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The structure of elliptical galaxies in the Virgo cluster. Results from the INT Wide Field Survey
We report on a complete CCD imaging survey of 226 elliptical galaxies inthe North-East quadrant of the Virgo cluster, representative of theproperties of giant and dwarf elliptical galaxies in this cluster. Wefit their radial light profiles with the Sersic r1/n model oflight distribution. We confirm the result of Graham & Guzman(\cite{Graham03}, AJ, 125, 2936) that the apparent dichotomy between Eand dE galaxies in the luminosity-< μ>e plane nolonger appears when other structural parameters are considered and canbe entirely attributed to the onset of ``core'' galaxies atBT -20.5 mag. When ``core'' galaxies are notconsidered, E and dE form a unique family with n linearly increasingwith the luminosity. For 90 galaxies we analyze the B-I color indices,both in the nuclear and in the outer regions. Both indices are bluertoward fainter luminosities. We find also that the outer color gradientsdo not show any significant correlation with the luminosity. The scatterin all color indicators increases significantly toward lowerluminosities, e.g. galaxies fainter than BT -15 have aB-I spread > 0.5 mag.Table 2, Figs. 13 and 14 are only available in electronic form athttp://www.edpsciences.org
| The luminosity function of the Virgo Cluster from MB=-22 to -11
We measure the galaxy luminosity function (LF) for the Virgo Clusterbetween blue magnitudes MB=-22 and -11 from wide-fieldcharge-coupled device (CCD) imaging data. The LF is only graduallyrising for -22
| Luminosity Functions of 10 Nearby Clusters of Galaxies. I. Data
Wide field CCD imaging was carried out in the RC band for 10nearby clusters of galaxies and four control fields to derive the totaland type-specific luminosity functions. Observation and data reductionprocedures are described. We extract galaxies down to RC~20mag and classify them into two broad types, r1/4-like andexponential-like, on the basis of the bulge-to-total luminosity ratioB/T estimated from Petrosian quantities. We describe our classificationscheme in detail. We apply a single classification scheme to both giantand dwarf galaxies. The consistency of our classification is verifiedfor giant galaxies using both simulated images and real data in theliterature. We set the boundary of our two types at B/T=0.35. Thisboundary gives 70% completeness to both the r1/4-like sample(for E/S0 galaxies) and the exponential-like sample (for Sa-Irrgalaxies). Our classification for dwarf galaxies is investigated usinghigher resolution images of some 20 dwarf galaxies in the Virgo Cluster.Galaxy catalogs are constructed, which include position, magnitude, andB/T. The projected sky distribution of each type of galaxies is shownfor the clusters and control fields.
| Stellar populations in dwarf elliptical galaxies.
Not Available
| Blue compact dwarf galaxies and new velocities in Virgo
We present new spectral observations of 303 galaxies brighter thanB_J=17.6 in the central 30 deg^2 of the Virgo cluster field. Thegalaxies were selected from two overlapping samples designed for asearch for blue compact dwarf (BCD) galaxies and for a more generalstudy of Virgo dwarf elliptical (dE) galaxies. Many of these galaxieswere designated `background' (i.e., not members of the Virgo cluster) onmorphological grounds by Binggeli, Sandage & Tammann in their VirgoCluster Catalog (VCC). Our principal aim was to measure radialvelocities of these galaxies in order to determine which were members ofthe cluster, looking in particular for any cluster members previouslymisclassified as background galaxies. We measured reliable velocitiesfor 291 galaxies, of which nine were found to be cluster members. Fiveof these were listed in the VCC as `members' and four as `possiblemembers'. We also confirmed that 10 VCC `background' galaxies werecorrectly identified, and determined that an additional three VCC`possible members' were background galaxies. These results show that theVCC membership estimates were generally correct. Our sample of candidateBCD galaxies was defined by objective criteria from digitized platematerial and therefore allows us to place new limits on the dwarf-galaxypopulation. We confirm the drop in the BCD luminosity function at anabsolute magnitude of M_B=-14 reported by Binggeli, Sandage &Tammann (using their Virgo distance modulus). We also show that if BCDsfade at the end of the current burst of star formation, such `dead'BCDs, if they exist, would all have to be fainter than our sample limitof B_J=17.6. We use a (U-B_J)(B_J-R_F) colour-colour diagram plottedfrom our photographic data to separate the different dwarf-galaxy typeseffectively and use this colour information to argue that there are noblue star-forming progenitors of dE galaxies in the cluster. Most of thegalaxies of compact appearance we selected were background objects whichwe show to be significantly younger than general field galaxies; thissample also shows considerable clustering in redshift space.
| Distances to 64 Virgo dwarf-elliptical galaxies and the depth in their spatial distribution
We derive distances for 64 dwarf ellipticals (dEs) in the direction ofthe Virgo cluster's (VC) core, by means of the luminosity-profilecurvature (L-n) relationship and by means of their global scalelengths,which we find to be correlated with the shapes of theirsurface-brightness profiles. The great depth we find in the spatialdistribution of Virgo dEs is not consistent with a unimodal distributiondue to a single spherically symmetric concentration of galaxies. Thisdepth is also sufficient to explain much of the disagreement over theVC's distance, and thereby much of the Hubble-constant (H_0)controversy.
| Dwarf galaxies in the Virgo cluster. II - Photometric techniques and basic data
Results are presented of photographic surface photometry carried out for305 (mostly dwarf) galaxies in the Virgo cluster, in which the galaxyimages were digitized on 14 of the 67 du Pont plates used for the Virgocluster survey. Azimuthally averaged surface brightness profiles areshown for all galaxies. The following model-free photometric parametersare derived and listed for each galaxy: total apparent blue magnitude,mean effective radius and surface brightness, and various isophotalradii, ellipticity, and position angle. Most galaxies were fitted by anexponential form and/or a King model profile. The best-fittingparameters, including the 'nuclear' (central residual) magnitudes fordE+dS0 galaxies, are listed.
| The kinematics of the Virgo cluster revisited
The paper updates the velocity data of Virgo cluster galaxies andreconsiders the kinematic structure of the Virgo cluster. New velocitiesare given for 144 galaxies listed in the Virgo Cluster Catalog (VCC).Improved velocities are given for another 131 VCC galaxies. The Virgocluster is disentangled from its surrounding clouds of galaxies, and thelikely members of each of these clouds are listed. The velocitydistribution of dwarf elliptical cluster members is found to be highlyasymmetric. This phenomenon is interpreted as evidence for the imminentmerging of two subclusters in the core region, which points to thedynamical youth of the Virgo cluster. The mean heliocentric velocity ofthe Virgo cluster is estimated at 1050 +/- 35 km/s.
| Dwarf galaxies in the Virgo cluster. I - The systematic photometric properties of early-type dwarfs
The azimuthally averaged surface brightness profiles of 200 faintearly-type Virgo cluster galaxies have been analyzed. Faint dwarfs arevery well described by an exponential or a King model. The magnitudes ofthe nuclei vary greatly at a given galaxian magnitude, but the maximumnuclear luminosity is a strong function of M(T). In the 0.1-1 kpc radiusrange, the logarithmically plotted profiles of all early-type galaxiescome in two well-defined classes identified with classical types versusdwarf types. The former are all classified E or S0, while the lattercomprise all galaxies classified dE or dS0, all morphologically'intermediate' types, and even two classified 'E'. The mean SB profilesof dS0 galaxies are indistinguishable from bright dE profiles. In 2D,the dS0s appear highly flattened and/or show asymmetric and irregularfeatures which may indicate their disk nature.
| Studies of the Virgo Cluster. II - A catalog of 2096 galaxies in the Virgo Cluster area.
The present catalog of 2096 galaxies within an area of about 140 sq degapproximately centered on the Virgo cluster should be an essentiallycomplete listing of all certain and possible cluster members,independent of morphological type. Cluster membership is essentiallydecided by galaxy morphology; for giants and the rare class of highsurface brightness dwarfs, membership rests on velocity data. While 1277of the catalog entries are considered members of the Virgo cluster, 574are possible members and 245 appear to be background Zwicky galaxies.Major-to-minor axis ratios are given for all galaxies brighter than B(T)= 18, as well as for many fainter ones.
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