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Constraining the nature of dark matter in galaxies with multi-tracer dynamical models

Leung, Ying Chi

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Abstract

The detailed mass distribution in galaxies provides important constraints on the nature of dark matter (DM), especially in relation to the baryonic content and feedback efficiency of a galaxy. In this thesis I use multiple kinematic tracers and a diverse set of dynamical models to simultaneously constrain DM density profiles, halo shapes and the evolutionary history of galaxies. I first show that the most common and advanced stellar dynamical models can reproduce the circular velocities (as traced independently by molecular gas rotation curves), to within ⇠10% accuracy. I further use high resolution observations to understand the sources (gravitational, feedback driven) of high velocity dispersion ionised gas. By incorporating realistic birth conditions for globular clusters (GCs) and flexible, self-consistent velocity distribution functions for the Fornax dSph, I am able to understand the survival of its five GCs. The comprehensive evolutionary model suggests that Fornax has a large DM core (&1.5 kpc) and has undergone a past merger of mass ratio ⇠1:2 to 1:5. Finally, by combining stellar and gas kinematic tracers together in a single dynamical model, I provide evidence that the isolated dwarf irregular galaxy WLM has a DM halo that has both an inner density core (! ⇠ 0.3±0.1), and a prolate axis ratio of 2:1. The recovered orbit structure (tangential anisotropic) is very similar to nearby dSph galaxies - suggesting that internal processes rather than tidal origin may lead to this dynamical configuration. The DM halo profile is consistent with the ⇤CDM cosmological picture when baryonic feedback is included. The prolate geometry is difficult for MOND and at the same time challenges self-interacting DM (SIDM) theories to create a thermalised DM core of the observed size, without sphericalising the halo. From both the dynamical models on WLM and Fornax, I am able to provide constraints on the particle mass of Bose-Einstein condensate DM models to 1.1 − 1.3 ⇥ 10−22 eV/c2, and interaction cross section for (velocity independent) SIDM particles of 0.8 . "/mSIDM . 3.1 cm2/g - though it remains to be seen that these can produce the proper core size and shape in the DM halos we find. Application of these new techniques and models to more galaxies will provide even tighter constraints on dark matter particle models.

Item Type: Dissertation
Supervisor: van der Ven, Prof. Dr. Glenn
Place of Publication: Heidelberg
Date of thesis defense: 16 July 2019
Date Deposited: 22 Oct 2019 13:05
Date: 2019
Faculties / Institutes: The Faculty of Physics and Astronomy > Dekanat der Fakultät für Physik und Astronomie
Subjects: 520 Astronomy and allied sciences
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