Constraining the Milky Way’s gravitational potential with the Helmi Streams’ clumps: a complex story involving resonances and chaos

Woudenberg, Hanneke C. (2022) Constraining the Milky Way’s gravitational potential with the Helmi Streams’ clumps: a complex story involving resonances and chaos. Master's Thesis / Essay, Astronomy.

Preview	Text Master_Thesis_Final.pdf Download (12MB) | Preview
	Text Toestemming.pdf Restricted to Registered users only Download (96kB)

Abstract

Stellar streams are promising tools to study the dark components of the Milky Way, such as the shape and mass of its DM halo. This thesis focuses on the phase-mixed Helmi Streams (HS), which orbit the inner Galaxy. They seem to be separated into two clumps in angular momentum space which differ in their degree of phase-mixing. This appears to be caused by dynamics specific to the Galactic potential, namely by orbital resonances. In the correct potential, the less phase-mixed clump is trapped by the Ω_ϕ:Ω_z is 1:1 resonance, while the other clump is located off-resonance. To maintain the gap between the clumps in time, a potential that transitions to being spherical in the region occupied by the HS is required. The gap could be formed by orbital diffusion due to a chaotic region in the potential. The separatrix of the Ω_z:Ω_R is 2:3 resonance is found to cause chaotic behaviour. If an ensemble of stars occupies the region of phase-space around this layer, a gap can be formed on small enough timescales (~6 Gyr). Modifying the analytic potential by varying its characteristic parameters using an MCMC shows that a too high mass enclosed is needed to make the resonance overlap with the HS. A similar result is found when the shape of the halo is explored in a novel way, by performing a low-order basis function expansion of an axisymmetric DM halo and varying the coefficients and their derivatives at the gridpoints using an MCMC. Thus, it seems that more complex models are necessary.

Item Type:	Thesis (Master's Thesis / Essay)
Supervisor name:	Helmi, A.
Degree programme:	Astronomy
Thesis type:	Master's Thesis / Essay
Language:	English
Date Deposited:	04 Aug 2022 06:32
Last Modified:	04 Aug 2022 06:32
URI:	https://fse.studenttheses.ub.rug.nl/id/eprint/28200

Actions (login required)

View Item