THE URSA-MAJOR CLUSTER OF GALAXIES .1. CLUSTER DEFINITION AND PHOTOMETRIC DATA

The Ursa Major Cluster has received remarkably little attention, altho ugh it is as near as the Virgo Cluster and contains a comparable numbe r of H I-rich galaxies. In this paper, criteria for group membership a re discussed and data are presented for 79 galaxies identified with th e group. Of these, all 79 have been imaged at B,R,I bands with CCDs, 7 0 have been imaged at K' with a HgCdTe array detector, and 70 have bee n detected in the H I 21 cm line. A complete sample of 62 galaxies bri ghter than M(B)=-16.5 is identified. Images and gradients in surface b rightness and color are presented at a common linear scale. As has bee n seen previously, the galaxies with the reddest global colors are red dest at the centers and get bluer at large radii. However, curiously, among the galaxies with the bluest global colors there are systems wit h very blue cores that get redder at large radii. (C) 1996 American As tronomical Society.