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Testing the Universality of the (U-V) Color-Magnitude Relations for Nearby Clusters of Galaxies
We present a detailed (U-V) color-magnitude relation (CMR) analysis forthree local (z<0.06) clusters of galaxies. From square-degree imagingof the Abell clusters A85, A496, and A754, we select 637 galaxies downto L~0.1L*V with spectroscopic membership, whichminimizes uncertain field contamination corrections. To characterize thedegree of CMR uniformity among nearby clusters, we use a maximumlikelihood technique to quantify the CMR properties of the red galaxiesin each cluster. We find that these clusters have similar CMRs with amean color of (U-V)=1.40 at MV=-20+5log10h and narrow limits of intrinsiccolor scatter [0.047, 0.079] and slope [-0.094, -0.075]. If we restrictour analysis to the core cluster population of red galaxies, theresulting CMRs are in close agreement with that of the Coma Cluster, theonly local cluster with a rest-frame (U-V) CMR determination ofcomparable precision. Therefore, the CMR uniformity of present-dayclusters spans a fairly wide range of cluster masses. We test howsensitive the CMR uniformity is to variations in color aperture size andsample selection, and we find at most slightly wider limits of scatter[0.047, 0.112] and slope [-0.104, -0.054]. This upper limit for (U-V)scatter is consistent with the bulk of the stellar populations of redcluster galaxies forming before z=1.2, with a maximum age spread of 5.2Gyr. In addition, we note that using colors from apertures containingequal fractions of galactic light does not remove the CMR slope and thatnone of the slopes exhibit a break as claimed by Metcalf and coworkers.Our findings expand the single Coma data point and provide a much neededz=0 baseline for comparisons to high-redshift cluster CMRs at the samerest-frame wavelengths. The range in CMR scatter that we find amongnearby clusters is consistent with the values reported for clusters athigher redshifts, further suggesting that there has been littleevolution in the stellar populations of red-sequence cluster galaxiesout to at least z~1. To identify the most recently accreted clustergalaxies, we divide each cluster's membership into three galaxypopulations based on (U-V) color relative to the well-defined CMR. Blueand moderately blue galaxies make up 18%-23% by number of each clusterpopulation more luminous than 0.1L*. Our color-magnitudedivision should represent a rough time since cluster accretion. Intesting this hypothesis, we find that blue galaxies are spatially,kinematically, and morphologically distinct from red cluster galaxies.Even in projection, the blue galaxies reside toward the outskirts of thecluster and appear to avoid the inner half-megaparsec, in contrast withthe increasing density of red-sequence galaxies toward the clustercenter. In addition, the blue galaxies have velocity distributionsrelative to the cluster rest frame that are flatter, and some havedifferent means, compared to the roughly Gaussian distribution of redmember velocities. Members with the bluest colors tend to be disklike orirregular in appearance compared to the red galaxies, which have mostlyearly-type (E/S0) morphologies. Moderately blue cluster galaxies may bean intermediate mix with a fraction of small bulge-to-disk ratio S0s,yet these require closer scrutiny. The spatial, kinematic, andmorphological distinctions between blue and red cluster galaxies providefurther evidence that CMR-relative color is related to time sincecluster infall and that bluer members are indeed the most recentlyaccreted field spirals as expected in a hierarchical universe.Observations reported here were obtained at Kitt Peak NationalObservatory, National Optical Astronomy Observatory, which is operatedby the Association of Universities for Research in Astronomy (AURA),Inc., under cooperative agreement with the National Science Foundation.
| Galaxy Luminosity Functions from Deep Spectroscopic Samples of Rich Clusters
Using a new spectroscopic sample and methods accounting forspectroscopic sampling fractions that vary in magnitude and surfacebrightness, we present R-band galaxy luminosity functions (GLFs) for sixnearby galaxy clusters with redshifts of 4000 kms-1
| A photometric catalogue of galaxies in the cluster Abell 496
We present two catalogues of galaxies in the direction of the richcluster Abell 496. The first one includes 3879 galaxies located in aregion of roughly +/- 1.3deg from the cluster centre. It hasbeen obtained from a list of more than 35000 galaxy candidates detectedby scanning part of a Schmidt photographic plate taken in the b_J band.Positions are very accurate in this catalogue but magnitudes are not.This led us to perform CCD imaging observations in the V and R bands tocalibrate these photographic magnitudes. A second catalogue gives a listof galaxies with CCD magnitudes in the V (239 galaxies) and R (610galaxies) bands for a much smaller region in the centre of the cluster.These two catalogues will be combined with a redshift catalogue of 466galaxies \cite[(Durret et al. 1999)]{dur99} to investigate the clusterproperties at optical wavelengths (Durret et al. in preparation), as acomplement to previous X-ray studies by a member of our group\cite[(Pislar 1998)]{pis98}. Based on plates scanned with the MAMAmicrodensitometer at CAI, Paris and on observations collected at theEuropean Southern Observatory, La Silla, Chile. Tables 1 and 2 are onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| A catalogue of velocities in the direction of the cluster of galaxies Abell 496
We present a catalogue of velocities for 466 galaxies in the directionof the cluster Abell 496, in a region covering about 160'x 160' (9.2x9.2Mpc for an average redshift for Abell 496 of 0.0331, assuming H_0 = 50km s-1 Mpc-1). This catalogue includes previouslypublished redshifts by \cite[Proust et al. (1987)]{pro87},\cite[Quintana & Ramírez (1990)]{qui90} and \cite[Malumuth etal. (1992)]{mal92}, redshifts from the CfA redshift survey, togetherwith our new measurements. A total of 274 galaxies have velocities inthe 7800-11800 km s-1 interval, and will be considered asmembers of the cluster. Abell 496 therefore becomes one of the fewclusters with a high number of measured redshifts; its physicalproperties are investigated in a companion paper. Based on observationscollected at the European Southern Observatory, La Silla, Chile. Tables3 and 4 are only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| An image database. II. Catalogue between δ=-30deg and δ=70deg.
A preliminary list of 68.040 galaxies was built from extraction of35.841 digitized images of the Palomar Sky Survey (Paper I). For eachgalaxy, the basic parameters are obtained: coordinates, diameter, axisratio, total magnitude, position angle. On this preliminary list, weapply severe selection rules to get a catalog of 28.000 galaxies, wellidentified and well documented. For each parameter, a comparison is madewith standard measurements. The accuracy of the raw photometricparameters is quite good despite of the simplicity of the method.Without any local correction, the standard error on the total magnitudeis about 0.5 magnitude up to a total magnitude of B_T_=17. Significantsecondary effects are detected concerning the magnitudes: distance toplate center effect and air-mass effect.
| A catalog of morphological types in 55 rich clusters of galaxies
Data are presented from a study of 55 rich clusters of galaxies. Thedata include positions, morphological types, estimated total magnitudes,bulge sizes, and ellipticities for about 6000 galaxies, as determinedfrom high scale photographic plates. Data reduction procedures aredescribed, and a brief analysis of cluster richness, which indicatesthat Abell richness classes are only rough indicators of total clustermembership, is included.
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