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A sample of X-ray emitting normal galaxies from the BMW-HRI Catalogue
We obtained a sample of 143 normal galaxies with X-ray luminosity in therange 1038{-}1043 erg s-1 from thecross-correlation of the ROSAT HRI Brera Multi-scale Wavelet (BMW-HRI)Catalogue with the Lyon-Meudon Extragalactic Database (LEDA). We findthat the average X-ray properties of this sample are in good agreementwith those of other samples of galaxies in the literature. We selected acomplete flux limited serendipitous sample of 32 galaxies from which wederived the log N-log S distribution of normal galaxies in the fluxrange 1.1{-} 110 × 10-14 erg cm-2s-1. The resulting distribution is consistent with theEuclidean -1.5 slope. Comparisons with other samples, such as theExtended Medium Sensitivity Survey, the ROSAT All Sky Survey, theXMM-Newton/2dF survey, and the Chandra Deep Field Survey indicate thatthe log N -log S distribution of normal galaxies is consistent with aEuclidean slope over a flux range of about 6 decades.
| 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.
| 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.
| 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.
| Globular Clusters in 19 Northern Abell Clusters.
We use the method developed by Blakeslee & Tonry (1995) to study theglobular cluster (GC) populations of 21 giant elliptical galaxies in 19Abell clusters. This method, applied here primarily in the R band, isbased on the surface brightness fluctuations technique of extragalacticdistance measurement. The sample galaxies range in redshift from 5000 to10,000 \kms, and were selected primarily from the Lauer & Postman(1994) survey of brightest cluster galaxies (BCGs). We find a tightcorrelation between the GC specific frequency S_N of the central brightgalaxy in the cluster and the cluster velocity dispersion. S_N alsocorrelates well with the cluster X-ray temperature and with the numberof bright neighboring galaxies, less well with the galaxy profile, andonly marginally with galaxy luminosity and overall cluster richness. Itdoes not correlate with cluster morphology class. Thus, unlike galaxyluminosity, S_N is determined by the cluster mass, or density. Toaccount for this situation, we propose that the GCs formed early and inproportion to the available mass, while the luminosity growth of thegalaxy was later halted, yielding the observed correlations of \sn\ withdensity. We introduce a quantity called eta_ {GC}, the numberof GCs per unit local cluster mass. For a simple cluster mass model,eta_ {GC} is found to be constant, indicating a uniform GCproduction rate per unit available mass. A measurement of the Gaussianwidth sigma of the GC luminosity function (GCLF) is one of thebyproducts of our analysis. In the cosmic microwave background frame,the mean width for this sample is < sigma >{=}1.43 mag, virtuallyidentical to the HST value for M87, the galaxy used to calibrate themean of the GCLF in this analysis.
| Brightest cluster galaxies as standard candles
We investigate the use of brightest cluster galaxies (BCGs) as standardcandles for measuring galaxy peculiar velocities on large scales. Wehave obtained precise large-format CCD surface photometry and redshiftsfor an all-sky, volume-limited (z less than or = 0.05) sample of 199BCG. We reinvestigate the Hoessel (1980) relationship between the metricluminosity, Lm, within the central 10 kpc/h of the BCGs andthe logarithmic slope of the surface brightness profile, alpha. TheLm-alpha relationship reduces the cosmic scatter inLm from 0.327 mag to 0.244 mag, yielding a typical distanceaccuracy of 17% per BCG. Residuals about the Lm-alpharelationship are independent of BCG luminosity, BCG B - Rccolor, BCG location within the host cluster, and richness of the hostcluster. The metric luminosity is independent of cluster richness evenbefore correcting for its dependence on alpha, which provides furtherevidence for the unique nature of the BCG luminosity function. Indeed,the BCG luminosity function, both before and after application of thealpha-correction, is consistent with a single Gaussian distribution.Half the BCGs in the sample show some evidence of small color gradientsas a function of radius within their central 50 kpc/h regions but withalmost equal numbers becoming redder as becoming bluer. However, withthe central 10 kpc/h the colors are remarkably constant -- the mean B -Rc color is 1.51 with a dispersion of only 0.06 mag. Thenarrow photometric and color distributions of the BCGs, the lack of'second-parameter' effects, as well as the unique rich clusterenvironment of BCGs, argue that BCGs are the most homogeneous distanceindicators presently available for large-scale structure research.
| Properties of nearby clusters of galaxies. II. A 151, A 637, A 646, A 649, A 655, A 1132, A 1314, A 1377, A 1570, A 1589.
We present F band photometry, from digitized 48-inch Palomar plates, of1167 galaxies brighter than m_3_+3 in 10 Abell clusters. For eachgalaxy, absolute coordinates, magnitude, size, ellipticity endorientation are given. For each cluster we provide finding charts andcontour maps of the galaxy surface density.
| Structures of small-size radio galaxies in clusters
We present high resolution maps of a sample of radio galaxies belongingto Abell clusters, showing linear size less than or approximately 20kpc, i.e. completely embedded within the optical galaxy. These radiogalaxies were unresolved or only sligtly resolved in previousinterferometric observations. Most of the sources are resolved at thepresent resolution. Radio maps of all the resolved sources are given.The correlation of the linear size versus the total radio power at 1.4GHz is derived for radio galaxies belonging to clusters and is comparedwith the results found in a non-cluster sample. The size of clustersources is slightly smaller on average than that of non-cluster ones,but the difference is not statistically significant. The tailedstructure, typical of cluster radio galaxies of large size, found inapproximately 24% of the sources of the present sample. This percentageis higher than in a non-cluster sample, but lower than ina clustersample of radio galaxies with larger size. Tailed radio galaxies aremostly located at the cluster centers, the smallest ones beingidentified with the brightest cluster member. Stripping of the hotinterstellar medium is suggested to be present in these galaxies.
| The ultraviolet spectra of nearby radio galaxies
New and archival IUE SWP spectra are reported for nine nearby radiogalaxies (V is less than 15 mag), together with optical emissionlikedata for these galaxies as well as a number of candidates with weakerline emission. Both their UV line and continuum properties, as well astheir UV and UV-optical line ratios, are examined. Ly-alpha emission isfound to be common among local radio galaxies, at modest luminosities(typically 10 exp 41-42 erg/s). No apparent relation is found betweenL(Ly-alpha) and radio power for the nearby radio galaxies alone. TheLy-alpha/H-alpha ratio in low power nearby radio galaxies is 2-5 timeslower than the prediction for case B recombination. The destruction ofLy-alpha photons by grains during resonant scattering can explain theobserved deficiency for reasonable metallicities. The nearby radiogalaxies have in general a small C IV/Ly-alpha ratio (less than 0.1).Comparison of the C IV and Ly-alpha strengths with those in luminous AGNsuggests that most of the UV continuum comes from the stellarpopulation, and not from the AGN.
| A 20 CM VLA survey of Abell clusters of galaxies. I - Distance class of not greater than 3 clusters
Nearby Abell clusters of distance class of not greater than 3 arestudied based on 20-cm VLA observations, Westerbork Synthesis RadioTelescope results, and Einstein Observatory X-ray data. No significantcorrelation is found between the 20-cm radio power and X-ray luminosity,and no evidence is found that regular-type clusters are statisticallymore likely to be radio loud than irregular-type clusters. A weakcorrelation is noted between X-ray-cooling mass-accretion rates andradio powers for central dominant galaxies in cooling-flow clusters,suggesting that either cooling accretion directly fuels the centralengine and/or cooling flows strongly interact with the radio plasma.
| Radio surveys and source counts at 408 MHz and 1420 MHz towards the Abell 1314 cluster of galaxies
Observations of the cluster of Abell 1314 galaxies were performed withthe Penticton synthesis telescope simultaneously at 408 MHz (with asensitivity of about 70 mJy) and at 1420 MHz (with a sensitivity ofabout 4.3 mJy). Detections have been made of 3 cluster sources, 64background radio sources at 1420 MHz, and 169 background sources at 408MHz. No candidate has been identified for very-steep-spectrum relicsources in this cluster of galaxies, nor for very-flat-spectrumblue-background radio galaxies behind the cluster.
| The 1 MPC giant head-tail radio galaxy IC 711 - 3-dimensional simulation and additional constraints on the Ram pressure theory
A three-dimensional simulation of the giant head-tail galaxy IC 711 hasbeen performed, constructing the radio trail cell by cell inside avolume of space composed of 8 million cells, with each cell beingassigned a proper radio emissivity. The results show a primary fastdecrease of the radio luminosity with time or distance from the opticalnucleus of the galaxy, and a secondary periodic variation of the radioluminosity every 500 kpc. It is suggested that edge brightening alongthe tail ridge is not necessary to explain the results.
| IC 711 - The longest head-tail galaxy known
The scale size of the largest structure in head-tail galaxies is notwell known. Previous observations of the head-tail galaxy IC 711 byVallee and Wilson (1976) have shown its tail to extend 13 arcmin beyondthe optical galaxy, making it the longest head-tail galaxy known. Newobservations at a longer wavelength of 74 cm with the synthesistelescope at Penticton show that the radio tail extends still further,to at least 17 arcmin, retaining its status as the longest head-tailgalaxy known today. Some theoretical models for the origin of suchgalaxies are discussed with particular reference to IC 711.
| Gravitational amplification of brightest cluster galaxies by foreground clusters
It is suggested that the Hubble diagram of brightest cluster galaxies(BCG) is strongly affected by gravitational amplifications due toforeground clusters of galaxies. Galaxies from Kristian et al.'s (1978)sample are placed with respect to foreground Zwicky clusters and theirdeviations from the mean magnitude-redshift relation are compared to thepredictions of Ricci gravitational amplification formula. It is foundthat the gravitational brightness increase reaches some tenth ofmagnitudes for these BCGs and that it has induced a strong selectioneffect artificially increasing the deceleration parameter q0.Once these effects are accounted for the Hubble diagram value ofq0 might agree with the low values obtained for the densityparameter sigma0 (0.1-0.2) without any need for rapidevolution.
| A Westerbork survey of clusters of galaxies. XIV - Abell 779 and Abell 1314
The clusters of galaxies Abell 779 and Abell 1314 observed with theWesterbork telescope at 610 MHz to a resolution of about 1 arcmin and asensitivity near 10 mJy are discussed. In all, 111 radio sources aredetected. It is shown through optical identification that 5 or 6 radiosources are probably associated with bright cluster galaxies. Thedifferential count of those radio sources apparently not associated withcluster galaxies is derived in the flux density range 10-500 mJy; it isfound to be similar to that obtained at 408 MHz in the 5C 5 survey.
| Orbital motion of the head-tail radio galaxy IC 708
VLA is used to map the head-tail radio galaxy IC 708 in the Abell 1314cluster of galaxies with resolutions from 0.5 to 3.3 arcsec at 4.89 GHz.The data suggest that the unusual structure of the source is due to agravitational interaction between IC 708 and IC 709, and the shape ofradio trails and their variation of intensity may be due to projectioneffects arising from the orbital motion of IC 708. Numerical simulationsof the orbital head-tail system are made, which incorporate variousmodels of the ejecta dynamics. The most satisfactory model is found tobe one with a pair of continuous supersonic jets that bend behind IC 708under ram pressure of the intracluster medium, and the distribution ofintensity and polarization over the trails of IC 708 resemble thoseobserved in straight radio jets in several low luminosity galaxies.
| The structures of the head-tail radio galaxies IC708 and IC711 at 1.4 GHz
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977A&A....58...79W&db_key=AST
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