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Title: Identifying and analysing protostellar disc fragments in smoothed particle hydrodynamics simulations
Authors: Hall, Cassandra
Forgan, Duncan
Rice, Ken
First Published: 20-May-2017
Publisher: Oxford University Press (OUP), Royal Astronomical Society
Citation: Monthly Notices of the Royal Astronomical Society, 2017, 470 (3), pp. 2517-2538
Abstract: We present a new method of identifying protostellar disc fragments in a simulation based on density derivatives, and analyse our data using this and the existing CLUMPFIND method, which is based on an ordered search over all particles in gravitational potential energy. Using smoothed particle hydrodynamics, we carry out nine simulations of a 0.25 M⊙ disc around a 1 M⊙ star, all of which fragment to form at least two bound objects. We find that when using all particles ordered in gravitational potential space, only fragments that survive the duration of the simulation are detected. When we use the density derivative method, all fragments are detected, so the two methods are complementary, as using the two methods together allows us to identify all fragments, and to then determine those that are likely to be destroyed. We find a tentative empirical relationship between the dominant azimuthal wavenumber in the disc m and the maximum semimajor axis a fragment may achieve in a simulation, such that amax∝1/m. We find the fragment destruction rate to be around half that predicted from population synthesis models. This is due to fragment–fragment interactions in the early gas phase of the disc, which can cause scattering and eccentricity pumping on short time-scales, and affects the fragment's internal structure. We therefore caution that measurements of eccentricity as a function of semimajor axis may not necessarily constrain the formation mechanism of giant planets and brown dwarfs.
DOI Link: 10.1093/mnras/stx1244
ISSN: 0035-8711
eISSN: 1365-2966
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: Copyright © 2017, Oxford University Press (OUP), Royal Astronomical Society. Deposited with reference to the publisher’s open access archiving policy. (
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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