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SGRS J0515-8100: A Fat-Double Giant Radio Galaxy
We present here the first detailed study of a giant radio galaxy of thefat-double type. The lobes of the double radio galaxy SGRS J0515-8100have transverse widths that are 1.3 times their extent from the center,their surface brightness is the lowest among known giant radio sources,and the lobes have relatively steep radio spectra. We infer that thesewide lobes were created as a result of a highly variable andintermittent jet whose axis direction also varied significantly: thefat-double lobes in this giant radio source are a result of the ejectionand deposition of synchrotron plasma over a wide range of angles overtime rather than the expansion of relic lobes. In addition, the opticalhost shows evidence for an ongoing galaxy-galaxy interaction. SGRSJ0515-8100 supports the hypothesis that interactions with companionsmight perturb the inner accretion disk that produces and sustains thejets at the centers of active galactic nuclei. As a result, it appearsunnecessary to invoke black hole coalescence to explain suchmorphologies, implying that the corresponding event rates predicted forgravitational wave detectors may be overestimates.
| FIRST-based survey of compact steep spectrum sources. IV. Multifrequency VLBA observations of very compact objects
Context: .Evidence has been mounting recently that activity in someradio-loud AGNs (RLAGNs) can cease shortly after ignition and thatperhaps even a majority of very compact sources may be short-livedphenomena because of a lack of stable fuelling from the black hole.Thus, they can fade out before having evolved to large, extendedobjects. Re-ignition of the activity in such objects is not ruledout. Aims: .With the aim of finding more examples of these objectsand to investigate if they could be RLAGNs switched off at very earlystages of their evolution, multifrequency VLBA observations of sixsources with angular sizes significantly less than an arcsecond, yethaving steep spectra, have been made. Methods: .Observations wereinitially made at 1.65 GHz using the VLBA with the inclusion ofEffelsberg telescope. The sources were then re-observed with the VLBA at5, 8.4 and 15.4 GHz. All the observations were carried out in a snapshotmode with phase referencing. Results: .One of the sources studied,0809+404, is dominated by a compact component but also has diffuse,arcsecond-scale emission visible in VLA images. The VLBI observations ofthe "core" structure have revealed that this is also diffuse and fadingaway at higher frequencies. Thus, the inner component of 0809+404 couldbe a compact fading object. The remaining five sources presented hereshow either core-jet or edge-brightened double-lobed structuresindicating that they are in an active phase. Conclusions: .Theabove result is an indication that the activity of the host galaxy of0809+404 may be intermittent. Previous observations obtained from theliterature and those presented here indicate that activity had ceasedonce in the past, then restarted, and has recently switched off again.
| The Bologna Complete Sample of Nearby Radio Sources
We present a new, complete sample of 95 radio sources selected from theB2 Catolog of Radio Sources and the Third Cambridge Revised Catalog(3CR), with z<0.1. Since no selection effect on the core radio power,jet velocity, or source orientation is present, this sample is wellsuited for statistical studies. In this first paper we present theobservational status of all sources on the parsec (milliarcsecond) andkiloparsec (arcsecond) scale; we give new parsec-scale data for 28sources and discuss their parsec-scale properties. By combining thesedata with those in the literature, information on the parsec-scalemorphology is available for a total of 53 radio sources with differentradio power and kiloparsec-scale morphologies. We investigate theirproperties. We find a dramatically higher fraction of two-sided sourcesin comparison with that of previous flux-limited VLBI surveys.
| FIRST-based survey of Compact Steep Spectrum sources. II. MERLIN and VLA observations of medium-sized symmetric objects
A new sample of candidate Compact Steep Spectrum (CSS) sources that aremuch weaker than the CSS source prototypes has been selected from theVLA FIRST catalogue. MERLIN "snapshot" observations of the sources at 5GHz indicate that six of them have an FR II-like morphology, but are notedge-brightened as is normal for Medium-sized Symmetric Objects (MSOs)and FR IIs. Further observations of these six sources with the VLA at4.9 GHz and MERLIN at 1.7 GHz, as well as subsequent full-trackobservations with MERLIN at 5 GHz of what appeared to be the two sourcesof greatest interest are presented. The results are discussed withreference to the established evolutionary model of CSS sources beingyoung but in which not all of them evolve to become old objects withextended radio structures. A lack of stable fuelling in some of them mayresult in an early transition to a so-called coasting phase so that theyfade away instead of growing to become large-scale objects. It ispossible that one of the six sources (1542+323) could be labelled as aprematurely "dying" MSO or a "fader".
| Are radio galaxies and quiescent galaxies different? Results from the analysis of HST brightness profiles
We present a study of the optical brightness profiles of early typegalaxies, using a number of samples of radio galaxies and opticallyselected elliptical galaxies. For the radio galaxy samples - B2 ofFanaroff-Riley type I and 3C of Fanaroff-Riley type II - we determined anumber of parameters that describe a "Nuker-law" profile, which werecompared with those already known for the optically selected objects. Wefind that radio active galaxies are always of the "core" type (i.e. aninner Nuker law slope γ < 0.3). However, there are core-typegalaxies which harbor no significant radio source and which areindistinguishable from the radio active galaxies. We do not find anyradio detected galaxy with a power law profile (γ > 0.5). Thisdifference is not due to any effect with absolute magnitude, since in aregion of overlap in magnitude the dichotomy between radio active andradio quiescent galaxies remains. We speculate that core-type objectsrepresent the galaxies that have been, are, or may become, radio activeat some stage in their lives; active and non-active core-type galaxiesare therefore identical in all respects except their eventualradio-activity: on HST scales we do not find any relationship betweenboxiness and radio-activity. There is a fundamental plane, defined bythe parameters of the core (break radius rb and breakbrightness μ_b), which is seen in the strong correlation betweenrb and μ_b. The break radius is also linearly proportionalto the optical Luminosity in the I band. Moreover, for the few galaxieswith an independently measured black hole mass, the break radius turnsout to be tightly correlated with MBH. The black hole masscorrelates even better with the combination of fundamental planeparameters rb and μ_b, which represents the centralvelocity dispersion.
| A transition in the accretion properties of radio-loud active nuclei
We present evidence for the presence of a transition in the accretionproperties of radio-loud sources. For a sample of radio galaxies andradio-loud quasars, selected based on their extended radio properties,the accretion rate is estimated from the black hole mass and nuclearluminosity. The inferred distribution is bimodal, with a paucity ofsources at accretion rates, in Eddington units, of the order of~10-2- assuming a radiative efficiency of 10 per cent - andpossibly spanning 1-2 orders of magnitude. Selection biases are unlikelyto be responsible for such behaviour. We discuss possible physicalexplanations, including a fast transition to low accretion rates, achange in the accretion mode/actual accretion rate/radiative efficiency,the lack of stable disc solutions at intermediate accretion rates or theinefficiency of the jet formation processes in geometrically thin flows.This transition might be analogous to spectral states (and jet)transitions in black hole binary systems.
| Spectral ageing in the relic radio galaxy B2 0924+30
The radio spectrum of the relic radio galaxy B2 0924+30 is investigatedusing integrated flux densities between 0.151 and 10.6 GHz, as well asimages at 0.325, 0.609, 1.400 and 4.750 GHz. Allowing for synchrotronand inverse Compton losses in this source, the observed spectralsteepening yields a break frequency of 7 GHz, implying a meanparticle age of about 50 Myrs. The corresponding particle advance speedis of the order of 2000 km s-1. This relatively smallparticle lifetime following the exhaustion of the central source canexplain the paucity of such sources and implies that such objects wouldeasily escape detection if searched for in the cm wavelength regime.
| Optical nuclei of radio-loud AGN and the Fanaroff-Riley divide
We investigate the nature of the point-like optical nuclei that havebeen found in the centres of the host galaxies of a majority of radiogalaxies by the Hubble Space Telescope. We examine the evidence thatthese optical nuclei are relativistically beamed, and look fordifferences in the behaviour of the nuclei found in radio galaxies ofthe two Fanaroff-Riley types. We also attempt to relate this behaviourto the properties of the optical nuclei in their highly beamedcounterparts (the BL Lac objects and radio-loud quasars) as hypothesizedby the simple Unified Scheme. Simple model-fitting of the data suggeststhat the emission may be coming from a non-thermal relativistic jet. Itis also suggestive that the contribution from an accretion disk is notsignificant for the FRI objects and for the narrow-line radio galaxiesof FRII type, while it may be significant for the Broad-line objects,and consistent with the idea that the FRII optical nuclei seem to sufferfrom extinction due to an obscuring torus while the FRI optical nucleido not. These results are broadly in agreement with the Unified Schemefor radio-loud AGNs.Appendix C is only available in electronic form athttp://www.edpsciences.org
| Unifying B2 radio galaxies with BL Lacertae objects
In an earlier paper we presented nuclear X-ray flux densities, measuredwith ROSAT, for the B2 bright sample of nearby low-luminosity radiogalaxies. In this paper we construct a nuclear X-ray luminosity functionfor the B2 radio galaxies, and discuss the consequences of our resultsfor models in which such radio galaxies are the parent population of BLLacertae (BL Lac) objects. Based on our observations of the B2 sample,we use Monte Carlo techniques to simulate samples of beamed radiogalaxies, and use the selection criteria of existing samples of BL Lacobjects to compare our simulated results to what is observed. We findthat previous analytical results are not applicable since the BL Lacsamples are selected on beamed flux density. A simple model in which BLLacs are the moderately beamed (γ~ 3) counterparts of radiogalaxies, with some random dispersion (~0.4 decades) in the intrinsicradio-X-ray relationship, can reproduce many of the features of theradio-selected and X-ray-selected BL Lac samples, including their radioand X-ray luminosity functions and the distributions of theirradio-to-X-ray spectral indices. In contrast, models in which the X-rayand radio emission have systematically different beaming parameterscannot reproduce important features of the radio-galaxy and BL Lacpopulations, and recently proposed models in which the radio-to-X-rayspectral index is a function of source luminosity cannot in themselvesaccount for the differences in the slopes of the radio- andX-ray-selected BL Lac luminosity functions. The redshift distributionand number counts of the X-ray-selected Einstein Medium SensitivitySurvey (EMSS) sample are well reproduced by our best models, supportinga picture in which these objects are beamed Fanaroff-Riley type I radiogalaxies with intrinsic luminosities similar to those of the B2 sample.However, we cannot match the redshift distribution of the radio-selected1-Jy sample, and it is likely that a population of Fanaroff-Riley typeII radio galaxies is responsible for the high-redshift objects in thissample, in agreement with previously reported results on the sample'sradio and optical emission-line properties.
| Redshifts for a Sample of Radio-selected Poor Clusters
Multifiber optical spectroscopy has been performed on galaxies in thevicinity of strong, nearby radio galaxies. These radio galaxies wereselected from the 3CR and B2 catalogs based on their exclusion from theAbell catalog, which is puzzling given the hypothesis that an externalmedium is required to confine the radio plasma of such galaxies.Velocities derived from the spectra were used to confirm the existenceof groups and poor clusters in the fields of most of the radio galaxies.We find that all radio galaxies with classical Fanaroff-Riley type Imorphologies prove to reside in clusters, whereas the other radiogalaxies often appear to be recent galaxy-galaxy mergers in regions oflow galaxy density. These findings confirm the earlier result that theexistence of extended X-ray emission combined with a statistical excessof neighboring galaxies can be used to identify poor clusters associatedwith radio galaxies.
| 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.
| HST images of B2 radio galaxies: A link between circum-nuclear dust and radio properties?
Almost 60% of the B2 low luminosity radio galaxies have been observedwith the Hubble Space Telescope. We present an analysis of the dustfeatures, which are often present in the form of circum-nuclear disks orlanes, and show that there are correlations between radio source anddust properties. It is found that nearby radio sources in which a jethas been detected tend to have dust more often than sources withoutjets; the dust is often in the form of disks or lanes. Moreover theradio jets are close to perpendicular to the disk or lane in the weakerradio sources (with P < 1024 WHz-1). Instronger sources the orientation effect appears to be weak or evenabsent. Also the dust masses found in the weaker radio sources aresmaller than in the stronger ones (log M/Msun ~ 3 against 5respectively). More generally it appears that there is a correlationbetween dust mass and total radio power (for those sources in which dusthas been detected); we show that this correlation is not induced byredshift. Based on observations with the NASA/ESA Hubble SpaceTelescope, obtained at the Space Telescope Science Institute, which isoperated by AURA, Inc., under NASA contract NAS 5-26555 and by STScIgrant GO-3594.01-91A.
| The HST survey of the B2 sample of radio-galaxies: Optical nuclei and the FR I/BL Lac unified scheme
We examine the optical properties of the nuclei of low luminosityradio-galaxies using snapshot HST images of the B2 sample. In agreementwith the results obtained from the analysis of the brighter 3C/FR Isample, we find a correlation between fluxes (and luminosities) of theoptical and radio cores. This provides further support for theinterpretation that the optical nuclear emission in FR I is dominated bysynchrotron emission and that accretion in these sources takes place ina low efficiency radiative regime. In the framework of the FR I/BL Lacsunified scheme, we find that the luminosity difference between FR I andBL Lac nuclei can be reproduced with a common beaming factor in both theradio and the optical band, independent of the extended radioluminosity, thus supporting such a scenario. The corresponding bulkLorentz factor is significantly smaller than is expected fromobservational and theoretical considerations in BL Lacs: this can beinterpreted as due to a velocity structure in the jet, with a fast spinesurrounded by a slower layer. Based on observations with the NASA/ESAHubble Space Telescope, obtained at the Space Telescope ScienceInstitute, which is operated by AURA, Inc., under NASA contract NAS5-26555 and by STScI grant GO-3594.01-91A.
| The Spectra and Energies of Classical Double Radio Lobes
We compare two temporal properties of classical double radio sources:(1) radiative lifetimes of synchrotron-emitting particles and (2)dynamical source ages. We discuss how these can be quite discrepant fromone another, rendering use of the traditional spectral aging methodinappropriate: we contend that spectral ages give meaningful estimatesof dynamical ages only when these ages are <<107 yr. Injuxtaposing the fleeting radiative lifetimes with source ages that aresignificantly longer, a refinement of the paradigm for radio sourceevolution is required. We move beyond the traditional bulk backflowpicture and consider alternative means of the transport of high Lorentzfactor (γ) particles, which are particularly relevant within thelobes of low-luminosity classical double radio sources. The changingspectra along lobes are explained, not predominantly by synchrotronaging but by gentle gradients in a magnetic field frozen into alow-γ matrix that illuminates an energy distribution of particles,N(γ), controlled largely by classical synchrotron loss in the highmagnetic field of the hot spot. A model of a magnetic field whosestrength decreases with increasing distance from the hot spot and in sodoing becomes increasingly different from the equipartition value in thehead of the lobe is substantiated by constraints from different types ofinverse Compton scattered X-rays. The energy in the particles is anorder of magnitude higher than that inferred from the minimum energyestimate, implying that the jet power is of the same order as theaccretion luminosity produced by the quasar central engine. This refinedparadigm points to a resolution of the 1994 findings of Rudnick et al.and Katz-Stone & Rudnick that both the Jaffe-Perola andKardashev-Pacholczyk model spectra are invariably poor descriptions ofthe curved spectral shape of lobe emission and, indeed, that for CygnusA all regions of the lobes are characterized by a ``universalspectrum.''
| Surface photometry of radio loud elliptical galaxies from the B2 sample
V-band CCD imaging is presented for 72 galaxies from the B2 radio sample(Colla et al. \cite{colla}; Fanti et al. \cite{fanti78}), with redshiftsup to 0.2 and radio powersP408=1023-1026.5 W Hz-1.According to the morphology on the optical images 57 galaxies areclassified as ellipticals, 6 as spirals and 7 as irregular. Surfacephotometry of the sample of ellipticals was obtained fitting ellipses tothe light distribution. The light profile of these galaxies generallyfollows a de Vaucouleurs law, although in three cases the profiles showlarge excesses relative to the r1/4 law at large radii. Thefitted mu_e and r_e parameters for the de Vaucouleurs galaxies are givenin the paper. Three of the ellipticals show a bright nucleus. One ofthem is a known broad line radio galaxy (B2 1833+32) and the remainingtwo are Markarian galaxies, classified in the literature as BL Lacobjects (B2 1101+38 and B2 1652+39). The radial profiles forellipticity, position angle, and B_4 term of the Fourier analysis arepresented in the paper, and the morphological peculiarities of theellipticals are described, including the presence of shells, tails,nuclear dust, isophote twisting, off-centering, and boxiness or disknessof the isophotes. Only one of the galaxies in this work is included inthe subsample of B2 radio galaxies with well-defined jets (Parma et al.\cite{parma87}). In this sense the present sample complements the sampleof 24 radio galaxies with well-defined radio jets in Parma et al. forwhich a similar study was presented in González-Serrano et al.(\cite{gserrano93}). The irregular galaxy B2 0916+33 appears to bemisclassified, and we suggest that the right identification of the radiosource is a nearby point like object with V=18.45 mag. The spiral galaxyassociated with B2 1441+26 is also misclassified. A point-like opticalobject with V=18.88 mag, located at ~ 36 arcsec from the originalidentification and coincident with the radio core is the most probablecounterpart. Table 4 is 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 Complete Figure 1 and Figure 2are only available at http://www.edpsciences.org
| The HST snapshot survey of the B2 sample of low luminosity radio-galaxies: a picture gallery
A Hubble Space Telescope snapshot survey of the B2 sample of lowluminosity radio galaxies has, at present, produced V and I images of 41objects. Together with 16 images of B2 sources taken from the HSTarchive, there are now high resolution optical data for ~ 57% of thesample. All host galaxies are luminous ellipticals, except one which isa spiral galaxy, while another one turns out to be a misidentification.We present an album of the images of the B2 radio galaxies observed sofar, and give a brief description of the optical morphology of thegalaxies. Dust features (in the form of disks, lanes or irregularpatches) are seen in most of the galaxies of the sample, ~ 58%. Compactoptical cores are also very common (18/57). A preliminary analysis hasrevealed the presence of an optical jet in three objects, indicatingthey can be detected in a sizeable percentage in these low luminosityradio sources. Brightness profiles of dust-free galaxies are wellrepresented by a Nuker law and all shows the existence of a resolvedshallow cusp. Based on observations with the NASA/ESA Hubble SpaceTelescope, obtained at the Space Telescope Science Institute, which isoperated by AURA, Inc., under NASA contract NAS 5-26555 and by STScIgrant GO-3594.01-91A
| X-ray observations of low-power radio galaxies from the B2 catalogue
We present an analysis of X-ray data, taken with ROSAT, for awell-defined sample of low-power radio galaxies from the Bologna B2catalogue. Where possible, the HRI has been used in order to takeadvantage of the high spatial resolution provided by this instrument. Avariety of models are fitted to radial profiles in order to separate theresolved and unresolved X-ray emission from the galaxies. We demonstratea strong, approximately linear, correlation between the luminosities ofthe unresolved X-ray components and the 5-GHz luminosities of the radiocores in this sample. This suggests a physical relationship between thesoft X-ray emission of radio galaxies and the jet-generated radio coreemission. We infer a nuclear jet-related origin for at least some of theX-ray emission.
| 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 Dynamics of Poor Systems of Galaxies
We assemble and observe a sample of poor galaxy systems that is suitablefor testing N-body simulations of hierarchical clustering and otherdynamical halo models. We (1) determine the parameters of the densityprofile rho(r) and the velocity dispersion profile sigma_p(R), (2)separate emission-line galaxies from absorption-line galaxies, examiningthe model parameters and as a function of spectroscopic type, and (3)for the best-behaved subsample, constrain the velocity anisotropyparameter, beta, which determines the shapes of the galaxy orbits. Oursample consists of 20 systems, 12 of which have extended X-ray emissionin the ROSAT All-Sky Survey. We measure the 877 optical spectra ofgalaxies brighter than m_R~15.4 within 1.5 h^-1 Mpc of the systemcenters (we take H_0=100 h km s^-1 Mpc^-1). Thus, we sample the systemmembership to a radius typically three times larger than other recentoptical group surveys. The average system population is 30 galaxies, andthe average line-of-sight velocity dispersion is ~300 km s^-1. TheNavarro, Frenk, & White universal profile and the Hernquist modelboth provide good descriptions of the spatial data. In most cases anisothermal sphere is ruled out. Systems with declining sigma_p(R) arewell-matched by theoretical profiles in which the star-forming galaxieshave predominantly radial orbits (beta>0) many of these galaxies areprobably falling in for the first time. There is significant evidencefor spatial segregation of the spectroscopic classes regardless ofsigma_p(R).
| Radiative ages in a representative sample of low luminosity radio galaxies
Two frequency observations, mainly at 1.4 and 5 GHz from the VLA, havebeen used to study spectral variations along the lobes of some nearbylow luminosity radio galaxies that constitute a representative sampleselected from the B2 catalogue. The variations of the spectral indexhave been interpreted as being due to synchrotron and inverse Comptonlosses and characteristic spectral ages are deduced for the relativisticelectrons. The radiative ages are in the range of several 10(7) years.These ages correlate well with the source sizes. They also appear to beconsistent with dynamical ages determined from ram-pressure arguments,if we make reasonable assumptions about the ambient gas density andallow for very moderate deviations from the equipartition conditions.There appears to be a significant difference between the radiative agesof sources in our sample and those of more powerful 3CR radio sources.We briefly discuss the possibility of re-acceleration processes andindicate some objects where these may occur.
| Radio properties of the Shapley Concentration - II. J1324-3138: a remnant of a radio galaxy in the Abell cluster A3556?
In this paper we present a detailed study of the radio galaxyJ1324-3138, located at a projected distance of 2arcmin from the centreof the Abell cluster of galaxies A3556, belonging to the core of theShapley Concentration, at an average redshift of z=0.05. We haveobserved J1324-3138 over a wide range of frequencies: at 327 MHz (VLA),843 MHz (MOST), and at 1376, 2382, 4790 and 8640 MHz (ATCA). Ouranalysis suggests that J1324-3138 is a remnant of a tailed radio galaxy,in which the nuclear engine has switched off and the radio source is nowat a late stage of its evolution, confined by the intracluster gas. Theradio galaxy is not in pressure equilibrium with the external medium, asis often found for extended radio sources in clusters of galaxies. Wefavour the hypothesis that the lack of observed polarized radio emissionin the source is a result of Faraday rotation by a foreground screen,i.e. the source is seen through a dense cluster gas, characterized by arandom magnetic field. An implication of the head-tail nature of thesource is that J1324-3138 is moving away from the core of A3556 andthat, possibly, a major merging event between the core of A3556 and thesubgroup hosting J1324-3138 has already taken place.
| Spectral aging in the relic source B2 0924+30.
Not Available
| 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.
| A Catalog of Stellar Velocity Dispersions. II. 1994 Update
A catalog of central velocity dispersion measurements is presented,current through 1993 September. The catalog includes 2474 measurementsof 1563 galaxies. A standard set of 86 galaxies is defined, consistingof galaxies with at least three reliable, concordant measurements. It issuggested that future studies observe some of these standard galaxies sothat different studies can be normalized to a consistent system. Allmeasurements are reduced to a normalized system using these standards.
| Relic sources and diffuse cluster radio emission
Late evolution of an extended radio source is studied in the context ofa simple model of magnetically driven expansion. The evolving radiospectrum is calculated by accounting for synchrotron, Compton, andexpansion energy losses of relativistic electrons in the varyingmagnetic field of the source. We estimate the Compton X-ray fluxes ofthe relics 0924+30 and 1253+275, and conclude that the latter source islikely to be a dominant component of the high-energy flux from the Comaregion, if measured by a detector with a large field of view (such asthe OSSE on board the Compton Gamma Ray Observatory). We briefly discussthe possibility that steep-spectrum relics and diffuse radio sources inclusters have a common origin.
| 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.
| Energy distributions of radio galaxies
Far-infrared observations of 140 radio galaxies which span a range ofover four orders of magnitude in radio power, (from weak nuclear sourcesin nearby galaxies, to powerful FR II doubled lobed sources at moderateredshift) are presented. The strength of the far-infrared emission ismore closely correlated with core than total radio emission.Far-infrared emission in radio galaxies represents star formation thatis more closely tied to the active nucleus than to the global propertiesof the galaxy. The far-infrared luminosity function shows goodcontinuity between radio galaxies and radio loud quasars.
| The megaparsec radio relic in supercluster, Rood No. 27
Observations of extended source of low surface brightness appear as a'relic' of a currently inactive radio galaxy. The largest dimension isapproximately 1.6 Mpc, the fractional polarization is high, and themagnetic field direction appears to be coherent over scales of at leastseveral hundred kpc. Polarization and morphologies of relics aredistinct from those of cluster halos, due to the different environmentprovided by cluster cores compared to that encountered in the outerfringes of the hot gas distribution which produces X-ray emission.
| Optical line-emitting gas and radio emission - Evidence for correlation in low-luminosity radio galaxies
Narrow-band H-alpha + (N II) images of a sample of low-luminosity B2radio sources are used to investigate the correlations between radio andoptical emission-line properties. It is shown that the correlationbetween radio and emission-line luminosity - previously established forhigh-power radio galaxies - extends over five decades in radioluminosity and includes the low-radio power sources. The compact radiosources have emission-line excesses relative to the other sources in thesample of the same radio power, as well as far-IR emissioncharacteristics of emission from cool dust. Although continuityarguments can be used to show that the ionized gas in most of thelow-luminosity sources is likely to be photoionized by the ActiveGalactic Nucleus, it is possible that additional ionizing sourcescontribute in the compact, emission-line excess objects. A program ofdetailed spectroscopic observations is required to investigate theunderlying physical mechanisms.
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