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The structure of elliptical galaxies in the Virgo cluster. Results from the INT Wide Field Survey
We report on a complete CCD imaging survey of 226 elliptical galaxies inthe North-East quadrant of the Virgo cluster, representative of theproperties of giant and dwarf elliptical galaxies in this cluster. Wefit their radial light profiles with the Sersic r1/n model oflight distribution. We confirm the result of Graham & Guzman(\cite{Graham03}, AJ, 125, 2936) that the apparent dichotomy between Eand dE galaxies in the luminosity-< μ>e plane nolonger appears when other structural parameters are considered and canbe entirely attributed to the onset of ``core'' galaxies atBT -20.5 mag. When ``core'' galaxies are notconsidered, E and dE form a unique family with n linearly increasingwith the luminosity. For 90 galaxies we analyze the B-I color indices,both in the nuclear and in the outer regions. Both indices are bluertoward fainter luminosities. We find also that the outer color gradientsdo not show any significant correlation with the luminosity. The scatterin all color indicators increases significantly toward lowerluminosities, e.g. galaxies fainter than BT -15 have aB-I spread > 0.5 mag.Table 2, Figs. 13 and 14 are only available in electronic form athttp://www.edpsciences.org
| Digital stacking of Tech Pan films and the photometry of faint galaxies.
We describe the processing and co-addition of digitised scans of TechPan films, and discuss the scientific and photometric gains obtainedfrom use of co-added films. This work is based on SuperCOSMOS scans at10μm resolution of small regions of the Virgo cluster, which formpart of a large-scale survey for low surface brightness galaxies inVirgo. Use of co-added Tech Pan films allows the detection and surfacephotometry of such galaxies to very faint limits, and therefore providesan invaluable tool for a deeper sampling of the cluster galaxyluminosity function over large areas of sky. The calibration stepsnecessary before the films can be stacked are described in detail, aswell as the stacking process itself. Median-stacking is found to be moreeffective than averaging or simple adding of individual images, mainlydue to its ability in removing spurious features present on singlefilms. We also discuss several of the properties of stacked Tech Panfilms, such as background variations, the extent of galaxy profiles andthe detectability of small, faint galaxies.
| A search for low surface brightness galaxies in Virgo using Tech Pan films.
We report on a pilot study for a new survey of low surface brightnessgalaxies in the Virgo Cluster using Kodak Technical Pan 4415 films fromthe UK Schmidt Telescope. The film offers significant gains in depth,resolution and S/N when compared with conventional photographic platedata. This translates to direct scientific benefits as we clearlydemonstrate with the effectiveness of Tech Pan in searching for faintextended objects. From only a small pilot region we present photometryon two newly discovered low surface brightness galaxies not found inprevious studies of Virgo. The new surface brightness and size limitsexpected for the overall automated survey are discussed.
| Galaxy Surface Photometry with Kodak Technical Pan Film
Recent tests at the UKST with large-format Kodak Technical Pan 4415 filmon a thick estar base have proved to be extremely successful. Deep, sky-limited photographs with excellent image quality and resolution havebeen obtained. In good seeing these reach a magnitude or more fainterthan equivalent IIIa-F plates, and have considerably lower grain noiseand greater photometric accuracy. Here we demonstrate quantitatively forthe first time the effectiveness of this film for galaxy photometry. Inparticular, we find that the limiting isophote for surface photometry onan R-band, deep Tech-Pan 4415 film is about 27 Rμ or about 0.2 percent of the measured sky background. This is over a magnitude lower thannormally attained with equivalent R-band IIIa-F plates. Such filmstherefore have a depth broadly equivalent to ~2-min CCD R exposures on a4.0-m telescope but with wide-angle (40 square degree) coverage.
| Virgo dwarfs - New light on faint galaxies
Photographically amplified UK Schmidt plates have been used to define anew sample of low surface brightness (LSB) galaxies in the VirgoCluster. One of these galaxies is the largest, most gas-rich spiralgalaxy known, located well beyond the Virgo Cluster. The rest of the 137galaxies appear to be dwarf ellipticals. CCD photometry shows that thefaint galaxies are well modeled by an exponential radial profile. Thecolors of very LSB galaxies in Virgo are unusually blue in B-V, bluerthan the metal-poor Galactic globular clusters. If these galaxies do notviolate the mass-metallicity relation, then they must have smaller meanages than Galactic globulars. It is confirmed that any faint galaxysurvey tends to choose objects of a luminosity and surface brightnessthat give them the maximum angular size on the discovery material.
| H I detection survey of a complete magnitude-limited sample of dwarf irregular galaxies in the Virgo Cluster area
New single-beam Arecibo H I observations of 298 late-type galaxies inthe Virgo Cluster drawn mostly from the new catalog of Binggeli,Sandage, and Tammann (1985) are presented. Two hundred seventeen ofthese constitute a magnitude-limited 'complete sample' of such galaxies,types Sdm through Im and BCD. Sixty-one percent of this 'completesample' was detected, greatly enhancing the store of redshifts and H Imasses for such galaxies in the Virgo Cluster. For detected galaxies,heliocentric velocities, 50 percent profile widths, and single-beamfluxes are presented. For those that escaped detection, upper limits arecomputed to the flux appropriate to the redshift range (-600 to +3000km/s).
| 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.
| A catalog of dwarf galaxies in Virgo
A catalog listing the location, apparent angular diameter, type,estimated central light concentration, and estimated brightness of 846dwarf galaxies in a 200-deg-sq region in Virgo is presented. Thegalaxies comprise 634 ellipticals, 137 IC-3475-type galaxies, 73 dwarfspirals and irregulars, and two objects which are jets of normalgalaxies, and were found on nine long-exposure IIIa-J-emulsion platesmade with the 1.2-m-Schmidt telescope at Palomar Observatory from 1971to 1976. Concordances to other catalogs, tables of additionalparameters, maps, graphs, and photographs are provided. The projecteddistributions of normal and dwarf galaxies and the dependence ofapparent luminosity on central light concentration are discussed. It isfound that dwarf ellipticals and IC-3475-type galaxies are probablemembers of the Virgo cluster, while dwarf spirals and possibly dwarfirregulars are not.
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