Galactic astronomy is experiencing a revolutionary increase in available data. A large number of international surveys, like the Gaia satellite mission, is mapping the positions, motions, and properties of our galaxy’s stars as well as external galaxies from ground and space, to reveal the structure, dynamics and history of our own Galaxy and compare it to disc galaxies in general. The number of stars for which we have good information on position, motion, and surface composition (which tells us where a star came from), has increased by a factor 10^4 or 10^5 compared to what we had 10 years ago. These data can only be fully understood with statistical methods and detailed chemodynamical models. MSSL/UCL has unique competence in both understanding the data from modern surveys and to apply them to constrain e.g. the distribution of dark matter, to understand the detailed structure, e.g. of the Galactic bar and spiral arms, and the history of the stellar populations within the Galaxy's disc and halo.
The PhD student on this project will tackle stellar kinematics and dynamics to map and constrain the dark matter content in different ways. There are two main (dynamics) strategies to learn about the dark matter content of galaxies like the Milky Way: a) mapping the current distribution of stars in an equilibrium model to find the part of the potential unexplained by visible matter (this path has been described in Project 2), and b) studying the structural evolution of the system to identify and quantify the impact of dark matter. This project employs strategy b). We can identify several such impacts:
• The dark matter halo influences the spiral patterns of the galaxy and their history can be inferred from the radial migration of stars.
• The dark halo is responsible for dynamical friction slowing dwarf galaxies in the outer halo, but also the Galactic bar near the centre. Quantifying dynamical friction constrains not only the dark halo density, but also potential degeneracy or velocity distribution of the dark matter.
• Dark matter influences disk heating: we know that stars today form from the cold gas in a very thin disc in the Galactic mid-plane. Yet, the stellar populations with increasing age form increasingly thicker discs around this midplane. We have to disentangle: i) heating by spiral structure (influenced partly by dark matter), ii) heating by scattering of stars by Galactic molecular clouds, iii) interactions with lumps in the galactic halo (e.g. accreted systems and subhaloes), and iv) higher turbulence in the past star forming ISM.
This project will develop laws/prescriptions for disc evolution by calculating analytical expectations and comparing them to tailored N-body simulations, e.g. to separate the signatures of galaxy mergers vs. secular heating by spiral arms, bar, and molecular clouds. The student can then impose these laws onto a distribution function model of the Galaxy, by which they can be compared to the observed data. Beyond constraining the dark matter, the project will quantify stellar migration and the merger history of the Milky Way.
Desired Knowledge and Skills
• Undergraduate in a subject of physics
• Strong computational skills and/or willingness to learn
• Good analytical skills
Applications submitted by 31st January 2020 will be given full consideration. We will continue accepting applications until all places are filled. After we receive your application, we will select candidates for interviews. If you are selected, you will be invited for an interview at MSSL. You will have the opportunity to see the laboratory, students' flats and talk to current students. The studentships are for the advertised projects only. In your application, please specify which project you want to apply for.
To apply, please visit the Online Application page, select department of "Space & Climate Physics" and programme type of "Postgraduate Research". After pushing "Search Now" button, select "RRDSPSSING01: Research Degree: Space and Climate Physics" for Full-time or Part-time mode.
Our Online Applications page can be found here: https://www.ucl.ac.uk/adminsys/search/
An upper second-class Bachelor’s degree, or a second-class Bachelor’s degree together with a Master's degree from a UK university in a relevant subject, or an equivalent overseas qualification.
Students from the UK or those from the EU who meet the residency requirements (3 years' full-time residency in the UK) are potentially eligible for a Science and Technology Facilities Council (STFC) studentship.