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An X-Ray Atlas of Groups of Galaxies
A search was conducted for a hot intragroup medium in 109 low-redshiftgalaxy groups observed with the ROSAT PSPC. Evidence for diffuse,extended X-ray emission is found in at least 61 groups. Approximatelyone-third of these detections have not been previously reported in theliterature. Most of the groups are detected out to less than half of thevirial radius with ROSAT. Although some spiral-rich groups do contain anintragroup medium, diffuse emission is restricted to groups that containat least one early-type galaxy.
| 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
| 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.
| A new list of extra-galactic radio jets
A catalogue of extra-galactic jets is very useful both in observationaland theoretical studies of active galaxies. With the use of new powerfulradio instruments, the detailed structures of very compact or weak radiosources are investigated observationally and many new radio jets aredetected. In this paper, we give a list of 661 radio sources withdetected radio jets known to us prior to the end of December 2000. Allreferences are collected for the observations of jets in radio, IR,optical, UV and X-ray wave-bands. Table 1 and references to Table 1 areonly available in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/381/757
| A catalogue and analysis of X-ray luminosities of early-type galaxies
We present a catalogue of X-ray luminosities for 401 early-typegalaxies, of which 136 are based on newly analysed ROSAT PSPC pointedobservations. The remaining luminosities are taken from the literatureand converted to a common energy band, spectral model and distancescale. Using this sample we fit the LX:LB relationfor early-type galaxies and find a best-fit slope for the catalogue of~2.2. We demonstrate the influence of group-dominant galaxies on the fitand present evidence that the relation is not well modelled by a singlepower-law fit. We also derive estimates of the contribution to galaxyX-ray luminosities from discrete-sources and conclude that they provideLdscr/LB~=29.5ergs-1LBsolar-1. Wecompare this result with luminosities from our catalogue. Lastly, weexamine the influence of environment on galaxy X-ray luminosity and onthe form of the LX:LB relation. We conclude thatalthough environment undoubtedly affects the X-ray properties ofindividual galaxies, particularly those in the centres of groups andclusters, it does not change the nature of whole populations.
| 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.
| Galactic H i Column Densities toward Quasars and Active Galactic Nuclei
We have determined accurate values of the Galactic neutral hydrogencolumn density, N_H_, toward 220 quasars and active galactic nuclei from21 cm H I measurements made on the 140 Foot Telescope (42.7 m). Accuratevalues of N_H_ have now been obtained for the whole PG bright quasarsample and most quasars that have been observed by ROSAT and the HubbleSpace Telescope through mid-1993. The spectra were corrected for stray21 cm radiation yielding values of NH with a typical uncertainty of 1 x1O^19^ cm^-2^ for high Galactic latitude directions. The H I columndensities will be useful for correcting for interstellar opacity at UVand soft X-ray wavelengths, and for estimating the reddening andextinction toward these objects.
| 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 multiparametric analysis of the Einstein sample of early-type galaxies. 1: Luminosity and ISM parameters
We have conducted bivariate and multivariate statistical analysis ofdata measuring the luminosity and interstellar medium of the Einsteinsample of early-type galaxies (presented by Fabbiano, Kim, &Trinchieri 1992). We find a strong nonlinear correlation betweenLB and LX, with a power-law slope of 1.8 +/- 0.1,steepening to 2.0 +/- if we do not consider the Local Group dwarfgalaxies M32 and NGC 205. Considering only galaxies with logLX less than or equal to 40.5, we instead find a slope of 1.0+/- 0.2 (with or without the Local Group dwarfs). Although E and S0galaxies have consistent slopes for their LB-LXrelationships, the mean values of the distribution functions of bothLX and LX/LB for the S0 galaxies arelower than those for the E galaxies at the 2.8 sigma and 3.5 sigmalevels, respectively. We find clear evidence for a correlation betweenLX and the X-ray color C21, defined by Kim,Fabbiano, & Trinchieri (1992b), which indicates that X-rayluminosity is correlated with the spectral shape below 1 keV in thesense that low-LX systems have relatively large contributionsfrom a soft component compared with high-LX systems. We findevidence from our analysis of the 12 micron IRAS data for our samplethat our S0 sample has excess 12 micron emission compared with the Esample, scaled by their optical luminosities. This may be due toemission from dust heated in star-forming regions in S0 disks. Thisinterpretation is reinforced by the existence of a strongL12-L100 correlation for our S0 sample that is notfound for the E galaxies, and by an analysis of optical-IR colors. Wefind steep slopes for power-law relationships between radio luminosityand optical, X-ray, and far-IR (FIR) properties. This last point arguesthat the presence of an FIR-emitting interstellar medium (ISM) inearly-type galaxies is coupled to their ability to generate nonthermalradio continuum, as previously argued by, e.g., Walsh et al. (1989). Wealso find that, for a given L100, galaxies with largerLX/LB tend to be stronger nonthermal radiosources, as originally suggested by Kim & Fabbiano (1990). We notethat, while LB is most strongly correlated withL6, the total radio luminosity, both LX andLX/LB are more strongly correlated with L6CO, the core radio luminosity. These points support the argument(proposed by Fabbiano, Gioia, & Trinchieri 1989) that radio cores inearly-type galaxies are fueled by the hot ISM.
| Collisions of Ellipticals and the Onset of Fanaroff-Riley Type I Radio Sources
This paper presents the first detailed quantitative study on themorphological characterization of Fanaroff-Riley type I radio source (FRI) host galaxies. The study is based on a two-dimensional isophoteanalysis of the largest sample (44) available so far of FR I hostgalaxies. FR I host galaxies are luminous ellipticals following the sameμ_e_ - r_e_ relation as nonradio ellipticals. However, a largefraction (60%) of FR I host galaxies in the sample show at least two ofthe following morphological peculiarities: (1) isophote twists which arelarger than 15^deg^, (2) isophote displacements which are larger than3.5%, (3) excesses over a de Vaucouleurs law which exceeds 0.10 magarcsec^-2^ at radii beyond r_e_, and (4) one companion galaxy at adistance of less than 50 kpc. These morphological peculiarities are thesignature of a recent strong gravitational collision. The collision,involving a pair of ellipticals, is characterized by (1) a median massratio (companion to FR I host galaxy) of ~0.2, (2) a median projecteddistance of ~23 kpc, (3) a median relative velocity of ~492 km s^-1^,(4) a median age of ~4.0 x 10^7^ years, and (5) a median interactionstrength parameter of 0.19. Collisions between ellipticals which sharethe above mentioned mean properties appear. to be very efficient ingenerating a FR I radio source. Therefore, the scenario of the onset ofan active nucleus by galaxy collisions, well established for veryluminous starbursts and radio galaxies, can also be extended to FR Iradio sources. In a broader scenario, the conclusions of this paper alsoreinforce the idea that collisions between different type of galaxiesgive rise to different type of activity in their nuclei: collisionsinvolving two spirals produce luminous circumnuclear starbursts,collisions involving one elliptical and one spiral generate powerfulFanaroff-Riley type II sources (FR II), which collisions between twoellipticals ignite FR I radio sources.
| ROSAT Observations of Five Poor Galaxy Clusters with Extended Radio Sources
We present the results of deep ROSAT PSPC observations of the poorclusters MKW2, N79-299A, S49-128, S49-132, and S49-140. These poorclusters all contain extended radio sources, generally with a bent,head- tail (HT) morphology. It had been previously thought that HTsshould only be found in rich clusters, which have sufficiently highintracluster medium (ICM) densities and velocity dispersions foreffective ram pressure bending of the radio jets. We have found that theX-ray emission associated with these poor clusters is generally quiteclumpy and asymmetrical. Often, the clumps are associated with subgroupsor individual galaxies, as well as with extended regions around theradio sources. Our results also indicate that there is a continuum ofX-ray properties from poor to rich clusters. In many respects, poorclusters seem to be a low-mass extension of rich clusters. We find thatthese poor clusters have baryon fractions ranging from 1% to 25%. Also,the radio sources within these clusters are probably thermally confinedby the ICM. Although four of our clusters have central X-ray luminosityexcesses, the implied cooling times are longer than a Hubble time. Weinterpret the central X-ray luminosity excesses as unresolved galaxyemission. We hypothesize that these poor clusters have recentlycollapsed out of large, loose clouds of galaxies. We believe that manyof the poor cluster properties are understandable in light of thishypothesis. First, four of these five clusters are embedded withinlarger Zwicky clusters. This may indicate that these large Zwickyclusters act as "incubators" of poor clusters. Second, the observedflat, broad velocity distributions may reflect the velocities associatedwith the larger-scale systems from which we believe that these poorclusters have collapsed. Third, some of these galaxies (such as NGC4061, within N79-299A) show signs of interactions with neighboringgalaxies with large relative velocities (~850 km/s). Fourth, theobserved ICM densities, coupled with velocity distributions which aresuggestive of unrelaxed systems, and the peculiar velocities of theradio galaxies may explain the ram pressure bending of the radio jets inthe HTs.
| Surface photometry of low-luminosity radio galaxies
We present the results on the optical morphology and structure of 25low-luminosity radio galaxies. The radial dependence of parameters likethe surface brightness, ellipticity, center, and position angle of theisophotes is presented to study the properties of the galaxies. Resultsfor individual objects are discussed.
| Why do head-tail sources exist in poor clusters of galaxies?
In a continuing study of nearby (z approximately 0.02-0.05) radiosources in poor clusters of galaxies, we obtained Very Large Array (VLA)observations of four head-tail (HT) sources as probes of theintracluster environments: NGC 742, NGC 1044, NGC 4061, and NGC 7503.NGC 742 apparently has a companion, NGC 741, in the midst of itsextended tail structure. NGC 7503 and NGC 4061 have horseshoe shapesvery similar to the archetypal HT radio galaxy, NGC 1265. Thesestructures are remarkable because the sources are found in poor groups,where both the average density of the intracluster medium (ICM) and thevelocities of the galaxies (thus the ram pressures) are supposedly muchlower than in the rich clusters. Yet these poor groups have narrow-angletail (NAT) sources with the same general morphologies as those in richclusters. There is not much difference between our poor-cluster NATsources and rich-cluster NAT sources, in terms of jet radii ofcurvature, jet opening angles, internal ram pressures within the jets,jet luminosity as a fraction of total source luminosity, and ICMdensities. It appears that the HT phenomenon is remarkably similarbetween the poor clusters and the rich clusters because the localconditions near these sources within their clusters are similar. An ICMdensity typical of that found in poor clusters (approximately10-4/cc and a galaxy velocity typical of the rich clusters(approximately 600 km/s) provide sufficient ICM ram pressure to bendradio jets into NAT morphologies. One explanation for the high relativevelocities of the poor cluster HT galaxies is that these clusters aredynamically young and are still collapsing.
| Head tail sources in poor clusters of galaxies
Head tail sources in poor clusters of galaxies have been studied usingthe VLA at wavelengths of 6 cm and 20 cm. Four sources (NGC 742, NGC1044, NGC 4061 and NGC 7503) were selected from a larger sample fordetailed study. These sources represent an exceptional opportunity tostudy radio jets and their interaction with the cluster environment, indetail, because of their proximity (z ~ 0.02 to 0.04). NGC 4061 and NGC7503 exhibit narrow-angle-tail (NAT) morphologies similar to the classicrich cluster NAT, NGC 1265. NGC 742 has a complex morphology while NGC1044 shows a wide-angle-tail (WAT) morphology. The NAT morphologies arebelieved to be the result of the intracluster medium (ICM) rampressures. The poor cluster NATs are thus remarkable because the poorcluster ICM ram pressure is expected to be much lower, in general, thanin rich clusters. Comparisons of the results of the poor cluster sourceswith those of NGC 1265 should reveal much about the radio source andcluster environment interaction. Most of the parameters calculated suchas jet luminosity as a fraction of total source luminosity, jet openingangle, jet radius of curvature and the ICM density surrounding thesources are quite similar between NGC 1265 and the poor cluster sources.This is a very surprising result and we conclude that ICM densitiestypical of poor clusters and a galaxy relative velocity ~ 1000 km s(-1)provide sufficient ram pressure to bend radio jets into NATmorphologies. Spectral indices and polarization structures have beencompared between the rich and poor clusters and are found to be similaras well. The spectral indices in the poor cluster sources (alpha_ {jet}~ -0.6 and alpha_ {tail} \approx -0.8) are similar to those of the richcluster sources. The fractional polarizations vary from \sim 10% in thejets to \sim 30%$ in the tails similar to the rich cluster HT sources.The magnetic field structure appears to follow the general structureseen in low luminosity radio sources. The overall result is theremarkable similarity between the HT phenomenon in the rich and poorclusters.
| Activity in colliding galaxies
A substantial body of evidence now exists that indicates that there is aconnection between the observed activity in galaxies and the apparentinvolvement of these active galaxies in tidal interactions with othergalaxies. To investigate this phenomenon, we are studying themorphologies and environments of various interacting galaxies showingevidence of activity. In particular, we present here some preliminaryresults from our investigations of the claimed interaction-activityconnection for a sample of colliding radio galaxies endowed with a bentradio jet morphology. We find that the timing of the jet activity isconsistent with a tidal-triggering hypothesis. Our results thereforelend further support to the idea that the galactic activity observed insome 'interactive' galaxies is in fact collision-induced.
| Why Do Head Tail Sources Exist In Poor Clusters Of Galaxies?
In a continuing study of radio sources in poor clusters of galaxies, wehave obtained VLA observations of four head-tail sources as probes ofthe intracluster environments: NGC 742, NGC 1044, NGC 4061, and NGC7503. These sources represent an exceptional opportunity for the studyof radio sources (and radio jets in particular). They are very nearby (z~ 0.02 to 0.04) and thus can be examined in great detail, much like NGC1265 in Perseus. The four sources contain some remarkable structures.NGC 742 apparently has a companion, NGC 741, in the midst of itsextended tail structure. NGC 7503 has a horseshoe shape very similar toNGC 1265. The NGC 4061 source maintains a very linear structure out toequal distances on either side of the galaxy center, where the lobes aresharply `swept back.' These structures are remarkable because thesources are found in poor groups, where both the density of the ICM andthe velocities of the galaxies (thus the ram pressures) are supposedlymuch lower than in the rich clusters. Yet these poor groups havenarrow-angle-tail sources (NATs) with the same general characteristicsas those in rich clusters. Our calculations indicate that there is notmuch difference between the poor cluster sources and NGC 1265 in ICMdensities, jet luminosity as a fraction of total source luminosity, andradii of curvature of the jets. These are very surprising results. Whilethe jets of two sources (NGC 4061 and NGC 7503) appear to have roughlytwice the opening angle of the NGC 1265 jet (which suggests lesserpressure-confinement in poor clusters), most of our evidence pointstoward remarkably similar environments for rich and poor cluster jets.
| An X-ray catalog and atlas of galaxies
An X-ray catalog and atlas of galaxies observed with the EinsteinObservatory imaging instruments (IPC and HRI) are presented. The catalogcomprises 493 galaxies, including targets of pointed observations, andRSA or RC2 galaxies serendipitously included in Einstein fields. A totalof 450 of these galaxies were imaged well within the instrumentalfields, resulting in 238 detections and 2123 sigma upper limits. Theother galaxies were either at the edge of the visible field of view orconfused with other X-ray sources. For these a rough measure of theirX-ray emission is also given. The atlas shows X-ray contour maps ofdetected galaxies superposed on optical photographs and givesazimuthally averaged surface brightness profiles of galaxies detectedwith a high signal-to-noise ratio.
| A finding list of extragalactic radio jets and statistical results
Extragalactic radio jets are a common phenomenon. Many more jets havebeen found since Bridle and Perley (1984) reviewed the subject. In thispaper, we list 276 radio jets known in December 1989. We investigate theratio of jet emission to core flux as a function of core luminosity andcompare it with the fraction of detections of jets given by Bridle andPerley. We find them to be consistent.
| Flux densities at 8400 MHz for a large sample of radio sources
This paper presents 8400-MHz flux densities for 1194 southern radiosources. The sources were selected from the Parkes 2700-MHz Survey toinclude all those stronger than 0.5 Jy at that survey's findingfrequency of 2700 MHz. The new fluxes have an accuracy of about 8percent, corresponding to 0.05 Jy for a typical source. It isanticipated that the data will be useful in defining the high-frequencyradio spectra of many sources as well as in pinpointing objects withwhich to improve the southern, astrometric absolute reference frame.
| Very large array observations of radio-selected dumbbell galaxies
An unbiased sample of radio sources associated with optical dumbbellgalaxies is presented. This sample has been assembled to study therelationship between the radio and optical properties of radio-louddumbbell galaxies. High-quality radio data already exist for a number ofthe sources in the sample, but those sources without good data have beenobserved with the very large array at 20 or 6 cm. These new observationsare described and radio images are presented. Analysis of both the radiostructure of the sources and their radio luminosity has been carriedout, and a comparison is made with the properties of a complete sampleof radio sources associated with single galaxies. Radio sourcesassociated with dumbbell galaxies are found on average to have moredistorted structures than sources associated with single galaxies,demonstrating the influence of the dumbbell dynamics in shaping thelarge-scale structure of the radio sources. It is shown that in therange 10 exp 24 - 10 exp 26 W/Hz at 408 MHz the radio luminosityfunction of dumbbell systems is flatter than that of single-galaxy radiosources, indicating that a close companion may trigger a radio source inthe main galaxy, or alternatively increase the luminosity of an existingradio source.
| Head-tail radio sources in poor clusters of galaxies : VLA Observations and comparisons to rich cluster HTs.
Not Available
| Optical observations of galaxies containing radio jets - A catalog of sources with redshift smaller than 0.15
CCD imaging of 47 radio sources from the Bridle and Perley list ofgalaxies with radio jets is reported. All the observed galaxies arewithin the redshift range z = 0.01 - 0.15 and are constrained inposition to delta - 15 deg or greater. The observations and thereduction procedure are described. Contour maps of all the sources arepresented. Comments on individual galaxies as well as morphologicalfeatures are given.
| A redshift survey toward a proposed void of galaxies suggested by the distribution of Abell clusters
A program of redshift measurements was carried out in a region of thesky in which a relative under-density of Abell clusters had been used toinfer the presence of a large (diameter about 40/h Mpc) void in thegeneral galaxy distribution. The purpose of this study was toinvestigate whether the large-scale distribution of galaxies is tracedby the distribution of rich clusters. Redshifts are presented for 308galaxies in the Zwicky Catalog in a 234 square degree region centered onR.A. about 2h, Decl. about 12 deg of which 229 have been newly measured.These data reveal a pattern of filamentary structure alternating withvoids of characteristic diameter about 25-30/h Mpc, throughout thevolume sampled. While the redshift data reveal an underdensity in thedistribution of galaxies in the general region suggested by the Abellcluster distribution, they do not support the existence there of a 40/hMpc diameter void.
| Interaction versus radio source generation - The properties of radio jet parent galaxies
This paper presents the first systematic survey at optical wavelengthsof galaxies with detected radio jets using CCD imaging. About 50 percentof the sample of low-redshift galaxies with radio jets have a largenearby companion and/or show peculiar optical morphology not detected inisolated ellipticals. Forty-five percent of the objects have a companiongalaxy at a distance shorter than 20 kpc. The multicomponent galaxies inthe sample form a very homogeneous group with little gas and dust, whilethe isolated galaxies have more heterogeneous radio properties, withlarge amounts of gas and warm dust in a large fraction of thesegalaxies. Intrinsic differences between the multicomponent galaxies andthe isolated ones are explained in terms of a different parent galaxyand interaction processes. It is concluded that, at least among galaxieswith radio jets, the amount of gas available and the interactions couldcontrol the energy generation, producing a very well-defined type ofradio source.
| The cluster environments of powerful radio galaxies
Results in the form of the ratio of the spatial cross-correlationamplitude to the autocorrelation amplitude are given as estimates of thelocal galaxy density around about 200 powerful radio sources. Lickgalaxy counts for z of less than 0.1 are extended to z of less than 0.25using deep galaxy samples from UK Schmidt plates. Although thelow-luminosity Fanaroff-Riley class I sources lie in richer clustersthan those of class II, a real scatter in properties is found. Theresults show no statistical evidence for the difference in environmentsuggested to exist between different subclasses of the class II sources.Compact radio sources are found to lie in regions of low galacticdensity.
| Catalogue of unambiguous (Faraday-thin, one-component, spectrum-selected) rotation measures for galaxies and quasars
This all-sky catalogue of unambiguous rotation measure (from aFaraday-thin, one-component, spectrum selection) for 674 galaxies orquasars has been compiled, ordered, and edited from the availableliterature. All the known applications of the RM distribution towardforeground objects in the Galaxy (i.e., magnetic field in 4 nearbyspiral arms and in 4 nearby interstellar magnetic bubbles) have alsobeen catalogued.
| KISO survey for ultraviolet-excess galaxies. VIII
The eighth list and identification charts of the UV-excess galaxieswhich have been detected on the multi-color plates taken with the KisoSchmidt telescope for 10 survey fields are presented. In the sky area ofsome 300 square degrees, 313 objects are cataloged down to thephotographic magnitude of about 17.5.
| Relative velocities of dumbbell galaxies
A systematic study of a morphologically-selected sample of dumbbellgalaxies is presented. A dumbbell/multiple nuclei subclassificationscheme is introduced. The single-object velocity dispersion of dumbbellcomponents in Abell-type clusters is 436 + or - 88 km/sec, which issignificantly smaller than that of normal cluster galaxies and ofmultiple nuclei systems. A detailed analysis of this sample, taking intoaccount various projection effects, indicates that the two components ofdumbbell pairs are physically associated, and probably in circularorbits around a common center. A relative rotation velocity of 1200km/sec at a separation of 40 kpc is indicated. This translates into asingle-object velocity of 600 km, intermediate between the typicalrotation velocity in the central part of a cD galaxy and that in thecluster-at-large. Furthermore, the rotation curve appears to be risingin this radial range. The data provide direct evidence of the existenceof a dark intracluster medium on a scale of 20-50 kpc.
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