Statistics – Applications
Scientific paper
May 1997
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997cgdr.conf...58a&link_type=abstract
Clusters of Galaxies at Different Redshifts, Ruidoso, NM, USA; May 1997; abstract booklet, ed. A. Klypin, p. 58
Statistics
Applications
Galaxies, Clusters Of Galaxies, Redshift, Velocity Dispersion
Scientific paper
Since the appearance of ACO's all-sky cluster catalog in 1989 (with 822 redshifts) no redshift compilation of the full sample appeared in print. We present an update of a compilation of measured redshifts for both A- and S-clusters we maintain since 1989 [1991ASPC...15..279A; 1995ApL&C..31...27A]. Different from most previous compilations, we systematically scan the literature for any galaxy redshifts in the direction of ACO clusters. Apart from compilations like ``ZCAT'' and ``SRC'', recent redshift surveys like the LCRS and APM bright galaxy surveys proved to be rich in ACO cluster redshifts, though these associations have not been reported in literature. We include redshifts within a factor of 4 of the currently best photometric estimate zest [1992MNRAS.259..494P], flagging those deviating by a factor of >2. Over the past 8 years the number of ACO clusters with measured redshifts has more than doubled. Our May 1997 version gives 2190 entries for 2063 distinct ACO clusters (1665 A- and 398 S-clusters), including subclusters or line-of-sight superpositions. Of these entries ˜2100 entries (for ˜2000 different ACO names) are within a factor 2 from zest. In Fig. 1 the number of clusters (Ncl) with redshifts for at least Nz member galaxies is plotted vs. Nz, for the ``SR91'' [1991ApJS...77..363S] compilation of northern ACO clusters, as well as for our previous [1995ApL&C..31...27A] and present full-sky compilations. Note that since SR91 [1991ApJS...77..363S] the fraction of clusters with ``reliable'' redshifts (i.e. Nz ≥ 3) has risen from ˜32% to no more than ˜45% now. There are ˜90 clusters with Nz>50, the typical minimum for dynamical studies. The total number of galaxies involved is 20,900, (10,700 for A-, 6900 for ACO-, and 3300 for S-clusters), neglecting some overlap for a few clusters. Whenever individual redshifts are available for N≥5 galaxies, we combine various sources and calculate a velocity dispersion σV. We quote σV for 517 different ACO clusters (590 subclusters). Their median is 690 km/s (Fig. 2). Our compilation (now based on 335 references) includes: Abell and subcomponent name (if any); an IAU-type position of the center including some updates since ACO89; R, D, and BM classes; mean z wrt the Local Group; a flag indicating the consistency between zobs and zest; Nz; references; σV, plus a reference and the number of galaxies contributing to σV, if different from that for z; detailed notes for nearly 40% of all entries, e.g. on alternative or additional redshifts. We shall use our data set to derive an improved m10-z relation, separately for northern, southern and supplementary ACO clusters, and and iteratively clean our sample from ``discordant'' redshifts. We show some applications on the large-scale structure of the nearby Universe.
Andernach Heinz
Tago Erik
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