The SDSS Coadd: 275 deg2 of Deep SDSS Imaging on Stripe 82
Abstract
We present details of the construction and characterization of the coaddition of the Sloan Digital Sky Survey Stripe 82 \ imaging data. This survey consists of 275 deg2 of repeated scanning by the SDSS camera of 2.5 of δ over -50 α 60 centered on the Celestial Equator. Each piece of sky has 20 runs contributing and thus reaches 2 magnitudes fainter than the SDSS single pass data, i.e. to r 23.5 for galaxies. We discuss the image processing of the coaddition, the modeling of the PSF, the calibration, and the production of standard SDSS catalogs. The data have r-band median seeing of 1.1, and are calibrated to 1%. Star color-color, number counts, and psf size vs modelled size plots show the modelling of the PSF is good enough for precision 5-band photometry. Structure in the psf-model vs magnitude plot show minor psf mis-modelling that leads to a region where stars are being mis-classified as galaxies, and this is verified using VVDS spectroscopy. As this is a wide area deep survey there are a variety of uses for the data, including galactic structure, photometric redshift computation, cluster finding and cross wavelength measurements, weak lensing cluster mass calibrations, and cosmic shear measurements.