Cosmology: from Galaxy Surveys to Dark Matter and Dark Energy

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The recent cosmological measurements support a `concordance' model in which the universe is flat and contains only 4 % ordinary matter, 21 % cold dark matter and 75 % dark energy. The next decade will see increased efforts to constrain the nature of dark energy and dark matter. One of the most promising cosmological probes is the use of galaxy redshift and imaging surveys. UCL Astrophysics is one of leading institutions in the effort to measure dark energy with such surveys. We have leading roles in the proposed Dark Energy Survey (DES), the Dark Universe Explorer (DUNE) and a Wide Field Multi-Object Spectrograph (WFMOS), all designed to contrast dark energy models with data. The proposal submitted is built around these surveys and three probes to constrain dark energy models, namely: cluster counts, galaxy clustering including baryon accoustic oscillations and cosmic lensing. In addition UCL Astrophysics will have access to a High Performance Computing system. In order to obtain precision constraints on dark energy, hundreds of millions of galaxies will be observed and their distance estimated. This requires fast methods based on galaxy colours ('photometric redshifts'). We propose to employ one PDRA and one PhD student who will explore the prospect of galaxy clustering measurements with these colour-based methods, and their systematic impacts. The second PDRA and a PhD student will concentrate on the study of cosmic lensing and involved systematics. The third PDRA will investigate how clusters (detected by the Sunyaev-Zel'dovich effect) can be calibrated with optical surveys and how to exploit them for cosmological measurements. Finally the fourth PDRA and a PhD student will work on N-body and hydro-simulations, studying the structure formation properties of dark energy, simulating clusters of galaxies and producing realistic mock catalogs for forecasting and exploiting weak lensing and galaxy clustering surveys. The Cosmology team at UCL is well placed for this project. The applicants are experienced in the fields of analysing large galaxy surveys, designing surveys for weak lensing observations and forecasting galaxy cluster surveys. The Cosmology team at UCL currently consists of 3 staff members, 5 PDRAs and 7 PhD students. Since the PDRA grants finish shortly, as outlined in the proposal, and 3 of the current students are funded by start-up grants, the proposed program would allow the continuation of these efforts. This is essential so that we can fulfill our commitments towards the proposed surveys and maintain our leadership in the science areas mentioned above within the UK and the international collaborations.