The Physics of the Accelerating Universe Camera

The Physics of the Accelerating Universe (PAU) Survey goal is to obtain photometric redshifts (photo-z) and spectral energy distributions (SEDs) of astronomical objects with a resolution roughly one order of magnitude better than current broadband (BB) photometric surveys. To accomplish this, a new large field-of-view (FoV) camera (PAUCam) has been designed, built, and commissioned and is now operated at the William Herschel Telescope (WHT). With the current WHT prime focus corrector, the camera covers an similar to 1 degrees diameter FoV, of which only the inner similar to 40' diameter is unvignetted. The focal plane consists of a mosaic of 18 2k x 4k Hamamatsu fully depleted CCDs, with high quantum efficiency up to 1 mu m in wavelength. To maximize the detector coverage within the FoV, filters are placed in front of the CCDs inside the camera cryostat (made out of carbon fiber) using a challenging movable tray system. The camera uses a set of 40 narrowband filters ranging from similar to 4500 to similar to 8500 angstrom complemented with six standard BB filters, ugrizY. The PAU Survey aims to cover roughly 100 deg(2) over fields with existing deep photometry and galaxy shapes to obtain accurate photometric redshifts for galaxies down to i(AB) similar to 22.5, also detecting galaxies down to i(AB) similar to 24 with less precision in redshift. With this data set, we will be able to measure intrinsic alignments and galaxy clustering and perform galaxy evolution studies in a new range of densities and redshifts. Here we describe the PAU camera, its first commissioning results, and its performance.