Research Fellows Directory
Dr Iohn Norberg
University of Durham
Galaxies are not distributed uniformly: they tend to clump together in groups and clusters. Our grasp of this distribution was revolutionised by large surveys that mapped out the distances of millions of galaxies by measuring their redshift. This key information on how galaxies are distributed in space contributed directly towards a standard model that describes the observed Universe, composed of three main parts and only 5% of it is ordinary matter. We believe 20% comes in the form or Cold Dark Matter (CDM), a theoretically motivated materia, yet to be directly detected, while ~75% is Dark Energy, a hypothetical form of energy filling the entire Universe. This drives my quest to further test the validity of the successful CDM model and to better understand what Dark Energy is.??
The properties of CDM are accurately predicted via computer models. Dark Matter tends to cluster, forming large clumps (halos) connected by filaments, and creates a so-called cosmic web. This is very similar to the observed distribution of galaxies. Hence, in this structure formation model, CDM becomes the natural skeleton on which galaxies form and evolve. The main problem is the lack of a unique signature for its existence and its non-detection in underground experiments.??
The GAMA survey will measure 270,000 new galaxy redshifts and provide a complete account of all galaxies in the nearby Universe. I designed the survey size and depth to constrain a key CDM model prediction: the number of Dark Matter halos per unit volume as function of their mass. My work will consist in detecting and then counting the number of galaxy groups in GAMA and finally measure their masses. Via my test, the CDM model will be either confirmed or rejected. Dark Energy, unlike CDM, is theoretically poorly understood and observationally its properties are barely constrained. Using the Pan-STARRS imaging survey, my aim is to provide the critical analyses enabling constraints on Dark Energy models to be obtained.
Interests and expertise (Subject groups)