Cataloging of the Northern Sky From Digitized POSS-II: A Progress Report
Session 118 -- WGAS
Oral presentation, Saturday, January 15, 10:15-11:45, Salon VI Room (Crystal Gateway)

## [118.01] Cataloging of the Northern Sky From Digitized POSS-II: A Progress Report

Digitization of the Second Palomar Observatory Sky Survey (POSS-II) is now in progress at STScI. The resulting data set, the Palomar-STScI Digital Sky Survey (DPOSS), will consist of $\sim 3$ TB of pixel data, or $\sim 1$ GB/plate (1 arcsec pixels, 2 bytes/pixel, $23040^2$ pixels/plate, $\sim 900$ survey fields in 3 colors). We have developed a software system to catalog, calibrate, classify, maintain, and analyse the plate scans and CCD calibration frames, Sky Image Cataloging and Analysis Tool (SKICAT). It incorporates novel AI software technologies, including machine learning, expert systems, machine-assisted discovery, etc., used for catalog generation and analysis, and should be useful for processing of massive digital sky surveys from other sources as well. We are also conducting an intensive program of CCD calibrations using Palomar 60-inch telescope; these CCD images are used both for magnitude zero-point calibrations, and as training and test data for star-galaxy object classifiers. The resulting Palomar Northern Sky Catalog (PNSC) is expected to contain at least $5 \times 10^7$ galaxies, and $> 2 \times 10^9$ stars, in 3 colors (JFN plates, calibrated to the Gunn $gri$ bands), down to the equivalent limiting magnitude of $B \simeq 22^m$, with the star-galaxy classification accurate to $\sim 90 - 95$\% down to $B \simeq 21^m$. The catalog will be continuously upgraded as more calibration data become available. It will be made available to the community via computer networks and/or suitable media as soon as scientific validation and quality checks are completed. Analysis software (parts of SKICAT) will also be freely available. The first, partial releases may be available within a year or two from now, depending on the funding support. A vast variety of scientific projects will be possible with this data base, including the studies of large-scale structure, Galactic structure, automatic identifications of sources from other wavelengths (radio through x-ray), generation of objective catalogs of clusters and groups of galaxies, searches for quasars, variable or extreme-color objects, etc.