Realizing the Promise of LSST Combined Probes of Dark Energy

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Among the most important projects planned for the Large Synoptic Survey Telescope (LSST) will be the measurement of the cosmological effects of dark energy. These effects will be detected through their influence on the growth of structure in the early universe and on weak gravitational lensing by galaxies and galaxy clusters. In order for these efforts to succeed, studies of the potential sources of error should begin now. The LSST survey, expected to comprise of order 1 billion galaxies, will have such small statistical errors that systematic errors - the most important being in the measurement of photometric redshift and weak gravitational lens shear - may dominate. In this project, the proposing team will carry out a comprehensive study of the origin and impact of these systematic effects in dark energy measurements, and develop algorithms, analysis tools and observing techniques to minimize their impact. They will use the improved understanding of the residual systematics to simulate the performance of LSST, as a precursor to construction. They have previously found that dark energy constraints are sensitive to systematics in ways that depend strongly on how separate techniques (such as weak lensing, cosmic shear, and baryon acoustic oscillations) are combined. The team intends to exploit this sensitivity and investigate new methods for controlling systematic error by combining several observational probes in an optimal way. They will use end-to- end simulations of LSST to develop and test these algorithms, and apply them to the current data from the Deep Lens Survey (DLS) to produce science in the near term. The team intends to make its techniques, data, and open-source software publicly available with no proprietary period, with the expectation that their photometric redshift algorithm will be widely used. In addition to contributing to education through the mentoring of a postdoctoral researcher, the project will also engage in public outreach and informal education by partnering in the development of new tools to visualize the dark and luminous structure of the Universe.