Measuring the mass and shape of the Milky Way’s dark matter halo with tidal streams entry

The Milky Way is surrounded by a large dark matter halo which is expected to be triaxial. This aim of this studentship is to measure its shape using tidal streams which will be a critical test of the cold dark matter paradigm.
Start date
3 years
Application deadline
Funding information

A directly funded project available to European/UK students only. A stipend of £14,777 per anum. Funding is provided for the duration of the PhD.


Tidal streams form as globular clusters and dwarf galaxies disrupt around galaxies like our own. More than 50 streams have been discovered around the Milky Way to date. These streams roughly follow orbits and are excellent tracers of the potential of our Galaxy. In addition, tidal streams are sensitive to perturbations from satellites of the Milky Way, ranging from the most massive satellites like the LMC down to dark matter subhaloes too small to form stars in the early universe.

The student will work on fitting these streams with dynamical models to measure the profile and shape of our Galaxy's dark matter halo. By using streams with a range of distances and orientations, the student will measure the mass and shape of the dark halo as a function of distance, while also constraining the perturbations from the largest satellites. These precise measurements will test one of the key predictions of Lambda Cold Dark Matter, that the dark halo around the Milky Way should be triaxial. Furthermore, the measurement of the Milky Way mass will be invaluable for understanding the Milky Way in a cosmological context and comparing local observations to simulations. Finally, the difference between the stream models and the observed streams will be used to search for the expected perturbations from low-mass dark matter subhaloes.

Eligibility criteria

Candidates should hold an undergraduate degree in physics or astronomy.

IELTS requirements: Overall grade of 6.5 with a minimum of 6.0 in each component.

How to apply

Formal applications can be made through our Physics PhD programme page. In your application, you must mention this studentship in order to be considered.

Informal applicant enquiries are recommended prior to submission and can be directly made to Dr Denis Erkal.

Interviews will be conducted by phone or Skype in early 2019.

Physics PhD

Application deadline

Contact details

Denis Erkal
12 BC 03
Telephone: +44 (0)1483 686990

The student will work in the Astrophysics Research Group at the University of Surrey with Dr Denis Erkal on modelling tidal streams around the Milky Way. The group consists of 7 faculty members and a cohort of graduate students and postdocs.

Studentships at Surrey

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