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Line emission in the brightest cluster galaxies of the NOAO Fundamental Plane and Sloan Digital Sky Surveys
We examine the optical emission-line properties of brightest clustergalaxies (BCGs) selected from two large, homogeneous data sets. Thefirst is the X-ray selected National Optical Astronomy ObservatoryFundamental Plane Survey (NFPS), and the second is the C4 catalogue ofoptically selected clusters built from the Sloan Digital Sky Survey DataRelease 3 (SDSS DR3). Our goal is to better understand the optical lineemission in BCGs with respect to properties of the galaxy and the hostcluster. Throughout the analysis we compare the line emission of theBCGs to that of a control sample made of the other bright galaxies nearthe cluster centre. Overall, both the NFPS and SDSS show a modestfraction of BCGs with emission lines (~15 per cent). No trend in thefraction of emitting BCGs as a function of galaxy mass or clustervelocity dispersion is found. However, we find that, for those BCGsfound in cooling flow clusters, 71+9-14 haveoptical emission. Furthermore, if we consider only BCGs within 50kpc ofthe X-ray centre of a cooling flow cluster, the emission-line fractionrises further to 100+0-15 per cent. Excluding thecooling flow clusters, only ~10 per cent of BCGs are line emitting,comparable to the control sample of galaxies. We show that the physicalorigin of the emission-line activity varies: in some cases it hasLINER-like line ratios, whereas in others it is a composite ofstar-formation and LINER-like activity. We conclude that the presence ofemission lines in BCGs is directly related to the cooling of X-ray gasat the cluster centre.
| Statistics of X-ray observables for the cooling-core and non-cooling core galaxy clusters
We present a statistical study of the occurrence and effects of thecooling cores in the clusters of galaxies in a flux-limited sample,HIFLUGCS, based on ROSAT and ASCA observations. About 49% of theclusters in this sample have a significant, classically-calculatedcooling-flow, mass-deposition rate. The upper envelope of the derivedmass-deposition rate is roughly proportional to the cluster mass, andthe fraction of cooling core clusters is found to decrease with it. Thecooling core clusters are found to have smaller core radii thannon-cooling core clusters, while some non-cooling core clusters havehigh β values (>0.8). In the relation of the X-ray luminosityvs. the temperature and the mass, the cooling core clusters show asignificantly higher normalization. A systematic correlation analysis,also involving relations of the gas mass and the total infraredluminosity, indicates that this bias is shown to be mostly due to anenhanced X-ray luminosity for cooling core clusters, while the otherparameters, like temperature, mass, and gas mass may be less affected bythe occurrence of a cooling core. These results may be explained by atleast some of the non-cooling core clusters being in dynamically youngstates compared with cooling core clusters, and they may turn intocooling core clusters in a later evolutionary stage.Tables 1-7 are only available in electronic form at http://www.aanda.org
| NOAO Fundamental Plane Survey. I. Survey Design, Redshifts, and Velocity Dispersion Data
We introduce the NOAO Fundamental Plane Survey (NFPS), a wide-fieldimaging/spectroscopic study of rich, low-redshift galaxy clusters. Thesurvey targets X-ray-selected clusters at 0.010
| 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.
| Redshift-Distance Survey of Early-Type Galaxies: Circular-Aperture Photometry
We present R-band CCD photometry for 1332 early-type galaxies, observedas part of the ENEAR survey of peculiar motions using early-typegalaxies in the nearby universe. Circular apertures are used to tracethe surface brightness profiles, which are then fitted by atwo-component bulge-disk model. From the fits, we obtain the structuralparameters required to estimate galaxy distances using theDn-σ and fundamental plane relations. We find thatabout 12% of the galaxies are well represented by a pure r1/4law, while 87% are best fitted by a two-component model. There are 356repeated observations of 257 galaxies obtained during different runsthat are used to derive statistical corrections and bring the data to acommon system. We also use these repeated observations to estimate ourinternal errors. The accuracy of our measurements are tested by thecomparison of 354 galaxies in common with other authors. Typical errorsin our measurements are 0.011 dex for logDn, 0.064 dex forlogre, 0.086 mag arcsec-2 for<μe>, and 0.09 for mRC,comparable to those estimated by other authors. The photometric datareported here represent one of the largest high-quality and uniformall-sky samples currently available for early-type galaxies in thenearby universe, especially suitable for peculiar motion studies.Based on observations at Cerro Tololo Inter-American Observatory (CTIO),National Optical Astronomy Observatory, which is operated by theAssociation of Universities for Research in Astronomy, Inc., undercooperative agreement with the National Science Foundation (NSF);European Southern Observatory (ESO); Fred Lawrence Whipple Observatory(FLWO); and the MDM Observatory on Kitt Peak.
| The HRX-BL Lac sample - Evolution of BL Lac objects
The unification of X-ray and radio selected BL Lacs has been anoutstanding problem in the blazar research in the past years. Recentinvestigations have shown that the gap between the two classes can befilled with intermediate objects and that apparently all differences canbe explained by mutual shifts of the peak frequencies of the synchrotronand inverse Compton component of the emission. We study the consequencesof this scheme using a new sample of X-ray selected BL Lac objectscomprising 104 objects with z<0.9 and a mean redshift bar {z} = 0.34.77 BL Lacs, of which the redshift could be determined for 64 (83%)objects, form a complete sample. The new data could not confirm ourearlier result, drawn from a subsample, that the negative evolutionvanishes below a synchrotron peak frequency log nupeak =16.5. The complete sample shows negative evolution at the 2sigma level(< Ve/Va > = 0.42 +/- 0.04). We concludethat the observed properties of the HRX BL Lac sample show typicalbehaviour for X-ray selected BL Lacs. They support an evolutionarymodel, in which flat-spectrum radio quasars (FSRQ) with high energeticjets evolve towards low frequency peaked (mostly radio-selected) BL Lacobjects and later on to high frequency peaked (mostly X-ray selected) BLLacs.Appendix (Tables 8 and 9, Fig. 8) is only available in electronic format http://www.edpsciences.org
| The Second Kiso Survey for ultraviolet-excess galaxies. III
The catalogue list and the identification chart of ultraviolet(UV)-excess galaxies which have been detected on two-color Kiso Schmidtplates are presented for 10 Schmidt fields. Catalogued are 710 objects,down to the photographic magnitude ~17.5 in the sky area of some 300square degrees. The total number of KUGs newly detected in the secondsurvey reaches 1,642.
| The Mass Function of an X-Ray Flux-limited Sample of Galaxy Clusters
A new X-ray-selected and X-ray flux-limited galaxy cluster sample ispresented. Based on the ROSAT All-Sky Survey, the 63 brightest clusterswith galactic latitude |bII|>=20° and fluxfX(0.1-2.4keV)>=2×10-11ergss-1cm-2 have been compiled. Gravitational masses havebeen determined utilizing intracluster gas density profiles, derivedmainly from ROSAT PSPC pointed observations, and gas temperatures, aspublished mainly from ASCA observations, assuming hydrostaticequilibrium. This sample and an extended sample of 106 galaxy clustersis used to establish the X-ray luminosity-gravitational mass relation.From the complete sample the galaxy cluster mass function is determinedand used to constrain the mean cosmic matter density and the amplitudeof mass fluctuations. Comparison to Press-Schechter type model massfunctions in the framework of cold dark matter cosmological models and aHarrison-Zeldovich initial density fluctuation spectrum yields theconstraints Ωm=0.12+0.06-0.04 andσ8=0.96+0.15-0.12 (90% c.l.).Various possible systematic uncertainties are quantified. Adding allidentified systematic uncertainties to the statistical uncertainty in aworst-case fashion results in an upper limitΩm<0.31. For comparison to previous results arelation σ8=0.43Ω-0.38m isderived. The mass function is integrated to show that the contributionof mass bound within virialized cluster regions to the total matterdensity is small; i.e.,Ωcluster=0.012+0.003-0.004 forcluster masses larger than6.4+0.7-0.6×1013h-150Msolar.
| The Infall Region of Abell 576: Independent Mass and Light Profiles
We describe observations of the nearby (cz=11,487 km s-1)cluster of galaxies Abell 576 beyond the virial radius and into theinfall region where galaxies are on their first or second pass throughthe cluster. Using 1057 redshifts, we use the infall pattern in redshiftspace to determine the mass profile of A576 to a radius of ~4h-1 Mpc. This mass estimation technique makes no assumptionsabout the equilibrium state of the cluster. Within ~1 h-1Mpc, the mass profile we derive exceeds that determined from X-rayobservations by a factor of ~2.5. At ~2.5 h-1 Mpc, however,the mass profile agrees with virial mass estimates. Our mass profile isconsistent with a Navarro, Frenk, & White or Hernquist profile, butit is inconsistent with an isothermal sphere. R-band images of a3°×3° region centered on the cluster allow an independentdetermination of the cluster light profile. We calculate the integratedmass-to-light ratio as a function of cluster radius; it decreasessmoothly from the core to M/LR~300 h at ~4 h-1Mpc. The differential M/LR profile decreases more steeply; wefind δM/δLR~100 h at ~4 h-1 Mpc, ingood agreement with the mass-to-light ratios of individual galaxies. Ifthe behavior of M/LR in A576 is general,Ωm<~0.4 at 95% confidence. For a Hernquist model,the best-fit mass profiles differ from the observed surface numberdensity of galaxies; the galaxies have a larger scale radius than themass. This result is consistent with the centrally peakedM/LR profile. Similarly, the scale radius of the lightprofile is larger than that of the mass profile. We discuss somepotential systematic effects; none can easily reconcile our results witha constant mass-to-light ratio.
| The Northern ROSAT All-Sky (NORAS) Galaxy Cluster Survey. I. X-Ray Properties of Clusters Detected as Extended X-Ray Sources
In the construction of an X-ray-selected sample of galaxy clusters forcosmological studies, we have assembled a sample of 495 X-ray sourcesfound to show extended X-ray emission in the first processing of theROSAT All-Sky Survey. The sample covers the celestial region withdeclination δ>=0deg and Galactic latitude|bII|>=20deg and comprises sources with a countrate >=0.06 counts s-1 and a source extent likelihood ofL>=7. In an optical follow-up identification program we find 378(76%) of these sources to be clusters of galaxies. It was necessary toreanalyze the sources in this sample with a new X-ray sourcecharacterization technique to provide more precise values for the X-rayflux and source extent than obtained from the standard processing. Thisnew method, termed growth curve analysis (GCA), has the advantage overprevious methods in its ability to be robust, to be easy to model and tointegrate into simulations, to provide diagnostic plots for visualinspection, and to make extensive use of the X-ray data. The sourceparameters obtained assist the source identification and provide moreprecise X-ray fluxes. This reanalysis is based on data from the morerecent second processing of the ROSAT Survey. We present a catalog ofthe cluster sources with the X-ray properties obtained as well as a listof the previously flagged extended sources that are found to have anoncluster counterpart. We discuss the process of source identificationfrom the combination of optical and X-ray data. To investigate theoverall completeness of the cluster sample as a function of the X-rayflux limit, we extend the search for X-ray cluster sources to the dataof the second processing of the ROSAT Survey for the northern sky regionbetween 9h and 14h in right ascension. We includethe search for X-ray emission of known clusters as well as a newinvestigation of extended X-ray sources. In the course of this search wefind X-ray emission from 85 additional Abell clusters and 56 veryprobable cluster candidates among the newly found extended sources. Acomparison of the X-ray cluster number counts of the NORAS sample withthe ROSAT-ESO Flux-limited X-Ray (REFLEX) Cluster Survey results leadsto an estimate of the completeness of the NORAS sample of ROSAT All-SkySurvey (RASS) I extended clusters of about 50% at an X-ray flux ofFX(0.1-2.4 keV)=3×10-12 ergs s-1cm-2. The estimated completeness achieved by adding thesupplementary sample in the study area amounts to about 82% incomparison to REFLEX. The low completeness introduces an uncertainty inthe use of the sample for cosmological statistical studies that will becured with the completion of the continuing Northern ROSAT All-Sky(NORAS) Cluster Survey project. Results reported here are based onobservations made with the Multiple Mirror Telescope, a joint facilityof the Smithsonian Institution and the University of Arizona.
| Arcsecond Positions of UGC Galaxies
We present accurate B1950 and J2000 positions for all confirmed galaxiesin the Uppsala General Catalog (UGC). The positions were measuredvisually from Digitized Sky Survey images with rms uncertaintiesσ<=[(1.2")2+(θ/100)2]1/2,where θ is the major-axis diameter. We compared each galaxymeasured with the original UGC description to ensure high reliability.The full position list is available in the electronic version only.
| The ROSAT Brightest Cluster Sample - I. The compilation of the sample and the cluster log N-log S distribution
We present a 90 per cent flux-complete sample of the 201 X-ray-brightestclusters of galaxies in the northern hemisphere (delta>=0 deg), athigh Galactic latitudes (|b|>=20 deg), with measured redshiftsz<=0.3 and fluxes higher than 4.4x10^-12 erg cm^-2 s^-1 in the0.1-2.4 keV band. The sample, called the ROSAT Brightest Cluster Sample(BCS), is selected from ROSAT All-Sky Survey data and is the largestX-ray-selected cluster sample compiled to date. In addition to Abellclusters, which form the bulk of the sample, the BCS also contains theX-ray-brightest Zwicky clusters and other clusters selected from theirX-ray properties alone. Effort has been made to ensure the highestpossible completeness of the sample and the smallest possiblecontamination by non-cluster X-ray sources. X-ray fluxes are computedusing an algorithm tailored for the detection and characterization ofX-ray emission from galaxy clusters. These fluxes are accurate to betterthan 15 per cent (mean 1sigma error). We find the cumulative logN-logSdistribution of clusters to follow a power law kappa S^alpha withalpha=1.31^+0.06_-0.03 (errors are the 10th and 90th percentiles) downto fluxes of 2x10^-12 erg cm^-2 s^-1, i.e. considerably below the BCSflux limit. Although our best-fitting slope disagrees formally with thecanonical value of -1.5 for a Euclidean distribution, the BCS logN-logSdistribution is consistent with a non-evolving cluster population ifcosmological effects are taken into account. Our sample will allow us toexamine large-scale structure in the northern hemisphere, determine thespatial cluster-cluster correlation function, investigate correlationsbetween the X-ray and optical properties of the clusters, establish theX-ray luminosity function for galaxy clusters, and discuss theimplications of the results for cluster evolution.
| 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.
| An image database. II. Catalogue between δ=-30deg and δ=70deg.
A preliminary list of 68.040 galaxies was built from extraction of35.841 digitized images of the Palomar Sky Survey (Paper I). For eachgalaxy, the basic parameters are obtained: coordinates, diameter, axisratio, total magnitude, position angle. On this preliminary list, weapply severe selection rules to get a catalog of 28.000 galaxies, wellidentified and well documented. For each parameter, a comparison is madewith standard measurements. The accuracy of the raw photometricparameters is quite good despite of the simplicity of the method.Without any local correction, the standard error on the total magnitudeis about 0.5 magnitude up to a total magnitude of B_T_=17. Significantsecondary effects are detected concerning the magnitudes: distance toplate center effect and air-mass effect.
| The ROSAT AGN content of the 87GB 5 GHz survey: bulk properties of previously optically identified sources.
The cross-correlation of the source list from the ROSAT All-Sky Surveywith the 5 GHz Green Bank survey yields a list of 2127 objects. Abouttwo thirds of them are optically unidentified. The majority of theobjects with known optical counterparts are quasars and radio galaxies,most of them detected in X-rays for the first time. In this paper wepresent a list of the previously optically identified objects with theirmain characteristics and discuss their general (bulk) properties. Wefind strong correlations between luminosities in the radio, optical, andX-ray bands which differ for quasars and radio galaxies. The fraction offlat radio spectrum sources increases with redshift and ~ 95% of allsources above z = 2 are of that type. In the relatively large group ofblazars, radio selected BL Lacs and highly polarized quasars show verysimilar properties while X-ray selected BL Lacs have markedly differentX-ray to radio flux ratios. The sample is large enough and ofsufficiently high quality to reveal clearly various detection biases andselection effects which strongly influence the physical interpretationof the correlations. Radio follow - up observations for thedetermination of the morphological and spectral properties as well asenvironmental conditions are needed for a statistically reliable studyof the sample. The very large group of sources with low radio fluxesremains to be optically identified.
| Optical positions and 327 MHz flux-densities of UGC galaxies in selected Westerbork fields
The study presents accurate optical positions of 421 UGC galaxies whichare used to search for 30 92-cm WSRT fields observed for emission fromthese galaxies. Good 92-cm flux densities were obtained for 140galaxies, marginal flux densities for 71 galaxies, and upper limits for210 galaxies. For 35 galaxies, spectral indices in the decimeterwavelength range are determined. The mean spectral index for spiralgalaxies (0.72 +/- 0.03) is very similar to that of elliptical galaxies(0.64 +/- 0.10). The four multiple systems in the sample have a muchflatter spectral index (-0.21 +/- 0.07), from which the presence of asignificant thermal component in their total radio emission issuggested. Comparison with IRAS results show that about half of thegalaxies detected at radio wavelengths are detected in the FIR. It isproposed that some spiral galaxies are anomalously weak in the IR ascompared with their radio brightness.
| Redshifts of galaxies in the winter plane
New redshifts for 57 bright galaxies and 98 fainter galaxies in thewinter galactic plane are presented. This list completes the redshiftsfor all galaxies in the merged Zwicky-Nilson catalog between 4 h and 8 hright ascension, above declination 0 deg, and with m(pg) of 14.5 orless. Three other bright objects in the Zwicky-Nilson catalog suspectedto be galaxies are found to be a planetary nebula, an open galactic starcluster, and a reflection nebula.
| The large-scale distribution of galaxies in the Linx-Gemini region
A redshift distribution study of a sample of 283 bright galaxies in an1800 square degree area in the Linx-Gemini region, including newredshifts for 59 galaxies, provides evidence for the existence ofseveral large scale structures. The Linx-Ursa supercluster with meanvelocity of 3500 km/s, a large cloud of galaxies extending for at least50/h Mpc around Abell 569, a low density filament in Gemini composedmainly of spirals, and a possible outstanding structure containing thecluster Abell 779, are found. The Abell 569 cloud is suggested as thestructure most likely connected with the Perseus supercluster across thegalactic dimming region.
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