Galaxy population in the cluster CL 0500-24.
Abstract
Results of B, V,R, I photometric observations and multislit spectroscopy in the field on the Southern Cluster Cl 0500-24 are presented. This rich and compact cluster has an average redshift of <z>=0.321. The B-V color distribution shows a rather large fraction of blue objects as in Butcher-Oemler effect is observed. All red galaxies but one, and 9 of the 12 blue objects with measured redshifts, are found to be cluster members. Two of the non cluster members (a red galaxy and a blue emission-line object) have a similar redshift of z~0.375. The observed spectra have been ranked according to the B-V color index which, at the redshift of the cluster, is very sensitive to the 4000 A break amplitude and thereby to recent star formation of nuclear activity. The blue objects studied so far have various spectral types some being unusual in nearby clusters : there are a) galaxies with spectra similar to those of low redshift spirals, b) two cases of post starburst galaxies with clearly visible Balmer absorption lines and no or little emission, c) objects with excitation emission, one of them having a spectrum suggestive of an active nucleus. The three blue non cluster members are emissionline galaxies.
- Publication:
-
Astronomy and Astrophysics Supplement Series
- Pub Date:
- April 1990
- Bibcode:
- 1990A&AS...83....1G
- Keywords:
-
- Active Galaxies;
- Galactic Clusters;
- Galactic Evolution;
- Red Shift;
- Spectrophotometry;
- Astronomical Photometry;
- Astronomical Spectroscopy;
- Star Formation;
- Astrophysics