Short term visitors programme, Newcastle University

Maps of the sky made at wavelengths longer than visible light are covered in random patterns. These patterns are imprinted on the observed radiation by events that occurred very early in the Universe's history and by the structure of our own Milky Way galaxy. So the mathematical properties of the maps can tell us a lot about the evolution of the Universe and our local neighbourhood: but first we have to separate the foreground of the Milky Way from the cosmic background. The randomness in the Milky Way emission arises from turbulence in the interstellar gas and associated tangling of the magnetic fields which pervade the space between stars. Cosmic rays (electrons travelling at close to the speed of light) spiral around the magnetic field lines and produce radio waves that are detected by satellite and ground based telescopes: in order to understand the data we need to relate the two-dimensional observations to the three-dimensional properties of the region from which they come. Part of our research plan is to develop new methods of analysing the observed maps in order to learn about the gas, magnetic field and cosmic rays in our Galaxy, particularly how these components fit together, and what we can learn about the ubiquitous turbulence that is characteristic of most astrophysical flows. From the cosmological perspective, the random patterns can be used to study the theory of inflation: the process that caused the Universe to rapidly expand shortly after the big bang. Two satellites, WMAP and the forthcoming PLANCK mission, provide data that will open a new window on the story of how our Universe evolved and on some of the most interesting problems of fundamental physics. We will be comparing the new observations with the predictions of different theoretical models of inflation. The astrophysical and cosmological aspects of our research are closely linked and we will be inviting international experts, both astronomers and theorists, to Newcastle to help us to make progress. Magnetic fields are present in nearly all astronomical objects, from stars and planets to the furthest reaches of intergalactic space. As well as the turbulent, tangled magnetic field already mentioned interstellar magnetic fields have a component that is arranged in enormous spiral patterns, on scales comparable to a whole galaxy. Our work leads us to ask where these fields come from and how they came to be organised on such large scales: the theory of astrophysical dynamos provides the most promising explanation. As part of this research project we will be developing models of galactic dynamo action, identifying signatures of a dynamo at work that can be observed and comparing the results with maps obtained by radio astronomers.