GROUPS OF GALAXIES IN THE NORTHERN CFA REDSHIFT SURVEY

We use a friends-of-friends algorithm to identify loose groups from th e northern CfA2 survey covering the region 8(h) less than or equal to alpha(1950) less than or equal to 17(h) and 8.5 degrees less than or e qual to delta(1950) less than or equal to 44.5 degrees. There are 406 groups; 149 of these contains five or more members within the survey. Geometric simulations guide our choice of the selection parameters; de lta rho/rho = 80 is the limiting density contrast and V-0 = 350 km s(- 1) is the fiducial velocity linking parameter. The geometric simulatio ns are particularly important for evaluating the impact of large-scale structure (e.g., the Great Wall) on group selection. The physical par ameters of this large sample are coincident with our earlier results [ 126 groups in Ramella et al. ApJ, 344, 522 (1989)]: the median velocit y dispersion in 192 (156; 229) km s(-1) and the median blue log(M/L) i s 2.38 (2.20; 2.52). The mass-to-light ratio (M/L) is in units of M./L . for an assumed Hubble constant, H-0 = 100 km/s/Mpc. The numbers in p arentheses are 99% confidence limits. This group catalog provides a su bstantially larger sample for statistical studies than has been previo usly available. For example, it provides a more substantial sample for estimation of the distribution of group velocity dispersions and of t he group-group correlation function. (C) 1997 American Astronomical So ciety.