CDROM/AJ/V109/P0874 MKW/AWM Poor Clusters (Beers+ 1995) ================================================================================ Kinematics and Dynamics of the MKW/AWM Poor Clusters Timothy C. Beers, Jeffrey R. Kriessler, Christina M. Bird, & John P. Huchra <1995, AJ, 109, 874> =1995AJ....109..874B ================================================================================ Abstract: We report 472 new redshifts for 416 galaxies in the regions of the 23 poor clusters of galaxies originally identified by Morgan, Kayser, and White, and Albert, White and Morgan. Eighteen of the poor clusters now have 10 or more available redshifts within 1.5h^-1 Mpc of the central galaxy; 11 clusters have at least 20 available redshifts. Based on the 21 clusters for which we have sufficient velocity information, the median velocity scale is 336 km/s, a factor of 2 smaller than found for rich clusters. Several of the poor clusters exhibit complex velocity distributions due to the presence of nearby clumps of galaxies. We check on the velocity of the dominant galaxy in each poor cluster relative to the remaining cluster members. Significantly high relative velocities of the dominant galaxy are found in only 4 of 21 poor clusters, 3 of which we suspect are due to contamination of the parent velocity distribution. Several statistical tests indicate that the D/cD galaxies are at the kinematic centers of the parent poor cluster velocity distributions. Mass-to-light ratios for 13 of the 15 poor clusters for which we have the required data are in the range 50 <= M/L_B(0) <= 200 Msun/Lsun. The complex nature of the regions surrounding many of the poor clusters suggests that these groupings may represent an early epoch of cluster formation. For example, the poor clusters MKW7 and MKW8 are shown to be gravitationally bound and likely to merge to form a richer cluster within the next several Gyrs. Eight of the nine other poor clusters for which simple two-body dynamical models can be carried out are consistent with being bound to other clumps in their vicinity. Additional complex systems with more than two gravitationally bound clumps are observed among the poor clusters. File Summary: -------------------------------------------------------------------------------- File Name Lrecl Records Explanations -------------------------------------------------------------------------------- table2.dat 71 1097 Velocities for galaxies in poor clusters -------------------------------------------------------------------------------- Comments for file: table2.dat -------------------------------------------------------------------------------- Table 2 summarizes the best available velocities for galaxies located within three degrees of the bright central galaxy in each MKW/AWM poor cluster. In assembling this data set, new measurements were supplemented with the extensive redshift catalog of Huchra et al. [1992, BCDS, 41, 31]. In general, the poor clusters have velocity dispersions that are less than 600 km/s (larger apparent dispersions are shown to be due to contamination of the poor cluster velocity distribution). Thus, for the purpose of the detailed kinematical analysis, a subset of galaxies are identified in the region of each poor cluster which have velocities within +/-2000 km/s of the D/cD galaxy. Galaxies in each poor cluster that have velocities in this range and that are located within 1.5h^-1 Mpc of the D/cD galaxy (at its redshift distance) are assigned to subsample A. Those galaxies within the velocity window that lie outside the 1.5h^-1 Mpc radial distance but inside the three degree circle are assigned to subsample B. -------------------------------------------------------------------------------- Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1-10 A10 --- Cluster MKW or AWM cluster number 11-25 A15 --- Galaxy *Name of the galaxy 26 1X --- --- Blank 27-35 A9 --- ID *Galaxy identification number with sample 36-38 I3 h RAh []? Right ascension 1950.0 39-43 F5.1 min RAm []? R.A. 44 1X --- --- Blank 45 A1 --- DE- Declination sign 1950.0 46-47 I2 deg DEd []? Dec. 48-50 I3 arcmin DEm []? Dec. 51-55 F5.1 mag mB0 []? Apparent magnitude on Zwicky B0 scale 56-61 I6 km/s RV Galaxy heliocentric radial velocity 62-65 I4 km/s e_RV Galaxy heliocentric radial velocity error 66 1X --- --- Blank 67-71 A5 --- Source *Source codes -------------------------------------------------------------------------------- Notes for file: table2.dat -------------------------------------------------------------------------------- Galaxy: If the galaxy name is blank the data in the remainder of the fields are continuations of the previous record. ID: This is the number of each galaxy within the sample followed by a subsample descriptor. Lower case letters a and b refer to redshifts which appear in two different subsamples according to: a Galaxies in common MKW 6 & MKW7/8 b Galaxies in common MKW 4s & AWM 2 Source: Codes given in Huchra et al. [1992, BCDS, 41, 31] or: -4 Bothun 1991, private communication -4-1 Mould 1991, private communication -4-2 Mould et al. 1991, private communication -5-2 Strauss et al. 1994, private communication -------------------------------------------------------------------------------- ================================================================================ (End) Lee Brotzman [ADS] 03-May-1995