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High-frequency radio observations of the Kühr sample and the epoch-dependent luminosity function of flat-spectrum quasars
We discuss our ATCA 18.5 and 22 GHz flux density measurements ofSouthern extragalactic sources in the complete 5 GHz sample of Kühret al. (1981, A&AS, 45, 367). The high frequency (5-18.5 GHz)spectral indices of steep-spectrum sources for which we have 18.5 GHzdata (66% of the complete sample) are systematically steeper than thelow frequency (2.7-5 GHz) ones, with median α^52.7 =0.76, median α18.55 = 1.18(Sν∝ ν-α), and median steepeningΔα = 0.32, and there is evidence of an anti-correlation ofΔα18.55 with luminosity. Thecompleteness of 18.5 GHz data is much higher (89%) for flat-spectrumsources (mostly quasars), which also exhibit a spectral steepening:median α^52.7=-0.14, medianα18.55=0.16 (Sν∝ν-α), and median Δα = 0.19. Takingadvantage of the almost complete redshift information on flat-spectrumquasars, we have estimated their 5 GHz luminosity function in severalredshift bins. The results confirm that their radio luminosity densitypeaks at z_peak ≃ 2.5 but do not provide evidence for deviationsfrom pure luminosity evolution as hinted at by other data sets. Acomparison of our 22 GHz flux densities with WMAP K-band data forflat-spectrum sources suggests that WMAP flux densities may be low by amedian factor of ≃1.2. The extrapolations of 5 GHz counts andluminosity functions of flat-spectrum radio quasars using the observeddistribution of the 5-18.5 GHz spectral indices match those deriveddirectly from WMAP data, indicating that the high frequency WMAP surveydoes not detect any large population of FSRQs with anomalous spectra.
| Stacking Searches for Gamma-Ray Emission above 100 MeV from Radio and Seyfert Galaxies
The EGRET telescope on board Compton Gamma Ray Observatory detected morethan 60 sources of high-energy gamma radiation associated with activegalactic nuclei (AGNs). All but one of those belong to the blazarsubclass; the only exception is the nearby radio galaxy Centaurus A.Since there is no obvious reason other than proximity to expect Cen A tobe the only nonblazar AGN emitting in high-energy gamma rays, we haveutilized the ``stacking'' technique to search for emission above 100 MeVfrom two nonblazar AGN subclasses, radio galaxies and Seyfert galaxies.Maps of gamma-ray counts, exposure, and diffuse background have beencreated, then co-added in varying numbers based on sorts by redshift, 5GHz flux density, and optical brightness, and finally tested forgamma-ray emission. No detection significance greater than 2 σ hasbeen found for any subclass, sorting parameter, or number of objectsco-added. Monte Carlo simulations have also been performed to validatethe technique and estimate the significance of the results.
| Emission-Line Diagnostics of the Central Engines of Weak-Line Radio Galaxies
A handful of well-studied weak-line radio galaxies (WLRGs) have beentraditionally classified as low-ionization nuclear emission-line regions(LINERs), suggesting that these two groups of active galactic nuclei(AGNs) might be related. In this paper, we present new opticalemission-line measurements for 20 WLRGs, which we supplement withmeasurements for an additional four from the literature. Classifyingthese objects by their emission-line ratios, we find that 50% of theobjects are robustly classified as LINERs, while an additional 25% arelikely to be LINERs. Photoionization calculations show that the spectralenergy distribution of the well-studied WLRG 3C 270 (NGC 4261) is ableto produce the observed emission-line ratios, but only if the UVemission seen by the narrow emission line gas is significantly higherthan that observed, implying AV=2.5-4.2 mag along our line ofsight to the nucleus. From the photoionization calculations, we findthat the emission-line gas must have an ionization parameter between10-3.5 and 10-4.0 and a wide range in hydrogendensity (102-106 cm-3) to reproduce themeasured emission-line ratios, similar to the properties inferred forthe emission-line gas in LINERs. Thus, we find that properties of theemission-line gas as well as the underlying excitation mechanism areindeed similar in LINERs and WLRGs. By extension, the central engines ofaccretion-powered LINERs and WLRGs, which do host an accreting blackhole, may be qualitatively similar.
| The black hole mass of low redshift radiogalaxies
We make use of two empirical relations between the black hole mass andthe global properties (bulge luminosity and stellar velocity dispersion)of nearby elliptical galaxies, to infer the mass of the central blackhole (CM MBH) in low redshift radiogalaxies. Using the mostrecent determinations of black hole masses for inactive early typegalaxies we show that the bulge luminosity and the central velocitydispersion are almost equally correlated (similar scatter) with thecentral black-hole mass. Applying these relations to two large andhomogeneous datasets of radiogalaxies we find that they host black-holeswhose mass ranges from ~ 5*E7 to ~ 6*E9CMMsun (average ~ 8.9). CMMBH is found to be proportional to the mass of the bulge (CMMbulge). The distribution of the ratio CM MBH/CMMbulge has a mean value of 8*E-4 and shows ascatter that is consistent with that expected from the associatederrors. At variance with previous claims no significant correlation isinstead found between CM MBH (or CM Mbulge) andthe radio power at 5 GHz.
| Intergalactic Magnetic Fields from Quasar Outflows
Outflows from quasars inevitably pollute the intergalactic medium (IGM)with magnetic fields. The short-lived activity of a quasar leaves behindan expanding magnetized bubble in the IGM. We model the expansion of theremnant quasar bubbles and calculate their distribution as a function ofsize and magnetic field strength at different redshifts. We genericallyfind that by a redshift z~3, about 5%-20% of the IGM volume is filled bymagnetic fields with an energy density >~10% of the mean thermalenergy density of a photoionized IGM (at ~104 K). As massivegalaxies and X-ray clusters condense out of the magnetized IGM, theadiabatic compression of the magnetic field could result in the fieldstrength observed in these systems without a need for further dynamoamplification. The intergalactic magnetic field could also provide anonthermal contribution to the pressure of the photoionized gas that mayaccount for the claimed discrepancy between the simulated and observedDoppler width distributions of the Lyα forest.
| A radio continuum survey of the southern sky at 1420 MHz. The atlas of contour maps
The results of an absolutely calibrated radio continuum survey of theSouth Celestial Hemisphere at a frequency of 1420 MHz are presented.Contour maps show the area 0h <= RA <= 24hfor the declination range -90degr to -10degr . Contour steps (50 mKTB 3 x rms noise) and angular resolution (HPBW 35\farcm 4) ofthe maps match the already existing Stockert northern sky survey at thesame frequency. We compare flux densities of compact and extendedsources with published data from the Parkes 64-m telescope and findexcellent agreement in general. The survey maps are sensitive enough toconstrain synchrotron and thermal emission components which mightinfluence studies of the cosmic microwave background. Figures 1 and 2are also 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/376/861
| The optical properties of low redshift radio galaxies
We present morphological and photometric properties of 79 low redshift(z<=0.12) radio galaxies extracted from two radio flux limitedsamples of radio sources. All objects are imaged in the R band and for asubsample we have also obtained B band images. The sample includessources of both FRI and FRII radio morphological type. Through thedecomposition of the luminosity profiles and the analysis of thestructural profiles (ellipticity, PA, c4) of the galaxies we are able tocharacterize in detail the optical properties of the radio galaxies. Itis found that most of host galaxies are luminous bulge dominated systemssimilar to normal giant ellipticals. Some cases of additional diskcomponents are found whose spheroid-to-disk luminosity ratio is similarto that found in S0 galaxies. The average absolute magnitude is =-24.0 with a clear trend for FRI sources tobe ~ 0.5 mag brighter than FRII galaxies. In about 40% of the objectsobserved we find an excess of light in the nucleus that is attributed tothe presence of a nuclear point source whose luminosity is on average ~1-2% of the total flux of the host galaxy. The luminosity of thesenuclear point sources appears correlated with the core radio power ofthe galaxies. Radio galaxies follow the same mu_e - R_e relationship asnormal elliptical galaxies. The distribution of ellipticity, the amountof twisting and shape of isophotes (boxy, disky) do not differsignificantly from other ellipticals. The evidence for recentinteractions is therefore rather modest. Finally on average radiogalaxies are bluer and have a color dispersion larger than normalelliptical galaxies, and the average color gradient in radio galaxiesappears slightly steeper than in normal ellipticals. These resultssupport a scenario where radio emission is weakly related with theoverall properties and/or the activity have negligible effects on theglobal characteristics of the host galaxy. Based on observationscollected at the European Southern Observatory, La Silla, Chile. Basedon observations collected at the Nordic Optical Telescope, La Palma.
| A 98 per cent spectroscopically complete sample of the most powerful equatorial radio sources at 408MHz
A new sample of very powerful radio galaxies is defined from theMolonglo Reference Catalogue, according to the criteriaS408MHz>5Jy, -30 deg<=δ<=10 deg and |b|>=10deg. The sample is selected to have similar properties to the northern3CR revised sample, and to be visible to a combination of existingnorthern telescopes such as the Very Large Array radio interferometerand large southern hemisphere telescope facilities. The sample contains178 sources, of which spectroscopic redshifts are available in theliterature for 128. For the remaining 50 sources, new radio imaging,optical imaging and spectroscopic observations are presented to identifythe host galaxies and determine their redshifts. With these newobservations the total sample is 100per cent optically identified andredshifts are available for 174 (98per cent) of the sources. The sampleconsists of one starburst galaxy, one Seyfert galaxy, 127 radio galaxiesand 49 quasars. Basic properties of the sample, such as thedistributions of the quasar and radio-galaxy populations in redshift andtheir locations on the radio power versus linear size (P-D) diagram,show no significant differences from the revised 3CR sample. Theequatorial location and the high spectroscopic completeness of thissample make it a valuable resource for detailed studies of the natureand environments of these important objects with the new generation ofsouthern hemisphere telescopes.
| An X-Ray and Optical Investigation of the Environments around Nearby Radio Galaxies
Investigations of the cluster environment of radio sources have notshown a correlation between radio power and degree of clustering.However, it has been demonstrated that extended X-ray luminosity andgalaxy clustering do exhibit a positive correlation. This studyinvestigates a complete sample of 25 nearby (z<=0.06) radio galaxiesthat are not cataloged members of Abell clusters. The environment ofthese radio galaxies is studied in both the X-ray and the optical bymeans of the ROSAT All-Sky Survey (RASS), ROSAT pointed observations,and the Palomar optical Digitized Sky Survey (DSS). X-ray luminositiesand extents are determined from the RASS, and the DSS is used toquantify the degree of clustering via the spatial two-point correlationcoefficient, Bgg. Of the 25 sources, 20 are >=3 σdetections in the X-ray and 11 possessed Bgg's significantlyin excess of that expected for an isolated galaxy. Adding the criterionthat the X-ray emission be resolved, 10 of the radio galaxies do appearto reside in poor clusters with extended X-ray emission suggestive ofthe presence of an intracluster medium. Eight of these galaxies alsopossess high spatial correlation coefficients. Taken together, thesedata suggest that the radio galaxies reside in a low-richness extensionof the Abell clusters. The unresolved X-ray emission from the othergalaxies is most likely associated with active galactic nucleusphenomena. Furthermore, although the sample size is small, it appearsthat the environments of FR I and FR II sources differ. FR I's tend tobe more frequently associated with extended X-ray emission (10 of 18),whereas FR II's are typically point sources or nondetections in theX-ray (none of the seven sources exhibit extended X-ray emission).
| Radio-loud and Radio-quiet Active Galactic Nuclei
We have generated a sample of 409 active galactic nuclei (AGNs) forwhich both the radio luminosity at 5 GHz and the line luminosity in [OIII] lambda5007 have been measured. The radio luminosity spans a rangeof 10 orders of magnitude, and the [O III] line luminosity spans a rangeof 8 orders of magnitude-both considerably larger than the ranges inprevious studies. We show that these two quantities are correlated in asimilar way for both radio-loud and radio-quiet AGNs. We demonstratethat the observed correlation can be explained in terms of a model inwhich jets are accelerated and collimated by a vertical magnetic field.
| The nature of the optical-radio correlations for powerful radio galaxies
The nature of the optical-radio correlations for powerful radio galaxiesis investigated using spectroscopic observations of a complete sample ofsouthern 2-Jy radio sources. In line with previous work, we find thatsignificant correlations exist between the luminosities of the[OIII]lambda5007, [OII]lambda3727 and Hβ emission lines and the radioluminosity. However, our observations are not easily reconciled with theidea that these correlations are caused by the increase in the power ofthe photoionizing quasar as the jet power increases, with average ISMproperties not changing appreciably with redshift or radio power: notonly do we find that the scatter in the L_[Oiii] versus L_radiocorrelation is significantly larger than in L_[Oii] versus L_radio andL_Hβ versus L_radio correlations, but the ionization state deducedfrom the emission lines does not increase with radio power as predictedby the simple, constant ISM, photoionization model. We conclude that (a)there exists a considerable range in the quasar ionizing luminosity at agiven redshift, and (b) the mean density of the emission-line clouds islarger in the high-redshift/high-power radio sources. The latter densityenhancement may be either a consequence of the increased importance ofjet-cloud interactions or, alternatively, the result of a higherpressure in the confining hot ISM, in the high-redshift objects. Apartfrom the general scatter in the correlations, we identify a distinctgroup of objects with [OIII]lambda5007 luminosities which are more thanan order of magnitude lower than in the general population radiogalaxies at similar redshift. These weak-line radio galaxies (WLRGs) arelikely to be sources in which the central ionizing quasars areparticularly feeble. Deep spectra show that many of the sources in oursample are broad-line radio galaxies (BLRGs). The fact that the BLRGsare observed out to the redshift limit of the survey, overlapping inredshift with the quasars, argues against the idea that BLRGs are simplythe low-radio-power counterparts of high-power, high-redshift quasars.Either there exists a considerable range in the intrinsic luminositiesof the broad-line AGN for a given redshift or radio power, or the BLRGsrepresent partially obscured quasars. The degree of scatter present inthe L_[Oiii] versus L_radio correlation supports the former possibility.
| The Molonglo Reference Catalog 1 Jy Radio Source Survey. II. Radio Structures of Galaxy Identifications
This is the second in a series of papers discussing the radio, optical,and near-IR properties of a large and complete sample of radio sourcesselected from the Molonglo Reference Catalog (MRC) at 408 MHz. Thesample consists of 557 radio sources from the MRC that have S_0.408>= 0.95 Jy, -30 deg < delta < -20 deg, and |b| >= 20 deg butexcluding the right ascension range of 14^h03^m-20^h20^m. While 111 ofthese are identified with quasars (including six with BL Lac objects), avast majority of the rest are identified with galaxies. Only a smallfraction (<~2%) appear to have no optical or near-IR counterpartsdown to an r magnitude of ~24 or a K magnitude of ~19. A similarfraction have ambiguous identifications. This paper presents the radiostructures of the 446 radio sources in the sample that are eitheridentified with galaxies or that have remained unidentified. Most of thestructural information given in the paper is based on high-resolution(~1"-10") observations made with the Very Large Array at a frequency of4.86 GHz. Several of the large or diffuse sources were also observed at1.41 GHz. Contour plots of the radio images are also presented for thewell-resolved sources. A substantial fraction (~20%) of the sources inthe galaxy sample is found to be of the ``compact steep spectrum''variety with alpha^4.86_0.408>0.5 and linear size l <~ 20 kpc (forH_0 = 50 km s^-1 Mpc^-1 q_0 = 0.5).
| 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
| H_2O megamaser emission from FR I radio galaxies
A systematic search for 22 GHz H_2O megamaser emission is reported for50 nearby (z la 0.15) FR I galaxies. No detection was obtained, implyingthat ultraluminous H_2O masers (L_H_2O > 10(3) Lsun) mustbe rare in early-type galaxies with FR I radio morphology. Despitehigher radio core luminosities the detection rate for our sample islower than in similar surveys of late-type Seyfert galaxies. Thispuzzling difference between Seyferts and low-power radio galaxies couldbe explained in several ways: a) the maser emission is saturated andtherefore independent of the radio core luminosity, b) the masers areunsaturated and originate in a thin circumnuclear gas disk, so the`seed' radio continuum would come from the far jet which isrelativistically dimmed or c) the amount, kinematics, or thedistribution of the molecular gas in the nuclei of Seyferts and radiogalaxies is different. Further studies of maser properties may provideclues to the differences between radio-loud and radio-quiet AGN.
| A study of cores in a complete sample of radio sources
The high resolution provided by the Parkes-Tidbinbilla real-timeinterferometer (PTI) has been used to measure the core flux density fora complete sample of radio sources. Lower resolution maps are alreadyavailable for most of these objects together with optical(spectroscopic) data. The new data show that an inverted spectral indexalpha~-0.3 (S~nu^-alpha) could be characteristic of all the nuclei,going from low-luminosity radio galaxies to powerful quasars. Takingthis spectral index into account, the measured flux density does notchange very much, going from a scale of tens of kpc (corresponding tothe low-resolution observations) to the sub-kpc scale of the newobservations. Thus, most of the flux observed in the central regionoriginates in a sub-kpc area. With the new PTI data we obtain a betterestimate of the radio core dominance (R), i.e. the ratio between thecore and the extended radio flux. This parameter is claimed to be a goodindicator of the orientation of the beamed radiation with respect to theline of sight, and hence a very important parameter for testing `unifiedschemes' for active galactic nuclei (AGN). Using this parameter,together with optical spectroscopic information, we find that the radiocore dominance shows different distributions for different radio andoptical characteristics. A statistically significant difference in thedistribution of R is observed between Fanaroff-Riley (FR) I and FR IIradio galaxies, supporting the idea that low-power sources are lessaffected by beaming because they have, on average, a lower Lorentzfactor. Among the FR II radio galaxies, narrow-line radio galaxies(NLRGs) show lower values of R while the broad-line radio galaxies(BLRGs) have the largest R. Moreover, the median value of R for BLRGs islower than for steep-spectrum quasars (SSQ) even after a number ofselection effects are taken into account. This result can be explainedin the framework of unified schemes for AGN assuming that in the BLRGswe are seeing more directly into the nucleus, although not as much as inSSQs.
| Optical surface photometry of radio galaxies - I. Observations and data analysis
This is the first paper of a series aimed at studying the structural andphotometric properties in the optical band of a sample of 95 radiogalaxies. Detailed surface photometry in the B and R bands is reportedhere for 29 objects. We give contour plots and complete structural(ellipticity, position angle, Fourier coefficients) and photometricprofiles as a function of the major axis for each object. The integratedobserved properties (isophotal and total magnitude, effective radius,etc.) as derived from detailed surface photometry, are reported. Therelationship between effective radius R_e and surface brightness mu_e,and the properties of the immediate environment are discussed. Commentson all individual objects are also included.
| The soft X-ray properties of a complete sample of radio sources.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996MNRAS.279.1331S&db_key=AST
| The Molonglo Reference Catalog/1 Jansky Radio Source Survey. I. Radio Galaxy Identifications
This is the first in a series of papers discussing the properties of acomplete set of radio sources selected near S_408_ = 1 Jy. We presentoptical or infrared identifications for a sample of 452 radio galaxies.The sources were selected from the 408 MHz Molonglo Reference Catalog,restricted only by flux density and position on the sky, as follows:S_408_ >= 0.95 Jy and -30^deg^ < decl. (1950) <-20^deg^, and9^h^20^m^ < R.A.(1950) < 14^h^4^m^ or 20^h^20^m^ < R.A.(1950)< 6^h^14^m^. This complete sample, the MRC/1 Jy survey, contains 558radio galaxies or quasars, of which six are occulted by bright stars orgalaxies and two are multiple confused sources. Of the remaining 550sources, 527, or 96%, are identified to an r magnitude of 25, and eightadditional sources are identified to K = 19. Of the 17 unoccultedobjects that remain unidentified, 15 are sources for which we haveeither poor radio maps or inadequate optical/IR images. This paperpresents finding charts and astrometric positions for the 452 sourcesthat are not identified as either quasars or BL Lacertae objects.Magnitudes in the r passband accurate to typically 0.1 mag are given for353 of the radio galaxy identifications. Redshifts for 268 of thegalaxies are also listed; these have been derived from 450 spectroscopicobservations. The radio observations, quasar and BL Lac identifications,spectroscopy, and near- IR images will be presented in subsequent papersin this series.
| 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.
| Parsecscale Radio Cores in Early Type Galaxies
We find compact (<0.03 arcsec) radio-continuum cores in about 70 percent of radio-emitting elliptical and S0 galaxies over a wide range intotal radio power (10^21^-,10^26^ W Hz^-1^ at 5 GHz). The cores usuallyhave a flat or rising spectrum between 2.3 and 8.4 GHz, with a medianspectral index of + 0.3. Even at low luminosities, the radio emissionfrom most elliptical galaxies appears to be powered by a parsec-scale`engine' like those in classical radio galaxies and quasars. The coreand total radio power are related (P_core_ is proportional toP_total_^0.7^ on average), and the parsec-scale cores of radio galaxiesare typically one hundred times more powerful than those in `normal'giant elliptical galaxies.
| Dumbbell galaxies and multiple nuclei in rich clusters: radio data
We present radio observations at 6 cm for 93 ACO clusters, in which thebrightest member consists of either two galaxies of roughly equalbrightness inside a common halo (a dumbbell) or has multiple nuclei. Asubsample of 27 dumbbell systems, belonging to a volume-limited sample,was observed with the VLA and ATCA. The remaining clusters were mappedwith the VLA. The detection rate in the volume-limited sample is 44%. Inall 93 clusters observed 43 brightest cluster members were detected inthe radio. Parameters are presented for all the radio sources detectedin the cluster fields.
| The optical identification status of the 1 Jy radio source catalogue
Optical identifications, magnitudes, redshifts, and polarization datahave been gathered from an extensive literature search to form an updateof the optical data for the radio sources of the 1 Jy catalogue. Of the527 radio sources in the revised catalogue, 97% have opticalcounterparts, and redshifts are given for 90% of the opticallyidentified sources. For all but a few sources, accurate interferometerradio position are provided. References are made to well knowncompilations as well as to individual papers, often supplemented byspecial notes on individual objects.
| The Radio Structures of Southern 2-JY Radio Sources
A subsample of the Wall & Peacock 2-Jy sample of radio sources, withredshift z < 0.7 or unknown and declination δ < + 10^deg^,has been selected and observed in the radio at 6 cm (or information wasobtained from the literature where appropriate) and in the optical withlow- dispersion spectroscopy. Here we present the new radio data. Weobserved 66 sources with the Very Large Array and seven southern sourceswith the Australia Telescope Compact Array. Together with the datacollected from the literature, we now have information about the radiostructure of 107 sources. These data will be discussed along withoptical spectra for the sample in a future paper.
| Optical Spectroscopy of a Complete Sample of Southern 2-JY Radio Sources
We present optical spectra for a complete sample of radio galaxies andquasars comprising all sources from the Wall & Peacock 2.7-GHzsample with redshifts z < 0.7 and declinations δ < +10^deg^; this sample is complete down to a flux density of 2 Jy.Although not all of the 2-Jy sources have spectroscopic redshifts, weargue that most of the unidentified objects are at high redshifts andthat our z < 0.7 sample is largely complete. The optical data will beanalysed in a future paper.
| 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.
| VLA : a l'ecoute DU Cosmos.
Not Available
| Detection of excess rotation measure due to intracluster magnetic fields in clusters of galaxies
The Faraday rotation measures of a sample of extragalactic radio sourcesprojected within a third of an Abell radius of a galaxy cluster werecompared with those of sources located further from cluster centers. Theresult strongly indicates that the distribution of the residual rotationmeasure (RRM) in the former population is broadened, at a confidencelevel exceeding 99 percent. The broadening is detectable out to1/h50 Mpc. The best present estimate of the excess Faradayrotation measure varies from 100 + or - 36 rad/sq m in the central sixthof an Abell radius to 36 + or - 15 rad/sq m further out. The combinationof these results with electron densities determined from X-ray data forsome of the clusters suggests that magnetic field strengths in clustergas are of order 1 microgauss.
| 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.
| Parkes radio sources in the directions of southern rich clusters
A listing of all Parkes radio sources coincident within 0.3 clusterradii of southern rich clusters of galaxies studied by Abell et al.(1989) is compiled. A pronounced peak of radio sources very near thecluster centers was found. Bautz Morgan type I clusters tend to havemore powerful radio sources and are radio-load about 5 times more oftenthan clusters without dominant central galaxies. There is no strongcorrelation between radio emission and richness class. It is found thatthe slope of the cluster-radio source two-point angular correlationfunction is twice that of the galaxy-galaxy correlation function.Furthermore, the correlation amplitude for stronger sources (greaterthan 0.65 Jy) is nearly twice that of the entire Parkes catalog samplesuggesting a tighter correlation with cluster centers for the strongersources. Finally, the distribution of spectral indices for Parkessources within ACO clusters is different from that outside the clusters;stronger cluster sources have steeper spectra on average.
| Molonglo Radio Sources in the Directions of Southern Abell Clusters
We present lists of the radio sources from the 408-MHz MolongloReference Catalogue which have projected separations less than 500kpc(0.33 R_Abell_) from rich southern clusters of galaxies in the newAbell, Corwin & Olowin catalogue. There are 107 such sources in thedirections of 94 clusters for the new southern catalogue, of which weestimate about 27 sources are chance alignments, not associated with thecluster concerned. We also list 89 sources similarly 'coincident' withclusters in the supplementary southern catalogue, and 99 for the revisednorthern catalogue (to the northern declination limit of the MolongloReference Catalogue, +18.5^deg^). We find a stronger concentration ofthe radio sources to the cluster centre than in previous work. Weattribute this to the effects of dominant galaxies at the clustercentres, as revealed by better positional accuracy than for previouslarge-scale radio surveys of clusters.
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