Work was carried on two fronts: (i) what is the Milky Way assembly history?, and (ii) what is the dark matter distribution within our galaxy.
Firstly, I have shown that the plane of satellites of the Milky Way indicates that its satellites were accreted in a very narrow plane, much narrower than expected for an average system of the Milky Way’s mass. The same highly anisotropic accretion is also expected for the dark matter halo, which is more flattened than the average dark halo (Shao, Cautun, et al 2019, 2021).
Secondly, I have developed a model for describing the dark matter distribution in galaxies such as our own. This is based on the results of several state-of-the-art hydrodynamical simulations, such as the EAGLE, AURIGA, and APOSTLE projects. The model can predict with high accuracy the dark matter profile of many halos (Cautun et al 2020; Callingham, Cautun, et al 2020). I then used this model to constraint the dark matter profile of our galaxy from its inner regions up to the edges of the Milky System (Cautun et al 2020). I showed how inaccuracies in previous models led to biased results and an inability to match rotation curve measurements with those based on satellite galaxies and globular clusters.
I used the population of Milky Way satellites to rule out dark matter models in which the dark matter particle is too light (Newton, Cautun, et al 2020). Such models do not produce enough substructure to host all the observed Milky Way satellites and can be ruled out as unphysical. The study provides the tightest constraints on the dark matter particle mass from all available astrophysical probes (Enzi, …, Cautun, et al 2020).
I also supervised five MSc students on various projects related to the Milky Way satellites, such as what are the orbits of the satellites in the presence of a massive Large Magellanic Cloud, using deep learning to determine the accretion times of the Milky Way satellites and implications for star-formation quenching, and what are the filaments and their dwarf galaxy populations around Milky Way analogues.
I presented these results at the following international conferences and meetings:
The Cosmic Web: From Galaxies to Cosmology (Edinburgh, UK, June 17-19 2019)
Small Galaxies, Cosmic Questions (Durham, UK, July 29 - August 2 2019)
Gaia Treasure Hunt (Cambridge, UK, September 3 - 5 2019)
Galaxy Angular Momentum Alignment (Shanghai, China, October 21 - 25 2019)
The Local Dark Matter Distribution (Durham, UK, December 3 2019)
Virgo Consortium for Computational Cosmology (Durham, UK, January 7 - 10 2020)
The Cosmic Web in the Local Universe (Leiden, the Netherlands, January 27 - 31 2020)
European Astronomical Society Annual Meeting (virtual meeting, June 29 - July 3 2020)
Streams 2021: Constraints on Dark MatterWorkshop (virtual meeting, February 22 - 26 2021)
