THE ASTRONOMICAL JOURNAL    VOLUME 113, NUMBER 2, PAGE 483     FEBRUARY 1997

            GROUPS OF GALAXIES IN THE NORTHERN CfA REDSHIFT SURVEY

                      MASSIMO RAMELLA AND ARMANDO PISANI

                     Osservatorio Astronomico di Trieste,
                  via G. B. Tiepolo, 11, 34131 Trieste, Italy
       Electronic mail: ramella@oat.ts.astro.it, pisani@oat.ts.astro.it

                              MARGARET J. GELLER

                 Harvard-Smithsonian Center for Astrophysics,
               60 Garden Street, Cambridge, Massachusetts 02138
                   Electronic mail: mgeller@cfa.harvard.edu

    We use a friends-of-friends algorithm to identify loose groups from the
    northern CfA2 survey covering the region 8h<=alpha_(1950)<=17h and 8.5
    deg<=delta_(1950)<=44.5 deg. There are 406 groups; 149 of these
    contains five or more members within the survey. Geometric simulations
    guide our choice of the selection parameters; delta rho/rho=80 is the
    limiting density contrast and V0=350 km/s is the fiducial velocity
    linking parameter. The geometric simulations are particularly important
    for evaluating the impact of large-scale structure (e.g., the Great
    Wall) on group selection. The physical parameters of this large sample
    are coincident with our earlier results [126 groups in Ramella et
    al. ApJ, 344, 522 (1989)]: the median velocity dispersion in 192 (156;
    229) km/s and the median blue log(M/L) is 2.38 (2.20; 2.52). The
    mass-to-light ratio (M/L) is in units of Msun/Lsun for an assumed
    Hubble constant, H0=100 km/s/Mpc. The numbers in parentheses are 99%
    confidence limits. This group catalog provides a substantially larger
    sample for statistical studies than has been previously available. For
    example, it provides a more substantial sample for estimation of the
    distribution of group velocity dispersions and of the group-group
    correlation function. (Copyright) 1997 American Astronomical Society.