CDROM/AJ/V113/P0483 Groups of Galaxies (Ramella+ 1997) ================================================================================ Groups of Galaxies in the Northern CfA Redshift Survey Massimo Ramella, Armando Pisani and Margaret J. Geller <1997, AJ, 113, 483> =1997AJ....113..483R ================================================================================ Abstract: 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. File Summary: -------------------------------------------------------------------------------- File Name Lrecl Records Explanations -------------------------------------------------------------------------------- table1.dat 66 406 List of the values of group parameters for dRho/Rho = 80 and V_0 = 350 km/s table1.tex 113 440 AASTeX version of table1.dat -------------------------------------------------------------------------------- Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 3 I3 --- ID Identification 4- 7 I4 --- N Number of members 8- 9 2X --- --- Blank 10-11 I2 h RAh Mean right ascension 1950 12-16 F5.1 min RAm R.A. 17 1X --- --- Blank 18 A1 --- DE- Sign declination (always blank) 19-20 I2 deg DEd Mean declination 1950 21-25 F5.1 arcmin DEm Dec. 26-31 I6 km/s cz Mean redshift of members 32-36 I5 km/s e_cz Velocity dispersion 37-42 F6.2 --- L Log of total luminosity in solar units 43-48 F6.3 Mpc Rh Virial radius 49-54 F6.3 H0-1 t_cr Crossing time (in units of Hubble time) 55-60 F6.2 --- M Log of virial mass in solar units 61-66 F6.2 --- M_L Log of mass-to-light ratio in solar units -------------------------------------------------------------------------------- ================================================================================ (End) Lee Brotzman [ADS] 04-Apr-1997