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|Spectrophotometry of galaxies in the Virgo cluster. II. The data|
Drift-scan mode (3600-6800 Å) spectra with 500
|Companions of Bright Barred Shapley-Ames Galaxies|
Companion galaxy environment for a subset of 78 bright and nearby barredgalaxies from the Shapley-Ames Catalog is presented. Among the spiralbarred galaxies, there are Seyfert galaxies, galaxies with circumnuclearstructures, galaxies not associated with any large-scale galaxy cloudstructure, galaxies with peculiar disk morphology (crooked arms), andgalaxies with normal disk morphology; the list includes all Hubbletypes. The companion galaxy list includes the number of companiongalaxies within 20 diameters, their Hubble type, and projectedseparation distance. In addition, the companion environment was searchedfor four known active spiral galaxies, three of them are Seyfertgalaxies, namely, NGC 1068, NGC 1097, and NGC 5548, and one is astarburst galaxy, M82. Among the results obtained, it is noted that theonly spiral barred galaxy classified as Seyfert 1 in our list has nocompanions within a projected distance of 20 diameters; six out of 10Seyfert 2 bar galaxies have no companions within 10 diameters, six outof 10 Seyfert 2 galaxies have one or more companions at projectedseparation distances between 10 and 20 diameters; six out of 12 galaxieswith circumnuclear structures have two or more companions within 20diameters.
|Hα surface photometry of galaxies in the Virgo cluster. II. Observations with the OHP and Calar Alto 1.2 m telescopes|
We present Hα line imaging observations of 122 galaxies obtainedwith the 1.20 m telescopes of the Observatoire de Haute Provence (OHP)and of Calar Alto. The observed galaxies are mostly Virgo clustermembers (95), along with 10 objects in the Coma/A1367 supercluster, 6 inthe clusters A2197 and A2199, and 11 nearby galaxies taken as fillers.Hα +[NII] fluxes and equivalent widths, as well as images of allthe detected targets, are presented. Based on observations taken at theObservatoire de Haute Provence (OHP) (France), operated by the FrenchCNRS, and Calar Alto Observatory (Spain), operated by theMax-Planck-Institut für Astronomie (Heidelberg) jointly with theSpanish National Commission for Astronomy. Figure 1 is only available inelectronic form at http://www.edpsciences.org
|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.
|Are nucleated dwarf galaxies genuine ellipticals?|
There are now six known dwarf elliptical galaxies outside the LocalGroup (mostly in the Virgo and Fornax clusters) that appear to containglobular-cluster systems of their own; all of them were discoveredaccidentally during surveys for other purposes. All six of these arenucleated (dE, N) dwarfs. This evidence, although quite preliminary,supports the suggestion of Ferguson and Sandage that nucleated dwarfsare 'genuine' E galaxies, generically more strongly related to largeE/S0 galaxies than are nonnucleated dwarfs of the same luminosity level.A more systematic search for globular cluster in both types of dE's isrecommended.
|Spectroscopy of globular clusters in M87 and M49|
Optical multislit spectra of globular clusters in two giant ellipticalgalaxies in the Virgo Cluster indicate average metal abundances ofone-sixth and one-tenth solar composition for M49 and M87, respectively.These estimates are based on the strength of Mg lines. Taken togetherwith observations of globular clusters in dwarf ellipticals thissuggests a direct relation between mean metallicity of the clustersystem and the luminosity of the parent galaxy which is an interestingconstraint on theories of cluster formation during the protogalacticepoch. Rotation is evident in both globular cluster systems. Theline-of-sight velocity dispersions of clusters in the two galaxies areestimated to be 340 + or - 50 km/s (M49) and 386 + or - 42 km/s (M87).Although sparsely sampled, the velocity dispersion profiles of thecluster systems are flat, suggesting the existence of an isothermal haloof dark matter in these ellipticals.
|Three-color surface photometry of a selected sample of early-type galaxies. I - Observations and data reduction|
This paper presents the results of two or three color surface photometryfor a sample of 36 early-type galaxies obtained at the Canada FranceHawaii Telescope with CCD cameras. The calibration and data reductionprocedures are described. A comparison of the results with previous workis made for NGC 3379. For each galaxy the B surface brightness profilealong the major axis, as well as ellipticity and color profiles aredisplayed.
|Three-color surface photometry of a selected sample of early-type galaxies. II - Color gradients|
Selected data from photometric observations of 35 early-type galaxies,obtained in two or three colors (B, R, and MgIb) with CCD cameras andreported by Vigroux et al. (1988), are compiled in graphs and analyzedto determine color gradients and their dependence on other parameters.Features noted include red nuclei and systematic reddening toward thecenter in high-luminosity galaxies with M(B) less than -18 (interpretedas a metallicity gradient), reddening at greater radial distance indwarf ellipticals with M(B) greater than -18 (attributed to an ageeffect), and maximum color gradients at M(B) = -20.5 (where ellipticalstend to become slow rotators). It is inferred that galaxies fainter thanthis critical luminosity have evolution dominated by internal processessuch as galactic winds and dissipation, while brighter galaxies areaffected by external processes such as mergers.
|Studies of the Virgo Cluster. II - A catalog of 2096 galaxies in the Virgo Cluster area.|
The present catalog of 2096 galaxies within an area of about 140 sq degapproximately centered on the Virgo cluster should be an essentiallycomplete listing of all certain and possible cluster members,independent of morphological type. Cluster membership is essentiallydecided by galaxy morphology; for giants and the rare class of highsurface brightness dwarfs, membership rests on velocity data. While 1277of the catalog entries are considered members of the Virgo cluster, 574are possible members and 245 appear to be background Zwicky galaxies.Major-to-minor axis ratios are given for all galaxies brighter than B(T)= 18, as well as for many fainter ones.
|Structure and stellar content of dwarf elliptical galaxies|
A small number of low-luminosity elliptical galaxies are studied usingphotoelectric and photographic techniques. The color-magnitude relationfor ellipticals now extends from M(v) = -23 to -15, and is linear overthat range with a slope of 0.10 in U-V per visual magnitude. Galaxieswhich are known to contain a large number of young stars are from 0.10to 0.20 mag bluer than the lower envelope of the ellipticalcolor-magnitude relation. This difference can be accounted for by a lackof the most massive stars in a young population. Thus, the Balmerabsorption line spectra of the dwarf ellipticals which have beenobserved by others can be best understood as the signature of a youngpopulation which no longer has an upper main sequence of stars.
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