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The Luminosity Function of the Fossil Group RX J1552.2+2013
We determine the first fossil group luminosity function based onspectroscopy of the member galaxies. The fossil group RX J1552.2+2013has 36 confirmed members, is at a mean redshift of 0.136, and has avelocity dispersion of 623 km s-1 (or 797 km s-1if four emission-line galaxies in the outskirts of the velocitydistribution are included). The luminosity function of RX J1552.2+2013,measured within the inner region of the system (~1/3Rvir) inthe range -23.5
| 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.
| ASCA Compilation of X-Ray Properties of Hot Gas in Elliptical Galaxies and Galaxy Clusters: Two Breaks in the Temperature Dependences
Utilizing ASCA archival data of about 300 objects of ellipticalgalaxies, groups, and clusters of galaxies, we performed systematicmeasurements of the X-ray properties of hot gas in their systems, andcompiled them in this paper. The steepness of the luminosity-temperature(LT) relation, LiX ∝ (kT)α, in therange of kT 1.5 ‑ 15 keV is α = 3.17 ± 0.15,consistent with previous measurements. In the relation, we find twobreaks at around ICM temperatures of 1 keV and 4 keV: α = 2.34± 0.29 above 4 keV, 3.74 ± 0.32 in 1.5-5 keV, and 4.03± 1.07 below 1.5keV. Such two breaks are also evident in thetemperature and size relation. The steepness in the LT relation at kT> 4 keV is consistent with the scale-relation derived from the CDMmodel, indicating that the gravitational effect is dominant in richerclusters, while poorer clusters suffer non-gravity effects. The steep LTrelation below 1keV is almost attributed to X-ray faint systems ofelliptical galaxies and galaxy groups. We found that the ICM mass withinthe scaling radius R1500 follows the relation ofMgas ∝ T2.33±0.07 from X-ray faintgalaxies to rich clusters. Therefore, we speculate that even such X-rayfaint systems contain a large-scale hot gas, which is too faint todetect.
| Construction of a Celestial Coordinate Reference Frame from VLBI Data
A large number (2 million) of VLBI observations have been reducedin order to refine the measured coordinates of the observed radiosources. The data reduction was carried out in the OCCAM package usingthe least squares colocation method. Corrections to the coordinates of642 objects were derived. The accuracy of the catalog is no worse than0.2 milliseconds of arc for stable sources.
| Radio-selected Galaxies in Very Rich Clusters at z <= 0.25. I. Multiwavelength Observations and Data Reduction Techniques
Radio observations were used to detect the ``active'' galaxy populationwithin rich clusters of galaxies in a nonbiased manner that is notplagued by dust extinction or the K-correction. We present wide-fieldradio, optical (imaging and spectroscopy), and ROSAT All-Sky Survey(RASS) X-ray data for a sample of 30 very rich Abell (R>=2) clusterswith z<=0.25. The VLA radio data samples the ultrafaint radio(L1.4>=2×1022 W Hz-1) galaxypopulation within these extremely rich clusters for galaxies withMR<=-21. This is the largest sample of low-luminosity 20cm radio galaxies within rich Abell clusters collected to date.The radio-selected galaxy sample represents the starburst (starformation rate >=5 Msolar yr-1) and activegalactic nuclei populations contained within each cluster. Archival andnewly acquired redshifts were used to verify cluster membership for most(~95%) of the optical identifications. Thus, we can identify all thestarbursting galaxies within these clusters, regardless of the level ofdust obscuration that would affect these galaxies being identified fromtheir optical signature. Cluster sample selection, observations, anddata reduction techniques for all wavelengths are discussed.
| A new catalogue of ISM content of normal galaxies
We have compiled a catalogue of the gas content for a sample of 1916galaxies, considered to be a fair representation of ``normality''. Thedefinition of a ``normal'' galaxy adopted in this work implies that wehave purposely excluded from the catalogue galaxies having distortedmorphology (such as interaction bridges, tails or lopsidedness) and/orany signature of peculiar kinematics (such as polar rings,counterrotating disks or other decoupled components). In contrast, wehave included systems hosting active galactic nuclei (AGN) in thecatalogue. This catalogue revises previous compendia on the ISM contentof galaxies published by \citet{bregman} and \citet{casoli}, andcompiles data available in the literature from several small samples ofgalaxies. Masses for warm dust, atomic and molecular gas, as well asX-ray luminosities have been converted to a uniform distance scale takenfrom the Catalogue of Principal Galaxies (PGC). We have used twodifferent normalization factors to explore the variation of the gascontent along the Hubble sequence: the blue luminosity (LB)and the square of linear diameter (D225). Ourcatalogue significantly improves the statistics of previous referencecatalogues and can be used in future studies to define a template ISMcontent for ``normal'' galaxies along the Hubble sequence. The cataloguecan be accessed on-line and is also available at the Centre desDonnées Stellaires (CDS).The catalogue is available in electronic form athttp://dipastro.pd.astro.it/galletta/ismcat and at the CDS via anonymousftp to\ cdsarc.u-strasbg.fr (130.79.128.5) or via\http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/405/5
| Non-confirmation of reported HI clouds without optical counterparts in the Hercules cluster
21 cm H I line observations were made with the Arecibo Gregoriantelescope of 9 H I clouds in the Hercules Cluster which were reported astentative detections in a VLA H I study of the cluster (Dickey\cite{Dickey97}) and for which our deep CCD imaging failed to find anyoptical counterparts. No sensitive observations could be made of one ofthese (sw-174) due to the presence of a close-by strong continuumsource. The other 8 tentative H I detections were not confirmed by theArecibo H I measurements. The CCD images did reveal faint, low surfacebrightness counterparts near the centres of two other VLA H I sourcesinvisible on the Palomar Sky Survey, sw-103 and sw-194.
| 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
| A catalogue and analysis of X-ray luminosities of early-type galaxies
We present a catalogue of X-ray luminosities for 401 early-typegalaxies, of which 136 are based on newly analysed ROSAT PSPC pointedobservations. The remaining luminosities are taken from the literatureand converted to a common energy band, spectral model and distancescale. Using this sample we fit the LX:LB relationfor early-type galaxies and find a best-fit slope for the catalogue of~2.2. We demonstrate the influence of group-dominant galaxies on the fitand present evidence that the relation is not well modelled by a singlepower-law fit. We also derive estimates of the contribution to galaxyX-ray luminosities from discrete-sources and conclude that they provideLdscr/LB~=29.5ergs-1LBsolar-1. Wecompare this result with luminosities from our catalogue. Lastly, weexamine the influence of environment on galaxy X-ray luminosity and onthe form of the LX:LB relation. We conclude thatalthough environment undoubtedly affects the X-ray properties ofindividual galaxies, particularly those in the centres of groups andclusters, it does not change the nature of whole populations.
| The K-band Hubble diagram for the brightest cluster galaxies: a test of hierarchical galaxy formation models
We analyse the K-band Hubble diagram for a sample of brightest clustergalaxies (BCGs) in the redshift range 02) that is evolvingpassively. We can thus use evolutionary population synthesis models toestimate the rate of growth in stellar mass for these systems. We findthat the stellar mass in a typical BCG has grown by a factor ~=2 sincez~=1 if q_0=0.0, or by factor ~=4 if q_0=0.5. These results are in goodagreement with the predictions of semi-analytic models of galaxyformation and evolution set in the context of a hierarchical scenariofor structure formation. The models predict a scatter in theluminosities of the BCGs that is somewhat larger than the observed one,but that depends on the criterion used to select the model clusters.
| The Deep X-Ray Radio Blazar Survey. I. Methods and First Results
We have undertaken a survey, the Deep X-Ray Radio Blazar Survey (DXRBS),of archived, pointed ROSAT Position Sensitive Proportional Counter datafor blazars by correlating the ROSAT WGACAT database with severalpublicly available radio catalogs, restricting our candidate list toserendipitous flat radio spectrum sources (alpha_r <= 0.70, whereS_nu ~ nu^-alpha_r . We discuss our survey methods, identificationprocedure, and first results. Our survey is found to be ~95% efficientat finding flat-spectrum radio-loud quasars (FSRQs; 59 of our first 85identifications) and BL Lacertae objects (22 of our first 85identifications), a figure that is comparable to or greater than thatachieved by other radio and X-ray survey techniques. The identificationspresented here show that all previous samples of blazars (even whentaken together) did not representatively survey the blazar population,missing critical regions of (L_X, L_R) parameter space within whichlarge fractions of the blazar population lie. Particularly important isthe identification of a large population of FSRQs (>~25% of DXRBSFSRQs) with ratios of X-ray to radio luminosity >~10^-6 (alpha_rx<~ 0.78). In addition, as a result of our greater sensitivity, theDXRBS has already more than doubled the number of FSRQs in completesamples with 5 GHz (radio) luminosities between 10^31.5 and 10^33.5 ergss^-1 Hz^-1, and fills in the region of parameter space betweenX-ray-selected and radio-selected samples of BL Lac objects. The DXRBSis the very first sample to contain statistically significant numbers ofblazars at low luminosities, approaching what should be the lower end ofthe FSRQ luminosity function. Based on observations collected at theEuropean Southern Observatory, La Silla, Chile; Kitt Peak NationalObservatory; Cerro Tololo Inter-American Observatory; and the AustraliaTelescope National Facility.
| Kinematics of the Hercules supercluster
The Hercules supercluster consists of the Abell clusters A2147, A2151,and A2152. Previous studies of the kinematics have been confounded bythe difficulty of correctly assigning galaxies to the individualclusters, which are not well separated. Our study has a total of 468available velocities for galaxies in the region, 175 of them new. Thereare 414 galaxies in the supercluster, about three times the number usedin the previous supercluster study. We verify the existence of the threeindividual clusters and compute their individual dynamical parameters.We investigate several techniques for assigning galaxy membership toclusters in this crowded field. We use the KMM mixture-modelingalgorithm to separate the galaxies into clusters; we find that A2152 hasa higher mean velocity than previous studies have reported. A2147 andA2152 also have lower velocity dispersions: 821 and 715 km/s,respectively. The assignment of galaxies to either A2152 or A2147requires velocity and position information. We study the kinematics ofthe supercluster using the two-body formalism of Beers et al. (1982) andconclude that A2147 and A2151 are probably bound to each other and thatthe supercluster as a whole may also be bound. The mass of thesupercluster, if bound, is (7.6 +/- 2.0) 10 exp 15/h M(solar); with thesupercluster luminosity, (1.4 +/- 0.2) 10 exp 13/sq h L(solar), thisyields 0.34 +/- 0.1.
| 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.
| A VLA Survey of the Hercules Cluster.I.The HI Data
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....113.1939D&db_key=AST
| A survey of the ISM in early-type galaxies. I. The ionized gas.
We present results of a CCD optical imaging survey of the ionized gas in73 luminous elliptical and lenticular galaxies, selected from the RC3catalog to represent a broad variety of X-ray, radio, infrared andkinematical properties. For each galaxy we have used broad-band R imagesand narrow-band images centered at the Hα and [NII] emission linesto derive the luminosity and distribution of the ionized gas. We foundthat a large fraction of E (72%) and S0 (85%) galaxies in our samplecontain ionized gas. The gas morphology appears to be rather smooth formost galaxies; however ~12% of the sample galaxies show a very extendedfilamentary structure. According to the morphology and size of the gasdistribution, the galaxies have been classified into three broad groups,named small disk (SD), regular extended (RE) and filamentary structure(F). The mean diameter of the emitting region ranges between 1 and10kpc; the derived mass of the ionized gas ranges between 10^3^ and10^5^ solar masses. A significant correlation between Hα+[NII] andX-ray luminosities is found for those galaxies (27% of the sample) forwhich we have detected ionized gas and are also listed as X-ray sources.However, there are relatively strong X-ray emitting galaxies for whichwe have not detected Hα+[NII] emission and objects which showemission-lines but are not listed either in the EINSTEIN or in the ROSATdatabases. The distribution of datapoint and upper limits in thisdiagram suggests that galaxies with warm gas are also X-ray emitters,while there are X-ray emitters without measurable Hα+[NII]emission. Similar characteristics are present in the correlation betweenthe infrared luminosity in the 12 μm band and L_Hα+[NII]_;correlations with other infrared wavelengths are weaker. A strongcorrelation was also found between the Hα+[NII] luminosity and theluminosity in the B band inside the region occupied by the line-emittinggas. We use these correlations to discuss the possible mechanismsresponsible for the gas ionization and excitation, analyzing inparticular the role of the post-AGB stars and the thermal conductionfrom the X-ray halo in providing the necessary source of ionization.
| 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.
| A multiparametric analysis of the Einstein sample of early-type galaxies. 1: Luminosity and ISM parameters
We have conducted bivariate and multivariate statistical analysis ofdata measuring the luminosity and interstellar medium of the Einsteinsample of early-type galaxies (presented by Fabbiano, Kim, &Trinchieri 1992). We find a strong nonlinear correlation betweenLB and LX, with a power-law slope of 1.8 +/- 0.1,steepening to 2.0 +/- if we do not consider the Local Group dwarfgalaxies M32 and NGC 205. Considering only galaxies with logLX less than or equal to 40.5, we instead find a slope of 1.0+/- 0.2 (with or without the Local Group dwarfs). Although E and S0galaxies have consistent slopes for their LB-LXrelationships, the mean values of the distribution functions of bothLX and LX/LB for the S0 galaxies arelower than those for the E galaxies at the 2.8 sigma and 3.5 sigmalevels, respectively. We find clear evidence for a correlation betweenLX and the X-ray color C21, defined by Kim,Fabbiano, & Trinchieri (1992b), which indicates that X-rayluminosity is correlated with the spectral shape below 1 keV in thesense that low-LX systems have relatively large contributionsfrom a soft component compared with high-LX systems. We findevidence from our analysis of the 12 micron IRAS data for our samplethat our S0 sample has excess 12 micron emission compared with the Esample, scaled by their optical luminosities. This may be due toemission from dust heated in star-forming regions in S0 disks. Thisinterpretation is reinforced by the existence of a strongL12-L100 correlation for our S0 sample that is notfound for the E galaxies, and by an analysis of optical-IR colors. Wefind steep slopes for power-law relationships between radio luminosityand optical, X-ray, and far-IR (FIR) properties. This last point arguesthat the presence of an FIR-emitting interstellar medium (ISM) inearly-type galaxies is coupled to their ability to generate nonthermalradio continuum, as previously argued by, e.g., Walsh et al. (1989). Wealso find that, for a given L100, galaxies with largerLX/LB tend to be stronger nonthermal radiosources, as originally suggested by Kim & Fabbiano (1990). We notethat, while LB is most strongly correlated withL6, the total radio luminosity, both LX andLX/LB are more strongly correlated with L6CO, the core radio luminosity. These points support the argument(proposed by Fabbiano, Gioia, & Trinchieri 1989) that radio cores inearly-type galaxies are fueled by the hot ISM.
| Integrated photoelectric magnitudes and color indices of bright galaxies in the Johnson UBV system
The photoelectric total magnitudes and color indices published in theThird Reference Catalogue of Bright Galaxies (RC3) are based on ananalysis of approximately equals 26,000 B, 25,000 B-V, and 17,000 U-Bmultiaperture measurements available up to mid 1987 from nearly 350sources. This paper provides the full details of the analysis andestimates of internal and external errors in the parameters. Thederivation of the parameters is based on techniques described by theVaucouleurs & Corwin (1977) whereby photoelectric multiaperture dataare fitted by mean Hubble-type-dependent curves which describe theintegral of the B-band flux and the typical B-V and U-B integrated colorgradients. A sophisticated analysis of the residuals of thesemeasurements from the curves was made to allow for the random andsystematic errors that effect such data. The result is a homogeneous setof total magnitudes BTA total colors(B-V)T and (U-B)T, and effective colors(B-V)e and (U-B)e for more than 3000 brightgalaxies in RC3.
| The complex structure of Abell 2151 (Hercules)
We analyzed the space distribution of 117 galaxies in an area of 0.9 degradius centered on NGC 6045 in the Hercules cluster in the velocityrange 9000 to 14,000 km/s. By taking advantage of 74 morphologies basedon CCD images, we succeed in isolating a cluster of galaxies with anaverage velocity of 11,467 km/s located to the NE of the assumedcentroid of A2151, where early and late type galaxies share the samedynamical properties. The implications of this result for the nature andidentification of the x-ray source is briefly discussed.
| Dark matter and dynamics in the Hercules Cluster (A2151)
New 21-cm observations of faint spiral galaxies in the Hercules cluster(A2151) are presented in order to investigate the dynamics throughoutthe cluster core, out to a projected radius of 1.8/h Mpc. The globaldynamical mass of Hercules is calculated using the virial theorem andthe projected mass estimator. These masses lie in the range 3-9 x 10 exp14 solar masses. The importance of subclustering in A2151 by eye isexamined via the statistical test of Dressler & Shectman (1988), andby considering the effects of the detected substructure on the dynamicalmass determination. The clumpy distribution is interpreted as a signthat the galaxies in the cluster have not reached dynamical equilibriumin the gravitational potential.
| The kinematics of dense clusters of galaxies. I - The data
We have measured redshifts in the fields of the 31 R greater than 1Abell clusters with z of 0.02-0.05 and absolute b exp II above 30 deg.At least ten of the fields are severely contaminated by superimposedvelocity peaks. We derive the mean velocities and velocity dispersionsof the 25 dense peaks in the sample. The abundance of peaks, 6.6 x 10exp -6 h-cubed Mpc exp -3, is consistent with the mean number density ofR above 1 Abell clusters. The range of velocity dispersions is 304-1346km/s. The median dispersion is 718 km/s. The subset of eight systemswith cD galaxies has a median velocity dispersion of 792 km/s, close tothat of non-cD systems (626 km/s). When these data are combined with 16cD cluster velocity dispersions from our previous study (Zabludoff etal., 1990, or ZHG) and Dunn (1991), eight of 25 cD galaxies havepeculiar motions larger than half the cluster velocity dispersions.These findings further support the conclusions of Beers and Geller(1983), ZHG, and Dunn (1991), who argue that cD galaxies do not lie inthe global kinematic center, but in local potential minima. If so,systems with speeding cD's are probably a guide to substructure indynamically evolving systems.
| Observations of 10 tailed radio sources at 10.6 GHz
We have used the Effelsberg 100-m telescope to map ten tailed radiosources at 10.6 GHz (lambda 2.8 cm). We find extended emission at theoutskirts of the tails, with degrees of linear polarization as high asthe theoretically expected values in some cases. At the sources' headswe generally find low degrees of polarization, most likely as result ofstrong beam depolarization caused by the strong initial bending of thejets along with magnetic fields. The orientation of the magnetic fieldis mostly along the tails in their outer reaches, and in some casestransverse closer to the central sources. We have detected somepronounced asymmetries of the polarization between the two lateralhalves of the tails, which is interpreted as an intrinsic difference inthe degree of ordering of the magnetic field. The total radio spectra ofthe radio galaxies in this sample are found to show a high-frequencysteepening, consistent with aging of radiating electrons.
| An X-ray catalog and atlas of galaxies
An X-ray catalog and atlas of galaxies observed with the EinsteinObservatory imaging instruments (IPC and HRI) are presented. The catalogcomprises 493 galaxies, including targets of pointed observations, andRSA or RC2 galaxies serendipitously included in Einstein fields. A totalof 450 of these galaxies were imaged well within the instrumentalfields, resulting in 238 detections and 2123 sigma upper limits. Theother galaxies were either at the edge of the visible field of view orconfused with other X-ray sources. For these a rough measure of theirX-ray emission is also given. The atlas shows X-ray contour maps ofdetected galaxies superposed on optical photographs and givesazimuthally averaged surface brightness profiles of galaxies detectedwith a high signal-to-noise ratio.
| The stellar content of central dominant galaxies. II - Colors of cD envelopes
The study presents deep g- and r-band CCD imaging of three richclusters, A2589, A2634, and A407, containing cD galaxies or structurespossibly relating to cD envelopes. Scattered light r exp -2 halos weremodeled and subtracted from the images. The (g-r) color profiles of thecDs NGC 7647 (A2589) and NGC 7720 (A2634) down to the start of theenvelopes are found to be quite flat. There is no evidence of a changein color at the surface brightness break that signifies the start of thecD envelope, nor are the colors of the envelope dramatically blue. Thecolor profile of the D galaxy NGC 7728 also in A2634 displays a steeperblueward color gradient than NGC 7720. A407, which has nine nuclei in acommon envelope, may also possess a red envelope in comparison to itshigher surface brightness region, and thus may evolve into a cD similarto NGC 7647. The implications for cD envelope formation and evolutionare discussed.
| The large-scale clustering of radio galaxies
An all-sky sample of radio galaxies at redshifts equal to or less than0.1 is used to study clustering in the universe on scales up to severalhundred Mpc. The two-point correlation function for these galaxies isconsistent with their high optical luminosity and location in moderatelyrich environment. Direct methods for obtaining the power spectrum of thedensity field traced by the radio galaxies are discussed taking intoaccount the selection function of the sample. The results of thepower-spectrum analysis indicate that the distribution of radio galaxiesis more uniform on very large scales than would be predicted from anextrapolation of the power-law clustering found on small scales.
| The ultraviolet spectra of nearby radio galaxies
New and archival IUE SWP spectra are reported for nine nearby radiogalaxies (V is less than 15 mag), together with optical emissionlikedata for these galaxies as well as a number of candidates with weakerline emission. Both their UV line and continuum properties, as well astheir UV and UV-optical line ratios, are examined. Ly-alpha emission isfound to be common among local radio galaxies, at modest luminosities(typically 10 exp 41-42 erg/s). No apparent relation is found betweenL(Ly-alpha) and radio power for the nearby radio galaxies alone. TheLy-alpha/H-alpha ratio in low power nearby radio galaxies is 2-5 timeslower than the prediction for case B recombination. The destruction ofLy-alpha photons by grains during resonant scattering can explain theobserved deficiency for reasonable metallicities. The nearby radiogalaxies have in general a small C IV/Ly-alpha ratio (less than 0.1).Comparison of the C IV and Ly-alpha strengths with those in luminous AGNsuggests that most of the UV continuum comes from the stellarpopulation, and not from the AGN.
| The surface brightness test for the expansion of the universe. III - Reduction of data for the several brightest galaxies in clusters to standard conditions and a first indication that the expansion is real
Petrosian radii, effective radii, apparent magnitudes, and averagesurface brightnesses are presented for the first few ranked galaxies in56 nearby clusters and groups. The correlations between (SB) and both Mand R are derived from the data, and a selection effect that imitates aTolman signal in these data but which is an artifact of the sample isdiscussed. Correction procedures are applied to the high-redshift galaxysample of Djorgovski and Spinrad (1981), and a well-defined Tolmansignal is found in the data. Although this appears to be strong proofthat the universe expands and therefore that the conventionalinterpretation of the redshift is correct, the reliability of theconclusion is cautioned. Methods to optimize the Tolman test in futureobservational programs are discussed.
| Radio emission and the hot interstellar medium of early-type galaxies
The results of an analysis of a sample of 84 elliptical and S0 galaxies,observed in X-rays with the Einstein Observatory and in radio continuumat 5 GHz, are reported. Radio flux densities result in some of thelowest radio powers yet reported for early-type galaxies. Radiostructures extending beyond the optical radius are found only ingalaxies with 5 GHz radio power greater than about 10 exp 29.5ergs/s/Hz. Radio and X-ray luminosities are correlated, although withlarge intrinsic scatter, suggesting that more than one mechanism may beinvolved. A correlation between core radio power and theX-ray-to-optical ratio suggests a connection between the hot ISM andnuclear radio sources and points to accreting cooling flows as the fuelfor the radio sources. For the same radio core power, extended radiolobes tend to be associated with galaxies with relatively smallerX-ray-to-optical ratios, pointing to the importance of the hot ISM indisrupting the radio jets and confining extended radio structures.
| 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.
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