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Virgo Cluster Early-Type Dwarf Galaxies with the Sloan Digital Sky Survey. I. On the Possible Disk Nature of Bright Early-Type Dwarfs
We present a systematic search for disk features in 476 Virgo Clusterearly-type dwarf (dE) galaxies. This is the first such study of analmost-complete, statistically significant dE sample, which includes allcertain or possible cluster members with mB<=18 that arecovered by the optical imaging data of the Sloan Digital Sky Survey DataRelease 4. Disk features (spiral arms, edge-on disks, or bars) wereidentified by applying unsharp masks to a combined image from threebands (g, r, and i), as well as by subtracting the axisymmetric lightdistribution of each galaxy from that image. Fourteen objects areunambiguous identifications of disks, 10 objects show ``probable disk''features, and 17 objects show ``possible disk'' features. The numberfraction of these galaxies, for which we introduce the term ``dEdi,''reaches more than 50% at the bright end of the dE population anddecreases to less than 5% for magnitudes mB>16. Althoughpart of this observed decline might be due to the lower signal-to-noiseratio at fainter magnitudes, we show that it cannot be caused solely bythe limitations of our detection method. The luminosity function of ourfull dE sample can be explained by a superposition of dEdis and ordinarydEs, strongly suggesting that dEdis are a distinct type of galaxy. Thisis supported by the projected spatial distribution: dEdis show basicallyno clustering and roughly follow the spatial distribution of spirals andirregulars, whereas ordinary dEs are distributed similarly to thestrongly clustered E/S0 galaxies. While the flattening distribution ofordinary dEs is typical for spheroidal objects, the distribution ofdEdis is significantly different and agrees with their being flat oblateobjects. We therefore conclude that the dEdis are not spheroidalgalaxies that just have an embedded disk component but are instead apopulation of genuine disk galaxies. Several dEdis display well-definedspiral arms with grand-design features that clearly differ from theflocculent, open arms typical for late-type spirals that have frequentlybeen proposed as progenitors of dEs. This raises the question of whatprocess is able to create such spiral arms-with pitch angles like thoseof Sab/Sb galaxies-in bulgeless dwarf galaxies.
| Galaxy Populations and Evolution in Clusters. IV. Deep H I Observations of Dwarf Elliptical Galaxies in the Virgo Cluster
In this paper we present deep Arecibo H I and WIYN optical observationsof Virgo Cluster dwarf elliptical galaxies. Based on this data we arguethat a significant fraction of low-mass galaxies in the Virgo Clusterrecently underwent evolution. Our new observations consist of H I 21 cmline observations for 22 classified dE galaxies with optical radialvelocities consistent with membership in the Virgo Cluster. Clustermembers VCC 390 and VCC 1713 are detected with H I massesMHI=6×107 and 8×107Msolar, respectively, while MHI values in theremaining 20 dE galaxies have upper limits as low as~5×105 Msolar. We combine our results withthose for 26 other Virgo Cluster dE galaxies with H I observations inthe literature, seven of which have H I detection claims. New opticalimages from the WIYN telescope of five of these H I-detected dEgalaxies, along with archival data, suggest that seven of the claimeddetections are true H I detections, yielding a ~15% detection rate.These H I-detected, classified dE galaxies are preferentially locatednear the periphery of the Virgo Cluster. Three Virgo dE galaxies haveobserved H I velocity widths greater than 200 km s-1,possibly indicating the presence of a large dark matter content ortransient extended H I. We discuss the possible origins of these objectsand argue that they originate from field galaxies accreted onto highangular momentum orbits by Virgo in the last few Gyr. As a result ofthis, we argue, these galaxies are slowly transformed within the clusterby gradual gas-stripping processes, associated truncation of starformation, and passive fading of stellar populations. Low-mass,early-type cluster galaxies are therefore currently being produced asthe product of cluster environmental effects. We utilize our results ina simple model to estimate the recent (past 1-3 Gyr) average massaccretion rate into the Virgo Cluster, deriving a value of M~50Msolar yr-1.
| New clues to the evolution of dwarf early-type galaxies
Surface photometry of 18 Virgo cluster dwarf elliptical (dE) and dwarflenticular (dS0) galaxies, made by Gavazzi et al. in the H band(1.65μm) and in the B band (0.44μm), shows that the ratio of theeffective radii of these stellar systems in the B and H bands, r eB /r eH , ranges between 0.7 and 2.2. In particular,dwarf ellipticals and lenticulars with a red total colour index B -H(i.e. with 3.2
| 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.
| Galaxy Populations and Evolution in Clusters. I. Dynamics and the Origin of Low-Mass Galaxies in the Virgo Cluster
Early-type dwarfs are the most common galaxy in the local universe, yettheir origin and evolution remain a mystery. Various cosmologicalscenarios predict that dwarf-like galaxies in dense areas are the firstto form and hence should be the oldest stellar systems in clusters. Byusing radial velocities of early-type dwarfs in the Virgo cluster wedemonstrate that these galaxies are not an old cluster population buthave signatures of production from the infall of field galaxies.Evidence of this includes the combined large dispersions andsubstructure in spatial and kinematic distributions for Virgo early-typedwarfs and a velocity dispersion ratio with giant ellipticals expectedfor virialized and accreted populations. We also argue that thesegalaxies cannot originate from accreted field dwarfs, but must havephysically evolved from a precursor population, of different morphology,that fell into Virgo some time in the past.
| 1.65 μm (H-band) surface photometry of galaxies. VII. Dwarf galaxies in the Virgo Cluster
We present near-infrared H-band (1.65 μm) observations and surfacebrightness profile decompositions for 75 faint (13.5 <~ mp<~ 18.5) galaxies, primarily taken among dwarf Ellipticals members ofthe Virgo cluster, with some Centaurus Cluster members, a BCD and twopeculiar galaxies taken as fillers. We model their surface brightnessprofiles with a de Vaucouleurs (D), exponential (E), mixed (bulge+diskor M) or truncated (T) law, and we derive for each galaxy the H bandeffective surface brightness (μe) and effective radius(re), the asymptotic total magnitude HT and thelight concentration index C31, defined as the ratio betweenthe radii that enclose 75% and 25% of the total light HT. Fora subsample we compare the NIR surface photometry with similar datataken in the B and V bands, and we give the B-H and B-V color profiles.Combining the present data with those previously obtained by our group(1157 objects) we analyze the NIR properties of a nearly completesample, representative of galaxies of all morphological types, spanning4 decades in luminosity. We confirm our earlier claim that the presenceof cusps and extended haloes in the light profiles (C31>5)is a strong, non-linear function of the total luminosity. We also findthat: i) among dE and dS0 galaxies D profiles are absent; 50% of thedecompositions are of type M, the remaining being of type E or T. ii)Less than 50% of the giant elliptical galaxies have pure D profiles, themajority being represented by M profiles. iii) Most giant galaxies (fromelliptical to Sb) have M profiles. iv) Most of late type spirals (Scd toBCD) have either E or T profiles. v) The type of decomposition is astrong function of the total H band luminosity, independent of theHubble classification: the fraction of type E decompositions decreaseswith increasing luminosity, while those of type M increase withluminosity. Pure D profiles are absent in the low luminosity rangeLH<1010 Lsolar and become dominantabove 1011 Lsolar, while T profiles are presentonly among low luminosity galaxies. vi) We find that dE-peculiargalaxies have structural parameters indistinguishable from those oflate-type dwarfs, thus they might represent the missing link between dEsand dIs. Based on observations taken with the ESO/NTT (ESO program64.N-0288), with the Telescopio Nazionale Galileo (TNG) operated on theisland of La Palma by the Centro Galileo Galilei of the CNAA at theSpanish Observatorio del Roque de los Muchachos of the IAC, with the SanPedro Martir 2.1~m telescope of the Observatorio Astronomico Nacional(OAN, Mexico), and with the OHP 1.2~m telescope, operated by the FrenchCNRS.
| Arcsecond Positions of UGC Galaxies
We present accurate B1950 and J2000 positions for all confirmed galaxiesin the Uppsala General Catalog (UGC). The positions were measuredvisually from Digitized Sky Survey images with rms uncertaintiesσ<=[(1.2")2+(θ/100)2]1/2,where θ is the major-axis diameter. We compared each galaxymeasured with the original UGC description to ensure high reliability.The full position list is available in the electronic version only.
| The ``Virgo photometry catalogue''; a catalogue of 1180 galaxies in the direction of the Virgo Cluster's core
We present a new catalogue of galaxies in the direction of the VirgoCluster's core: the Virgo Photometry Catalogue (VPC)*. This cataloguecontains 1180 galaxies (including background objects) within a 23square-degree area of the sky centred on R.A._{1950.0} = 12h 26m anddec._{1950.0} = 13(deg) 08'. The VPC galaxy sample comprises ofnon-stellar objects brighter than B_J25 = 19.0; thecompleteness limits being B_J25 ~18.5 for the northern halfof the survey area and B_J25 ~18.0 for the southern half.Independently-calibrated photographic surface photometry is presentedfor over 1000 galaxies in the U, B_J and R_C bands. Parameters listedfor catalogued galaxies include: equatorial coordinates, morphologicaltypes, surface-brightness profile parameters (which preserve themajority of the original surface photometry information), U, B_J &R_C isophotal magnitudes, B_J and [transformed] B total magnitudes,(U-B_J) and (B_J-R_C) equal-area and total colours, apparent angularradii, ellipticities, position angles, heliocentric radial velocitiesand alternative designations. All total magnitudes and total colours areextrapolated according to a new system denoted t in order to distinguishit from the T system already in use. The VPC is based primarily on four(one U, two B_J and one R_C) UK-Schmidt plates, all of which weredigitised using the Royal Observatory Edinburgh's (ROE) COSMOS measuringmachine. All magnitudes, colours and surface-brightness parameters arederived from numerical integrations of segmented plate-scan data, exceptfor (in 109 cases) saturated or (in 51 cases) inextricably-mergedimages; our segmentation software being able to cope with the vastmajority of image mergers. * Appendices B, C and E, which contain thesurface photometry, the main catalogue and the summary cataloguerespectively, are only available in electronic form. They can beobtained from La Centre des Donees astronomiques de Strasbourg (CDS) viaanonymous ftp 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.
| General study of group membership. II - Determination of nearby groups
We present a whole sky catalog of nearby groups of galaxies taken fromthe Lyon-Meudon Extragalactic Database. From the 78,000 objects in thedatabase, we extracted a sample of 6392 galaxies, complete up to thelimiting apparent magnitude B0 = 14.0. Moreover, in order to considersolely the galaxies of the local universe, all the selected galaxieshave a known recession velocity smaller than 5500 km/s. Two methods wereused in group construction: a Huchra-Geller (1982) derived percolationmethod and a Tully (1980) derived hierarchical method. Each method gaveus one catalog. These were then compared and synthesized to obtain asingle catalog containing the most reliable groups. There are 485 groupsof a least three members in the final catalog.
| The pattern of H I deficiency in the Virgo cluster
A sample of 160 galaxies in the Virgo region, including 16 new 21-cmprofiles in the Virgo 5-degree core obtained with the 305-m Arecibotelescope, are examined to investigate the severe depletion ofinterstellar H I within spiral galaxies in the Virgo cluster core. Asimilar and non-Gaussian distribution is found for the distribution of HI deficiencies of both faint galaxies and brighter spirals, andpopulations of galaxies with normal abundances of interstellar H I, andthose of gas poor objects exhibiting a late-type morphology, are bothnoted. One-sixth of the sample within the Virgo 5-degree core have lostmore than 90 percent by mass of their original neutral hydrogen, andthree quarters of the galaxies found within 2.5 degrees of M87 are H Ipoor by more than a factor of three. The most deficient galaxies arealso found to be the ones with the smallest ratios of H I to opticaldisk size, and H I poor galaxies are redder than normal, indicating thatstar formation has been quenched.
| 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.
| On the Largescale Distribution of Faint Blue Galaxies
Not Available
| Faint blue galaxies in the Virgo cluster region
Finding charts, coordinates, B magnitudes, U-B color estimates, andsurface brightnesses are given for 110 faint blue galaxies located nearthe center of the Virgo cluster of galaxies. The galaxies were found byblinking on plates taken with the Tautenburg 52-in. Schmidt telescope.
| Studies of the Virgo cluster. III - A classification system and an illustrated atlas of Virgo cluster dwarf galaxies
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1984AJ.....89..919S&db_key=AST
| Radial Velocities of Galaxies in the Virgo Cluster
Not Available
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