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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.
| 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.
| Seeing Galaxies through Thick and Thin. I. Optical Opacity Measures in Overlapping Galaxies
We describe the use of partially overlapping galaxies to provide directmeasurements of the effective absorption in galaxy disks, independent ofassumptions about internal disk structure. The nonoverlapping parts ofthe galaxies and symmetry considerations are used to reconstruct, viadifferential photometry, how much background galaxy light is lost inpassing through the foreground disks. Extensive catalog searches andfollow-up imaging yield ~15-25 nearby galaxy pairs suitable for varyingdegrees of our analysis; 11 of the best such examples are presentedhere. From these pairs, we find that interarm extinction is modest,declining from AB~1 mag at 0.3RB25 toessentially zero by RB25; the interarm dust has ascale length consistent with that of the disk starlight. In contrast,dust in spiral arms and resonance rings may be optically thick(AB>2) at virtually any radius. Some disks have flatterextinction curves than the Galaxy, with AB/AI~1.6this is probably the signature of clumpy dust distributions. Even thoughtypical spirals are not optically thick throughout their disks, wherethey are optically thick is correlated with where they are mostluminous: in spiral arms and inner disks. This correlation betweenabsorption and emission regions may account for their apparent surfacebrightness being only mildly dependent on inclination, erroneouslyindicating that spirals are generally optically thick. Taken as anensemble, the opacities of spiral galaxies may be just great enough tosignificantly affect QSO counts, though not enough to cause theirhigh-redshift cutoff. Based in part on archival observations with theNASA/ESA Hubble Space Telescope (HST) obtained at the Space TelescopeScience Institute, which is operated by the Association of Universitiesfor Research in Astronomy, Inc., under NASA contract NAS5-26555.
| The Southern Sky Redshift Survey
We report redshifts, magnitudes, and morphological classifications for5369 galaxies with m_B <= 15.5 and for 57 galaxies fainter than thislimit, in two regions covering a total of 1.70 sr in the southerncelestial hemisphere. The galaxy catalog is drawn primarily from thelist of nonstellar objects identified in the Hubble Space TelescopeGuide Star Catalog (GSC). The galaxies have positions accurate to ~1"and magnitudes with an rms scatter of ~0.3 mag. We compute magnitudes(m_SSRS2) from the relation between instrumental GSC magnitudes and thephotometry by Lauberts & Valentijn. From a comparison with CCDphotometry, we find that our system is homogeneous across the sky andcorresponds to magnitudes measured at the isophotal level ~26 magarcsec^-2. The precision of the radial velocities is ~40 km s^-1, andthe redshift survey is more than 99% complete to the m_SSRS2 = 15.5 maglimit. This sample is in the direction opposite that of the CfA2; incombination the two surveys provide an important database for studies ofthe properties of galaxies and their large-scale distribution in thenearby universe. Based on observations obtained at Cerro TololoInter-American Observatory, National Optical Astronomy Observatories,operated by the Association of Universities for Research in Astronomy,Inc., under cooperative agreement with the National Science Foundation;Complejo Astronomico El Leoncito, operated under agreement between theConsejo Nacional de Investigaciones Científicas de laRepública Argentina and the National Universities of La Plata,Córdoba, and San Juan; the European Southern Observatory, LaSilla, Chile, partially under the bilateral ESO-ObservatórioNacional agreement; Fred Lawrence Whipple Observatory;Laboratório Nacional de Astrofísica, Brazil; and the SouthAfrican Astronomical Observatory.
| The ESO Nearby Abell Cluster Survey. V. The catalogue: Contents and instructions for use
We present the catalogue resulting from the ESO Nearby Abell ClusterSurvey (the ENACS), which contains redshifts and magnitudes for 5634galaxies in the directions of 107 rich, nearby southern Abell clustercandidates. We describe the contents of the catalogue and discuss theresults of a comparison between the ENACS catalogue and the COSMOSGalaxy Catalogue. When cross-correlating the two catalogues we findthat, at least in the areas of the ENACS clusters, the completeness ofthe COSMOS catalogue is somewhat lower than was estimated previously forthe carefully analyzed and well-calibrated part of the COSMOS catalogueknown as the Edinburgh-Durham Southern Galaxy Survey (EDSGC). The galaxypositions in the COSMOS and ENACS catalogues are found to be on the samesystem to within about one arcsecond. For the clusters for which thephotometry in the ENACS and COSMOS catalogues is based on the samesurvey plates, the two magnitude scales agree very well. We confirm thatthe photometric calibration in the EDSGC subset of the COSMOS catalogueis of higher quality than in the EDSGC complement. The ENACS galaxysamples are unbiased subsets of the COSMOS catalogue as far as theprojected galaxy distribution is concerned, except in only a few cases.We summarize how the ENACS galaxy samples are subsets of the COSMOScatalogues in the ENACS apertures, with respect to magnitude. For theENACS catalogue as a whole, we describe the apparent incompleteness atfaint magnitudes and towards higher redshifts. Finally, we provide somedetailed information about the ENACS catalogue that is essential for itsproper statistical use and we summarize some facts that must beremembered when selecting subsets of galaxies from it. Based onobservations collected at the European Southern Observatory (La Silla,Chile).
| On the morphology of peculiar ring galaxies
It is proposed that peculiar ring galaxies can be divided into fiveprincipal types according to the morphology of the ring and bulge, basedon the visual inspection of 489 selected objects. Those objects havebeen named ``peculiar'' following the ``Catalogue of Southern PeculiarGalaxies and Associations'' by \cite[Arp & Madore (1986]{am6}) Table2 with its notes is only available electronically via anonymous ftp130.79.128.5 or http://cdsweb.u-strasbg.fr.
| 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.
| VLA : a l'ecoute DU Cosmos.
Not Available
| Rotation measure variations across the lobes of extragalactic radio sources
It is shown through a high-resolution, three-dimensional smoothedparticle hydrodynamics simulation of a transonic shear layer thatlarge-scale nonlinear surface waves can form on the lobes ofextragalactic radio sources through the successive merging of smallerwaves generated by the Kelvin-Helmholtz instability. A theory isproposed relating these surface waves to substantial variations inrotation measure. The magnetic field is advected into the surroundingmedium by an associated low level of turbulence, and changes directionon a scale approximately equal to the half-wavelength of theKelvin-Helmholtz waves. The mixing of magnetic field from the lobe withthe surrounding thermal plasma causes large positive and negativerotation measure excursions. The peak-to-peak variation in rotationmeasure is estimated and favorably compared with values in five regionsof Cygnus A and in the northern lobe of a newly studied radio source PKS2104 - 25N.
| New observations and a photographic atlas of polar-ring galaxies
A photographic atlas of polar-ring galaxies and related objects ispresented. The atlas includes kinematically confirmed polar-ringgalaxies (category A), good condidates based on their morphologicalappearance (category B), possible candidates (category C), and possiblyrelated objects (category D). New photometric and kinematic observationsare reported for several galaxies in the catalog, including observationsthat show that UGC 7576 and UGC 9796 ( = II ZW 73) are S0 galaxies withpolar rings. Roughly 0.5 percent of all nearby S0 galaxies appear tohave polar rings. When corrected for various selection effects (e.g.,nonoptimal viewing orientation, possible dimming, or limited lifetime ofthe ring) the percentage increases to about 5 percent of S0 galaxieswhich have, or have had a polar ring.
| An extended galaxy redshift survey. I - The catalogue
Redshifts and blue magnitudes are presented for a sample of 264 'field'galaxies virtually complete to a limiting magnitude of 16.80 mag. Thegalaxies were selected by sampling one galaxy in every three in order ofapparent magnitude on each of nine high-latitude UK Schmidt (UKST)fields. The spectral data came from observations with the 1.9-mtelescope at the South African Astronomical Observatory (SAAO), and theresulting radial velocities have a precision of 130 + or - km/s. Thissurvey augments substantially the Durham/AAT redshift survey. Theobservational techniques and reduction procedures are discussed.
| Southern Galaxy Catalogue.
Not Available
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