Exploring dark matter locally via a hierarchy of stellar systems
Repository URI
Repository DOI
Type
Change log
Authors
Abstract
Most of our knowledge of the cosmos comes from the light from astronomical sources. However, in the last 40 years a concensus has emerged in the astronomical community that most of the matter in the -universe is invisible i.e it does not absorb or emit electromagnetic radiation. The nature of this dark matter remains an unsolved mystery. In this thesis we attempt to discover what constraints can be placed on dark matter from an analysis of a variety of stellar systems in the Local Group. The simplest composite stellar system is a stellar binary. The separation distribution function of wide binaries is sensitive to the presence of massive compact bodies such as MACHOs. Extending earlier work we use radial velocities measurements to validate a number of objects in the existing sample of wide halo binary candidates, and with the updated sample we study the constraints on MACHOs, arriving at the conclusion that the current wide binaries sample places only very weak constraints on MACHOs, in constrast to earlier work which concluded that the separation distribution of wide halo binaries may be used to rule out MACHOs as a significant component of the dark sector. Motivated by the need to increase the sample size of wide binaries in order to derive more robust constraints, we conducted a search in the Stripe 82 catalog for new systems. A small number of new wide binary systems were detected. These by themselves do not have significant implications for MACHOs, but we outline with illustrations their potential scientific importance, including for testing ideas about wide binary formation. Stepping up the stellar hierarchy we investigate the effect of a lumpy potential on the profile of the tidal tails of a disrupting globular cluster and compare our results to the Pal 5 tidal tail system. We find that a close encounter with a massive dark matter subhalo could produce features in the tails that resemble the current observations. We also show that the Pal 5 system can be used to place new, although not very tight, constraints on MACHOs. The final stellar system we consider is the galactic-wide Planetary Nebula system in the Andromeda galaxy. Along with the galaxy's rotation curve, we use the Planetary Nebulae to constrain dynamical models of the galaxy, with a view to pinning down the parameters of the dark matter halo. We find that the current data is not able to lift the disk/dark matter degeneracy, and show that better gas rotation curve data rather than Planetary Nebulae data may provide the best way forward to achieve this goal.
Description
This thesis is not available on this repository until the author agrees to make it public. If you are the author of this thesis and would like to make your work openly available, please contact us: thesis@repository.cam.ac.uk.
Cambridge University Library can make a copy of this work available only for the purposes of private study and non-commercial research. Copies should not be shared or saved in any shared facilities. Copyright over the content of these works is with their authors. Theses from the Library collection are considered unpublished works and according to UK legislation quoting from them is not allowed without permission from their author.
If you can commit to these terms, please complete the request form which you can find through this link: https://imagingservices.lib.cam.ac.uk/
Please note that print copies of theses may be available for consultation in the Cambridge University Library's Manuscript reading room. Admission details are at http://www.lib.cam.ac.uk/collections/departments/manuscripts-university-archives