next previous
Up: Looking for fine

2. Observational approach

The objects selected for this work (see Table 1) have been extracted from a sample of Ring and Elliptical galaxies of which structural properties like surface brightness and color distributions, morphology, and fine structure are being thoroughly studied. The observations were performed at the 1.6 m-telescope of the Observatório do Pico dos Dias of the Laboratório Nacional de Astrofısica, Brazil, with direct CCD camera and BVRI Kron-Cousins filters, and the 1 m-telescope at Las Campanas Observatory, Chile, also direct CCD images with  g  and  r  Gunn filters. For each object, only results for one filter will be presented, which suffices for the purposes of this work. Complete results will appear in forthcoming papers.

All the images quoted in Table 1 are the mode of at least 3 frames, and have been pre-processed with IRAF and STSDAS packages, cleaned as much as possible by combination of multiple images, subtraction of cosmic rays, bad pixels, and stars, and correction for background gradients and sky contribution. The removal of the sky background has also the effect of smoothing the sudden discontinuity in flux level at the borders of the image, thus reducing the introduction of artifact when filtering in the linear domain. The possibility of spurious features due to the truncation of the spatial frequency power spectrum remains, nonetheless. The combination of frames suppresses artificial faint haloes around the filtered images due to the reduced background noise.


Object tex2html_wrap_inline1518 tex2html_wrap_inline1520 Telescope Filter Type Ref.
HRG 54103 01 16 19.2 -19 53 17.3 1.6 m OPD B SA(r)tex2html_wrap_inline1526 1, 2, 3
NGC 5193/5193A 13 29 02.9 -32 58 38.0 1.0 m LCO Gunn g Ep/S0 2
NGC 5761 14 46 18.0 -20 10 12.0 1.0 m LCO Gunn g S0 pec 2
ESO 143-G7 20 01 57.0 -60 21 12.0 1.6 m OPD B (R)SAB(rs)ab 1, 2
Table 1: The observed objects

Ref:  (1) Buta (1995),  (2) NASA Extragalactic Database,  (3) Faúndez-Abans et al. (1992).

next previous
Up: Looking for fine

Copyright by the European Southern Observatory (ESO)