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The Dynamical Evolution of Young Stellar Regions

Griffiths, Daniel (2018) The Dynamical Evolution of Young Stellar Regions. PhD thesis, University of Sheffield.

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Abstract

Young stars are generally found in groups we call 'young stellar regions’, which dynamically evolve. This thesis aims to provide insight on how these regions evolve, by focusing primarily on the dynamical formation and destruction of binary systems and the effect of stellar relaxation. Observations of massive stars in Cyg OB2 show that they can reside in binary systems with separations of a few thousand AU, which we call massive wide binaries (MWBs). We perform N-body simulations to show that, due to the dynamical formation and destruction of binaries in dense regions, a bound cluster will typically produce an average of one MWB. Therefore, any region that contains many massive wide binaries (such as Cyg OB2) must have been composed of many individual subregions. Observations of G-dwarfs in the Galactic field show that approximately 5% reside in binary systems with separations greater than 10000 AU, which we call very wide binaries (VWBs). One possible way of forming VWBs is via the `soft capture’ mechanism during the dissolution of a stellar association. We perform N-body simulations to show that it is not likely that this mechanism accounts for the observed field VWB population on its own. Gas expulsion is a common explanation for the destruction of young stellar regions, but gas expulsion depends on the region’s effective star formation efficiency. We perform hybrid N-body/SPH simulations to show that relaxation between stars in a dense cluster causes dynamical gas depletion in the cluster’s core, decreasing the possibility that gas expulsion will unbind the cluster.

Item Type: Thesis (PhD)
Keywords: Star Formation Cluster N-body Smoothed Particle Hydrodynamics Binary Stars
Academic Units: The University of Sheffield > Faculty of Science (Sheffield)
The University of Sheffield > Faculty of Science (Sheffield) > Physics and Astronomy (Sheffield)
Identification Number/EthosID: uk.bl.ethos.772874
Depositing User: Mr Daniel Griffiths
Date Deposited: 29 Apr 2019 08:20
Last Modified: 25 Sep 2019 20:07
URI: http://etheses.whiterose.ac.uk/id/eprint/23547

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