Astron. Astrophys. Suppl. Ser. 141, 1-22
Colour distributions in E-S0 galaxies.
R. Michard1,2 - P. Poulain3
Send offprint request: R. Michard
1 - Observatoire de la Côte d'Azur, Dept. Augustin Fresnel, BP. 4229, F-06304 Nice Cedex 4, France
2 - Observatoire de Paris, DEMIRM, 77 avenue Denfert-Rochereau, F-75015 Paris, France
3 - Observatoire Midi-Pyrénées, 14 avenue Edouard Bélin, F-31400 Toulouse, France
Received May 12; accepted September 29, 1999
Great attention has been given to reduce the effects of "differential seeing", resulting from different PSF's in the two frames needed for a colour measurement. Errors from various sources, and their effect upon measured quantities, have been evaluated from the study of pseudo-colours (obtained by applying our measuring techniques to pair of frames taken in the same passband), and from the comparison of colours data from our various series.
Data are given about the following topics:
- Radial isophotal colour profiles, leading to reference colours at
and gradients in 4 colour indices (except for missing data);
- Reference colours and gradients in possibly dustless regions of nearly pure bulge or disk, allowing a comparison between the two components;
- Dust patterns, seen in 7 objects;
- Systematic differences between major and minor axis colours upon isophotal contours (outside dust patterns). Both a redder or bluer major axis are encountered depending upon the object, or the central distance in a given object. The observations may sometimes be explained by local dust concentration in disks. In other cases population differences between spheroidal and disk components should be invoked;
- Asymmetries in light and colour distributions along the minor axis in 3 objects, due to dust concentrated in the disk;
- Correlations between ring structure and major axis colour profiles.
Key words: galaxies: elliptical and lenticulars, CD -- galaxies: ISM