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Публикации по объекту
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.
| A new catalogue of ISM content of normal galaxies
We have compiled a catalogue of the gas content for a sample of 1916galaxies, considered to be a fair representation of ``normality''. Thedefinition of a ``normal'' galaxy adopted in this work implies that wehave purposely excluded from the catalogue galaxies having distortedmorphology (such as interaction bridges, tails or lopsidedness) and/orany signature of peculiar kinematics (such as polar rings,counterrotating disks or other decoupled components). In contrast, wehave included systems hosting active galactic nuclei (AGN) in thecatalogue. This catalogue revises previous compendia on the ISM contentof galaxies published by \citet{bregman} and \citet{casoli}, andcompiles data available in the literature from several small samples ofgalaxies. Masses for warm dust, atomic and molecular gas, as well asX-ray luminosities have been converted to a uniform distance scale takenfrom the Catalogue of Principal Galaxies (PGC). We have used twodifferent normalization factors to explore the variation of the gascontent along the Hubble sequence: the blue luminosity (LB)and the square of linear diameter (D225). Ourcatalogue significantly improves the statistics of previous referencecatalogues and can be used in future studies to define a template ISMcontent for ``normal'' galaxies along the Hubble sequence. The cataloguecan be accessed on-line and is also available at the Centre desDonnées Stellaires (CDS).The catalogue is available in electronic form athttp://dipastro.pd.astro.it/galletta/ismcat and at the CDS via anonymousftp to\ cdsarc.u-strasbg.fr (130.79.128.5) or via\http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/405/5
| Redshift-Distance Survey of Early-Type Galaxies. I. The ENEARc Cluster Sample
This paper presents data on the ENEARc subsample of the larger ENEARsurvey of nearby early-type galaxies. The ENEARc galaxies belong toclusters and were specifically chosen to be used for the construction ofa Dn-σ template. The ENEARc sample includes newmeasurements of spectroscopic and photometric parameters (redshift,velocity dispersion, line index Mg2, and the angular diameterdn), as well as data from the literature. New spectroscopicdata are given for 229 cluster early-type galaxies, and new photometryis presented for 348 objects. Repeat and overlap observations withexternal data sets are used to construct a final merged catalogconsisting of 640 early-type galaxies in 28 clusters. Objectivecriteria, based on catalogs of groups of galaxies derived from completeredshift surveys of the nearby universe, are used to assign galaxies toclusters. In a companion paper, these data are used to construct thetemplate Dn-σ distance relation for early-typegalaxies, which has been used to estimate galaxy distances and derivepeculiar velocities for the ENEAR all-sky sample. Based on observationsat Complejo Astronomico El Leoncito, operated under agreement betweenthe Consejo Nacional de Investigaciones Científicas de laRepública Argentina and the National Universities of La Plata,Córdoba, and San Juan; Cerro Tololo Inter-American Observatory,National Optical Astronomical Observatory, which is operated by theAssociation of Universities for Research in Astronomy, Inc., undercooperative agreement with the National Science Foundation; the EuropeanSouthern Observatory (ESO), partially under the ESO-ON agreement; theFred Lawrence Whipple Observatory; the Observatório do Pico dosDias, operated by the Laboratório Nacional de Astrofísicaand the MDM Observatory at Kitt Peak.
| 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.
| On the dependence of spectroscopic indices of early-type galaxies on age, metallicity and velocity dispersion
We investigate the Mg-σ and -σ relations in asample of 72 early-type galaxies drawn mostly from cluster and groupenvironments using a homogeneous data set which is well calibrated on tothe Lick/IDS system. The small intrinsic scatter in Mg at a givenσ gives upper limits on the spread in age and metallicity of 49and 32 per cent respectively, if the spread is attributed to onequantity only, and if the variations in age and metallicity areuncorrelated. The age/metallicity distribution as inferred from theHβ versus diagnostic diagram reinforces this conclusion,as we find mostly galaxies with large luminosity-weighted ages spanninga range in metallicity. Using Monte Carlo simulations, we show that thegalaxy distribution in the Hβ versus plane cannot bereproduced by a model in which galaxy age is the only parameter drivingthe index-σ relation. In our sample we do not find significantevidence for an anticorrelation of ages and metallicities which wouldkeep the index-σ relations tight while hiding a large spread inage and metallicity. As a result of correlated errors in theage-metallicity plane, a mild age-metallicity anticorrelation cannot becompletely ruled out by the current data. Correcting the line-strengthindices for non-solar abundance ratios, following the recent paper byTrager et al., leads to higher mean metallicity and slightly younger ageestimates while preserving the metallicity sequence. The [Mg/Fe] ratiois mildly correlated with the central velocity dispersion, and rangesfrom [Mg/Fe]=0.05 to 0.3 for galaxies withσ>100kms-1. Under the assumption that there is noage gradient along the index-σ relations, theabundance-ratio-corrected Mg-σ, Fe-σ and Hβ-σrelations give consistent estimates ofΔ[M/H]/Δlogσ~=0.9+/-0.1. The slope of theHβ-σ relation limits a potential age trend as a function ofσ to 2-3Gyr along the sequence.
| 1.65 μm (H-band) surface photometry of galaxies. III. observations of 558 galaxies with the TIRGO 1.5 m telescope
We present near-infrared H-band (1.65 μm ) surface photometry of 558galaxies in the Coma Supercluster and in the Virgo cluster. This dataset, obtained with the Arcetri NICMOS3 camera ARNICA mounted on theGornergrat Infrared Telescope, is aimed at complementing, withobservations of mostly early-type objects, our NIR survey of spiralgalaxies in these regions, presented in previous papers of this series.Magnitudes at the optical radius, total magnitudes, isophotal radii andlight concentration indices are derived. We confirm the existence of apositive correlation between the near-infrared concentration index andthe galaxy H-band luminosity Based on observations taken at TIRGO(Gornergrat, Switzerland). TIRGO is operated by CAISMI-CNR, Arcetri,Firenze, Italy. Tables 1 and 2 are only available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| 1.65 μm (H-band) surface photometry of galaxies. V. Profile decomposition of 1157 galaxies
We present near-infrared H-band (1.65 μm) surface brightness profiledecomposition for 1157 galaxies in five nearby clusters of galaxies:Coma, A1367, Virgo, A262 and Cancer, and in the bridge between Coma andA1367 in the ``Great Wall". The optically selected (mpg≤16.0) sample is representative of all Hubble types, from E to Irr+BCD,except dE and of significantly different environments, spanning fromisolated regions to rich clusters of galaxies. We model the surfacebrightness profiles with a de Vaucouleurs r1/4 law (dV), withan exponential disk law (E), or with a combination of the two (B+D).From the fitted quantities we derive the H band effective surfacebrightness (μe) and radius (re) of each component, theasymptotic magnitude HT and the light concentration indexC31. We find that: i) Less than 50% of the Ellipticalgalaxies have pure dV profiles. The majority of E to Sb galaxies is bestrepresented by a B+D profile. All Scd to BCD galaxies have pureexponential profiles. ii) The type of decomposition is a strong functionof the total H band luminosity (mass), independent of the Hubbleclassification: the fraction of pure exponential decompositionsdecreases with increasing luminosity, that of B+D increases withluminosity. Pure dV profiles are absent in the low luminosity rangeLH<1010 L\odot and become dominantabove 1011 L\odot . Based on observations taken atTIRGO, Gornergrat, Switzerland (operated by CAISMI-CNR, Arcetri,Firenze, Italy) and at the Calar Alto Observatory (operated by theMax-Planck-Institut für Astronomie (Heidelberg) jointly with theSpanish National Commission for Astronomy). Table 2 and Figs. 2, 3, 4are available in their entirety only in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| 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.
| A catalogue of Mg_2 indices of galaxies and globular clusters
We present a catalogue of published absorption-line Mg_2 indices ofgalaxies and globular clusters. The catalogue is maintained up-to-datein the HYPERCAT database. The measurements are listed together with thereferences to the articles where the data were published. A codeddescription of the observations is provided. The catalogue gathers 3541measurements for 1491 objects (galaxies or globular clusters) from 55datasets. Compiled raw data for 1060 galaxies are zero-point correctedand transformed to a homogeneous system. Tables 1, 3, and 4 areavailable in electronic form only at the CDS, Strasbourg, via anonymousftp 130.79.128.5. Table 2 is available both in text and electronic form.
| 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.
| 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.
| Morphological classification and structural parameters for early-type galaxies in the Coma cluster.
We present the results of an isophotal shape analysis of three samplesof galaxies in the Coma cluster. Quantitative morphology, together withstructural and photometric parameters, is given for each galaxy. Specialemphasis has been placed on the detailed classification of early-typegalaxies. The three samples are: i) a sample of 97 early-type galaxiesbrighter than m_B_=17.00 falling within one degree from the center ofthe Coma cluster; these galaxies were observed with CCD cameras, mostlyin good to excellent resolution conditions; ii) a magnitude completesample of 107 galaxies of all morphological types down to m_B_=17.00falling in a circular region of 50arcmin diameter, slightly offcenteredto the North-West of the cluster center; the images for this and thenext sample come from digitized photographic plates; iii) a completecomparison sample of 26 galaxies of all morphological types down tom_R_=16.05 (or m_B_=~17.5), also in a region of 50arcmin diameter, butcentered 2.6degrees West of the cluster center. The reliability of ourmorphological classifications and structural parameters of galaxies,down to the adopted magnitude limits, is assessed by comparing theresults on those galaxies for which we had images taken with differentinstrumentation and/or seeing conditions, and by comparing our resultswith similar data from other observers.
| The fundamental plane of early-type galaxies: stellar populations and mass-to-light ratio.
We analyse the residuals to the fundamental plane (FP) of ellipticalgalaxies as a function of stellar-population indicators; these are basedon the line-strength parameter Mg_2_ and on UBVRI broad-band colors, andare partly derived from new observations. The effect of the stellarpopulations accounts for approximately half the observed variation ofthe mass-to-light ratio responsible for the FP tilt. The residual tiltcan be explained by the contribution of two additional effects: thedependence of the rotational support, and possibly that of the spatialstructure, on the luminosity. We conclude to a constancy of thedynamical-to-stellar mass ratio. This probably extends to globularclusters as well, but the dominant factor would be here the luminositydependence of the structure rather than that of the stellar population.This result also implies a constancy of the fraction of dark matter overall the scalelength covered by stellar systems. Our compilation ofinternal stellar kinematics of galaxies is appended.
| A Catalog of Stellar Velocity Dispersions. II. 1994 Update
A catalog of central velocity dispersion measurements is presented,current through 1993 September. The catalog includes 2474 measurementsof 1563 galaxies. A standard set of 86 galaxies is defined, consistingof galaxies with at least three reliable, concordant measurements. It issuggested that future studies observe some of these standard galaxies sothat different studies can be normalized to a consistent system. Allmeasurements are reduced to a normalized system using these standards.
| 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).
| Galaxy Properties at the North Galactic Pole. I. Photometric Properties on Large Spatial Scales
A two-color study of the galaxies detected on POSS-I in a 289 squaredegree region centered on the North Galactic Pole is presented. We use avariety of mapping techniques to characterize the large-scale spatialdistribution of galaxies. The depth and sample size of this new surveyallows, for the first time, the isolation of large photometricsubsamples of galaxies in high- and low-density environments on thescale of superclusters. Our principal finding is a statisticallysignificant difference between the mean photometric properties of thesesubsamples in the sense that galaxies in the high-density Coma andfilament environments have redder colors and larger concentrationindices than galaxies drawn from low-density interfilament regions.These results are in accord with the known morphology-density relation.Thus, appropriately chosen photometric and morphological parameters, inconcert with a galaxy surface density map, can be used to selectstructures from the projected galaxy distribution which correspond toregions of high density. An illustration of this point is our discoveryof a concentration of blue galaxies identified in our maps near the coreof the Coma cluster. This feature is comprised of early-type galaxieswhich exhibit signs of current or recent star formation. These resultsare predicated on relations between morphological type and photometricparameters derived from APS scans of POSS-I. We therefore discuss theimage calibration procedures used to compile our catalog of physicallysignificant photometric parameters. We demonstrate the morphologicaltype dependence among quantities such as mean color and imageconcentration index, and the lack of such a dependence for mean surfacebrightness.
| 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.
| A revised catalog of CfA1 galaxy groups in the Virgo/Great Attractor flow field
A new identification of groups and clusters in the CfA1 Catalog ofHuchra et al. is presented, using a percolation algorithm to identifydensity enhancements. It is shown that in the resulting catalog,contamination by interlopers is significantly reduced. The Schechterluminosity function is redetermined, including the Malmquist bias.
| The environmental dependence of the Mg2 correlations for elliptical galaxies
New measurements of Mg2 for Coma cluster ellipticals were made in orderto assess the level of any environmental dependence in the fundamentalrelationships of early-type galaxies, with emphasis on ellipticals thatlie in the outer areas of the cluster. The sigma-Mg2 and D-Mg2 relationsare compared for ellipticals located in the inner region of the clusterand in the cluster halo. It is shown that the Mg2 correlations possess asmall environmental effect. From the sigma-Mg2 relation, it is foundthat halo ellipticals have, on average, for a given sigma, Mg2 lower by0.017 +/-0/005 mag compared to inner ellipticals. A similar effect isobserved in the D-Mg2 relation. At a fixed D, ellipticals in the clusterhalo have, on average, Mg2 lower by 0.025 +/-0.008 mag. The possibilitythat the observed offsets in the sigma-Mg2 and D-Mg2 relations arecaused by star formation continuing to a more recent epoch in haloellipticals is also investigated.
| New D-sigma results for Coma cluster ellipticals
A total of 51 ellipticals in the Coma cluster are described in terms ofphotometric diameters (Ds) and velocity dispersions (sigmas) to evaluatethe environmental dependence of the D-sigma relation. Observations aredescribed of the ellipticals in the outer part of the cluster as well assome from the central region based on spectra between 4800-5600 A.Aperture photometry is employed to derive effective diameter, effectivesurface brightness, and photometric diameter. The zero point of theD-sigma relation varies very little from the Coma core, and the outerellipticals possess somewhat larger Ds at fixed values of sigma. TheD-sigma relation is considered a robust indicator with nosurface-brightness bias, and the sample indicates that planes defined bythe Virgo and Coma clusters are not fundamentally different.
| Groups of galaxies in the Center for Astrophysics redshift survey
By applying the Huchra and Geller (1982) objective group identificationalgorithm to the Center for Astrophysics' redshift survey, a catalog of128 groups with three or more members is extracted, and 92 of these areused as a statistical sample. A comparison of the distribution of groupcenters with the distribution of all galaxies in the survey indicatesqualitatively that groups trace the large-scale structure of the region.The physical properties of groups may be related to the details oflarge-scale structure, and it is concluded that differences among groupcatalogs may be due to the properties of large-scale structures andtheir location relative to the survey limits.
| On the relationship between radio emission and optical properties in early-type galaxies
To study the origin of radio activity in early-type galaxies, thepossible dependence of their radio emission on basic optical parameters,such as the absolute magnitude, the central velocity dispersion sigma,and the mean surface brightness mu is explored. A sample of 743 E and SOgalaxies is used which is based on three independent radio surveys ofoptically selected galaxies with virtually complete information onmagnitudes, morphological types, redshift distances, diameters, andradio fluxes. For both E and SO galaxies, only the absolute magnitudeappears to be directly related to the radio activity, while sigma and mudo not. Also, a significant dependence of the apparent flattening onradio power is confirmed for E galaxies. Some relevant implications ofthese results are discussed.
| Cosmology from a galaxy group catalog. I - Binaries
A new, completely objective group-finding algorithm is described andapplied to the CfA redshift catalog. The binary galaxies are isolatedfor analysis. The assumptions underlying the analysis are (1) that lighttraces mass, (2) that our binary galaxy subsets are representative lighttracers, and (3) that the binary orbits are circular. The primary resultof the work is that the resulting bias-free binary catalogs are afunction of the assumed cosmological model. For virtually any inputvalue of Omega(0) in the range 0.01-5.00, there is a reasonablyconsistent interpretation of the CfA survey such that the specifiedvalue of Omega(0) can be derived from the binary sample obtained underthat interpretation. A secondary result is that the higher the inputvalue of Omega(0), the broader the intrinsic distribution in M/L, andhence the less valid the assumption that light traces mass.
| Statistics of galaxy orientations - Morphology and large-scale structure
Using the Uppsala General Catalog of bright galaxies and the northernand southern maps of the Lick counts of galaxies, statistical evidenceof a morphology-orientation effect is found. Major axes of ellipticalgalaxies are preferentially oriented along the large-scale features ofthe Lick maps. However, the orientations of the major axes of spiral andlenticular galaxies show no clear signs of significant nonrandombehavior at a level of less than about one-fifth of the effect seen forellipticals. The angular scale of the detected alignment effect forUppsala ellipticals extends to at least theta of about 2 deg, which at aredshift of z of about 0.02 corresponds to a linear scale of about 2/hMpc.
| A search for features in early-type galaxies
Using data from the CCD surface-photometry survey of Djorgovski (1985),images of 159 galaxies were examined for the presence of dust lanes,incipient stellar disks, bars, shells, and other features that signifydeviations from elliptical symmetry. The sample contained 116 ellipticalgalaxies, 33 SO galaxies and 10 intermediate galaxies. It was found thatforty-two of the ellipticals either definitely or very likely containdust, either in patches or in well-defined lanes or rings. Five of theE/SO galaxies also show possible or definite dust, as do 15 of the SOs.Three of the elliptical galaxies definitely contain stellar disks, withseveral more possible candidates. The presence of these features inalmost half of the elliptical galaxies studied demonstrates thatelliptical galaxies are not the featureless objects they were oncethought to be. Moreover, the finding of weak stellar disks in some ofthem further blurs the distinction between ellipticals and SOs.
| Spectroscopy and photometry of elliptical galaxies. III - UBV aperture photometry, CCD photometry, and magnitude-related parameters
Photoelectric aperture photometry of nearly 2000 individual observationsof 449 elliptical galaxies combined with published measurements usingthe self-consistent UVB color catalog developed by Burstein et al.(1987) are presented. The data are placed on a standard magnitude andcolor system, and 'total' magnitudes and effective diameters are derivedby comparison with the standard elliptical magnitude growth curve. Agraphical representation of the standard growth curve and the residualsfrom it for each galaxy are given, and a new diameter measurement Dn ispresented which can be measured reliably for elliptical galaxies andserves as an accurate distance indicator when combined with centralvelocity dispersion. Individual magnitudes, surface brightnesses,effective diameters, and values of Dn are summarized for each galaxy incatalog form.
| Spectroscopy and photometry of elliptical galaxies. II - The spectroscopic parameters
Radial velocities, velocity dispersions, and Mg line-strength indicesare measured for 469 elliptical galaxies using four telescope/detectorconfigurations. The data have been put on a common scale; the scatter ofrepeat measurements indicates an uncertainty of + or - 10 percent and +or - 0.01 mag for single determinations of sigma and Mg2, respectively.A correction for the change in linear aperture size as a function ofdistance has been derived, and mean corrected values of sigma and Mg2are adopted. The galaxies have been assigned to groups by combining thepresent velocities with those in the redshift catalog of Huchra et al.(1983) and using the algorithm of Huchra and Geller (1982).
| Radio sources in giant E and S0 galaxies
An optically selected sample of 67 giant E and S0 galaxies has beenobserved with radio telescopes of high sensitivity to low-brightnessemission. Correlations between radio emission and galaxy type andbetween radio emission and environment are confirmed, and the fractionof E galaxies with M(B) less than -21.75 that have radio powers Pgreater than 10 to the 23rd W/Hz at 2380 MHz is found to be 0.4 + or -0.1. For all of the 19 sources with P greater than 10 to the 23rd W/Hzthere is evidence on high-resolution maps of continuing centralactivity. Sensitive observations at 151 MHz are used to put limits onthe number of steep-spectrum radio sources, which may be relics of pastactivity in other sample galaxies, more effectively than has previouslybeen possible. Based on the expected lifetime at 151 MHz of radiativelydecaying sources, the time-scale over which typical radio galaxiesremain active is determined to be greater than a few billion yr. This isin conflict with the small linear sizes of many radio sources in thissample, and it is likely that other effects (such as expansion losses inunconfined sources) render the older parts of these objects invisible.
| Taxonomical analysis of superclusters. II - The A1367/Coma supercluster
The nonhierarchical taxonomical method has been applied to a sample of185 galaxies, complete to m not greater than 15, in the A1367/Comaregion. Once the fore- and background galaxies have been identified, theanalysis of the A1367 cluster shows it composed by two gravitationallybound clumps at essentially the same redshift, 6396 km/s and 6562 km/s,respectively. Central Coma is traced by three different groups whosegravitational binding does not appear clearly. However, accepting theunique dynamical entity of Central Coma, some other neighboring groupswould be part of the cluster. In that case, the average radial velocityand dispersion of the Coma cluster would be 7013 and 423 km/s,respectively. The M/L ratios for the groups evidenced by the taxonomyrange from 13 to 170. The missing mass problem only appears when all thegalaxies in the sample are considered as members of a unique dynamicalstructure. The relationship found in other systems between the redshift,the morphological type and the radioemissivity is also present in thesample.
| Radio continuum survey of the Coma/A1367 supercluster. II - 1.5 GHz observations of 396 CGCG galaxies
1.5 GHz VLA radio continuum observations of 396 relatively isolated CGCGgalaxies in the Coma/A1367 supercluster yielded the detection of 95objects. These observations, added to the ones presented in previouspapers, form a complete sample of optically selected objects with m(p)equal to or less than 15.3. Two wide-angle-tailed sources have beenfound in smaller groups within the supercluster.
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