WIKISKY.ORG
 Home Getting Started To Survive in the Universe News@Sky Astro Photo The Collection Forum Blog New! FAQ Press Login

# PGC 41036

Contents

### Images

DSS Images   Other Images

### Related articles

 Completing H I observations of galaxies in the Virgo clusterHigh sensitivity (rms noise  0.5 mJy) 21-cm H I line observationswere made of 33 galaxies in the Virgo cluster, using the refurbishedArecibo telescope, which resulted in the detection of 12 objects. Thesedata, combined with the measurements available from the literature,provide the first set of H I data that is complete for all 355 late-type(Sa-Im-BCD) galaxies in the Virgo cluster with mp ≤ 18.0mag. The Virgo cluster H I mass function (HIMF) that was derived forthis optically selected galaxy sample is in agreement with the HIMFderived for the Virgo cluster from the blind HIJASS H I survey and isinconsistent with the Field HIMF. This indicates that both in this richcluster and in the general field, neutral hydrogen is primarilyassociated with late-type galaxies, with marginal contributions fromearly-type galaxies and isolated H I clouds. The inconsistency betweenthe cluster and the field HIMF derives primarily from the difference inthe optical luminosity function of late-type galaxies in the twoenvironments, combined with the HI deficiency that is known to occur ingalaxies in rich clusters.Tables \ref{t1, \ref{sample_dat} and Appendix A are only available inelectronic form at http://www.edpsciences.org Catalog of Double Nucleus Disk GalaxiesWe have compiled a catalog of disk galaxies that have a double nucleus,through systematic examination of existing catalogs and publications.The Catalog of Double Nucleus Disk Galaxies includes 107 objects,together with their basic data. The aim of the catalog is to provide amore systematic and homogeneous basis for the study of the relevance ofgalaxy interactions and minor mergers in the formation of these doublenuclei. We have also investigated possible correlations betweengeometric and photometric parameters of the double nuclei and their hostgalaxies. The preliminary results indicate the presence of severalsignificant correlations that should be considered in any theoreticalscenario describing minor mergers and disk galaxy evolution. Globular Clusters as Candidates for Gravitational Lenses to Explain Quasar-Galaxy AssociationsWe argue that globular clusters (GCs) are good candidates forgravitational lenses in explaining quasar-galaxy associations. Thecatalog of associations (Bukhmastova 2001) compiled from the LEDAcatalog of galaxies (Paturel 1997) and from the catalog of quasars(Veron-Cetty and Veron 1998) is used. Based on the new catalog, we showthat one might expect an increased number of GCs around irregulargalaxies of types 9 and 10 from the hypothesis that distant compactsources are gravitationally lensed by GCs in the halos of foregroundgalaxies. The King model is used to determine the central surfacedensities of 135 GCs in the Milky Way. The distribution of GCs incentral surface density was found to be lognormal. Companions of Bright Barred Shapley-Ames GalaxiesCompanion galaxy environment for a subset of 78 bright and nearby barredgalaxies from the Shapley-Ames Catalog is presented. Among the spiralbarred galaxies, there are Seyfert galaxies, galaxies with circumnuclearstructures, galaxies not associated with any large-scale galaxy cloudstructure, galaxies with peculiar disk morphology (crooked arms), andgalaxies with normal disk morphology; the list includes all Hubbletypes. The companion galaxy list includes the number of companiongalaxies within 20 diameters, their Hubble type, and projectedseparation distance. In addition, the companion environment was searchedfor four known active spiral galaxies, three of them are Seyfertgalaxies, namely, NGC 1068, NGC 1097, and NGC 5548, and one is astarburst galaxy, M82. Among the results obtained, it is noted that theonly spiral barred galaxy classified as Seyfert 1 in our list has nocompanions within a projected distance of 20 diameters; six out of 10Seyfert 2 bar galaxies have no companions within 10 diameters, six outof 10 Seyfert 2 galaxies have one or more companions at projectedseparation distances between 10 and 20 diameters; six out of 12 galaxieswith circumnuclear structures have two or more companions within 20diameters. Uncovering Additional Clues to Galaxy Evolution. II. The Environmental Impact of the Virgo Cluster on the Evolution of Dwarf Irregular GalaxiesThe impact of the cluster environment on the evolution of dwarf galaxiesis investigated by comparing the properties of a sample of dwarfirregular galaxies (dI's) in the Virgo Cluster with a control sample ofnearby (field'') dI's having oxygen abundances derived from [O III]λ4363 measurements and measured distances from resolved stellarconstituents. Spectroscopic data are obtained for H II regions in 11Virgo dI's distributed in the central and outer regions of the cluster.To ensure that oxygen abundances are derived in a homogeneous manner,oxygen abundances for field and Virgo dI's are computed using thebright-line method and compared with abundances directly obtained from[O III] λ4363, where available. They are found to agree to withinabout 0.2 dex, with no systematic offset. At a given optical luminosity,there is no systematic difference in oxygen abundance between the sampleof Virgo dI's and the sample of nearby dI's. However, five of the 11Virgo dI's exhibit much lower baryonic gas fractions than field dI's atcomparable oxygen abundances. Using field dI's as a reference, agas-deficiency index for dI's is constructed, making it possiblequantitatively to identify which galaxies have lost gas. For the Virgosample, some of the dwarfs are gas-deficient by a factor of 30. The gasdeficiency correlates roughly with the X-ray surface brightness of theintracluster gas. Ram pressure stripping can best explain the observedgas-poor dI's in the cluster sample. Together with the lack ofsignificant fading and reddening of the gas-poor dI's compared withgas-normal dI's, these observations suggest that the gas-poor dI's inVirgo have recently encountered the intracluster medium for the firsttime. Faded remnants of gas-poor dI's in Virgo will resemble brightdwarf elliptical galaxies currently seen in the cluster core. The UZC-SSRS2 Group CatalogWe 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. The Frequency of Active and Quiescent Galaxies with Companions: Implications for the Feeding of the NucleusWe analyze the idea that nuclear activity, either active galactic nuclei(AGNs) or star formation, can be triggered by interactions by studyingthe percentage of active, H II, and quiescent galaxies with companions.Our sample was selected from the Palomar survey and avoids selectionbiases faced by previous studies. This sample was split into fivedifferent groups, Seyfert galaxies, LINERs, transition galaxies, H IIgalaxies, and absorption-line galaxies. The comparison between the localgalaxy density distributions of the different groups showed that in mostcases there is no statistically significant difference among galaxies ofdifferent activity types, with the exception that absorption-linegalaxies are seen in higher density environments, since most of them arein the Virgo Cluster. The comparison of the percentage of galaxies withnearby companions showed that there is a higher percentage of LINERs,transition galaxies, and absorption-line galaxies with companions thanSeyfert and H II galaxies. However, we find that when we consider onlygalaxies of similar morphological types (elliptical or spiral), there isno difference in the percentage of galaxies with companions amongdifferent activity types, indicating that the former result was due tothe morphology-density effect. In addition, only small differences arefound when we consider galaxies with similar Hα luminosities. Thecomparison between H II galaxies of different Hα luminositiesshows that there is a significantly higher percentage of galaxies withcompanions among H II galaxies with L(Hα)>1039 ergss-1 than among those with L(Hα)<=1039ergs s-1, indicating that interactions increase the amount ofcircumnuclear star formation, in agreement with previous results. Thefact that we find that galaxies of different activity types have thesame percentage of companions suggests that interactions betweengalaxies is not a necessary condition to trigger the nuclear activity inAGNs. We compare our results with previous ones and discuss theirimplications. Nearby Optical Galaxies: Selection of the Sample and Identification of GroupsIn this paper we describe the Nearby Optical Galaxy (NOG) sample, whichis a complete, distance-limited (cz<=6000 km s-1) andmagnitude-limited (B<=14) sample of ~7000 optical galaxies. Thesample covers 2/3 (8.27 sr) of the sky (|b|>20deg) andappears to have a good completeness in redshift (97%). We select thesample on the basis of homogenized corrected total blue magnitudes inorder to minimize systematic effects in galaxy sampling. We identify thegroups in this sample by means of both the hierarchical and thepercolation friends-of-friends'' methods. The resulting catalogs ofloose groups appear to be similar and are among the largest catalogs ofgroups currently available. Most of the NOG galaxies (~60%) are found tobe members of galaxy pairs (~580 pairs for a total of ~15% of objects)or groups with at least three members (~500 groups for a total of ~45%of objects). About 40% of galaxies are left ungrouped (field galaxies).We illustrate the main features of the NOG galaxy distribution. Comparedto previous optical and IRAS galaxy samples, the NOG provides a densersampling of the galaxy distribution in the nearby universe. Given itslarge sky coverage, the identification of groups, and its high-densitysampling, the NOG is suited to the analysis of the galaxy density fieldof the nearby universe, especially on small scales. Arcsecond Positions of UGC GalaxiesWe 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 Intrinsic Shapes of Low Surface Brightness Dwarf Irregular Galaxies and Comparison to Other Types of Dwarf GalaxiesIn this paper, we measure the ellipticities of 30 low surface brightness(LSB) dwarf irregular (dI) galaxies and compare the ellipticitydistribution with that of 80 dwarf elliptical (dEs) and 62 blue-compactdwarfs (BCDs). We find that the ellipticity distribution of LSB dIs isvery similar to that of BCDs, and marginally different from that of dEs.We then determine the distribution of intrinsic shapes of dI galaxiesand compare this to the distributions of other types of dwarf galaxiesunder various assumptions. First, we assume that LSB dIs are either alloblate or all prolate, and use a nonparametric analysis to find thebest-fitting distribution of intrinsic shapes. With this assumption, wefind that the scarcity of nearly circular LSB dIs implies, at the 99%confidence level, that they cannot be a population of randomly orientedoblate or prolate objects, implying that LSB dIs are highly unlikely tobe disk-shaped systems. Next, we assume that dIs are triaxial, and use aparametric analysis to find permissible distributions of intrinsicshapes. We find that if the intrinsic axis ratios beta and gamma aredistributed according to a Gaussian with means beta_0 and gamma_0 and acommon standard deviation of sigma, the best-fitting set of parametersfor LSB dIs is (beta_0, gamma_0, sigma) = (0.66, 0.50, 0.15), and thebest fit for BCDs is (beta_0, gamma_0, sigma) = (0.66, 0.55, 0.16),while the best fit for dEs is (beta_0, gamma_0, sigma) = (0.78, 0.69,0.24). The dIs and BCDs thus have very similar shape distributions,given this triaxial hypothesis, while the dEs peak at a somewhat morespherical shape. Therefore, our results provide strong observationalevidence to support the evolutionary scenario in which the three typesof dwarf galaxy have a close relation with each other. Surface Photometry of Low Surface Brightness Dwarf Irregular GalaxiesWe present CCD B and I surface brightness and color profiles for asample of 51 dwarf and low surface brightness (LSB) galaxies. Thegalaxies were drawn mainly from the sample of UGC dwarf and LSB galaxiesdetected in H I by Schneider et al. We focus our attention on extremedwarf irregulars (dIs) where turbulent motions are as important as ormore important than rotational motions, so that the majority of thedwarfs were chosen to have narrow H I line widths ({DELTA}V_20_ < 100km s^-1^), in addition to being nearby (v_0_ < 1500 km s^-1^).Foreach dI galaxy, we derive structural parameters for the underlying lowsurface brightness disk component on which are superimposed thestar-forming regions. We found that the central surface brightness ofthe underlying exponential component of dIs is similar to that of dwarfellipticals (dEs) but ~1.5 mag fainter than that of blue compact dwarfs(BCDs). As for the scale lengths, the dIs divide into two groups; onewhere, for a given B luminosity, the scale length of the underlyingexponential component is comparable to that of dEs and a factor of ~2larger than that of BCDs, and one group where the scale length of thedIs is comparable to that of BCDs but a factor of 2 smaller than that ofdEs. These differences in structural parameters put strong constraintson evolutionary scenarios among the three types of dwarfs. We use theCCD images to set up a tentative morphological classification scheme forLSB dIs based of the shape of the underlying low surface brightnesscomponent and the morphology and location of the star-forming regions ontop of it. The division of the dIs into two groups appears to becorrelated with morphology. There are a few dwarf spirals in our sample,which show fragments of low surface brightness spiral arms. We foundthat Nilson and Zwicky magnitudes are systematically too faint fordwarfs and LSB galaxies by 1-2 mag. The underlying disks in dIs have B-Icolors ~1.5, corresponding to a stellar population of G and Kmain-sequence or giant stars and are redder than those of BCDs. Thecolor profiles of the galaxies in the sample are generally flat, with nostrong gradient. Near Infrared Imaging of Dwarf Ellipticals Irregulars and Blue Compact Galaxies in the Virgo ClusterNew near-IR images are presented for 13 dwarf galaxies in the Virgocluster. Together with previous data these provide a data base of JHKimaging for 26 dwarf ellipticals (dEs), dwarf irregulars (dIs) and bluecompact dwarfs (BCDs). These images show the dIs to be highly asymmetricand unrelaxed, implying that they are dynamically young and unevolved.This is consistent with their blue near-IR and optical-IR colours whichare most easily explained by young stellar populations. The dEs aresymmetrical and apparently relaxed, with very uniform colours indicatingthat they are dominated by old stars. They generally have exponentiallight profiles, but the brighter galaxies tend to exhibit more cuspedlight distributions, similar to the de Vaucouleurs profiles of brightellipticals. The BCDs have moderately asymmetric light profiles, andparadoxically red colours, possibly indicating an intermediate-agestellar population. They are probably dEs which have undergone bursts ofstar formation in the last few X 10^9^ years, whilst the dIs are afundamentally distinct population. Colour gradients are present in manyof the galaxies, invariably in the sense that the nuclei are redder thanthe surrounding galaxy light. Distribution of the spin vectors of the disk galaxies of the Virgo cluster. I. The catalogue of 310 disk galaxies in the Virgo area.Not Available General study of group membership. II - Determination of nearby groupsWe 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. Dwarf galaxies in the Virgo cluster. II - Photometric techniques and basic dataResults 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. Groups of galaxies within 80 Mpc. II - The catalogue of groups and group membersThis paper gives a catalog of the groups and associations obtained bymeans of a revised hierarchical algorithm applied to a sample of 4143galaxies with diameters larger than 100 arcsec and redshifts smallerthan 6000 km/s. The 264 groups of galaxies obtained in this way (andwhich contain at least three sample galaxies) are listed, with the looseassociations surrounding them and the individual members of eachaggregate as well; moreover, the location of every entity among 13regions corresponding roughly to superclusters is specified. Finally,1729 galaxies belong to the groups, and 466 to the associations, i.e.,the total fraction of galaxies within the various aggregates amounts to53 percent. An infrared study of dwarf galaxies in the Virgo clusterJHK surface photometry is presented for a total of 13 dwarf irregular(dI) and dwarf elliptical (dE) galaxies in the Virgo cluster, drawn fromthe bright end of the dwarf luminosity function. These images are usedto show that the structures defined by the old stellar populationsdiffer significantly between the two types of dwarfs. In particular, thedIs have more flattened and asymmetric stellar light distributions, andthere are no dIs with H-band luminosities or surface brightnesses ashigh as those of the brightest dEs. This is strong evidence against themodels in which dEs are formed by the gas-stripping of dIs. However, atight surface brightness-luminosity relation is found in the H-band,with a scatter of only 0.25 mag, including dwarfs of both types. This ispotentially a very powerful redshift-independent distance indicator. Oneof the galaxies studied, IC 3328, is found to have a prominent nucleuswith significant redder near-IR colors than the remainder of the galaxy. Imaging and spectrophotometry of Virgo cluster irregular galaxiesLarge-aperture spectrophotometric observations and CCD images in theH-alpha and R bands have been obtained for Virgo cluster Magellanic,dwarf, and amorphous irregular galaxies. Although a small number ofVirgo cluster irregulars have optical and H I properties consistent withrecent gas loss, the rate of production of gas-poor irregulars is toolow to account for the large population of Virgo cluster dE galaxies orto explain the deficiency in the number of irregulars relative tospirals. Radial brightness profiles reveal that only NGC 4641 followsthe r exp 1/4 law of classical ellipticals, that four of the galaxieshave exponential brightness distributions, and that one system has anindeterminant profile form. It is shown that the properties of Virgocluster irregular galaxies can be best understood in terms ofenvironmental modifications of normal systems in the circumclusterenvironment and in the cluster core. H I detection survey of a complete magnitude-limited sample of dwarf irregular galaxies in the Virgo Cluster areaNew single-beam Arecibo H I observations of 298 late-type galaxies inthe Virgo Cluster drawn mostly from the new catalog of Binggeli,Sandage, and Tammann (1985) are presented. Two hundred seventeen ofthese constitute a magnitude-limited 'complete sample' of such galaxies,types Sdm through Im and BCD. Sixty-one percent of this 'completesample' was detected, greatly enhancing the store of redshifts and H Imasses for such galaxies in the Virgo Cluster. For detected galaxies,heliocentric velocities, 50 percent profile widths, and single-beamfluxes are presented. For those that escaped detection, upper limits arecomputed to the flux appropriate to the redshift range (-600 to +3000km/s). UBV colors of Virgo cluster irregular galaxiesPhotoelectric UBV aperture photometry is presented for 65 dwarfirregular and morphologically related types of galaxies that areprobable Virgo cluster members. Virgo cluster Irr galaxies cover a widerrange in color than typical samples of field Irr systems, primarily dueto the presence of unusually red Im galaxies in Virgo. The extremelyblue 'blue compact dwarf' and the red amorphous galaxies in Virgo alsostand out on a UBV color-color plot, but the majority of Virgo Irrs areundistinguished in terms of UBV colors. Statistical correlations arefound between colors and location within the cluster. Red Irrs often arein elliptical galaxy rich, dense areas of the cluster, while the blueIrrs roughly follow the spiral distribution pattern. Thus a connectionexists between environment and the properties of Irrs. Simplestatistical tests for ongoing stripping as the source of red Irrs,however, yields null results. HI-observations of galaxies in the Virgo cluster of galaxies. I - The dataNew H I-data for a large number of bright galaxies inside the 10 degradius area of the Virgo cluster of galaxies have been obtained with the100 m radiotelescope at Effelsberg. A total of 234 galaxies was observedfor the first time. Among them, 53 have been detected providing newaccurate radial velocities. Data from the literature have been compiled.Together with the new data, they form a (nearly homogeneous) set of H Iobservations for more than 450 galaxies. Candidate Galaxies for Study of the Local Velocity Field and Distance Scale Using Space Telescope - Part Three - Galaxies in the Virgo Cluster CoreAbstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1985AJ.....90.2006S&db_key=AST 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. A catalog of dwarf galaxies in VirgoA catalog listing the location, apparent angular diameter, type,estimated central light concentration, and estimated brightness of 846dwarf galaxies in a 200-deg-sq region in Virgo is presented. Thegalaxies comprise 634 ellipticals, 137 IC-3475-type galaxies, 73 dwarfspirals and irregulars, and two objects which are jets of normalgalaxies, and were found on nine long-exposure IIIa-J-emulsion platesmade with the 1.2-m-Schmidt telescope at Palomar Observatory from 1971to 1976. Concordances to other catalogs, tables of additionalparameters, maps, graphs, and photographs are provided. The projecteddistributions of normal and dwarf galaxies and the dependence ofapparent luminosity on central light concentration are discussed. It isfound that dwarf ellipticals and IC-3475-type galaxies are probablemembers of the Virgo cluster, while dwarf spirals and possibly dwarfirregulars are not.
Submit a new article