J/ApJ/496/39 J/ApJ/496/39 Properties of poor groups of galaxies. I. A I Zabludoff J S Mulchaey Astrophys. J. 496 39 1998 1998ApJ...496...39Z Clusters, galaxy Radial velocities galaxies: clusters: general galaxies: distances and redshifts galaxies: elliptical and lenticular, cD galaxies: evolution galaxies: interactions large-scale structure of universe X-rays: galaxies We use multifiber spectroscopy of 12 poor groups of galaxies to address (1) whether the groups are bound systems or chance projections of galaxies along the line of sight; (2) why the members of each group have not already merged to form a single galaxy, despite the groups' high galaxy densities, short crossing times, and likely environments for galaxy-galaxy mergers; and (3) how galaxies might evolve in these groups, where the collisional effects of the intragroup gas and the tidal influences of the global potential are weaker than in rich clusters. Each of the 12 groups has fewer than about five cataloged members in the literature. Our sample consists of 1002 galaxy velocities, 280 of which are group members. The groups have mean recessional velocities between 1600 and 7600km/s. Nine groups, including three Hickson compact groups, have the extended X-ray emission characteristic of an intragroup medium (see Paper II, 1998ApJ...496...73M).

Name Galaxy name --- RAh Right ascension (J2000.0) h RAm Right ascension (J2000.0) min RAs Right ascension (J2000.0) s DE- Declination sign --- DEd Declination (J2000.0) deg DEm Declination (J2000.0) arcmin DEs Declination (J2000.0) arcsec HRV Heliocentric radial velocity number=1 The velocities are either emission-line velocities, absorption-line velocities, or a weighted average of the two km/s e_HRV rms uncertainty on HRV km/s Line Type of measurement number=2 0: absorption lines 1: emission lines 2: combination of both --- MType Morphological type number=3 E: early type S: late type --- Plate Plate/CCD number=4 p: plate c: CCD --- r_HRV Heliocentric radial velocity reference number=5 N: from NED --- Group Group name --- RAh Right ascension of the group optical projected centroid in J2000 h RAm Right ascension of the group optical projected centroid in J2000 min RAs Right ascension of the group optical projected centroid in J2000 s DE- Declination sign --- DEd Declination of the group optical projected centroid in J2000 deg DEm Declination of the group optical projected centroid in J2000 arcmin DEs Declination of the group optical projected centroid in J2000 arcsec Ntot Total number of galaxies with measured redshifts in the fiber field --- Ngroup Number of group members --- HRV Biweight estimators of the mean heliocentric velocity km/s e_HRV rms uncertainty on HRV km/s sigma Line-of-sight velocity dispersion km/s E_sigma Error on sigma (upper limit) km/s e_sigma Error on sigma (lower limit) km/s rsample Physical radius of the group sampled by the fiber field (h^-1^Mpc) Mpc rp Pair radius (h^-1^Mpc) Mpc rh Mean harmonic (virial )radius (h^-1^Mpc) Mpc Mvir Virial mass (h^-1^Mpc) solMass tc/tH Ratio of the crossing time to Hubble time --- James Marcout, Patricia Bauer CDS 1998Jun15 UNKNOWN UNKNOWN From ApJ electronic version J_ApJ_496_39.xml