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Nearby Optical Galaxies: Selection of the Sample and Identification of Groups
In this paper we describe the Nearby Optical Galaxy (NOG) sample, whichis a complete, distance-limited (cz<=6000 km s-1) andmagnitude-limited (B<=14) sample of ~7000 optical galaxies. Thesample covers 2/3 (8.27 sr) of the sky (|b|>20deg) andappears to have a good completeness in redshift (97%). We select thesample on the basis of homogenized corrected total blue magnitudes inorder to minimize systematic effects in galaxy sampling. We identify thegroups in this sample by means of both the hierarchical and thepercolation ``friends-of-friends'' methods. The resulting catalogs ofloose groups appear to be similar and are among the largest catalogs ofgroups currently available. Most of the NOG galaxies (~60%) are found tobe members of galaxy pairs (~580 pairs for a total of ~15% of objects)or groups with at least three members (~500 groups for a total of ~45%of objects). About 40% of galaxies are left ungrouped (field galaxies).We illustrate the main features of the NOG galaxy distribution. Comparedto previous optical and IRAS galaxy samples, the NOG provides a densersampling of the galaxy distribution in the nearby universe. Given itslarge sky coverage, the identification of groups, and its high-densitysampling, the NOG is suited to the analysis of the galaxy density fieldof the nearby universe, especially on small scales.
| 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.
| 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.
Not Available
| 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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