Contents
Images
Upload your image
DSS Images Other Images
Related articles
The scaling relation of early-type galaxies in clusters. II. Spectroscopic data for galaxies in eight nearby clusters
Aims.We present low and intermediate resolution spectroscopic datacollected for 152 early type galaxies in 8 nearby clusters with z ≤0.10. Methods: .We use low resolution data to produce the redshiftand the K-correction for each galaxy, as well as to give their overallspectral energy distribution and some spectral indicators, including the4000 Å break, the Mg2 strength and the NaD equivalent width. Wehave also obtained higher resolution data for early type galaxies inthree of the clusters, to determine their central velocity dispersion. Results: .The effect of the resolution on the measured parametersis discussed. Conclusions: .A new accurate systemic redshift andvelocity dispersion is presented for four of the surveyed clusters, A98,A3125, A3330, and DC2103-39. We have found that the K-correction valuesfor E/S0 bright galaxies in the given nearby clusters are very similar.We also find that the distribution of the line indicators significantlydiffers from cluster to cluster.
| Variable Object in Bootes
IAUC 8518 available at Central Bureau for Astronomical Telegrams.
| Black Hole Masses and Host Galaxy Evolution of Radio-Loud Active Galactic Nuclei
We report stellar velocity dispersion measurements for a sample of 28active galactic nucleus (AGN) host galaxies, including our previouswork. Using the mass-dispersion (M•-σ) and thefundamental plane relations, we estimate the black hole mass for asample of 66 BL Lac objects and investigate the role of black hole massin the energetics of BL Lac objects. The black hole mass range fordifferent BL Lac spectral types is similar,107
| The scaling relations of early-type galaxies in clusters. I. Surface photometry in seven nearby clusters
This is the first paper of a series investigating the scaling relationsof early-type galaxies in clusters. Here we illustrate the multi-bandimagery and the image reduction and calibration procedures relative tothe whole sample of 22 clusters at 0.05 <~ z <~ 0.25. We alsopresent detailed surface photometry of 312 early-type galaxies in 7clusters in the first redshift bin, z ≈0.025-0.075. We give for eachgalaxy the complete set of luminosity and geometrical profiles, and anumber of global, photometric and morphological parameters. They havebeen evaluated taking into account the effects of seeing. Internalconsistency checks and comparisons with data in the literature confirmthe quality of our analysis. These data, together with the spectroscopicones presented in the second paper of the series, will provide the localcalibration of the scaling relations. Tables 6, 7a-7g, the colour printsof Figs. 12a-12g AND Figs. 13a-13g are only available in electronic format http://www.edpsciences.com. The complete set of profiles is availableupon request from the authors. Tables 7a-7g are also available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.188.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/387/26
| Structure of the Clusters of Galaxies A 2634, A 1983, and DC 0428-53
The hierarchical and dynamical structure of three clusters of galaxies,A 2634, A 1983, and DC 0428-53, is investigated. Based on their example,we can say that the central cD galaxies play the leading role inclusters, affecting the course of their evolution. Radio and x-raygalaxies are not always part of the substructure. The morphologicalcomposition of various hierarchical subgroups depends on the stage ofevolution. Clusters have a tendency to be oriented in the directiontoward the nearest neighbor.
| 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.
| 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.
| Kinematical models of double radio sources and the unified scheme. II. The database
A large database of 1038 edge-brightened double radio sources has beencollected from the literature with special emphasis on finding the bestradio map for each source and on obtaining flux information of theextended radio lobes and the core component. The data are collected withtwo goals in mind. The first goal is to provide the data for ourstatistical study of double radio source symmetry and the unified schemein the theoretical framework of \cite[Baryshev & Teerikorpi (1995,Paper I)]{bar:tee}. It is also believed that the data are useful to theresearch community and thus extensive data are given in tabular form.Tables 1 and 2 are only available 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
| 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.
| 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.
| 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.
| Radio sources observed with the Culgoora circular array
Presented is a final updated and recalibrated list of sources that wereobserved with the Culgoora circular array in the interval 1970-1984. Thepresent list contains all the sources that were contained in theCulgoora-1, 2, 3 Lists plus additional sources resulting from a surveyof 353 Abell clusters of galaxies. The electronic version of theCulgoora List, with appropriate documentation, is available from theEinstein On-Line Service.
| The ROSAT AGN content of the 87GB 5 GHz survey: bulk properties of previously optically identified sources.
The cross-correlation of the source list from the ROSAT All-Sky Surveywith the 5 GHz Green Bank survey yields a list of 2127 objects. Abouttwo thirds of them are optically unidentified. The majority of theobjects with known optical counterparts are quasars and radio galaxies,most of them detected in X-rays for the first time. In this paper wepresent a list of the previously optically identified objects with theirmain characteristics and discuss their general (bulk) properties. Wefind strong correlations between luminosities in the radio, optical, andX-ray bands which differ for quasars and radio galaxies. The fraction offlat radio spectrum sources increases with redshift and ~ 95% of allsources above z = 2 are of that type. In the relatively large group ofblazars, radio selected BL Lacs and highly polarized quasars show verysimilar properties while X-ray selected BL Lacs have markedly differentX-ray to radio flux ratios. The sample is large enough and ofsufficiently high quality to reveal clearly various detection biases andselection effects which strongly influence the physical interpretationof the correlations. Radio follow - up observations for thedetermination of the morphological and spectral properties as well asenvironmental conditions are needed for a statistically reliable studyof the sample. The very large group of sources with low radio fluxesremains to be optically identified.
| 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.
| On the redshift-apparent size diagram of double radio sources
We review the data on the angular sizes of double radio sources. Thereis a positive correlation between the true radio source size and radiopower among low-luminosity radio galaxies. This may be partly explainedthrough sample selection effects. There is a negative correlationbetween radio size and power among high luminosity radio galaxies andall quasars. It follows the constant total energy envelope closely.There is no significant difference between the radio sizes of radiogalaxies and quasars of the same luminosity. However, it is possiblethat real differences in the radio sizes of the two populations arehidden by selection effects in our sample. The angular size-redshiftdiagram shows a deficiency of large radio sources at high redshiftswhich is fully explained by the above-mentioned negative correlationwithout need for cosmic evolution of radio source size. However, thepossibility of some cosmic evolution is not totally ruled out by thedata.
| A list of some corrections to Zwicky's Catalogue of Galaxies and Clusters of Galaxies
Not Available
| A dynamical analysis of twelve clusters of galaxies
Four-hundred-twenty-eight new redshift measurements for galaxies in thevicinity of 12 Abell clusters are presented. The data are supplementedby previously published data with 3 deg of each cluster center. Thecluster selection, the variety of telescopes and instrumentation used toobtain the galaxy redshifts, and the available X-ray observations arediscussed. Each cluster is exmained in some detail, with the emphasisplaced on the nature of the observed velocity distributions. Robust andresistant estimators of the velocity location and scale are applied inorder to quantify these distributions. The offset in velocity space ofthe dominant galaxy in each cluster or subcluster is considered withrespect to the central location in the velocity space of the cluster asa whole, and the physical implications of significant offsets found inseveral clusters are discussed. Dynamical estimates of the masses ofclusters and/or subclusters are obtained; for clearly bimodal systems,two-body models are employed to specify their likely dynamical state.
| UGC galaxies stronger than 25 mJy at 4.85 GHz
UGC galaxies in the declination band +5 to +75 deg were identified byposition coincidence with radio sources stronger than 25 mJy on theGreen Bank 4.85 GHz sky maps. Candidate identifications were confirmedor rejected with the aid of published aperture-synthesis maps and new4.86 GHz VLA maps having 15 or 18 arcsec resolution, resulting in asample of 347 nearby radio galaxies plus five new quasar-galaxy pairs.The radio energy sources in UGC galaxies were classified as 'starbursts'or 'monsters' on the basis of their infrared-radio flux ratios, infraredspectral indices, and radio morphologies. The rms scatter in thelogarithmic infrared-radio ratio q is not more than 0.16 for starburstgalaxies selected at 4.85 GHz. Radio spectral indices were obtained fornearly all of the UGC galaxies, and S0 galaxies account for adisproportionate share of the compact flat-spectrum (alpha less than0.5) radio sources. The extended radio jets and lobes produced bymonsters are preferentially, but not exclusively, aligned within about30 deg of the optical minor axes of their host galaxies. The tendencytoward minor-axis ejection appears to be independent of radio-sourcesize and is strongest for elliptical galaxies.
| 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 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.
| Radio identifications of UGC galaxies - Starbursts and monsters
New and previously published observational data on galaxies withdeclination less than +82 deg from the Uppsala General Catalog (Nilson,1973) are compiled in extensive tables and characterized in detail.Optical positions are confirmed by measurement of Palomar Sky Survey Oprints, and radio identifications for 176 galaxies are made on the basisof 1.4-GHz Green Bank sky maps or 1.49-GHz observations obtained withthe C configuration of the VLA in November-December 1986; contour mapsbased on the latter observations are provided. Radio-selected andIR-selected galaxy populations are found to be similar (and distinctfrom optically selected populations), and three radio/IR criteria aredeveloped to distinguish galaxies powered by starbursts from those withsupermassive black holes or other 'monster' energy sources.
| 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.
| New evidence for galaxy luminosity evolution
Near-infrared photometry for 61 elliptical galaxies is used withpreviously published data to demonstrate that little or no colorevolution is observed at infrared wavelengths, while galaxies near z = 1are brighter than those at low redshift. Optically selected galaxies arecompared with radio galaxies, and no differences in infrared propertiesare found. Evolution of a stellar population with an initial massfunction similar to that observed in the solar neighborhood coupled witha value for q0 near 0.5 provides the best fit to the color andluminosity data.
| Weak nuclei of powerful radio sources - Spectra and polarizations
Observations are presented of the spectra and polarizations of the weakcores of extended extragalactic radio sources. These cores typicallyshow peaked spectra, and, below a luminosity of about 10 to the 26thW/Hz, are unpolarized with 90 percent confidence upper limits of about0.6 percent. In both of these properties the cores distinguishthemselves as a class from strong, active compact sources, such as thosethat show superluminal motion. The relation between these weak cores andother classes of compact sources and the implications for 'unified'models based on relativistic beaming are briefly discussed. It isconcluded that there is a distinct class of compact objects, differentfrom relativistic jets, which appear in the form of separate weak ordominant cores, or as the base component in superluminal jets.
| A correlation between ellipticity and core-strength in extended radio galaxies
It is shown that in the case of extended radio sources a correlationexists between the fraction of the radio flux retained in the corecomponent and the ellipticity of the underlying galaxy. The correlationis in the sense that stronger cores occur in flatter galaxies. It wouldseem that there exists a class of intrinsically rounder, redder, massiveellipticals with larger velocity dispersions and metallicities, that canform extended radio sources more efficiently. Thus the occurrence of aradio source appears to be related to the dynamical and chemicalevolution of the Galaxy.
| Flickering of extragalactic radio sources
Variability on time scales of 2-20 days, called 'flickering' in thispaper, has been studied at 9-cm wavelength. Measurements of 226 sourceswere made on about 25 consecutive days in each of three observingsessions. The observing list includes roughly equal numbers of steepspectrum (SC) and flat or complex spectrum (F) sources. The SC sourcesdo not flicker while F sources do, with an average amplitude of about1.5 percent. Observations of a smaller number of sources at 6-cmwavelength suggest that the amplitude of flickering is about the same at6 and 9 cm. Flickering may be caused by scintillation in theinterstellar or near-source medium, or it may be intrinsic to thesource.
| Relative orientations of the axes of radio sources and the elliptical galaxies associated with them
A study is made of the relationship between the major axes of radiogalaxies and the elliptical galaxies associated with them. It is foundthat if the ratio of the major axes of the radio galaxies to thediameters of the radio components is greater than 2.5 there is a clearcorrelation between the directions of the major axes of the radiogalaxies and the minor axes of the optical galaxies. But if the ratio isless than 2.5, then the directions of the major axes of the radio andthe optical galaxies are well correlated. This result agrees well with amechanism of formation of radio galaxies in which it is assumed thatthey are formed from clouds of relativistic particles that are ejectedfrom the central regions of the elliptical galaxies and move in thedipole magnetic field of these galaxies.
| Are there correlations between radio and optical axes of radio galaxies
The relative orientations of radio and optical axes of radio galaxieshave been examined on the basis of combined material from several smallsamples. Rotation axes of some radio galaxies have been redeterminedassuming that the published measurements refer to rotational motionsonly. It is found that the rotation axis is quite different from thoseprevious determinations, where rotation-expansion models were used. Inparticular, the correlation between radio source axes and rotation axesdisappears when the allowance for expansion is dropped. No statisticallysignificant correlation between optical major axes of the galaxay imageand radio source axes is found when all existing measurements, notexceeding 140, are combined.
| Spectra, dimensions and luminosities of radio sources in the Culgoora-3 list
About 2000 spectra of radio sources in the Culgoora-3 list are analyzed.Each spectrum is fitted with a first-degree polynomial, and an attemptis made to define the second and third-degree curvatures in variousgroups of identified sources. The distributions of spectral index forvarious classes of optical identification are given, and the intrinsicluminosities of Culgoora-3 sources which have been identified withvarious classes of optical object with measured redshift are discussed.The results of fitting elliptical Gaussian brightness distributions tothe 163 Culgoora-3 maps is described, and an analysis of the barelyresolved sources is presented. The results of examining the opticalfields of 59 previously unidentified Culgoora-3 sources are given. Theoverall results indicate that QSOs differ from radio galaxies in havinga distribution of linear spectral indices with a pronounced tail towardsthe low values of spectral index.
|
Submit a new article
Related links
Submit a new link
Member of following groups:
|
Observation and Astrometry data
Catalogs and designations:
|
NEWS@SKY (Science&Space News)
