Abstract

Wide field extragalactic surveys (galaxy and CMB maps) have changed our understanding of the Universe, with evidence for dark matter and cosmic acceleration. But we need new ideas and more accurate data to understand this picture. The combination and cross-talk of spectroscopic and photometric techniques to measure galaxy clustering, weak gravitational lensing and redshift space distortion can be used for accurate estimation of the cosmic expansion and growth history. I will present some ideas of how to approach this goal. I will also review the status of novel photometric survey (PAU) from the 4m William Herschel Telescope (WHT) using a new camera called PAU Cam which employs 48 narrow band (100A) filters in the range 370-850nm and 6 broad band filters in the range 300-1000nm. The PAU Survey will be unique due to sampling a wide range of galaxy types and reaching a high surface density of objects. PAU will produce low resolution spectra for millions of galaxies, yielding photometric redshifts an order of magnitude better than is possible with broad band photometry. This provides an ideal survey for studies of galaxy formation and a to apply the cross-talk techniques to measure cosmology.