J/A+AS/130/341 Groups of Galaxies in PPS (Trasarti-Battistoni 1998) ================================================================================ Loose Groups of Galaxies in the Perseus-Pisces Survey Trasarti-Battistoni R. =1998A&AS..130..341T (SIMBAD/NED BibCode) ================================================================================ ADC_Keywords: Galaxy catalogs ; Velocity dispersion Keywords: catalogs - Galaxies: cluster of ; luminosity function - Cosmology: Large Scale Structure of the Universe. Abstract: We present a large catalog of galaxy loose groups in the Southern Galactic Hemisphere, selected from the Perseus-Pisces redshift Survey (PPS). Particular care is taken in order to obtain group samples as homogeneous as possible to previously published catalogs. Groups are identified with the adaptive Friends-of-Friends (FoF) algorithm of Huchra & Geller (1982ApJ...257..423H), with suitable normalizations V_0_=350km/s and D_0_=0.231h.Mpc. As a necessary ingredient of FoF algorithms, we obtain the galaxy luminosity function (LF) for PPS. Its Schechter parameters ({alpha}=-1.15+/-0.15, M_*_=-19.3+/-0.1) are in good agreement with similar LF estimates from samples previously used to select groups. The LF normalizations {phi}_*_=0.02h^3^/Mpc^3^ appropriate for PPS yields a density threshold {delta}n/n~180 for the adopted D_0_, apparently rather different from the desired {delta}n/n~80 used in previous studies. We then consider several other link normalizations, and briefly discuss their effect on group properties. We suggest to replace the customarily adopted {delta}n/n parametrization with the more direct D_0_ parametrization. All our catalogs contain N_G_~200 groups, significantly more than in most previous studies where group samples were obtained from galaxy data sets of comparable quality to (but smaller extent than) PPS. The group properties are rather sensitive to the adopted D_0_ and V_0_, but vary little with different redshift corrections, redshift cut-off, and galaxy LF. Loose groups in PPS nicely trace the large scale structure (LSS) in the parent galaxy sample. Physical properties of groups in PPS and in other directly comparable samples are in good agreement. There seems to be a complex interplay among LSS features, FoF grouping procedure, and group properties. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 70 188 List of the values of group parameters for D_0_=0.231Mpc/h and V_0_=350km/s -------------------------------------------------------------------------------- See also: J/AJ/105/1251 : Pisces-Perseus supercluster. V. (Wenger+, 1993) J/AJ/105/1271 : Pisces-Perseus supercluster. VI (Giovanelli+, 1993) Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 3 I3 --- ID Identification of group 5- 7 I3 --- Nmemb Number of members 9- 11 I3 h RAh Mean right ascension 1950 (1) 13- 16 F4.1 min RAm Mean right ascension 1950 (1) 18 A1 --- DE- Sign declination (always blank) 19- 20 I2 deg DEd Mean declination 1950 22- 25 F4.1 arcmin DEm Mean declination 1950 27- 31 I5 km/s cz Mean redshift of members 33- 36 I4 km/s sigma Velocity dispersion 38- 41 F4.2 Mpc Rp Mean pairwise separation of members (2) 43- 46 F4.2 Mpc Rh Mean harmonic (virial) radius (2) 48- 52 F5.2 [solLum] log(L) Log of total luminosity (2) (3) 54- 58 F5.2 [solMass] log(M) Log of virial mass (2) 60- 64 F5.2 [Sun] log(M/L) Log of mass-to-light ratio (2) (3) 66- 70 F5.3 Mpc.s/km t(cr) Crossing time (2) (4) -------------------------------------------------------------------------------- Note (1): RA was originally assigned values in the interval [-1:30.0, +3:00.0], but without any value in the range [0, -1]. There was clearly an omission of the minus sign in that range, and the negative RA values were turned to standard RA values. but it is not clear whether group #54 is 23:59.9 or 00:00.1 (mail exchange with the author, July 1998) Note (2): Assuming h=1.0, i.e. Hubble constant H_0=100km/s/Mpc Note (3): Observed luminosity, not corrected for the missed faint member galaxies Note (4): Defined as (2R_p_)/(sqrt(3)sigma) -------------------------------------------------------------------------------- Acknowledgements: Roberto Trasarti-Battistoni ================================================================================ (End) Francois Ochsenbein, Patricia Bauer [CDS] 20-Aug-1998