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|A CCD Photometric and Morphological Study of the Extended Halo and Filaments of ESO 383-45: A Galaxy Undergoing Ram Pressure Stripping, or a Tidal Merger Remnant?|
We present BV CCD surface photometry, profiles, and images of the galaxyESO 383-45, together with other galaxies in the same CCD field. We alsopresent a B-V color map of the field and images of the galaxies enhancedby self-correlation of pixel values and by digital ``unsharp masking.''The extended halo and system of filaments of ESO 383-45 are seenclearly. We suggest that the evidence (radio jets and their curvatureand areas of diffuse optical emission) of a dense intergalactic medium(IGM) in this field toward the center of the IC 4296 cluster mayindicate that the galaxy ESO 383-45 is still undergoing ram pressurestripping of its gas, forming stars in the filaments, while the centralgalaxy has evolved to have a lenticular morphology. On the other hand,there are ``knots'' in the filaments that look like tidal dwarf galaxiesin formation, and previous simulations of the tidal interaction of twodisk galaxies have produced galaxies that can resemble ESO 383-45 fromcertain viewing angles. Other galaxies in the field appear to lie beyondthe IC 4296 cluster and may be part of sheets of galaxies previouslyidentified as connecting the Abell clusters of the Shapley supercluster.We identify many uncataloged faint extended objects that may representbackground clusters of galaxies or knots (possibly of star formation)associated with the filaments and diffuse IGM of ESO 383-45. The presentwork represents the first multicolor surface photometric study for allof these galaxies, and only ESO 383-45 has previously been studiedmorphologically, using digitally co-added Schmidt plates obtained bysome of the authors.
|FLASH redshift survey - I. Observations and catalogue|
The FLAIR Shapley-Hydra (FLASH) redshift survey catalogue consists of4613 galaxies brighter than bJ= 16.7 (corrected for Galacticextinction) over a 700-deg2 region of sky in the generaldirection of the Local Group motion. The survey region is a70°× 10° strip spanning the sky from the ShapleySupercluster to the Hydra cluster, and contains 3141 galaxies withmeasured redshifts. Designed to explore the effect of the galaxyconcentrations in this direction (in particular the Supergalactic planeand the Shapley Supercluster) upon the Local Group motion, the 68 percent completeness allows us to sample the large-scale structure betterthan similar sparsely-sampled surveys. The survey region does notoverlap with the areas covered by ongoing wide-angle (Sloan or 2dF)complete redshift surveys. In this paper, the first in a series, wedescribe the observation and data reduction procedures, the analysis forthe redshift errors and survey completeness, and present the surveydata.
|Globular Cluster Systems in Four Brightest Cluster Galaxies: A262, A3560, A3565, and A3742|
We have used deep I-band (F814W) images from the Hubble Space Telescopearchive to study the globular cluster systems around the brightestcluster galaxies (BCGs) in A262, A3560, A3565, and A3742. Three of theseBCGs have inner dust lanes and peculiar structural features thatindicate past histories of low-level interaction and accretion. The deepI-band WFPC2 images have photometric limits that, for all four galaxies,reach near or just beyond the globular cluster luminosity function(GCLF) turnover point. Their specific frequencies are 8.24+/-1.65,4.66+/-0.93, 2.58+/-0.52, and 2.62+/-0.52, respectively, all within afactor of 2 of the normal range for giant elliptical galaxies. We obtainnew estimates of the GCLF turnover magnitudes, which are shown to beconsistent with an adopted Hubble constant of H0~=70 kms-1 Mpc-1 on the ``Hubble diagram'' of GCLFturnover apparent magnitude versus redshift, on a distance scale wherethe fundamental GCLF calibrator E galaxies (M87 and others) in Virgo areat d=16 Mpc. Based on observations with the NASA/ESA Hubble SpaceTelescope, obtained at the Space Telescope Science Institute, which isoperated by the Association of Universities for Research in Astronomy,Inc., under NASA contract NAS 5-26555. These observations are associatedwith proposal ID 5910.
|Nearby Optical Galaxies: Selection of the Sample and Identification of Groups|
In 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.
|Two Galaxy Clusters: A3565 and A3560|
We report 102 new redshifts and magnitudes for a sample of galaxies toR_F~15.5 mag in a 2.17dx2.17d region centered on the galaxy IC 4296, themost luminous member of the A3565 Cluster. Up to the limiting magnitude,we find 29 cluster members and measure a velocity dispersion ofsigma=228 km s^-1. The estimated total mass for this system is~3.0x10^13 h^-1 M_solar [where h=H_0/(100 km s^-1 Mpc^-1)], and itsdynamical properties are quite typical of poor clusters presenting X-rayemission. We also find that galaxies with absorption lines are moreconcentrated toward the center of the cluster, while systems withemission lines are mainly located in the outer parts. The small velocitydispersion of the cluster, coupled with the known presence of aninteracting pair of galaxies, and the large extent of the brightestcluster galaxy, could indicate that galaxy formation through mergers maystill be underway in this system. The surveyed region also containsgalaxies belonging to the Shapley concentration cluster A3560. Within30' of the cluster center, we detect 32 galaxies, for which we measure avelocity dispersion of 588 km s^-1 and a mass of ~2x10^14 h^-1 M_solar.However, because our sample is restricted to galaxies brighter than M^*,these values should be considered only as rough estimates.
|Galaxy coordinates. II. Accurate equatorial coordinates for 17298 galaxies|
Using images of the Digitized Sky Survey we measured coodinates for17298 galaxies having poorly defined coordinates. As a control, wemeasured with the same method 1522 galaxies having accurate coordinates.The comparison with our own measurements shows that the accuracy of themethod is about 6 arcsec on each axis (RA and DEC).
|Total magnitude, radius, colour indices, colour gradients and photometric type of galaxies|
We present a catalogue of aperture photometry of galaxies, in UBVRI,assembled from three different origins: (i) an update of the catalogueof Buta et al. (1995) (ii) published photometric profiles and (iii)aperture photometry performed on CCD images. We explored different setsof growth curves to fit these data: (i) The Sersic law, (ii) The net ofgrowth curves used for the preparation of the RC3 and (iii) A linearinterpolation between the de Vaucouleurs (r(1/4) ) and exponential laws.Finally we adopted the latter solution. Fitting these growth curves, wederive (1) the total magnitude, (2) the effective radius, (3) the colourindices and (4) gradients and (5) the photometric type of 5169 galaxies.The photometric type is defined to statistically match the revisedmorphologic type and parametrizes the shape of the growth curve. It iscoded from -9, for very concentrated galaxies, to +10, for diffusegalaxies. Based in part on observations collected at the Haute-ProvenceObservatory.
|Integrated photoelectric magnitudes and color indices of bright galaxies in the Johnson UBV system|
The photoelectric total magnitudes and color indices published in theThird Reference Catalogue of Bright Galaxies (RC3) are based on ananalysis of approximately equals 26,000 B, 25,000 B-V, and 17,000 U-Bmultiaperture measurements available up to mid 1987 from nearly 350sources. This paper provides the full details of the analysis andestimates of internal and external errors in the parameters. Thederivation of the parameters is based on techniques described by theVaucouleurs & Corwin (1977) whereby photoelectric multiaperture dataare fitted by mean Hubble-type-dependent curves which describe theintegral of the B-band flux and the typical B-V and U-B integrated colorgradients. A sophisticated analysis of the residuals of thesemeasurements from the curves was made to allow for the random andsystematic errors that effect such data. The result is a homogeneous setof total magnitudes BTA total colors(B-V)T and (U-B)T, and effective colors(B-V)e and (U-B)e for more than 3000 brightgalaxies in RC3.
|The structure of the halo of the giant elliptical galaxy IC 4296|
Images of the giant elliptical galaxy IC 4296, and the wider fieldaround it, are presented at differing contrast levels. The data comesfrom a co-added array of digitized Schmidt plates. The isophote map ofIC 4296 suggests that the outer parts of the halo are elongated towardsthe nearby spiral IC 4299, indicative of a tidal interaction between thetwo galaxies. This is confirmed from the changes on position angle withradius of ellipses fitted to the iosphotes of IC 4296. The ellipticityof the isophotes also increases at the lowest surface brightnesses. Thesurface brightness profile (traced to less than 2% of the sky level) isfound to be well represented by an R1/4 law in the innerregions but contains less light than this law suggests in the outermostregions investigated, suggesting that the outer regions of IC 4296 aretidally limited by IC 4299. On the high contrast print the halo has adiameter of approximately 0.16 Mpc. Possible optical emission isdetected in the directions of peak radio emission asociated with theradio lobes of IC 4296. However, brighter diffuse optical emission isdetected E of IC 4296 in a direction not associtated with any part ofthe radio source, presumably representing intergalctic media (IGM) ofthe IC 4296 group.
|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.
|I-band CCD surface photometry of spiral galaxies in 16 nearby clusters|
Results of I-band CCD surface photometry for 284 spiral galaxies in 16clusters in the redshift range from 3000 to 11,000 km/s are presented.Various effects on surface photometry are discussed, and the relevantcorrections are outlined.
|Groups of galaxies within 80 Mpc. II - The catalogue of groups and group members|
This 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.
|The supergalactic plane redshift survey|
Redshift measurements, about 1000 of which are new, are presented for1314 galaxies in a survey toward the apex of the large-scale streamingflow for ellipticals. The velocity histogram shows that the excess ingalaxy number counts in this area is due to a substantial concentrationof galaxies with discrete peaks at V about 3000 km/s and V about 4500km/s. After correction for the sampling function, the centroid of thedensity distribution is found to be near V about 4500 km/s.Normalization to the more extensive SSRS survey, which was selected bythe same criteria, shows that the region studied contains a considerableoverdensity of galaxies from 2000 to 6000 km/s. This result is in goodagreement with the 'great attractor' model suggested by Lynden-Bell etal. (1988) which attributes the peculiar motions of elliptical galaxiesover a large region of space to an extensive mass overdensity whichincludes the Hydra-Centaurus and Pavo-Indus superclusters. The centroidof the density enhancement is also consistent with new data by Dresslerand Faber (1990) of peculiar motions of elliptical and spiral galaxies,both of which show a zero crossing of the Hubble line at approximately4500-5000 km/s.
|Southern Galaxy Catalogue.|
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