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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.
| The Environmental Dependence of Brightest Cluster Galaxies: Implications for Large-Scale Flows
In a much-noticed recent study Lauer & Postman found that theinertial frame defined by a sample of 119 nearby Abell clusters withczȯ < 15,000 km s-1 showed a highly significant motion withrespect to the cosmic microwave background (CMB) frame. We construct asubsample of their sample which comprises 64 Abell/ACO clusters withX-ray luminosities from ROSAT and brightest cluster galaxy (BCG)photometry from Lauer & Postman. We find that both BCG metricluminosities and residuals from the Lm- alpha relation of Lauer &Postman are significantly correlated with the X-ray luminosity of thehost cluster at the 99.6% confidence level, in the sense that more X-rayluminous clusters have brighter BCGs. The strength of this correlationincreases with increasing X-ray luminosity and with increasing values ofthe structure parameter alpha . Taking this correlation into account, weobtain a new distance indicator for BCGs, the Lm- alpha -LX relation.Applying the Lm- alpha -LX relation to our sample, we find that theframe defined by these clusters has a bulk motion of 494 km s-1 toward l= 285 deg, b = 47 deg with respect to the CMB frame but the 95%confidence range on the amplitude is 306--1419 km s-1. When thecovariance of the components of the bulk motion is properly taken intoaccount, these results are inconsistent with this frame being at rest inthe CMB frame at only the 98.6% confidence level but are consistent withthe 300--400 km s-1 amplitude flows found by other studies on scales cz<~ 6000 km s-1. In order to obtain an estimate of the bulk flow onscales beyond local perturbations such as the "Great Attractor," we havealso examined the subsample of 57 clusters with X-ray data and czLG >6000 km s-1. For this subsample, the random errors in the bulk motionare large. We find that the bulk motion is consistent both with nomotion in the CMB frame and with the motion found by Lauer &Postman. However, our analysis of all 107 Lauer & Postman BCGs withczLG > 6000 km s-1 indicates that, even with no X-ray correction, themotion of these clusters with respect to the CMB frame is notsignificantly different from zero. Furthermore, the correction to thebulk motion of the subsample with X-ray data goes in the sense ofreducing the amplitude (by 663 km s-1) and significance (from 98.8% to83.8%) of its motion in the CMB frame, as well as reducing the internalinconsistency between its motion and that of the remainder of the Lauer& Postman sample with no X-ray data. Claims of large-scale,large-amplitude bulk flows should therefore be regarded with cautionuntil X-ray data become available for more clusters or until clusterdistances are confirmed by independent methods.
| 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.
| The Virgo cluster as a test for quantization of extragalactic redshifts
Tifft's (1972, 1977) hypothesis that redshifts are partially quantizedwith a periodicity in the range 70-75 km/s is tested for samples ofbright spiral and dwarf irregular galaxies with accurate H I redshiftsin the region of the Virgo cluster. The heliocentric redshifts arecorrected for solar motion, first by adopting an estimate of the sun'smotion with respect to the centroid of the Local Group, and then byallowing the solar velocity vector to vary in direction over the wholesky. Power spectrum analyses of the corrected redshifts are used tosearch for a significant periodicity in the prescribed range 70-75 km/s.No such periodicity is found for the dwarf irregulars, but there is apossible periodicity of about 71.1 km/s for the bright spirals. In afurther exploratory study, the sample of 112 spirals is divided upaccording to environment. The spirals in high-density regions of thecluster show no quantization, whereas those in low-density regionsappear to be partially quantized in intervals of about 71.0 km/s.
| BV photometry of southern elliptical galaxies
Photometric data for 78 elliptical galaxies observed in V and B colorswith the Cerro Tololo Inter-American Observatory 0.9-m telescope duringApril and November 1983 are examined. Lamberts' data from the ESO surveyof the ESO (B) Atlas are presented. The data are analyzed in order tostudy the motion of the Local Group and the spatial distribution ofgalaxies in the local region of the universe. The photometric data arecompared to the data in the photometry catalog of Longo and deVaucouleurs (1983, 1985) and good correlation between the observationsis detected.
| Southern Galaxy Catalogue.
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| On the variation of ellipticity with radius in elliptical galaxies
Ellipticity profiles and isophotal structures of 75 elliptical galaxieswith declinations south of approximately -23 deg are compared. Thesample studied includes both isolated ellipticals and members of pairs,multiplets, groups, and clusters. It is found that: (1) ellipticalgalaxies present four trends as a function of radius, viz., constant,peaked, decreasing, and increasing outward; (2) there is a correlationbetween ellipticity profile and membership in groups or clusters; (3)the brightest ellipticals in rich groups and compact clusters haveellipticity profiles that increase with radius; and (4) rotation of themajor axis of the isophotes is correlated with asymmetry of theisophotes, regardless of the class of ellipticity profile.
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