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On the origin of the stellar initial mass function and multiple stellar systems

Nelson, Katy 2014. On the origin of the stellar initial mass function and multiple stellar systems. PhD Thesis, Cardiff University.
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Abstract

I first perform a statistical analysis on a distribution of pre-stellar core masses. Each core is split into a small number of stars, and two stars are chosen using a prescription based on stellar masses to form a binary system. The rest of the stars are taken to be singles. From this sample of binaries and singles, I compute the stellar initial mass function, the binary frequency and mass ratio distribution as a function of primary mass. I then test if the observed binary frequencies and mass ratios are compatible with this self-similar mapping of cores into stars. I show that self-similar mapping can reproduce the observed binary frequencies and mass ratios well, so long as the efficiency is rather high (100%), and each core fragments into about 4 or 5 stars. Using the code Seren view, I then perform N-body simulations with core-clusters. I investigate the formation of multiple systems, and qualify the dependence of their parameters and longevity on certain initial conditions, including (i) the number of stars in a core-cluster, (ii) the variance of masses in those stars, (iii) the virial ratio and (iv) radial dependence of stellar density. I expand on those results by including (a) a prescription for the influence of disks during stellar ybys, (b) different initial spatial configurations of the stars (i.e. line and ring clusters) and (c) a background potential due to residual gas in the core-cluster. The full range of periods observed in the field cannot be explained by the distribution of periods of pure binaries alone, which is too narrow. However, the wide range can be explained either by combining the periods of pair-wise orbits of all multiple systems, i.e. the widest periods observed are in fact pair-wise orbits of higher-order multiples with unresolved companions, or by considering a distribution of pre-stellar cores that have a range of virial ratios.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Uncontrolled Keywords: star formation, multiple systems, pre-stellar cores
Funders: STFC
Date of First Compliant Deposit: 30 March 2016
Last Modified: 19 Mar 2016 23:47
URI: http://orca-mwe.cf.ac.uk/id/eprint/65971

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