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Abstract: abridged Vortices are believed to play a role in the formation of km-sizedplanetesimals. However, vortex dynamics is commonly studied innon-self-gravitating discs. The main goal here is to examine the effects ofdisc self-gravity on vortex dynamics. For this purpose, we employ the 2Dself-gravitating shearing sheet approximation. A simple cooling law with aconstant cooling time is adopted, such that the disc settles down into aquasi-steady gravitoturbulent state. In this state, vortices appear astransient structures undergoing recurring phases of formation, growth to sizescomparable to a local Jeans scale and eventual shearing and destruction due tothe combined effects of self-gravity and background Keplerian shear. Each phasetypically lasts about 2 orbital periods or less. As a result, inself-gravitating discs the overall dynamical picture of vortex evolution isirregular consisting of many transient vortices at different evolutionarystages and, therefore, with various sizes up to the local Jeans scale. Vorticesgenerate density waves during evolution, which turn into shocks. Therefore, thedynamics of density waves and vortices are coupled implying that, in general,one should consider both vortex and spiral density wave modes in order to get aproper understanding of self-gravitating disc dynamics. Our results suggestthat given such an irregular and rapidly varying character of vortex evolutionin self-gravitating discs, it may be difficult for such vortices to effectivelytrap dust particles. Further study of the behaviour of dust particles embeddedin a self-gravitating gaseous disc is, however, required to strengthen thisconclusion.

Author: G. R. Mamatsashvili, W. K. M. Rice

Source: https://arxiv.org/

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