they could collapse. We investigate these issues numerically in two dimensions via shearing box simulations with driven turbulence and also in three dimensions with a model of instantaneously applied turbulent velocity kicks. In the former setting turbulent driving leads to additional disc heating that tends to make discs more, rather than less, stable to gravitational instability. In the latter setting, the formation of high-density regions due to convergent velocity kicks is found to be quickly followed by decompression, as expected. We therefore conclude that driven turbulence does not promote disc fragmentation in protoplanetary discs and instead tends to make the discs more stable. We also argue that sustaining supersonic turbulence is very difficult in discs that cool slowly.

Funding

K.R. gratefully acknowledges support from Science and Technology Facilities Council (STFC) grant ST/M001229/1. The research leading to these results also received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement number 313014 (ETAEARTH). S.N. acknowledges support by STFC grant ST/K001000/1, the ALICE High Performance Computing Facility at the University of Leicester, and the STFC DiRAC HPC Facility (grant ST/H00856X/1 and ST/K000373/1). DiRAC is part of the National E-Infrastructure.

History

Citation

Monthly Notices of the Royal Astronomical Society, 2018, 475 (1), pp. 921-931 (11)

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy

Version

  • VoR (Version of Record)

Published in

Monthly Notices of the Royal Astronomical Society

Publisher

Oxford University Press (OUP), Royal Astronomical Society

issn

0035-8711

eissn

1365-2966

Acceptance date

2017-12-13

Copyright date

2017

Available date

2018-08-14

Publisher version

https://academic.oup.com/mnras/article/475/1/921/4768273

Language

en