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Line emission in the brightest cluster galaxies of the NOAO Fundamental Plane and Sloan Digital Sky Surveys
We examine the optical emission-line properties of brightest clustergalaxies (BCGs) selected from two large, homogeneous data sets. Thefirst is the X-ray selected National Optical Astronomy ObservatoryFundamental Plane Survey (NFPS), and the second is the C4 catalogue ofoptically selected clusters built from the Sloan Digital Sky Survey DataRelease 3 (SDSS DR3). Our goal is to better understand the optical lineemission in BCGs with respect to properties of the galaxy and the hostcluster. Throughout the analysis we compare the line emission of theBCGs to that of a control sample made of the other bright galaxies nearthe cluster centre. Overall, both the NFPS and SDSS show a modestfraction of BCGs with emission lines (~15 per cent). No trend in thefraction of emitting BCGs as a function of galaxy mass or clustervelocity dispersion is found. However, we find that, for those BCGsfound in cooling flow clusters, 71+9-14 haveoptical emission. Furthermore, if we consider only BCGs within 50kpc ofthe X-ray centre of a cooling flow cluster, the emission-line fractionrises further to 100+0-15 per cent. Excluding thecooling flow clusters, only ~10 per cent of BCGs are line emitting,comparable to the control sample of galaxies. We show that the physicalorigin of the emission-line activity varies: in some cases it hasLINER-like line ratios, whereas in others it is a composite ofstar-formation and LINER-like activity. We conclude that the presence ofemission lines in BCGs is directly related to the cooling of X-ray gasat the cluster centre.
| The Centers of Early-Type Galaxies with Hubble Space Telescope. VI. Bimodal Central Surface Brightness Profiles
We combine several HST investigations on the central structure ofearly-type galaxies to generate a large sample of surface photometry.The studies selected were those that used the ``Nuker law'' tocharacterize the inner light distributions of the galaxies. The samplecomprises WFPC1 and WFPC2 V-band observations published earlier by ourgroup, R-band WFPC2 photometry of Rest et al., NICMOS H-band photometryby Ravindranath et al. and Quillen et al., and the brightest clustergalaxy WFPC2 I-band photometry of Laine et al. The distribution of thelogarithmic slopes of the central brightness profiles strongly affirmsthat the central structure of elliptical galaxies withMV<-19 is bimodal, based on both parametric andnonparametric analysis. At the HST resolution limit, most galaxies areeither power-law systems, which have steep cusps in surface brightness,or core systems, which have shallow cusps interior to a steeper envelopebrightness distribution. A rapid transition between the two forms occursover the luminosity range -22
| The Masses of Nuclear Black Holes in Luminous Elliptical Galaxies and Implications for the Space Density of the Most Massive Black Holes
Black hole (BH) masses predicted from the M•-σrelationship conflict with predictions from the M•-Lrelationship for high-luminosity galaxies, such as brightest clustergalaxies (BCGs). The M•-L relationship predicts thatsome BCGs may harbor BHs with M• approaching1010 Msolar, while the M•-σrelationship always predictsM•<3×109 Msolar. We arguethat the M•-L relationship is a plausible descriptionfor galaxies of high luminosity. If the cores in central stellar densityare formed by binary BHs, the inner core cusp radius,rγ, may be an independent witness ofM•. Using central structural parameters derived from alarge sample of early-type galaxies observed by HST, we argue that L issuperior to σ as an indicator of rγ. Further, therγ-M• relationship for 11 core galaxieswith measured M• appears to be consistent with theM•-L relationship for BCGs. BCGs have large coresappropriate for their large luminosities that may be difficult togenerate with the more modest BH masses inferred from theM•-σ relationship. M•~M would beexpected for BCGs, if they were formed in dissipationless mergers, whichshould preserve the ratio of BH to stellar mass, M. This scenarioappears to be consistent with the slow increase in σ with L andthe more rapid increase in effective radii with L seen in BCGs ascompared to less luminous galaxies. If BCGs have large BHs commensuratewith their luminosities, then the local BH mass function forM•>3×109 Msolar would benearly an order of magnitude richer than that inferred from theM•-σ relationship. The volume density of the mostluminous QSOs may favor the M•-L relationship.Based on observations made with the NASA/ESA Hubble Space Telescope,obtained at the Space Telescope Science Institute, which is operated bythe Association of Universities for Research in Astronomy, Inc., underNASA contract NAS 5-26555. These observations are associated with GO andGTO proposals 5236, 5446, 5454, 5512, 5943, 5990, 5999, 6099, 6386,6554, 6587, 6633, 7468, 8683, and 9107.
| X-Ray Thermal Coronae of Galaxies in Hot Clusters: Ubiquity of Embedded Mini-Cooling Cores
We present a systematic investigation of X-ray thermal coronae in 157early-type and 22 late-type galaxies from a survey of 25 hot (kT>3keV), nearby (z<0.05) clusters, based on Chandra archival data. Coolgalactic coronae (kT=0.5-1.1 keV generally) have been found to becommon, >60% in LKs>2L* galaxies.These embedded coronae in hot clusters are generally smaller, lessluminous, and less massive than coronae in poor environments,demonstrating the negative effects of hot cluster environments ongalactic coronae. Nevertheless, these coronae still manage to surviveICM stripping, evaporation, rapid cooling, and powerful AGN outflows,making them a rich source of information about gas stripping,microscopic transport, and feedback processes in the clusterenvironment. Heat conduction across the boundary of the coronae has tobe suppressed by a factor of >~100, which implies that the X-ray gasin early-type galaxies is magnetized and the magnetic field plays animportant role in energy transfer. The luminous, embedded coronae, withhigh central density (0.1-0.4 cm-3), are miniversions ofgroup and cluster cooling cores. As the prevalence of coronae of massivegalaxies implies a long lifetime (>~several Gyr), there must be aheat source inside coronae to offset cooling. While we argue that AGNheating may not generally be the heat source, we conclude that SNheating can be enough as long as the kinetic energy of SNe can beefficiently dissipated. Diffuse thermal coronae have also been detectedin at least 8 of 22 late-type galaxies in our sample. The fraction ofluminous X-ray AGNs (>1041 ergs s-1) is notsmall (~5%) in our sample.
| Unification in the low radio luminosity regime: evidence from optical line emission
We address the question of whether or not the properties of alllow-luminosity flat spectrum radio sources, not just the obvious BL Lacobjects, are consistent with them being the relativistically beamedcounterparts of the low radio luminosity radio galaxies (theFanaroff-Riley type 1, FR I). We have accumulated data on a well-definedsample of low redshift, core-dominated, radio sources all of which haveone-sided core-jet structures seen with very long baselineinterferometry, just like most BL Lac objects. We first compare theemission-line luminosities of the sample of core-dominated radio sourceswith a matched sample of FR I radio galaxies. The emission lines in thecore-dominated objects are on average significantly more luminous thanthose in the comparison sample, inconsistent with the simplest unifiedmodels in which there is no orientation dependence of the line emission.We then compare the properties of our core-dominated sample with thoseof a sample of radio-emitting UGC galaxies selected without bias to corestrength. The core-dominated objects fit well on the UGC correlationbetween line emission and radio core strength found by Verdoes Kleijn etal. The results are not consistent with all the objects participating ina simple unified model in which the observed line emission isorientation independent, though they could fit a single, unified modelprovided that some FR I radio galaxies have emission line regions thatbecome more visible when viewed along the jet axis. However, they areequally consistent with a scenario in which, for the majority ofobjects, beaming has minimal effect on the observed core luminosities ofa large fraction of the FR I population and that intrinsically strongercores simply give rise to stronger emission lines. We conclude that FR Iunification is much more complex than usually portrayed, and modelscombining beaming with an intrinsic relationship between core andemission line strengths need to be explored.
| Hubble Space Telescope Imaging of Brightest Cluster Galaxies
We used the Hubble Space Telescope Wide Field Planetary Camera 2 toobtain I-band images of the centers of 81 brightest cluster galaxies(BCGs), drawn from a volume-limited sample of nearby BCGs. The imagesshow a rich variety of morphological features, including multiple ordouble nuclei, dust, stellar disks, point-source nuclei, and centralsurface brightness depressions. High-resolution surface brightnessprofiles could be inferred for 60 galaxies. Of those, 88% havewell-resolved cores. The relationship between core size and galaxyluminosity for BCGs is indistinguishable from that of Faber et al.(published in 1997, hereafter F97) for galaxies within the sameluminosity range. However, the core sizes of the most luminous BCGs fallbelow the extrapolation of the F97 relationshiprb~L1.15V. A shallower relationship,rb~L0.72V, fits both the BCGs and thecore galaxies presented in F97. Twelve percent of the BCG sample lacks awell-resolved core; all but one of these BCGs have ``power law''profiles. Some of these galaxies have higher luminosities than anypower-law galaxy identified by F97 and have physical upper limits onrb well below the values observed for core galaxies of thesame luminosity. These results support the idea that the centralstructure of early-type galaxies is bimodal in its physical propertiesbut also suggest that there exist high-luminosity galaxies withpower-law profiles (or unusually small cores). The BCGs in the lattercategory tend to fall at the low end of the BCG luminosity function andtend to have low values of the quantity α (the logarithmic slopeof the metric luminosity as a function of radius, at 10 kpc). Sincetheoretical calculations have shown that the luminosities andα-values of BCGs grow with time as a result of accretion, thissuggests a scenario in which elliptical galaxies evolve from power-lawprofiles to core profiles through accretion and merging. This isconsistent with theoretical scenarios that invoke the formation ofmassive black hole binaries during merger events. More generally, theprevalence of large cores in the great majority of BCGs, which arelikely to have experienced several generations of galaxy merging,underscores the role of a mechanism that creates and preserves cores insuch merging events.Based on observations made with the NASA/ESA Hubble Space Telescope,obtained at the Space Telescope Science Institute, which is operated bythe Association of Universities for Research in Astronomy, Inc., underNASA contract NAS 5-26555. These observations are associated withproposal 8683.
| 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.
| 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 peculiar motions of early-type galaxies in two distant regions - II. The spectroscopic data
We present the spectroscopic data for the galaxies studied in the EFARproject, which is designed to measure the properties and peculiarmotions of early-type galaxies in two distant regions. We have obtained1319 spectra of 714 early-type galaxies over 33 observing runs on 10different telescopes. We describe the observations and data reductionsused to measure redshifts, velocity dispersions and the Mgb and Mg_2Lick linestrength indices. Detailed simulations and intercomparison ofthe large number of repeat observations lead to reliable error estimatesfor all quantities. The measurements from different observing runs arecalibrated to a common zero-point or scale before being combined,yielding a total of 706 redshifts, 676 velocity dispersions, 676 Mgblinestrengths and 582 Mg_2 linestrengths. The median estimated errors inthe combined measurements are Delta cz=20 km s^-1, Delta sigma sigma=9.1 per cent, Delta Mgb Mgb=7.2 per cent and Delta Mg_2=0.015 mag.Comparison of our measurements with published data sets shows nosystematic errors in the redshifts or velocity dispersions, and onlysmall zero-point corrections to bring our linestrengths on to thestandard Lick system. We have assigned galaxies to physical clusters byexamining the line-of-sight velocity distributions based on EFAR andZCAT redshifts, together with the projected distributions on the sky. Wederive mean redshifts and velocity dispersions for these clusters, whichwill be used in estimating distances and peculiar velocities and to testfor trends in the galaxy population with cluster mass. The spectroscopicparameters presented here for 706 galaxies combine high-quality data,uniform reduction and measurement procedures, and detailed erroranalysis. They form the largest single set of velocity dispersions andlinestrengths for early-type galaxies published to date.
| 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.
| Kinematics of the Hercules supercluster
The Hercules supercluster consists of the Abell clusters A2147, A2151,and A2152. Previous studies of the kinematics have been confounded bythe difficulty of correctly assigning galaxies to the individualclusters, which are not well separated. Our study has a total of 468available velocities for galaxies in the region, 175 of them new. Thereare 414 galaxies in the supercluster, about three times the number usedin the previous supercluster study. We verify the existence of the threeindividual clusters and compute their individual dynamical parameters.We investigate several techniques for assigning galaxy membership toclusters in this crowded field. We use the KMM mixture-modelingalgorithm to separate the galaxies into clusters; we find that A2152 hasa higher mean velocity than previous studies have reported. A2147 andA2152 also have lower velocity dispersions: 821 and 715 km/s,respectively. The assignment of galaxies to either A2152 or A2147requires velocity and position information. We study the kinematics ofthe supercluster using the two-body formalism of Beers et al. (1982) andconclude that A2147 and A2151 are probably bound to each other and thatthe supercluster as a whole may also be bound. The mass of thesupercluster, if bound, is (7.6 +/- 2.0) 10 exp 15/h M(solar); with thesupercluster luminosity, (1.4 +/- 0.2) 10 exp 13/sq h L(solar), thisyields 0.34 +/- 0.1.
| The peculiar motions of early-type galaxies in two distant regions. III - The photometric data
We present R-band CCD photometry for 776 galaxies observed in the EFARproject. The photometry is compared with photoelectric data, showingthat a common zero-point good to better than 1 per cent and a precisionof 0.03 mag per zero-point have been achieved. We give the circularlyaveraged surface brightness profiles and the photometric parameters ofthe 762 program galaxies, D(n) diameters, half-luminosity radii, totalmagnitudes, and average effective surface brightnesses. More than 80percent of the profiles have a global S/N ratio larger than 300. Theextrapolation needed to derive total magnitudes is less than 10 percentfor 80 percent of the fits. More than 80 percent of the galaxies havemean effective surface brightness larger than the observed skybrightness. In 90 percent of the profiles the estimate of thecontamination of the sky by the galaxy light is less than 1 percent. Wederive total magnitudes and half-luminosity radii to better than 0.15mag and 25 percent, respectively, for 90 percent of our sample. Incontrast, external comparisons show that data in the literature can bestrongly affected by systematic errors due to large extrapolations,small radial range, sky subtraction errors, seeing effects, and the useof a simple R exp 1/4 fit. The resulting errors can easily amount tomore than 0.5 mag in the total magnitudes and 50 percent in thehalf-luminosity radii.
| A 20 Centimeter VLA Survey of Abell Clusters of Galaxies. VII. Detailed Radio Images
We present detailed radio images, and models, obtained with the VeryLarge Array at 20 cm for 199 radio galaxies in Abell clusters ofgalaxies.
| The Peculiar Motions of Early-Type Galaxies in Two Distant Regions. I. Cluster and Galaxy Selection
The EFAR project is a study of 736 candidate elliptical galaxies in 84clusters lying in two regions, toward Hercules-Corona Borealis andPerseus-Pisces-Cetus, at distances cz ~ 6000-15,000 km s^-1^. In thispaper (the first of a series), we present an introduction to the EFARproject and describe in detail the selection of the clusters andgalaxies in our sample. Fundamental data for the galaxies and clustersare given, including accurate new positions for each galaxy andredshifts for each cluster. The galaxy selection functions aredetermined by using diameters measured from Schmidt sky survey imagesfor 2185 galaxies in the cluster fields. Future papers in this serieswill present the spectroscopic and photometric observations of thissample, investigate the properties of the fundamental plane forelliptical galaxies, and determine the large- scale peculiar velocityfields in these two regions of the universe.
| 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.
| 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.
| Optical Spectroscopy of Radio Galaxies in Abell Clusters II. BL Lacs and FR I Unification
As part of our optical spectroscopic study of radio galaxies in Abellclusters, we report a search for BL Lac phenomena in our sample. As anindicator of possible nonthermal activity in the nuclei of our radiogalaxies, we report D(4000), a measure of the 4000 A break, for 190objects. None of the objects in our sample are found which meet thetions for BL Lac objects both for D(4000) and for weakness of emissionlines. We do find 15 objects which have diluted 4000 A breaks[D(4000)<= 1.8], and these are discussed individually. At least fourof them appear to have weak nonthermal activity which may be related tothe BL Lac phenomena. These results appear to be in conflict with thesimplest BL Lac/FR I unification model. Several ways out of this dilemmaare discussed. Perhaps the most likely change in this model is theinclusion of FR II radio galaxies as part of the parent population of BLLac objects.
| A 20 CM Survey of Abell Clusters of Galaxies. V. Optical Observations and Surface Photometry
We present results from a program of optical imaging of 265 radiogalaxies in rich clusters. Using isophotal surface photometry, weinvestigate the optical properties such as the morphology, surface-brightness profiles, surface-brightness/size relationships,ellipticities, and the frequency of nonelliptical isophotes. The resultsare compared to a "normal" nonradio-selected sample of ellipticalgalaxies from the same clusters. The goal is to determine if the parentpopulation of FR I radio galaxies can be distinguished optically fromradio-quiet galaxies. The results of the analysis are that clusterellipticals are a very homogeneous class of objects. The opticalproperties are consistent with a one-parameter family, where the opticalluminosity is the fundamental parameter. In all tests considered, radio-loud FR I galaxies cannot be distinguished optically from radio-quietgalaxies selected from the same environment. The local density of nearbycompanions (<20 kpc) and the frequency of morphological peculiaritiesor tidal interactions are not statistically different between theradio-loud and quiet samples. There is some suggestion from comparisonto published samples of non-cluster radio galaxies, that the clusterenvironment is not condusive to long-lived tidal interactions, and thatsuch events may be more important to galaxy evolution in poor groups andlower density environments. Such events appear to have little influenceon the formation of FR I radio galaxies in rich clusters. The resultsare consistent with the idea that all elliptical galaxies may at sometime (or many times) contain powerful (rR I) radio sources.
| A 20 CM VLA Survey of Abell clusters of galaxies. 4: The radio sample and cluster properties
This is the fourth in a series of papers describing an in depth study ofa large statistical sample of radio galaxies in Abell clusters. Thissample forms the basis of a detailed optical and radio study of the hostgalaxy properties, environments, and evolutionary models for radiogalaxies as a class of objects. In this paper, we examine the radiodetection statistics as a function of cluster morphological type, galaxyrichness, and spatial location within the cluster distribution. Theserelationships are also parameterized as a funtion of radio power. Thespatial distributions of the radio sources as a function of distancefrom the cluster center indicate that radio galaxies are preferentiallylocated at small radii from the center of the cluster potential. This isobserved as a factor of 2-3 excess over that predicted by a King-modelsurface-density distribution. The excess is higher in the upper radiopower bin. This result is easily explained, however, from the spatialdistribution of the brightest galaxies and the relationship betweenradio and optical luminosity. The sample is divided into richnessclasses 0, 1, and 2, according to Abell's criterion. and in two radiopower ranges. While simple counting shows that richer clusters have moreradio galaxies in both radio power bins, when the detections are scaledto the number of galaxies surveyed in each cluster, no significantcorrelations are found. This result implies that the number of radiogalaxies detected simply scales with the number of galaxies surveyed.The higher galaxy density (and presumably higher ICM gas density) inricher clusters does not appear to affect the rate of radio sourceformation. The clusters are divided into Rood-Sastry and Bautz-Morganmorphological types. While it would appear that the more regularclusters have higher radio detection rates, when the classes arenormalized to the number of galaxies, the radio detection rates arefound to be identical regardless of cluster morphology. In conclusion,it is the optical properties of the host galaxy which most influenceboth the radio detection rate and the radio source properties. Thecluster properties, galaxy density, and spatial location of the galaxydo not significantly affect the observed radio statistics.
| Brightest cluster galaxies as standard candles
We investigate the use of brightest cluster galaxies (BCGs) as standardcandles for measuring galaxy peculiar velocities on large scales. Wehave obtained precise large-format CCD surface photometry and redshiftsfor an all-sky, volume-limited (z less than or = 0.05) sample of 199BCG. We reinvestigate the Hoessel (1980) relationship between the metricluminosity, Lm, within the central 10 kpc/h of the BCGs andthe logarithmic slope of the surface brightness profile, alpha. TheLm-alpha relationship reduces the cosmic scatter inLm from 0.327 mag to 0.244 mag, yielding a typical distanceaccuracy of 17% per BCG. Residuals about the Lm-alpharelationship are independent of BCG luminosity, BCG B - Rccolor, BCG location within the host cluster, and richness of the hostcluster. The metric luminosity is independent of cluster richness evenbefore correcting for its dependence on alpha, which provides furtherevidence for the unique nature of the BCG luminosity function. Indeed,the BCG luminosity function, both before and after application of thealpha-correction, is consistent with a single Gaussian distribution.Half the BCGs in the sample show some evidence of small color gradientsas a function of radius within their central 50 kpc/h regions but withalmost equal numbers becoming redder as becoming bluer. However, withthe central 10 kpc/h the colors are remarkably constant -- the mean B -Rc color is 1.51 with a dispersion of only 0.06 mag. Thenarrow photometric and color distributions of the BCGs, the lack of'second-parameter' effects, as well as the unique rich clusterenvironment of BCGs, argue that BCGs are the most homogeneous distanceindicators presently available for large-scale structure research.
| Optical spectroscopy of radio galaxies in Abell clusters. 1: Redshifts and emission-line properties
We present results of a program of optical spectroscopy of radiogalaxies in rich clusters. Redshifts are reported for 268 radio galaxiesor close companions in Abell clusters and 36 objects which turned out tobe foreground or background objects. Absolute line strengths are alsoreported for the 3727 A (O II) line and the (N II)/H alpha complex. Wefind no evidence that the radio activity in our sample of mostly FR Iradio galaxies is associated with emission-line luminosities above thosefound in normal galaxies of the same absolute magnitude and opticaltype. We also find that the radial velocity differences between radiogalaxies and the cluster mean seem mainly to be a function of galaxyabsolute magnitude rather than radio properties.
| Galaxy structures in the Hercules region
216 redshifts have been obtained in a region of 981 sq deg south of theHercules supercluster. 172 of these redshifts are of galaxies withmpg less than or equal to 15.1, 110 of which had no previousvelocity measurement. 44 new redshifts are of galaxies fainter thanmpg = 15.1. With these new data we have been able to define asample in a vast region (approximately 1700 sq deg) around Herculeslimited to mpg less than or equal to 15.1 with a velocitycompleteness of 81.5%. 189 galaxies have been morphologically classifiedso that all galaxies in the sample with known velocity now also haveknown morphology. The magnitude limited sample, including 556 galaxies,is then used to identify and describe galaxy structures in the region.We find that the overdense volume is small, that its overall appearanceis that of a coral branch floating in a sea of nothing and that earlyand late type galaxies defined different structures.
| Photoelectric and CCD photometry of E and S0 galaxies
We present BR photoelectric photometry for 352 E and S0 galaxies thatare part of a large survey of the properties and peculiar motions ofgalaxies in distant clusters. Repeat measurements show our internalerrors to be 2-3 percent in B and R and 1-2 percent in B-R. Comparisonsof BR and BVR reductions for 10 galaxies also observed in V show smallsystematic errors due to differences between the spectral energydistributions of stars and galaxies. External comparisons with B-Vcolors in the literature confirm that these colors are good to 1percent. We also describe R-band CCD observations for 95 of the galaxiesand place these on a BR photometric system for photoelectric and CCDphotomerry, with a common zero-point good to better than 1 percent. Wefind the rms precision of both our photoelectric and CCD R magnitudes tobe 2-3 percent for galaxies as faint as R = 15.
| A 20 CM VLA survey of Abell clusters of galaxies. I - Distance class of not greater than 3 clusters
Nearby Abell clusters of distance class of not greater than 3 arestudied based on 20-cm VLA observations, Westerbork Synthesis RadioTelescope results, and Einstein Observatory X-ray data. No significantcorrelation is found between the 20-cm radio power and X-ray luminosity,and no evidence is found that regular-type clusters are statisticallymore likely to be radio loud than irregular-type clusters. A weakcorrelation is noted between X-ray-cooling mass-accretion rates andradio powers for central dominant galaxies in cooling-flow clusters,suggesting that either cooling accretion directly fuels the centralengine and/or cooling flows strongly interact with the radio plasma.
| The structure of brightest cluster members. III - cD envelopes
Single-band photographic and CCD surface photometry is used to determineluminosity and structural properties of the extended, faint envelopesaround 27 cD galaxies. The distribution of envelope light follows asimilar slope as other cluster luminous material. Several correlationsbetween envelope luminosity and cluster properties substantiatearguments for the dynamical formation of envelopes. A correlationbetween underlying galaxy luminosity and envelope luminosity implies aparallel but separate process between the growth of the first-rankedelliptical by mergers and cD envelope formation. Strong color gradients,in particular the blue disk colors as predicted by other studies, werenot found upon examination of multicolor profiles for three cDenvelopes.
| The structure of brightest cluster members. II - Mergers
Surface photometry of 342 bright elliptical galaxies in 103 clusters isanalyzed for evidence of mergers. Structural differences betweenbrightest cluster members (BCMs) and normal ellipticals can besummarized as having enlarged characteristic radii and shallow profileslopes (beta greater than -1.7). Profile morphology criteria for theelliptical types gE, D, and cD are outlined. Comparison of observationswith numerical simulations of mergers strongly suggests a past historyof dynamical growth for BCMs. Weak correlations of global clusterproperties to BCMs supports the hypothesis proposed by Merritt (1984)that mergers are important in early subgroups before virialization andformation of a cluster identity.
| The Distance to the Hercules Supercluster. II. Application of Tertiary Indicators and an Estimate of the Hubble Constant
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1986ApJS...62..283B&db_key=AST
| The distance to the Hercules supercluster. I - Basic data for 220 galaxies in CGCG field 108.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1986ApJS...62..255B&db_key=AST
| Catalogue of central velocity dispersions of galaxies
A total of 880 measurements of velocity dispersions for 546 galaxieshave been compiled. These data have been used to look for biasesintroduced by the observational techniques and reduction procedures. Twomain effects have been corrected for, due to the reference and the slitwidth. A catalog of homogeneous data has been compiled, where the rawdata are corrected for these effects.
| The X-ray emission from the Hercules supercluster
Results are reported for Ariel 5 X-ray observations of Zwicky clusterNo. 7, a supercluster containing the three rich Abell clusters ofgalaxies A2151 (the Hercules cluster), A2152, and A2147. Six detectionswith the Sky Survey Instrument are shown to be consistent with thepresence of a single source, designated A1600+16, having a steadyintensity level of about 0.7 Ariel count/sec. This source is tentativelyidentified with cluster A2147, and the X-ray, optical, and radioproperties of A2147 and A2151 are compared. It is suggested that theobserved X-rays originate from a hot intracluster gas.
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