The Distribution and Evolution of Dark and Luminous Matter in the Universe

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Most of the Universe is dark: dark energy, dark matter, and dark baryons collectively dominate the density budget leaving only a few percent in luminous stars or gas. Understanding the nature and behaviour of these dark components is a key goal of modern cosmological studies, but one which is observationally challenging. In contrast, the luminous sector, in the form of stars and gas in galaxies and clusters, is readily observable. But the astrophysical processes that led to the formation of stars and galaxies are complex, and there remain many important, open questions.**This proposal is focussed on both of these inter-linked sectors of the Universe, with an emphasis on projects in two different areas: (1) using gravitational lensing to probe the distribution of dark matter around galaxies over an unprecedented range of scales and redshifts; (2) a study of large-scale structure and velocity fields to determine how dark matter, galaxies and, in particular, dark baryons are organized on large scales. Below I will summarize proposed work in each of these two areas.**Weak gravitational lensing allows one to (statistically) detect dark matter, either on cosmic scales through shape correlation statistics or around galaxies. Up until now, studies have focussed on one or the other of these two scales. I will propose a new comprehensive approach using existing CFHTLenS data to understand the relationship between light and dark matter on all scales and to build a full 3D model of the dark matter distribution, based on the locations of existing galaxies in groups and clusters. In a sense, the observed galaxies are the skeleton of the structure but weak lensing shows how much meat is on the bones. **In the longer term, a very powerful approach is to combine weak lensing with large-scale multi-object spectroscopy. At present there is little overlap between large-scale surveys of each type, with the exception of Sloan Digital Sky Survey for which the lensing data is poor. I will propose a new large-scale weak lensing imaging survey using the Canada-France-Hawaii Telescope that covers the regions with the best spectroscopic data. Such a survey would open up a new regime in galaxy-galaxy lensing allowing a detailed understanding of dark matter distribution in more complex structures such as groups and filaments, as well as physical phenomena such as tidal stripping.**Peculiar velocities are the observed deviations from the uniform expansion of the Universe. By comparing these observations with predictions from our map of the nearby Universe, quantify the relationship between galaxies and dark matter on large scales, measure the cosmological parameters, and test gravity itself.**A long standing challenge has been to identify the "missing" baryons, presumed to be ionized hydrogen in the intergalactic medium (IM). Much of this IM has been difficult to detect directly because of its low density and temperature. In principle, the IM can be detected via the kinetic Sunyaev-Zeldovich effect in the Cosmic Microwave Background, which is sensitive to the momentum of the free electrons. Our group as recently made a tentative detection of this effect by comparing the predictions of our map of the local density and velocity fields with the Wilkinson Microwave Anisotropy Probe (WMAP) temperature map. We will extending this analysis to Planck satellite temperatures. The additional sensitivity and resolution over WMAP should allow, for the first time, a significant detection of all of the missing baryons in the IM, and may allow us to determine their spatial distribution with respect to galaxies.**By combining results from these approaches we will gain new insight into the link between the light and dark sides of the Universe.