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R. Gal (Johns Hopkins University), R. de Carvalho (CNPq/Observatorio Nacional, Brazil), A. Mahabal (Caltech), S.C. Odewahn (Arizona State U.), S.G. Djorgovski, P. Lopes, R. Brunner (Caltech), DPOSS Team
We present the final photometric calibration of the Digitized Second Palomar Observatory Sky Survey (DPOSS), to generate the Palomar-Norris Sky Catalog (PNSC). Plates are first corrected for vignetting. Objects are then matched in the plate overlap regions, and instrumental magnitude transformations derived for each plate pair. These transformations are propagated within sets of nine plates, to bring them to a homogeneous instrumental magnitude system. We then match all of the available CCD data, from extensive imaging at the Palomar 60", to the nine plate area, and derive a calibration from the JFN instrumental magnitudes to the Gunn gri system. All procedures are performed independently for stars and galaxies, with over 1,000 calibrating objects of each type per plate. This procedure is repeated for for each plate, using it's eight neighbors to increase the number of calibration objects. Finally, we apply empirical color corrections to the j plate data, and an extinction correction. Final photometric errors, based on comparison of objects in plate overlap regions and between CCD and plate data, are 0.2 mag in g and r, and 0.3 mag in i.
To date, we have calibrated the entire Northern sky at galactic latitudes b>30\circ. We show some results of the Northern Sky Optical Cluster Survey, which utilizes the calibrated DPOSS galaxy catalogs to detect galaxy clusters. We find approximately 18000 clusters in the 6300 square degrees surveyed.
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The author(s) of this abstract have provided an email address for comments about the abstract: rrg@pha.jhu.edu