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Molecular gas in the galaxy cluster Abell 262. CO observations of UGC 1347 and other galaxies of the cluster
We present millimeter CO line emission observations of 12 galaxieswithin the Abell 262 cluster, together with L_FIRdata, in the context of a possible molecular gas deficiency within theregion of the cluster center. Several indications of the presence ofsuch a deficiency are highlighted and connected to a model ofcirrus-like cloud stripping. The model predicts a drop in the average100 μm flux density of galaxies in the core of the cluster comparedto the average 100 μm flux density in the outer regions, which isactually indicated in the IRAS data of the cluster members. This drop isexplained by the decrease in the total hydrogen column density N(H) and,therefore, also includes a decrease in the molecular gas content. Inaddition to results for the global CO content of the galaxy sample,high-resolution interferometric CO(1-0) observations of one of thecluster members, UGC 1347, exemplify the spatial distribution of themolecular gas in a galaxy of the cluster. With these observations, itwas possible to confirm the existence of a bright off-nuclearCO-emission source and to derive molecular masses and line ratios forthis source and the nucleus.
| Water-Vapor Maser Survey for Active Galactic Nuclei: A Megamaser in NGC 6926
We made a survey of water-vapor maser emission for 93 AGNs with theNobeyama 45-m and Mopra 22-m telescopes from 1999 to 2002. A megamaserwas detected in a Seyfert 2 galaxy, NGC 6926, at a distance of 80Mpc, in2002 June. [Greenhill et al. (2003a) have also reported a detection ofthe megamaser at the close date.] The peak flux density was 110mJy, andthe total isotropic luminosity was 340 Lȯ. The masershows triply peaked spectrum, suggesting an edge-on disk. A narrow-linefeature of the maser components at VLSR = 6001 kms-1 was strongly variable with a time scale of a few tens ofdays, and the variation should be of intrinsic origin. We also showed apossibility of variability of water-vapor maser emission of a megamaserpreviously detected in a Seyfert/ultraluminous FIR galaxy, NGC 6240.
| Captures of Red Giant Stars by Black Holes in Elliptical Galaxies: Feedback to the Hot Gas
The highly disturbed hot gas in elliptical galaxies, as revealed in manyChandra X-ray images, implies a source of energy in the galacticnucleus. In some elliptical galaxies, faint X-ray ``ghost'' cavitiesappear without corresponding radio lobes. It has been suggested thatghost cavities are caused by short-lived activity with a timescale of~103-104 yr, but this is difficult to understandwithin the popular paradigm of active galactic nuclei. We suggest anepisode model for ghost cavities, invoking captures of red giant starsby the black hole located at the center of elliptical galaxies at atypical rate of 10-5 yr-1 per galaxy. Theaccretion of tidally disrupted red giant stars onto the black holepowers activity in a timescale of a few years. The total energychanneled into the jet/outflow during the cooling time of the hot gas is~1056 ergs, which is the typical work required to form theobserved cavities. In this scenario, the faint cavities are produced bythe feedback following accretion of the debris of the captured red giantstars onto the black holes. We apply the present model to severalelliptical galaxies and find that it can explain the formation of theghost cavities. This model can be tested in the future by comparisonsbetween radio and X-ray observations.
| The Bologna Complete Sample of Nearby Radio Sources
We present a new, complete sample of 95 radio sources selected from theB2 Catolog of Radio Sources and the Third Cambridge Revised Catalog(3CR), with z<0.1. Since no selection effect on the core radio power,jet velocity, or source orientation is present, this sample is wellsuited for statistical studies. In this first paper we present theobservational status of all sources on the parsec (milliarcsecond) andkiloparsec (arcsecond) scale; we give new parsec-scale data for 28sources and discuss their parsec-scale properties. By combining thesedata with those in the literature, information on the parsec-scalemorphology is available for a total of 53 radio sources with differentradio power and kiloparsec-scale morphologies. We investigate theirproperties. We find a dramatically higher fraction of two-sided sourcesin comparison with that of previous flux-limited VLBI surveys.
| A wide-field photometric study of the globular cluster system of NGC 4636
Previous smaller-scale studies of the globular cluster system of NGC4636, an elliptical galaxy in the southern part of the Virgo cluster,have revealed an unusually rich globular cluster system. Were-investigate the cluster system of NGC 4636 with wide-field Washingtonphotometry. The globular cluster luminosity function can be followedroughly 1 mag beyond the turn-over magnitude found at {V} =23.31±0.13 for the blue cluster sub-population. This correspondsto a distance modulus of ({m}-{M})=31.24±0.17, 0.4 mag largerthan the distance determined from surface brightness fluctuations. Thehigh specific frequency is confirmed, yet the exact value remainsuncertain because of the uncertain distance: it varies between5.6±1.2 and 8.9±1.2. The globular cluster system has aclearly bimodal color distribution. The color peak positions show noradial dependence and are in good agreement with the values found forother galaxies studied in the same filter system. However, a luminositydependence is found: brighter clusters with an“intermediate” color exist. The clusters exhibit a shallowradial distribution within 7´, represented by a power-law with anexponent of -1.4. Within the same radial interval, the galaxy light hasa distinctly steeper profile. Because of the difference in the clusterand light distribution the specific frequency increases considerablywith radius. At 7´ and 9´ the density profiles of the redand blue clusters, respectively, change strongly: the power-law indicesdecrease to around -5 and become similar to the galaxy profile. Thissteep profile indicates that we reach the outer rim of the clustersystem at approximately 11´. This interpretation is supported bythe fact that in particular the density distribution of the blue clusterpopulation can be well fit by the projection of a truncated power-lawmodel with a core. This feature is seen for the first time in a globularcluster system. While the radial distribution of the cluster and fieldpopulations are rather different, this is not true for the ellipticityof the system: the elongation as well as the position angle of thecluster system agree well with the galaxy light. We compare the radialdistribution of globular clusters with the light profiles for a sampleof elliptical galaxies. The difference observed in NGC 4636 is typicalof an elliptical galaxy of this luminosity. The intrinsic specificfrequency of the blue population is considerably larger than that of thered one.Tables A.1 to A.6 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/cgi-bin/qcat?J/A+A/433/43
| Obscuration and Origin of Nuclear X-Ray Emission in FR I Radio Galaxies
We present X-ray observations of the nuclear region of 25 Fanaroff-Rileytype I (FR I) radio galaxies from the 3CRR and B2 catalogs, using datafrom the Chandra and XMM-Newton archives. We find the presence of aX-ray central compact core (CCCX) in 13/25 sources; in 3/25 sources thedetection of a CCCX is uncertain, while in the remaining 9/25 sources noCCCX is found. All the sources are embedded in a diffuse soft X-raycomponent, generally on kiloparsec scales, which is in agreement withthe halo of the host galaxy and/or with the intracluster medium. TheX-ray spectra of the cores are described by a power law with photonindices Γ=1.1-2.6. In eight sources excess absorption over theGalactic value is detected, with rest-frame column densitiesNzH~1020-1021cm-2 thus, we confirm the previous claim, based on opticaldata, that most FR I radio galaxies lack a standard optically thicktorus. We find significant correlations between the X-ray coreluminosity and the radio and optical luminosities, suggesting that atleast a fraction of the X-ray emission originates in a jet; however, theorigin of the X-rays remains ambiguous. If the X-ray emission isentirely attributed to an isotropic, accretion-related component, wefind very small Eddington ratios,Lbol/LEdd~10-3to10-8, and wecalculate the radiative efficiency to beη~10-2to10-6 on the basis of the Bondiaccretion rates from the spatial analysis. This suggests thatradiatively inefficient accretion flows are present in the cores oflow-power radio galaxies.
| 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.
| Chandra Observation of the Central Region of the Cooling Flow Cluster A262: A Radio Source That Is a Shadow of Its Former Self?
We present a Chandra observation of the cooling flow cluster A262.Spectral fits show that the intracluster medium (ICM) in A262 cools by afactor of 3, from 2.7 to 0.9 keV, at the cluster center. A massdeposition rate of M=19+6-5Msolaryr-1 is measured. Complex structure is found in the veryinner regions of the cluster, including knots of emission and a cleardeficit of emission to the east of the cluster center. The bright X-raystructures are located in the same regions as optical line emission,indicating that cooling to low temperatures has occurred in theseregions. The X-ray deficit is spatially coincident with the easternradio lobe associated with the active galactic nucleus hosted by thecentral cD galaxy. The region surrounding the X-ray hole is cool andshows no evidence that it has been strongly shocked. This joins theranks of other cooling flow clusters with Chandra-detected bubbles blownby central radio sources. This source is different from the otherwell-known cases, in that the radio source is orders of magnitude lessluminous and has produced a much smaller bubble. Comparing the energyoutput of the radio source with the luminosity of the cooling gas showsthat energy transferred to the ICM from the radio source is insufficientto offset the cooling flow unless the radio source is currentlyexperiencing a less powerful than average outburst and was more powerfulin the past.
| Radio and Far-Infrared Emission as Tracers of Star Formation and Active Galactic Nuclei in Nearby Cluster Galaxies
We have studied the radio and far-infrared (FIR) emission from 114galaxies in the seven nearest clusters (<100 Mpc) with prominentX-ray emission to investigate the impact of the cluster environment onthe star formation and active galactic nucleus (AGN) activity in themember galaxies. The X-ray selection criterion is adopted to focus onthe most massive and dynamically relaxed clusters. A large majority ofcluster galaxies show an excess in radio emission over that predictedfrom the radio-FIR correlation, the fraction of sources with radioexcess increases toward cluster cores, and the radial gradient in theFIR/radio flux ratio is a result of radio enhancement. Of theradio-excess sources, 70% are early-type galaxies, and the same fractionhost an AGN. The galaxy density drops by a factor of 10 from thecomposite cluster center out to 1.5 Mpc, yet galaxies show no change inFIR properties over this region and show no indication of masssegregation. We have examined in detail the physical mechanisms thatmight impact the FIR and radio emission of cluster galaxies. Whilecollisional heating of dust may be important for galaxies in clustercenters, it appears to have a negligible effect on the observed FIRemission for our sample galaxies. The correlations between radio and FIRluminosity and radius could be explained by magnetic compression fromthermal intracluster medium pressure. We also find that simple delayedharassment cannot fully account for the observed radio, FIR, and mid-IRproperties of cluster galaxies.
| 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.
| Unifying B2 radio galaxies with BL Lacertae objects
In an earlier paper we presented nuclear X-ray flux densities, measuredwith ROSAT, for the B2 bright sample of nearby low-luminosity radiogalaxies. In this paper we construct a nuclear X-ray luminosity functionfor the B2 radio galaxies, and discuss the consequences of our resultsfor models in which such radio galaxies are the parent population of BLLacertae (BL Lac) objects. Based on our observations of the B2 sample,we use Monte Carlo techniques to simulate samples of beamed radiogalaxies, and use the selection criteria of existing samples of BL Lacobjects to compare our simulated results to what is observed. We findthat previous analytical results are not applicable since the BL Lacsamples are selected on beamed flux density. A simple model in which BLLacs are the moderately beamed (γ~ 3) counterparts of radiogalaxies, with some random dispersion (~0.4 decades) in the intrinsicradio-X-ray relationship, can reproduce many of the features of theradio-selected and X-ray-selected BL Lac samples, including their radioand X-ray luminosity functions and the distributions of theirradio-to-X-ray spectral indices. In contrast, models in which the X-rayand radio emission have systematically different beaming parameterscannot reproduce important features of the radio-galaxy and BL Lacpopulations, and recently proposed models in which the radio-to-X-rayspectral index is a function of source luminosity cannot in themselvesaccount for the differences in the slopes of the radio- andX-ray-selected BL Lac luminosity functions. The redshift distributionand number counts of the X-ray-selected Einstein Medium SensitivitySurvey (EMSS) sample are well reproduced by our best models, supportinga picture in which these objects are beamed Fanaroff-Riley type I radiogalaxies with intrinsic luminosities similar to those of the B2 sample.However, we cannot match the redshift distribution of the radio-selected1-Jy sample, and it is likely that a population of Fanaroff-Riley typeII radio galaxies is responsible for the high-redshift objects in thissample, in agreement with previously reported results on the sample'sradio and optical emission-line properties.
| Measuring Distances and Probing the Unresolved Stellar Populations of Galaxies Using Infrared Surface Brightness Fluctuations
To empirically calibrate the IR surface brightness fluctuation (SBF)distance scale and probe the properties of unresolved stellarpopulations, we measured fluctuations in 65 galaxies using NICMOS on theHubble Space Telescope. The early-type galaxies in this sample includeelliptical and S0 galaxies and spiral bulges in a variety ofenvironments. Absolute fluctuation magnitudes in the F160W (1.6 μm)filter (MF160W) were derived for each galaxy using previouslymeasured I-band SBF and Cepheid variable star distances. F160W SBFs canbe used to measure distances to early-type galaxies with a relativeaccuracy of ~10%, provided that the galaxy color is known to ~0.035 magor better. Near-IR fluctuations can also reveal the properties of themost luminous stellar populations in galaxies. Comparison of F160Wfluctuation magnitudes and optical colors to stellar population modelpredictions suggests that bluer elliptical and S0 galaxies havesignificantly younger populations than redder ones and may also be moremetal-rich. There are no galaxies in this sample with fluctuationmagnitudes consistent with old, metal-poor (t>5 Gyr, [Fe/H]<-0.7)stellar population models. Composite stellar population models implythat bright fluctuations in the bluer galaxies may be the result of anepisode of recent star formation in a fraction of the total mass of agalaxy. Age estimates from the F160W fluctuation magnitudes areconsistent with those measured using the Hβ Balmer-line index. Thetwo types of measurements make use of completely different techniquesand are sensitive to stars in different evolutionary phases. Bothtechniques reveal the presence of intermediate-age stars in theearly-type galaxies of this sample.Based on observations with the NASA/ESA Hubble Space Telescope, obtainedat the Space Telescope Science Institute, which is operated by AURA,Inc., under NASA contract NAS 5-26555.
| The X-Ray Properties of Nearby Abell Clusters from the ROSAT All-Sky Survey: The Sample and Correlations with Optical Properties
We present an analysis of the X-ray emission for a complete sample of288 Abell clusters spanning the redshift range 0.016<=z<=0.09 fromthe ROSAT All-Sky Survey. This sample is based on our 20 cm VLA surveyof nearby Abell clusters. We find an X-ray detection rate of 83%. Wereport cluster X-ray fluxes and luminosities and two different fluxratios indicative of the concentration and extent of the emission. Weexamine correlations between the X-ray luminosity, Abell richness, andBautz-Morgan and Rood-Sastry cluster morphologies. We find a strongcorrelation between LX and cluster richness coupled with adependence on the optical morphological type. These results areconsistent with the observed scatter between X-ray luminosity andtemperature and a large fraction of cooling flows. For each clusterfield, we also report the positions, peak X-ray fluxes, and flux ratiosof all X-ray peaks above 3 σ significance within a box of2×2h-175 Mpc centered on Abell's position.
| Redshift-Distance Survey of Early-Type Galaxies: Spectroscopic Data
We present central velocity dispersions and Mg2 line indicesfor an all-sky sample of ~1178 elliptical and S0 galaxies, of which 984had no previous measures. This sample contains the largest set ofhomogeneous spectroscopic data for a uniform sample of ellipticalgalaxies in the nearby universe. These galaxies were observed as part ofthe ENEAR project, designed to study the peculiar motions and internalproperties of the local early-type galaxies. Using 523 repeatedobservations of 317 galaxies obtained during different runs, the dataare brought to a common zero point. These multiple observations, takenduring the many runs and different instrumental setups employed for thisproject, are used to derive statistical corrections to the data and arefound to be relatively small, typically <~5% of the velocitydispersion and 0.01 mag in the Mg2 line strength. Typicalerrors are about 8% in velocity dispersion and 0.01 mag inMg2, in good agreement with values published elsewhere.
| Line-of-Sight Reddening Predictions: Zero Points, Accuracies, the Interstellar Medium, and the Stellar Populations of Elliptical Galaxies
Revised (B-V)0-Mg2 data, which are used to testreddening predictions, are presented for 402 elliptical galaxies. Thesereddening predictions can tell us both what the intrinsic errors are inthis relationship among gE galaxy stellar populations as well as detailsof nearby structure in the interstellar medium (ISM) of our Galaxy, andof the intrinsic errors in reddening predictions. Using least-squaresfits, the explicit 1 σ errors in reddenings predicted by theBurstein-Heiles (BH) method and the Schlegel and coworkers (IR) methodare calculated, as well as the 1 σ observational error in the(B-V)0-Mg2 for gE galaxies. It is found that indirections with E(B-V)<0.100 mag (where most of these galaxies lie),1 σ errors in the IR reddening predictions are 0.006-0.009 mag inE(B-V), those for BH reddening predictions are 0.011 mag, and the 1σ agreement between the two reddening predictions is 0.007 mag.The IR predictions have an accuracy of 0.010-0.011 mag in directionswith E(B-V)>=0.100 mag, significantly better than those of the BHpredictions (0.024-0.025). Both methods yield good evidence thatgas-to-dust variations that vary by a factor of 3, both high and low,exist along many lines of sight in our Galaxy. Both methods also predictmany directions with E(B-V)<0.015 mag, despite the difference in zeropoint that each has assumed. The ~0.02 higher reddening zero point inE(B-V) previously determined by Schlegel and coworkers is confirmed,primarily at the Galactic poles. Independent evidence of reddening atthe north Galactic pole (NGP) is reviewed, with the conclusion thatdirections still exist at the NGP that have E(B-V)<<0.01. Twolines of evidence suggest that IR reddenings are overpredicted indirections with high gas-to-dust ratios. As high gas-to-dust directionsin the ISM also include the Galactic poles, this overprediction is thelikely cause of the E(B-V)~0.02 mag larger IR reddening zero pointrelative to that of BH.
| Hubble Space Telescope Imaging of Brightest Cluster Galaxies
We used the Hubble Space Telescope Wide Field Planetary Camera 2 toobtain I-band images of the centers of 81 brightest cluster galaxies(BCGs), drawn from a volume-limited sample of nearby BCGs. The imagesshow a rich variety of morphological features, including multiple ordouble nuclei, dust, stellar disks, point-source nuclei, and centralsurface brightness depressions. High-resolution surface brightnessprofiles could be inferred for 60 galaxies. Of those, 88% havewell-resolved cores. The relationship between core size and galaxyluminosity for BCGs is indistinguishable from that of Faber et al.(published in 1997, hereafter F97) for galaxies within the sameluminosity range. However, the core sizes of the most luminous BCGs fallbelow the extrapolation of the F97 relationshiprb~L1.15V. A shallower relationship,rb~L0.72V, fits both the BCGs and thecore galaxies presented in F97. Twelve percent of the BCG sample lacks awell-resolved core; all but one of these BCGs have ``power law''profiles. Some of these galaxies have higher luminosities than anypower-law galaxy identified by F97 and have physical upper limits onrb well below the values observed for core galaxies of thesame luminosity. These results support the idea that the centralstructure of early-type galaxies is bimodal in its physical propertiesbut also suggest that there exist high-luminosity galaxies withpower-law profiles (or unusually small cores). The BCGs in the lattercategory tend to fall at the low end of the BCG luminosity function andtend to have low values of the quantity α (the logarithmic slopeof the metric luminosity as a function of radius, at 10 kpc). Sincetheoretical calculations have shown that the luminosities andα-values of BCGs grow with time as a result of accretion, thissuggests a scenario in which elliptical galaxies evolve from power-lawprofiles to core profiles through accretion and merging. This isconsistent with theoretical scenarios that invoke the formation ofmassive black hole binaries during merger events. More generally, theprevalence of large cores in the great majority of BCGs, which arelikely to have experienced several generations of galaxy merging,underscores the role of a mechanism that creates and preserves cores insuch merging events.Based on observations made with the NASA/ESA Hubble Space Telescope,obtained at the Space Telescope Science Institute, which is operated bythe Association of Universities for Research in Astronomy, Inc., underNASA contract NAS 5-26555. These observations are associated withproposal 8683.
| 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
| 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.
| H0 measurement from VLT deep I-band surface brightness fluctuations in NGC 564 and NGC 7619
We have measured the Hubble constant H0 in NGC 564 at cz ~5800 km s-1 and in NGC 7619 at cz ~ 3700 km s-1with deep I-band Surface Brightness Fluctuation distance measurements atthe ESO Very Large Telescope (VLT). We obtain H0 = 70 +/- 7+/- 6 km s-1/Mpc for NGC 564 and H0 = 68 +/- 6 +/-6 for NGC 7619. The actual SBF sample used for the measurement ofH0 in the Hubble Space Telescope Key Project on theExtragalactic Distance Scale (Freedman et al. 2001) amounts to sixgalaxies. When we combine the measurements from this work with ourprevious VLT I-band SBF distance measurement in IC 4296 (Mei et al.2000), we obtain: H0 = 68 +/- 5 +/- 6 km s-1/Mpc.When we add the Freedman et al. (2001) SBF sample, we obtainH0 = 71 +/- 4 +/- 6 km s-1/Mpc.Based on observations performed at the European Southern Observatory,Paranal, Chile ESO program No 66.A-0361.
| Active Galactic Nucleus Black Hole Masses and Bolometric Luminosities
Black hole mass, along with mass accretion rate, is a fundamentalproperty of active galactic nuclei (AGNs). Black hole mass sets anapproximate upper limit to AGN energetics via the Eddington limit. Wecollect and compare all AGN black hole mass estimates from theliterature; these 177 masses are mostly based on the virial assumptionfor the broad emission lines, with the broad-line region size determinedfrom either reverberation mapping or optical luminosity. We introduce200 additional black hole mass estimates based on properties of the hostgalaxy bulges, using either the observed stellar velocity dispersion orthe fundamental plane relation to infer σ these methods assumethat AGN hosts are normal galaxies. We compare 36 cases for which blackhole mass has been generated by different methods and find, forindividual objects, a scatter as high as a couple of orders ofmagnitude. The less direct the method, the larger the discrepancy withother estimates, probably due to the large scatter in the underlyingcorrelations assumed. Using published fluxes, we calculate bolometricluminosities for 234 AGNs and investigate the relation between blackhole mass and luminosity. In contrast to other studies, we find nosignificant correlation of black hole mass with luminosity, other thanthose induced by circular reasoning in the estimation of black holemass. The Eddington limit defines an approximate upper envelope to thedistribution of luminosities, but the lower envelope depends entirely onthe sample of AGNs included. For any given black hole mass, there is arange in Eddington ratio of up to 3 orders of magnitude.
| Globular Cluster Systems in Four Brightest Cluster Galaxies: A262, A3560, A3565, and A3742
We have used deep I-band (F814W) images from the Hubble Space Telescopearchive to study the globular cluster systems around the brightestcluster galaxies (BCGs) in A262, A3560, A3565, and A3742. Three of theseBCGs have inner dust lanes and peculiar structural features thatindicate past histories of low-level interaction and accretion. The deepI-band WFPC2 images have photometric limits that, for all four galaxies,reach near or just beyond the globular cluster luminosity function(GCLF) turnover point. Their specific frequencies are 8.24+/-1.65,4.66+/-0.93, 2.58+/-0.52, and 2.62+/-0.52, respectively, all within afactor of 2 of the normal range for giant elliptical galaxies. We obtainnew estimates of the GCLF turnover magnitudes, which are shown to beconsistent with an adopted Hubble constant of H0~=70 kms-1 Mpc-1 on the ``Hubble diagram'' of GCLFturnover apparent magnitude versus redshift, on a distance scale wherethe fundamental GCLF calibrator E galaxies (M87 and others) in Virgo areat d=16 Mpc. Based on observations with the NASA/ESA Hubble SpaceTelescope, obtained at the Space Telescope Science Institute, which isoperated by the Association of Universities for Research in Astronomy,Inc., under NASA contract NAS 5-26555. These observations are associatedwith proposal ID 5910.
| Evolution of Star-forming and Active Galaxies in Nearby Clusters
We have used optical spectroscopy to investigate the active galaxypopulations in a sample of 20 nearby Abell clusters. The targets wereidentified on the basis of 1.4 GHz radio emission, which identifies themas either active galactic nuclei (AGNs) or galaxies forming stars atrates comparable to or greater than that of the Milky Way. The spectrawere used to characterize the galaxies via their emission and absorptionfeatures. The spectroscopy results reveal a significant population ofstar-forming galaxies with large amounts of nuclear dust extinction.This extinction eliminates bluer emission lines such as [O II] from thespectra of these galaxies, meaning their star formation could easily beoverlooked in studies that focus on such features. Around 20% of thecluster star-forming galaxies have spectra of this type. The radialdistributions of active galaxies in clusters show a strong segregationbetween star-forming galaxies and AGNs, with star-forming galaxiesbroadly distributed and AGNs preferentially in the cluster cores. Theradial distribution of the dusty star-forming galaxies is more centrallyconcentrated than the star-forming galaxies in general, which arguesthat they are a consequence of some cluster environmental effect.Furthermore, we note that such galaxies may be identified using their4000 Å break strengths. We find that discrepancies in reportedradio luminosity functions for AGNs are likely the result ofclassification differences. There exists a large population of clustergalaxies whose radio fluxes, far-infrared fluxes, and optical magnitudessuggest their radio emission may be powered by stars yet whose spectralack emission lines. Understanding the nature of these galaxies iscritical to assessing the importance of AGNs in the radio luminosityfunction at low luminosities. We also find that regardless of thispopulation, the crossover point where the radio luminosity function iscomposed equally of star-forming galaxies and AGNs occurs at lowerluminosities in clusters than in the field. This is likely a simpleconsequence of the reduction in star formation in cluster galaxies andthe morphological mix in clusters compared with the field.Based in part on observations obtained with the Apache Point Observatory(APO) 3.5 m telescope, which is owned and operated by the AstrophysicalResearch Consortium.
| Redshift-Distance Survey of Early-Type Galaxies. I. The ENEARc Cluster Sample
This paper presents data on the ENEARc subsample of the larger ENEARsurvey of nearby early-type galaxies. The ENEARc galaxies belong toclusters and were specifically chosen to be used for the construction ofa Dn-σ template. The ENEARc sample includes newmeasurements of spectroscopic and photometric parameters (redshift,velocity dispersion, line index Mg2, and the angular diameterdn), as well as data from the literature. New spectroscopicdata are given for 229 cluster early-type galaxies, and new photometryis presented for 348 objects. Repeat and overlap observations withexternal data sets are used to construct a final merged catalogconsisting of 640 early-type galaxies in 28 clusters. Objectivecriteria, based on catalogs of groups of galaxies derived from completeredshift surveys of the nearby universe, are used to assign galaxies toclusters. In a companion paper, these data are used to construct thetemplate Dn-σ distance relation for early-typegalaxies, which has been used to estimate galaxy distances and derivepeculiar velocities for the ENEAR all-sky sample. Based on observationsat Complejo Astronomico El Leoncito, operated under agreement betweenthe Consejo Nacional de Investigaciones Científicas de laRepública Argentina and the National Universities of La Plata,Córdoba, and San Juan; Cerro Tololo Inter-American Observatory,National Optical Astronomical Observatory, which is operated by theAssociation of Universities for Research in Astronomy, Inc., undercooperative agreement with the National Science Foundation; the EuropeanSouthern Observatory (ESO), partially under the ESO-ON agreement; theFred Lawrence Whipple Observatory; the Observatório do Pico dosDias, operated by the Laboratório Nacional de Astrofísicaand the MDM Observatory at Kitt Peak.
| The UZC-SSRS2 Group Catalog
We apply a friends-of-friends algorithm to the combined Updated ZwickyCatalog and Southern Sky Redshift Survey to construct a catalog of 1168groups of galaxies; 411 of these groups have five or more members withinthe redshift survey. The group catalog covers 4.69 sr, and all groupsexceed the number density contrast threshold, δρ/ρ=80. Wedemonstrate that the groups catalog is homogeneous across the twounderlying redshift surveys; the catalog of groups and their membersthus provides a basis for other statistical studies of the large-scaledistribution of groups and their physical properties. The medianphysical properties of the groups are similar to those for groupsderived from independent surveys, including the ESO Key Programme andthe Las Campanas Redshift Survey. We include tables of groups and theirmembers.
| HST images of B2 radio galaxies: A link between circum-nuclear dust and radio properties?
Almost 60% of the B2 low luminosity radio galaxies have been observedwith the Hubble Space Telescope. We present an analysis of the dustfeatures, which are often present in the form of circum-nuclear disks orlanes, and show that there are correlations between radio source anddust properties. It is found that nearby radio sources in which a jethas been detected tend to have dust more often than sources withoutjets; the dust is often in the form of disks or lanes. Moreover theradio jets are close to perpendicular to the disk or lane in the weakerradio sources (with P < 1024 WHz-1). Instronger sources the orientation effect appears to be weak or evenabsent. Also the dust masses found in the weaker radio sources aresmaller than in the stronger ones (log M/Msun ~ 3 against 5respectively). More generally it appears that there is a correlationbetween dust mass and total radio power (for those sources in which dusthas been detected); we show that this correlation is not induced byredshift. Based on observations with the NASA/ESA Hubble SpaceTelescope, obtained at the Space Telescope Science Institute, which isoperated by AURA, Inc., under NASA contract NAS 5-26555 and by STScIgrant GO-3594.01-91A.
| Far-infrared emission from intracluster dust in Abell clusters
The ISOPHOT instrument aboard ISO has been used to observe extended FIRemission of six Abell clusters. Strip scanning measurements withcrossing position angles centered on the clusters were carried out at120 μ m and 180 μ m. The raw profiles of the I120 μm/I180 μ m surface brightness ratio includingzodiacal light show a bump towards Abell 1656 (Coma), dips towards Abell262 and Abell 2670, and are without clear structure towards Abell 400,Abell 496, and Abell 4038. After subtraction of the zodiacal light, thebump towards Abell 1656 is still present, while the dips towards Abell262 and Abell 2670 are no longer noticable. This indicates a localizedexcess of emitting material outside the Galaxy towards Abell 1656 withproperties different from the galactic foreground cirrus, while thebehavior in Abell 262 and Abell 2670 can be reconciled with galacticcirrus structures localized on the line-of-sight to these clusters. Theexcess of ≈0.2 MJy/sr seen at 120 μ m towards Abell 1656 (Coma) isinterpreted as being due to thermal emission from intracluster dustdistributed in the hot X-ray emitting intracluster medium. Theintegrated excess flux within the central region of 10 arcmin--15 arcmindiameter is ≈2.8 Jy. Since the dust temperature is poorlyconstrained, only a rough estimate of the associated dust mass ofMD ≈ 107 Msolar can be derived. Theassociated visual extinction is negligible (AV << 0.1mag) and much smaller than claimed from optical observations. Noevidence is found for intracluster dust in the other five clustersobserved. The absence of any signature for intracluster dust in fiveclusters and the rather low inferred dust mass in Abell 1656 indicatesthat intracluster dust is likely not responsible for the excess X-rayabsorption seen in cooling flow clusters. These observations therebyrepresent a further unsuccessful attempt in detecting the presumed finalstage of the cooling flow material, in accord with quite a number ofprevious studies in other wavelengths regions. Finally, the observeddimming of the high-redshift supernovae is unlikely be attributable toextinction caused by dust in the intracluster or even a presumedintercluster medium. Based on observations with ISO, an ESA project withinstruments funded by ESA Member States (especially the PI countries:France, Germany, The Netherlands and the UK) and with the participationof ISAS and NASA.
| The HST survey of the B2 sample of radio-galaxies: Optical nuclei and the FR I/BL Lac unified scheme
We examine the optical properties of the nuclei of low luminosityradio-galaxies using snapshot HST images of the B2 sample. In agreementwith the results obtained from the analysis of the brighter 3C/FR Isample, we find a correlation between fluxes (and luminosities) of theoptical and radio cores. This provides further support for theinterpretation that the optical nuclear emission in FR I is dominated bysynchrotron emission and that accretion in these sources takes place ina low efficiency radiative regime. In the framework of the FR I/BL Lacsunified scheme, we find that the luminosity difference between FR I andBL Lac nuclei can be reproduced with a common beaming factor in both theradio and the optical band, independent of the extended radioluminosity, thus supporting such a scenario. The corresponding bulkLorentz factor is significantly smaller than is expected fromobservational and theoretical considerations in BL Lacs: this can beinterpreted as due to a velocity structure in the jet, with a fast spinesurrounded by a slower layer. Based on observations with the NASA/ESAHubble Space Telescope, obtained at the Space Telescope ScienceInstitute, which is operated by AURA, Inc., under NASA contract NAS5-26555 and by STScI grant GO-3594.01-91A.
| A new list of extra-galactic radio jets
A catalogue of extra-galactic jets is very useful both in observationaland theoretical studies of active galaxies. With the use of new powerfulradio instruments, the detailed structures of very compact or weak radiosources are investigated observationally and many new radio jets aredetected. In this paper, we give a list of 661 radio sources withdetected radio jets known to us prior to the end of December 2000. Allreferences are collected for the observations of jets in radio, IR,optical, UV and X-ray wave-bands. Table 1 and references to Table 1 areonly 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/381/757
| 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 Radio Galaxy Populations of Nearby Northern Abell Clusters
We report on the use of the NRAO VLA Sky Survey (NVSS) to identify radiogalaxies in 18 nearby Abell clusters. The listings extend from the coresof the clusters out to radii of 3 h-175 Mpc, whichcorresponds to 1.5 Abell radii and approximately 4 orders of magnitudein galaxy density. To create a truly useful catalog, we have collectedoptical spectra for nearly all of the galaxies lacking public velocitymeasurements. Consequently, we are able to discriminate between thoseradio galaxies seen in projection on the cluster and those that are inactuality cluster members. The resulting catalog consists of 329 clusterradio galaxies plus 138 galaxies deemed foreground or backgroundobjects, and new velocity measurements are reported for 273 of theseradio galaxies. The motivation for the catalog is the study of galaxyevolution in the cluster environment. The radio luminosity function is apowerful tool in the identification of active galaxies, as it isdominated by star-forming galaxies at intermediate luminosities andactive galactic nuclei (AGNs) at higher luminosities. The flux limit ofthe NVSS allows us to identify AGNs and star-forming galaxies down tostar formation rates less than 1 Msolar yr-1. Thissensitivity, coupled with the all-sky nature of the NVSS, allows us toproduce a catalog of considerable depth and breadth. In addition tothese data, we report detected infrared fluxes and upper limits obtainedfrom IRAS data. It is hoped that this database will prove useful in anumber of potential studies of the effect of environment on galaxyevolution. Based in part on observations obtained with the Apache PointObservatory 3.5 m telescope, which is owned and operated by theAstrophysical Research Consortium (ARC).
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