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For refcode 1995AJ....110.2009O:
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1995AJ....110.2009O GALAXY PROPERTIES AT THE NORTH GALACTIC POLE. I. PHOTOMETRIC PROPERTIES ON LARGE SPATIAL SCALES S C. ODEWAHN AND G. ALDERING Department of Astronomy, University of Minnesota, Minneapolis, Minnesota 55455 Electronic mail: (sco,aig)@apsl.spa.umn.edu Received 1995 February 21; revised 1995 July 20 ABSTRACT A two-color study of the galaxies detected on POSS-I in a 289 square degree region centered on the North Galactic Pole is presented. We use a variety of mapping techniques to characterize the large-scale spatial distribution of galaxies. The depth and sample size of this new survey allows, for the first time, the isolation of large photometric subsamples of galaxies in high- and low-density environments on the scale of superclusters. Our principal finding is a statistically significant difference between the mean photometric properties of these subsamples in the sense that galaxies in the high-density Coma and filament environments have redder colors and larger concentration indices than galaxies drawn from low-density interfilament regions. These results are in accord with the known morphology-density relation. Thus, appropriately chosen photometric and morphological parameters, in concert with a galaxy surface density map, can be used to select structures from the projected galaxy distribution which correspond to regions of high density. An illustration of this point is our discovery of a concentration of blue galaxies identified in our maps near the core of the Coma cluster. This feature is comprised of early-type galaxies which exhibit signs of current or recent star formation. These results are predicated on relations between morphological type and photometric parameters derived from APS scans of POSS-I. We therefore discuss the image calibration procedures used to compile our catalog of physically significant photometric parameters. We demonstrate the morphological type dependence among quantities such as mean color and image concentration index, and the lack of such a dependence for mean surface brightness.
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