Joshua Williamson

I study the connection between galaxy distribution and dark matter concentrations in the universe.

Project title: Field-level galaxy biasing from DES Y3 weak lensing mass and galaxy maps

Research Group: Astrophysics

Supervisor(s): Prof Ofer Lahav

Introduction: 

I completed my undergraduate degree in Astrophysics at King's College London, followed by a master's in Mechanical Engineering at Imperial College London. Currently, I am a CDT researcher studying cosmology in the Astrophysics Department. My research focuses on the connection between the distribution of galaxies in the universe and the underlying concentrations of dark matter on the largest scales of our observed universe. This work primarily involves using state-of-the-art, large-volume simulations of our universe and applying machine learning techniques.

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Project description:  

Our current models of galaxy biasing limit our ability to constratin cosmology using galaxy positions as tracers of the underlying Large Scale Structure of the universe. In this work, we use DES Y3 weak lensing mass maps and galaxy density maps to constrain galaxy biasing models and their respectives parameters using stimulation-based inference (SBI). We forward model realistic DES Y3 survey systematics from our suite of n-body 'Gower Street' simulations, produced at UCL. We develop novel summary statistics, such as machine learning to extract information on galaxy bias at the map level, as well as studying the environmental dependence on galaxy bias to local galaxy properties.

First year group project: NCC

Placement: 

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