Cosmos Data Products Version Peter Capak (Caltech) May, 23, 2005 Kyoto Cosmos Meeting

Data processing flow chart Image products Masks Catalog generation Pros/Cons of present method

Data processing Raw Data First Catalogs Flat Fielding First Images Astrometric Mapping Astrometric Maps Photometric Mapping Photometric Maps Photometric Correction and Masking Master Astrometry Photometric Images Image re-sampling Image Combination Images and Exposure Maps

Image products All data products are divided into 144 sub- images –12x12 grid covering 4 sq. degrees –Numbering starts at 000 in the SE corner and increases W then N –Each sub image has 4000 unique pixels, with a 48 pixel margin of duplicated pixels on all sides So each image overlaps its neighbors by 96 pixels or 14.4’ on all sides Only the central 10x10 images contain deep data

Image Products Each data image comes with an exposure map in units of  -2 –Flat field, photometric scaling and masked pixels all taken into account At least two data images are generated for each band –One with the original PSF –One which is PSF homogenized –A best PSF image is also generated for B J, r +, and i + bands

Masking Image masking –Saturation spikes –Cosmic rays –Manual masking of reflections and trails Catalog masking –Generated manually on chi-squared image

Catalog Pipeline Sextractor used for detection and photometry Imcat used to combine sextractor output and manage data flow and PSF match images Can generate multi-color catalog for an arbitrary detection image Can easily add additional bands Uses parallel processing

Problems Sextractor measures all shape parameters on the detection image –Does not allow for optimal de-blending –Problems with isophotal and total magnitudes PSF homogenization bug –Will be fixed once more disk space comes on line K band exposure map needs improvement

Secondary Products Filter profiles Stellar colors Galaxy/AGN colors Depth maps