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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.
| K-band Properties of Galaxy Clusters and Groups: Brightest Cluster Galaxies and Intracluster Light
We investigate the near-infrared K-band properties of the brightestcluster galaxies (BCGs) in a sample of 93 X-ray galaxy clusters andgroups, using data from the Two Micron All Sky Survey. Our clustersample spans a factor of 70 in mass, making it sensitive to any clustermass-related trends. We derive the cumulative radial distribution forthe BCGs in the ensemble and find that 70% of the BCGs are centered inthe cluster to within 5% of the virial radius r200; thisquantifies earlier findings that BCG position coincides with the clustercenter as defined by the X-ray emission peak. We study the correlationsbetween the luminosity of the BCGs (Lb) and the mass and theluminosity of the host clusters, finding that BCGs in more massiveclusters are more luminous than their counterparts in less massivesystems and that the BCGs become less important in the overall clusterlight (L200) as cluster mass increases. By examining a largesample of optically selected groups, we find that these correlationshold for galactic systems less massive than our clusters(<3×1013 Msolar). From the differencesbetween luminosity functions in high- and low-mass clusters, we arguethat BCGs grow in luminosity mainly by merging with other luminousgalaxies as the host clusters grow hierarchically; the decreasing BCGluminosity fraction (Lb/L200) with cluster massindicates that the rate of luminosity growth in BCGs is slow compared tothe rate at which clusters acquire galaxy light from the field or othermerging clusters. Utilizing the observed correlation between the clusterluminosity and mass and a merger tree model for cluster formation, weestimate that the amount of intracluster light (ICL) increases withcluster mass; our calculations suggest that in 1015Msolar clusters more than 50% of total stellar mass is inICL, making the role of ICL very important in the evolution andthermodynamic history of clusters. The cluster baryon fractionaccounting for the ICL is in good agreement with the value derived fromcosmic microwave background observations. The inclusion of ICL reducesthe discrepancy between the observed cluster cold baryon fraction andthat found in hydrodynamical simulations. Based on the observed ironabundance in the intracluster medium, we find that the ICL predicted byour model, together with the observed galaxy light, match the ironmass-to-light ratio expected from simple stellar population models,provided that the Salpeter initial mass function is adopted. The ICLalso makes it easier to produce the ``iron excess'' found in the centralregions of cool-core clusters.
| 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 athttps://www.edpsciences.org
| Spatially resolved X-ray spectroscopy of cooling clusters of galaxies
We present spatially resolved X-ray spectra taken with the EPIC camerasof XMM-Newton of a sample of 17 cooling clusters and three non-coolingclusters for comparison. The deprojected spectra are analyzed with amulti-temperature model, independent of any a priori assumptions aboutthe physics behind the cooling and heating mechanisms. All coolingclusters show a central decrement of the average temperature, most ofthem of a factor of 2. Three clusters (Sérsic 159-3, MKW 3sand Hydra A) only show a weak temperature decrement, while two others (A399 and A 2052) have a very strong temperature decrement. All coolingclusters show a weak pressure gradient in the core. More important, ateach radius within the cooling region the gas is not isothermal. Thedifferential emission measure distribution shows a strong peak near themaximum (ambient) temperature, with a steep decline towards lowertemperatures, approximately proportional to T3, oralternatively a cut-off at about a quarter to half of the maximumtemperature. In general, we find a poor correlation between radio fluxof the central galaxy and the temperature decrement of the cooling flow.This is interpreted as evidence that except for a few cases (like theHydra A cluster) heating by a central AGN is not the most common causeof weak cooling flows. We investigate the role of heat conduction byelectrons and find that the theoretically predicted conductivity ratesare not high enough to balance radiation losses. The differentialemission measure distribution has remarkable similarities with thepredictions from coronal magnetic loop models. Also the physicalprocesses involved (radiative cooling, thermal conduction along theloops, gravity) are similar for clusters loops and coronal loops. Ifcoronal loop models apply to clusters, we find that a few hundred loopsper scale height should be present. The typical loop sizes deduced fromthe observed emission measure distribution are consistent with thecharacteristic magnetic field sizes deduced from Faraday rotationmeasurements.
| 870 Micron Observations of Nearby 3CRR Radio Galaxies
We present submillimeter continuum observations at 870 μm of thecores of low-redshift 3CRR radio galaxies, observed at the HeinrichHertz Submillimeter Telescope. The cores are nearly flat-spectrumbetween the radio and submillimeter, which implies that thesubmillimeter continuum is likely to be synchrotron emission and notthermal emission from dust. The emitted power from nuclei detected atoptical wavelengths and in the X-rays is similar in the submillimeter,optical, and X-rays. The submillimeter-to-optical and X-ray power ratiossuggest that most of these sources resemble misdirected BL Lac-typeobjects with synchrotron emission peaking at low energies. However, wefind three exceptions, the FR I galaxy 3C 264 and the FR II galaxies 3C390.3 and 3C 338 with high X-ray-to-submillimeter luminosity ratios.These three objects are candidate misdirected high- orintermediate-energy peaked BL Lac-type objects. With additional infraredobservations and from archival data, we compile spectral energydistributions for a subset of these objects. The steep dips observednear the optical wavelengths in many of these objects suggest thatextinction inhibits the detection and reduces the flux of opticalcontinuum core counterparts. High-resolution near- or mid-infraredimaging may provide better measurements of the underlying synchrotronemission peak.
| The Ultraviolet Continuum Emission of FR I and FR II Radio Galaxies and a Proposal for a Unified AGN Model for FR I sources
This paper is the second in a series of two on the UV continuum emission(in the range from 1400 to 3700 Å) of radio galaxies that wereextracted from the Hubble Space Telescope (HST) Archives. The sampleconsists of 31 3C and Parkes radio galaxies that have redshifts below0.2 (the majority have redshifts of ~0.03) and radio powers of~1025-1027 W Hz-1 (usingH0=50 km-1 s-1 Mpc andq0=0.0). Paper I describes the sample selection and theproperties of individual sources; this paper deals with the analysis. Wefind that only about half the radio galaxies display any UV flux atwavelengths shorter than 2300 Å. More specifically, those galaxiesthat are dominated by a nuclear UV component are either BL Lac objectsor radio galaxies with broad emission lines. We detect a nuclear and anextended UV component only among half the radio galaxies with narrowemission lines. Although we do not find a correlation of the UVluminosity with emission-line luminosity or radio power, there doesappear to be a dependence on radio morphology. While (narrow line) FR IIsources do not show a nuclear UV component, FR I's do, however, only ifthey also have an optical jet (this is the case for seven of 21 FR I's).These results are broadly consistent with orientation-dependentunification models. In radio galaxies in which the torus does notobscure our view of the engine, the observed UV radiation appears to bepoint source-like. This is the case for broad-line radio galaxies and BLLac objects. In other radio galaxies that are oriented at an angle tous, the torus presumably blocks the nuclear UV component. Thenarrow-line FR I galaxies with optical jets can then be interpreted asobjects at a critical angle at which some, but not all, nuclear UVemission is blocked. The UVλ luminosities (withλ ranging from 1400 to 3700 Å) and theUVλ-V colors of radio galaxies show a larger scatterthan those of radio-quiet elliptical galaxies. At wavelengths shorterthan 2300 Å, some radio galaxies have on average bluer colors, butbeyond 3000 Å, their colors are on average slightly redder. Thispicture is also consistent with unification models-the galaxies withbluer colors are either BL Lac objects or broad-line radio galaxies. Allother radio galaxies (including the jetted FR I's) have somewhat reddercolors than radio-quiet elliptical galaxies. We suspect that this isprimarily due to reddening by dust, which we know is present in some ofthe radio galaxies in the sample. At longer wavelengths (>3000 Å),all radio galaxies (14 of 14) show an extended component. The morphologyof the extended emission is in most, but not all, cases comparable tothe morphology at optical wavelengths, implying that this is likely tobe starlight. However, the polarization images of two of seven radiogalaxies indicate that scattered light from the active galactic nucleusmay also contribute toward the UV luminosity.
| The Hamburg/RASS Catalogue of optical identifications. Northern high-galactic latitude ROSAT Bright Source Catalogue X-ray sources
We present the Hamburg/RASS Catalogue (HRC) of optical identificationsof X-ray sources at high-galactic latitude. The HRC includes all X-raysources from the ROSAT Bright Source Catalogue (RASS-BSC) with galacticlatitude |b| >=30degr and declination delta >=0degr . In thispart of the sky covering ~ 10 000 deg2 the RASS-BSC contains5341 X-ray sources. For the optical identification we used blue Schmidtprism and direct plates taken for the northern hemisphere Hamburg QuasarSurvey (HQS) which are now available in digitized form. The limitingmagnitudes are 18.5 and 20, respectively. For 82% of the selectedRASS-BSC an identification could be given. For the rest either nocounterpart was visible in the error circle or a plausibleidentification was not possible. With ~ 42% AGN represent the largestgroup of X-ray emitters, ~ 31% have a stellar counterpart, whereasgalaxies and cluster of galaxies comprise only ~ 4% and ~ 5%,respectively. In ~ 3% of the RASS-BSC sources no object was visible onour blue direct plates within 40\arcsec around the X-ray sourceposition. The catalogue is used as a source for the selection of(nearly) complete samples of the various classes of X-ray emitters.
| 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 athttps://dipastro.pd.astro.it/galletta/ismcat and at the CDS via anonymousftp to\ cdsarc.u-strasbg.fr (130.79.128.5) or via\https://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/405/5
| The death of FR II radio sources and their connection with radio relics
Radio relic sources in galaxy clusters are often described as theremnants of powerful radio galaxies. Here we develop a model for theevolution of such relics after the jets cease to supply energy to thelobes. This includes the treatment of a relic overpressured with respectto its gaseous surroundings even after the jets switch off. We alsodetermine the radio emission of relics for a large variety ofassumptions. We take into account the evolution of the strength of themagnetic field during the phase of relativistic particle injection intothe lobes. The resulting spectra show mild steepening at around 1 GHzbut avoid any exponential spectral cut-offs. The model calculations areused to fit the observed spectra of seven radio relics. The quality ofthe fits is excellent for all models discussed. Unfortunately, thisimplies that it is virtually impossible to determine any of theimportant source parameters from the observed radio emission alone.
| 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.
| Understanding the nature of FR II optical nuclei: A new diagnostic plane for radio galaxies
We extend our study of the nuclei of 3CR FR II radio galaxies throughHST optical images up to z = 0.3. In the majority of them an unresolvednucleus (central compact core, CCC) is found. We analyze their positionin the plane formed by the radio and optical nuclear luminosities inrelation to their optical spectral properties. The broad-lined objects(BLO) have the brightest nuclei: they are present only at opticalluminosities nu Lnu >~ 4x 1042 ergs-1 which we suggest might represent a threshold in theradiative efficiency combined with a small range of black hole masses.About 40% of the high and low excitation galaxies (HEG and LEG) show CCCwhich resemble those previously detected in FR I galaxies, in apparentcontrast to the unification model. The equivalent width of the [OIII]emission line (with respect to the nuclear luminosity) reveals thenature of these nuclei, indicating that the nuclei of HEG are obscuredto our line of sight and only scattered radiation is observed. Thisimplies that the population of FR II is composed of objects withdifferent nuclear properties, and only a fraction of them can be unifiedwith quasars. Based on observations obtained at the Space TelescopeScience Institute, which is operated by the Association of Universitiesfor Research in Astronomy, Incorporated, under NASA contract NAS5-26555.
| A sample of 669 ultra steep spectrum radio sources to find high redshift radio galaxies
Since radio sources with Ultra Steep Spectra (USS; alpha ≲ -1.30; S~ nu alpha ) are efficient tracers of high redshift radiogalaxies (HzRGs), we have defined three samples of such USS sourcesusing the recently completed WENSS, TEXAS, MRC, NVSS and PMNradio-surveys. Our combined sample contains 669 sources withS1400 > 10 mJy and covers virtually the entire sky outsidethe Galactic plane (|b|>15\arcdeg). For our 2 largest samples,covering delta > -35arcdeg , we selected only sources with angularsizes Theta < 1arcmin . For 410 sources, we present radio-maps with0\farcs3 to ~ 5'' resolution from VLA and ATCA observations or from theFIRST survey, which allows the optical identification of these radiosources. Comparison with spectrally unbiased samples at similar fluxdensity levels, shows that our spectral index, flux density, and angularsize selections do not affect the angular size distribution of thesample, but do avoid significant contributions by faint foregroundspiral galaxies. We find that the spectral index distribution of 143 000sources from the WENSS and NVSS consists of a steep spectrum galaxy anda flat spectrum quasar population, with the relative contribution offlat spectrum sources doubling from S1400>0.1 Jy toS1400>2.5 Jy. The identification fraction of our USSsources on the POSS (R ≲ 20) is as low as 15%, independent ofspectral index alpha < -1.30. We further show that 85% of the USSsources that can be identified with an X-ray source are probablycontained in galaxy clusters, and that alpha < -1.6 sources areexcellent Galactic pulsar candidates, because the percentage of thesesources is four times higher in the Galactic plane. Our sample has beenconstructed to start an intensive campaign to obtain a large sample ofhigh redshift objects (z>3) that is selected in a way that does notsuffer from dust extinction or any other optical bias. Appendices B, Cand D are available in electronic form only, athttps://www.edpsciences.org.
| The HST view of the FR I / FR II dichotomy
In order to explore how the FR I / FR II dichotomy is related to thenuclear properties of radio galaxies, we studied a complete sample of 26nearby FR II radio galaxies using Hubble Space Telescope (HST) imagesand compared them with a sample of FR I previously analyzed. FR I nucleilie in the radio-optical luminosity plane along a tight linearcorrelation, which argues for a common synchrotron origin. FR II show amore complex behavior, which is however clearly related to their opticalspectral classification. Broad line FR II radio galaxies (BLRG) arelocated overall well above the FR I correlation, suggesting that acontribution from thermal (disc) emission is present. Three narrow line(NLRG) and one weak line radio galaxy (WLRG), in which no nuclear sourceis seen, can be interpreted as the obscured counter-parts of BLRG, inagreement with the current unification schemes. Conversely, in 5 sourcesof the sample, all of them NLRG or WLRG, optical cores are located onthe same correlation defined by FR I and with similar radio and opticalluminosities. This suggests that, in analogy to FR I, the emission isdominated by synchrotron radiation and represents the opticalcounter-part of the non-thermal radio cores. Interestingly, all thesegalaxies are located in clusters, an environment typical of FR I. Theseresults imply that, at least at low redshifts, the FR II population isnot homogeneous. Furthermore, the traditional dichotomy between edgedarkened and brightened radio morphology is not unequivocally connectedwith the innermost nuclear structure, as we find FR II with FR I-likenuclei and this has interesting bearings from the point of view of theAGN unified models. 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
| 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.
| Hubble Space Telescope Snapshot Survey of 3CR Radio Source Counterparts. III. Radio Galaxies with z<0.1
We present and describe optical counterparts to 46 3CR radio galaxies ofredshifts less than 0.1 that were imaged with the Hubble SpaceTelescope's (HST) WFPC2 camera through the broadband F702W filter aspart of the 3CR Snapshot Survey. This is the fifth and last such paperdescribing the 252 radio galaxies of this R-band survey. At the 0.1"resolution of the images, a wealth of detail is visible. Approximately89% of the galaxies are ellipticals, and nearly all reside in groups orclusters of galaxies of various richness and compactness. Nearbyelliptical companions of slightly smaller size and mass are common. Dustis prevalent in the cores of the 3C hosts; nearly half of the galaxiespossess some type of dust structure, such as irregular dust lanes,filaments, or disks. Besides the well-known dust disks of 3C 264 and 3C270, we have found five new candidates in 3C 31, 3C 40, 3C 296, 3C 449,and 3C 465, as well as in the central regions of the nearby neighbors of3C 31 and 3C 465. Our sample includes six confirmed optical synchrotronjets in 3C 15, 3C 66B, 3C 78, 3C 264, 3C 274, and 3C 371, orapproximately 13% of the sample. Unresolved nuclei, consistent with thepoint spread function of WFPC2, are found in 43%-54% of the galaxies andin the majority of galaxies with dust disks and optical jets.
| Interaction of Abell Cluster 2063 and the Group of Galaxies MKW3s
The changes of the dynamical properties of A2063 with the distance tothe center of the cluster are discussed. The velocity dispersionincreases with the distance from the central region of the cluster anddecreases in its outer rings. Such an inverted profile of velocitydispersion might be the result of occurrence of dynamical subclustersand/or of circularization of galactic orbits. The existence of subclumpsof galaxies in A2063 has been confirmed by the values of theDressler-Shectman delta-parameter and the spatial distribution ofgalaxies. Besides, the ratio of the number of ellipticals and the SOgalaxies to that of spirals and irregulars decreases with distance fromcluster center. The cD galaxy of A2063 has statistically significantpeculiar velocity and does not lay at the minimum of gravitationalpotential of the cluster. The dynamical properties of A2063 and MKW3smay result from the encounter (merger) event.
| The Ultraviolet Continuum Emission of Radio Galaxies. I. Description of Sources from the Hubble Space Telescope Archives
This paper describes the UV continuum radiation in the range from 1400to 3700 A of radio galaxies. The analysis is deferred to the next paperin this series. The sample of radio galaxies was compiled by searchingthe Hubble Space Telescope (HST) archives for images taken with theFaint Object Camera (FOC) prior to 1993. Altogether the sample consistsof 30 3C and Parkes radio galaxies that have redshifts below 0.2 (themajority have redshifts of ~0.03) and radio powers of ~1025-27 WHz-1(using H0 = 50 km s-1 Mpc-1 and q0 = 0.0). We show the FOC contour plotsof the radio galaxies and calculate the UV fluxes and magnitudes withinthe standard HST medium and wide filter bands (F130M, F140M, F152M,F165W, F170M, F190M, F231M, F320W, F342M, and F372M). We detect UVemission at wavelengths <=2300 A only for FR II galaxies that arebroad emission line galaxies BLRGs and for FR I galaxies that haveoptical jets, that are BL Lac objects or that are BLRGs. The UVmagnitudes range from 15.0 to 18.0, and the fluxes range from 10-28.5 to10-30.5 W m-2 Hz-1. For sources without UV emission, upper limits aretypically ~19.0 mag or ~10-31 W m-2 Hz-1. We model the UV emission byassuming a combination of a point source (the nuclear componentexcluding the jet) and an extended galaxy component. We find that thenuclear contribution at wavelengths <=2300 A is close to 100% for BLLacs and BLRGs and ranges from 20% to 70% for FR I galaxies with opticaljets. At longer wavelengths >=3100 A, the nuclear contribution tendsto be less (not for BL Lacs which are still dominated by the nuclearcomponent) and extended UV components are detected for all FR I and FRII galaxies in the sample. We compare the structure of the extended UVemission to optical (mostly R-band HST-WFPC2) images. At wavelengths<=2300 A, the extended UV emission looks roughly spherical and showssome differences to the optical structure. Thus, we speculate thatscattered light is an important contributor to the extended UV lightwavelengths <=2300 A. At wavelengths >=3100 A, the extended UV andthe optical images are roughly comparable although somewhat "blobbier."Thus, the extended flux at wavelengths >=3100 A is probably due tohot stars. However, since some of the polarization images showdifferences in the UV emission, scattered light from the active galacticnuclei may also contribute.
| VLBI Observations of a Complete Sample of Radio Galaxies. VIII. Proper Motion in 3C 338
We present new VLA, MERLIN, and VLBI images for the radio galaxy 3C 338and the results of the monitoring of its arcsecond core flux density.Present high-sensitivity observations allow us to investigate the radiostructure of this source and to confirm the presence of two symmetricparsec-scale jets. Morphological changes between different epochs areevident, and a proper motion with beta ~ 0.4 h-1 has been derived. Thisallows us to give a lower limit for the Hubble constant. While thesteep-spectrum large-scale structure of 3C 338 could be a relicemission, the small-scale structure looks young, similar to thehigh-power medium-sized symmetric objects (MSOs) found at high redshift.
| A catalogue of Mg_2 indices of galaxies and globular clusters
We present a catalogue of published absorption-line Mg_2 indices ofgalaxies and globular clusters. The catalogue is maintained up-to-datein the HYPERCAT database. The measurements are listed together with thereferences to the articles where the data were published. A codeddescription of the observations is provided. The catalogue gathers 3541measurements for 1491 objects (galaxies or globular clusters) from 55datasets. Compiled raw data for 1060 galaxies are zero-point correctedand transformed to a homogeneous system. Tables 1, 3, and 4 areavailable in electronic form only at the CDS, Strasbourg, via anonymousftp 130.79.128.5. Table 2 is available both in text and electronic form.
| 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.
| [O III] 500.7 spectroscopy of 3C galaxies and quasars at redshift z>1
We present near infrared spectra of z>1 quasars and radio galaxiesfrom the 3CR and 3CRR catalogues. [O III] is detected in all but six ofthe 28 objects. These data extend the known correlation between the [OIII] and radio luminosities of radio sources to higher radioluminosities with no increase in scatter. The previously reporteddifference in [O III] luminosities between radio-luminous galaxies andquasars at z<0.8 is smaller at higher redshift and/or radioluminosity. In the context of orientation-based unified schemes of radiogalaxies and quasars, this implies that the [O III] emitting region ispartially hidden in the most radio-luminous galaxies seen at lowredshift (z~0.3) but less obscured in the even more radio-luminousgalaxies seen at z~1. Alternatively, such schemes do not apply to allobjects - perhaps there is a class of radio galaxies with highexcitation narrow emission lines but no luminous quasar nucleus.Equivalent widths of [O III] in the z>1 quasars are similar to thoseat lower z, implying no change in the excitation mechanism with z orradio luminosity.
| An Einstein X-Ray Survey of Optically Selected Galaxies. I. Data
We present the results of a complete Einstein imaging proportionalcounter X-ray survey of optically selected galaxies from theShapley-Ames Catalog, the Uppsala General Catalogue, and the EuropeanSouthern Observatory Catalog. Well-defined optical criteria are used toselect the galaxies, and X-ray fluxes are measured at the opticallydefined positions. The result is a comprehensive list of X-ray detectionand upper limit measurements for 1018 galaxies. Of these, 827 haveeither independent distance estimates or radial velocities. Associatedoptical, redshift, and distance data have been assembled for thesegalaxies, and their distances come from a combination of directlypredicted distances and those predicted from the Faber-Burstein GreatAttractor/Virgocentric infall model. The accuracy of the X-ray fluxeshas been checked in three different ways; all are consistent with thederived X-ray fluxes being of <=0.1 dex accuracy. In particular,there is agreement with previously published X-ray fluxes for galaxiesin common with a 1991 study by Roberts et al. and a 1992 study byFabbiano et al. The data presented here will be used in further studiesto characterize the X-ray output of galaxies of various morphologicaltypes and thus to enable the determination of the major sourcescontributing to the X-ray emission from galaxies.
| Extragalactic Globular Clusters. IV. The Data
We have explored the use of absorption line strength indices, measuredfrom integrated globular cluster spectra, to predict mean metallicity inlate-type stellar systems. In previous papers we identified the bestindices for such metallicity calibrations out of ~13 measured in a largesample of galactic and M31 cluster spectra. In this paper we present theindividual measurements of 13 indices and averages of multiplemeasurements, where appropriate. Data are given for 151 M31 globularclusters, 88 galaxies, 22 M33 cluster candidates, 10 M87 clusters, eightM81 globular clusters, three Fornax dwarf galaxy clusters, "standard"stars from the lists of Faber et al., stars in the open cluster NGC 188and, for completeness, other stars observed as candidate globularclusters.
| 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.
| Intracluster Globular Clusters
Globular cluster populations of supergiant elliptical galaxies are knownto vary widely, from extremely populous systems like that of UGC 9799,the centrally dominant galaxy in Abell 2052, to globular-cluster--poorgalaxies such as NGC 5629 in Abell 2666. Here we propose that thesevariations point strongly to the existence of a population of globularclusters that are not bound to individual galaxies but, rather, movefreely throughout the cores of clusters of galaxies. Such intraclusterglobular clusters may have originated as tidally stripped debris fromgalaxy interactions and mergers, or, alternatively, they may have formedin situ in some scenarios of globular cluster formation.
| Kinematics and dynamics of the MKW/AWM poor clusters
We report 472 new redshifts for 416 galaxies in the regions of the 23poor clusters of galaxies originally identified by Morgan, Kayser, andWhite (MKW), and Albert, White, and Morgan (AWM). Eighteen of the poorclusters now have 10 or more available redshifts within 1.5/h Mpc of thecentral galaxy; 11 clusters have at least 20 available redshifts. Basedon the 21 clusters for which we have sufficient velocity information,the median velocity scale is 336 km/s, a factor of 2 smaller than foundfor rich clusters. Several of the poor clusters exhibit complex velocitydistributions due to the presence of nearby clumps of galaxies. We checkon the velocity of the dominant galaxy in each poor cluster relative tothe remaining cluster members. Significantly high relative velocities ofthe dominant galaxy are found in only 4 of 21 poor clusters, 3 of whichwe suspect are due to contamination of the parent velocity distribution.Several statistical tests indicate that the D/cD galaxies are at thekinematic centers of the parent poor cluster velocity distributions.Mass-to-light ratios for 13 of the 15 poor clusters for which we havethe required data are in the range 50 less than or = M/LB(0)less than or = 200 solar mass/solar luminosity. The complex nature ofthe regions surrounding many of the poor clusters suggests that thesegroupings may represent an early epoch of cluster formation. Forexample, the poor clusters MKW7 and MKWS are shown to be gravitationallybound and likely to merge to form a richer cluster within the nextseveral Gyrs. Eight of the nine other poor clusters for which simpletwo-body dynamical models can be carried out are consistent with beingbound to other clumps in their vicinity. Additional complex systems withmore than two gravitationally bound clumps are observed among the poorclusters.
| 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.
| CO(1-0) observations of the cooling flow galaxy NGC 1275 with the IRAM interferometer.
High resolution ^12^CO(1-0) interferometric observations are presentedof NGC 1275 (3C84, Perseus A), which is the dominant galaxy of thePerseus cluster (Abell 426) and is believed to have a strong coolingflow. No CO absorption was detected towards the powerful point-likenucleus although CO emission may have been detected in an areasurrounding the nucleus. The constraints placed by these observationsand existing data on the massive cooling flow scenario are examined.Contrary to some claims, the covering fraction of neutral gas has beenfound to be much less than unity in all cooling flows where thenecessary data are available. As the cooling gas presumably formslow-mass stars or sub-stellar objects, the possibility of large massesof neutral gas escaping detection is investigated in detail. The gas,with or without dust, should not cool down to T_gas_=~3K as has beenclaimed but should remain >8K through X-ray heating at columndensities up to N_H2_=~5x10^22^/cm2. Greater column densities may bephysically reasonable if the magnetic field is strong enough to supportthe cloud against fragmentation. In this case, ambi-polar diffusion ormagnetic slip-ion heating becomes important and should maintain thetemperature T_gas_>10K. If the clouds contain dust, then although thedust radiates away most of the energy, the absorbed starlight keeps thetemperature T_dust_>10K. Lack of CO or very broad lines do not appearto be feasible means of reconciling large molecular (or atomic) gasmasses with the global lack of detections and tight upper limits. Theprimary conclusion is that the real mass inflow rates must be much lowerthat frequently claimed. It should then be noted that present-daycooling flows, if not so massive, lose much of their cosmologicalimportance. The FIR and CO emission from NGC 1275 correspond exactly towhat is found in gas-rich spirals. Rather than a massive cooling flow,the gas may come from accretion of one or more gas-rich galaxies. Since,however, at least 14 other central galaxies would have been detected inCO if they contained similar quantities of gas, such events must bequite rare, very roughly 1/15Gyr^-1^ if the time required for a largefraction of the gas to disappear is 10^9^yr.
| Samples of ultra-steep spectrum radio sources.
Radio sources with ultra-steep spectra (USS) have been found to beexcellent tracers of galaxies at redshifts z>~2. In order to obtain alarge sample of z>~2 galaxies, we have defined several newflux-limited samples of USS radio sources. These samples are selected ata range of frequencies from 38MHz to 408MHz and are fainter by a factorof three than the previously well-studied 4C samples of USS sources. Wefind that complete samples of radio sources with angular diameters<~1arcmin selected at 38MHz contain relatively fewer USS sources thansamples of small radio sources selected at higher (>~150MHz)frequencies. This is interpreted as due to flattening of the spectra ofdistant USS sources at frequencies <100MHz. As a preliminary tooptical imaging and spectroscopy, snapshot observations of sources fromthese samples have been made with the VLA at 1.5arcsec resolution. Wepresent the positions, flux densities and radio structures for a totalnumber of 605 sources derived from these observations. Our VLA imagesindicate that samples of USS sources selected at 38MHz contain a smallerproportion of small sources and a larger proportion of diffuse sourcesthan USS sources selected at higher (>~150MHz) frequencies. This isconsistent with the samples of 38MHz - selected USS sources containing alarger fraction of relatively nearby radio sources, perhaps in clustersof galaxies.
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