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|Study of the Structure of the Coma Cluster Based on a Hierarchical Force Clustering Method|
Six subclusters in the Coma cluster have been selected on the basis of ahierarchical clustering method that takes the gravitational interactionamong galaxies into account. Of these, 3 central subclusters around thegalaxies NGC 4889, NGC 4874, and NGC 4839 have been singled out. We haveused the objective statistical criterion applied by Vennik and Anosovain studies of close groups of galaxies to evaluate each member includedin a subcluster with a high probability. Galaxies with a significantdeficit of hydrogen HI, including objects from the Bravo-Alfaro list,have been identified with members of the subclusters, with the greatestnumber of them in the subclusters around NGC 4874 and NGC 4839. Aquantitative estimate of the hydrogen deficit using the HI index in theRCG3 catalog reveals a statistically significant excess value for thosegalaxies that are members of the subclusters compared to galaxies with ahydrogen deficit in the overall Coma cluster field. A substantial numberof the spiral galaxies with a hydrogen deficit in the subclusters turnedout to be radio galaxies as well.
|Tidally Triggered Star Formation in Close Pairs of Galaxies. II. Constraints on Burst Strengths and Ages|
Galaxy-galaxy interactions rearrange the baryons in galaxies and triggersubstantial star formation; the aggregate effects of these interactionson the evolutionary histories of galaxies in the universe are poorlyunderstood. We combine B- and R-band photometry and optical spectroscopyto estimate the strengths and timescales of bursts of triggered starformation in the centers of 190 galaxies in pairs and compact groups.Based on an analysis of the measured colors and EW(Hα), wecharacterize the preexisting and triggered populations separately. Thebest-fitting burst scenarios assume stronger reddening corrections forline emission than for the continuum and continuous star formationlasting for >~100 Myr. The most realistic scenarios require aninitial mass function that is deficient in the highest mass stars. Thecolor of the preexisting stellar population is the most significantsource of uncertainty. Triggered star formation contributessubstantially (probably >~50%) to the R-band flux in the centralregions of several galaxies; tidal tails do not necessarily accompanythis star formation. Many of the galaxies in our sample have bluercenters than outskirts, suggesting that pre- or nonmerger interactionsmay lead to evolution along the Hubble sequence. These objects wouldappear blue and compact at higher redshifts; the older, redder outskirtsof the disks would be difficult to detect. Our data indicate thatgalaxies with larger separations on the sky contain weaker, and probablyolder, bursts of star formation on average. However, confirmation ofthese trends requires further constraints on the colors of the olderstellar populations and on the reddening for individual galaxies.
|The UZC-SSRS2 Group Catalog|
We apply a friends-of-friends algorithm to the combined Updated ZwickyCatalog and Southern Sky Redshift Survey to construct a catalog of 1168groups of galaxies; 411 of these groups have five or more members withinthe redshift survey. The group catalog covers 4.69 sr, and all groupsexceed the number density contrast threshold, δρ/ρ=80. Wedemonstrate that the groups catalog is homogeneous across the twounderlying redshift surveys; the catalog of groups and their membersthus provides a basis for other statistical studies of the large-scaledistribution of groups and their physical properties. The medianphysical properties of the groups are similar to those for groupsderived from independent surveys, including the ESO Key Programme andthe Las Campanas Redshift Survey. We include tables of groups and theirmembers.
|Redshifts for 2410 Galaxies in the Century Survey Region|
The Century Survey strip covers 102 deg2 within the limits8h5<=α<=16h5, 29.0d<=δ<=30.0d, equinoxB1950.0. The strip passes through the Corona Borealis supercluster andthe outer region of the Coma cluster. Within the Century Survey region,we have measured 2410 redshifts that constitute four overlappingcomplete redshift surveys: (1) 1728 galaxies with Kron-CousinsRph<=16.13 covering the entire strip, (2) 507 galaxieswith Rph<=16.4 in right ascension range8h32m<=α<=10h45m, equinox B1950.0, (3) 1251 galaxies withabsorption- and K-corrected RCCDc<=16.2 (where ``c''indicates ``corrected'') covering the right ascension range8h5<=α<=13h5, equinox B1950.0, and (4) 1255 galaxieswith absorption- and K-corrected VCCDc<=16.7 also coveringthe right ascension range 8h5<=α<=13h5, equinoxB1950.0. All these redshift samples are more than 98% complete to thespecified magnitude limit. We derived samples 1 and 2 from scans of thePOSS1 red (E) plates calibrated with CCD photometry. We derived samples3 and 4 from deep V and R CCD images covering the entire region. Weinclude coarse morphological types for all the galaxies in sample 1. Thedistribution of (V-R)CCD for each type correspondsappropriately with the classification. Work reported here is basedpartly on observations obtained at the Michigan-Dartmouth-MITObservatory.
|V- and R-band Galaxy Luminosity Functions and Low Surface Brightness Galaxies in the Century Survey|
We use 64 deg2 of deep V and R CCD images to measure thelocal V- and R-band luminosity functions of galaxies. TheV0<16.7 and R0<16.2 redshift samples contain1255 and 1251 galaxies and are 98.1% and 98.2% complete, respectively.We apply k-corrections before the magnitude selection so that thecompleteness is to the same depth for all spectral types. The V and Rfaint-end slopes are surprisingly identical: α=-1.07+/-0.09.Representative Schechter function parameters for H0=100 are:M*R=-20.88+/-0.09,φ*R=0.016+/-0.003 Mpc-3 andM*V=-20.23+/-0.09,φ*V=0.020+/-0.003 Mpc-3. The V andR local luminosity densities,jR=(1.9+/-0.6)×108 Lsolar andjV=(2.2+/-0.7)×108 Lsolar, are inessential agreement with the recent 2 Degree Field Galaxy RedshiftSurvey and Sloan Digital Sky Survey determinations. All low surfacebrightness (LSB) galaxies fall in the large-scale structure delineatedby high surface brightness galaxies. The properties and surface numberdensity of our LSB galaxies are consistent with the LSB galaxy catalogof O'Neil, Bothun & Cornell, suggesting that our samples arecomplete for LSB galaxies to the magnitude limits. We measure colors,surface brightnesses, and luminosities for our samples, and find strongcorrelations among these galaxy properties. The color-surface brightnessrelation is(V-R)0=(-0.11+/-0.05)μR,0+(2.6+/-0.9).
|The distribution of the rotation axes of the disk galaxies in the Coma cluster: statistical samples.|
|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.
|Automated surface photometry for the Coma Cluster galaxies: The catalog|
A homogeneous photometry catalog is presented for 450 galaxies withB25.5 less than or equal to 16 mag located in the 9.8 deg x9.8 deg region centered on the Coma Cluster. The catalog is based onphotographic photometry using an automated surface photometry softwarefor data reduction applied to B-band Schmidt plates. The catalogprovides accurate positions, isophotal and total magnitudes, major andminor axes, and a few other photometric parameters including rudimentarymorphology (early of late type).
|Cross identification of 238 galaxies and use of a colour magnitude relation in the coma cluster|
A catalog of 238 galaxies is obtained by the cross identification ofdata from Kent and Gunn (1982), Godwin and Peach (1977) and Godwin etal. (1983). It contains the radial velocities, bvr magnitudes, colorindices, isophotal radii, and other characteristics of individualgalaxies. This leads to the definition of various samples of radialvelocities complete to various limiting magnitudes depending on radius.The use of a color magnitude relation is discussed to define a class of1340 objects likely to belong to the cluster from their photometry only.
|The Coma Cluster - Part One - a Catalogue of Magnitudes Colours Ellipticities and Position Angles for 6724 Galaxies in the Field of the Coma Cluster|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1983MNRAS.202..113G&db_key=AST
|The dynamics of rich clusters of galaxies. I - The Coma cluster|
Self-consistent analytical dynamical models are used to study theendpoint of cluster formation, concentrating on the Coma cluster.Particular attention is paid to the effects of anisotropy in thevelocity dispersion and variations in the energy-distribution functionon the cluster structure, the effect on the core structure of a massivecentral object, the dynamical consequences of morphological segregation,cosmological infall and the edge of a cluster, the distribution of darkmatter in a cluster, and the implications of X-ray observations for thedistribution of gravitating material in a cluster. Radial velocity datais displayed, and new and repeated redshifts are reported for a numberof galaxies in the central regions of the cluster. Cluster membership isdetermined and a velocity-dispersion profile is derived. A compositesurface-density profile is derived, and amazing examples are shown ofmodels with virtually identical surface-density profiles but otherwisecompletely different internal dynamics.
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