Institute for Astronomy

Cosmology PhD projects

Research projects on offer in our Cosmology Group:

Constraining inflationary models with the large-scale structure of the Universe

Florian Beutler

Video: Constraining inflationary models with the large-scale structure of the Universe
Constraining inflationary models with the large-scale structure of the Universe

This project uses data from galaxy redshift surveys to constrain the early expansionary phase of the Universe (inflation) by trying to detect the non-Gaussianity signal in the galaxy power spectrum and bispectrum.

Inflation is one of the most interesting phases of the Universe, since it laid the seeds of later structure formation and so far is very poorly understood. Many theories have been proposed for how Inflation might have happened, but it has been difficult so far to test it with cosmological datasets. The Cosmic Microwave Background has put some constraints on the inflationary potential, but future constraints will be driven by galaxy surveys.

This project will develop an analysis pipeline to drive such measurements. It will make use of new estimators for the bispectrum: 

  • The project will involve theoretical aspects, since we need to use perturbation theory to develop a better model for the bispectrum.

  • This project also has computational aspects, since we need to implement these estimators, optimize for performance (e.g. using parallel computing libraries like MPI) and run them on supercomputers.

The student should bring some experience in any higher order programming language (e.g. C++ or Python). However, using the supercomputer facilities is easy to learn on the fly.

The student is expected to work within several international collaborations. During the first part of this project the student will work closely together with my collaborators Shun Saito (MST, USA), Hee-Jong Seo (Ohio, USA) and Naonori Sugiyama (Kyoto, Japan) to develop the analysis pipeline. When moving to the actual data, the student will work within the Dark Energy Spectroscopic Instrument (DESI) and the Euclid space-satellite collaborations, which will involve attending international collaboration meetings and weekly teleconferences. 

This project is funded through a grant by the European Research Council.

 

Gravitational Lensing in the GPU era

Joe Zuntz

Weak gravitational lensing is one of the most powerful measurements cosmologists have of the dark universe - by detecting coherent distortion in the shapes of high-redshift galaxies we can map gravitational fields across the Universe.

The statistics of gravitational fields give us information about the laws of gravity, the history of the Hubble expansion, and the growth rate of structure (the clustering of dark matter into galaxies) across a huge range in cosmic time.  Measuring it accurately is a huge challenge, but our reward is an unprecedented ability to model the contents, laws, and history of the Universe.

In this project you'll help advance the computational tools and methods we have for simulating and analyzing lensing data. The supercomputing systems we use for this task are being transformed by the rise of graphical processing units (GPUs), which run massively parallel computations originally designed for image rendering, but now used in machine learning, matrix calculations, and image processing.  In this computationally-focussed project you will transform how we do lensing analyses by learning how we can use this hardware for lensing science.

 

Connecting galaxies with their parent dark matter haloes with WAVES

Catherine Heymans and Konrad Kuijken

Video: Galaxy Halo Connection with WAVES
Joint UoE-Leiden Astrophysics PhD Project

How galaxies form in dark matter halos is still not understood in detail. This project is an observational study of the link between the galaxies we see and the dark matter: both in terms of the large-scale structure, and of the properties of the dark halos themselves. It builds on work already done combining the GAMA (Galaxy And Mass Assembly) galaxy catalogue with weak lensing studies using the Kilo-Degree Survey (KiDS). Both GAMA and KiDS are state of the art, but are about to be superseded by even larger and more powerful surveys.

KiDS was performed with the 2.6m VST on Paranal in Chile. Right now a project on the 8m Subaru telescope is already underway with more sensitive lensing measurements, and in 2022 two new observatories - the Rubin observatory in Chile and the Euclid satellite of the European Space Agency - will start to map large areas of the sky with even higher precision, transforming this research field.

At the same time, massive spectroscopic galaxy surveys will eclipse GAMA, which contains data for some 300,000 galaxies. In particular the WAVES survey will measure millions of galaxies, over a wider area and to fainter limits than GAMA.

The combination of these next-generation data sets will allow us to study the galaxy-halo connection with much higher precision, and in more detail, than was possible so far. This information is vital, fundamental input to galaxy formation theory.

This project will be supervised jointly by Profs. Catherine Heymans (Edinburgh) and Koen Kuijken (Leiden), as part of their long-standing collaboration on the KiDS survey.  Students can apply to be primarily based in either Leiden or Edinburgh.

Under the Galaxy Formation and Evolution projects see also:

  • Galaxy Formation and Cosmology Using the Equilibrium Model Romeel Davé