People involved at OAB: Cappi.
A. Cappi is investigating the nature of galaxy systems hosting
optically very luminous galaxies (VLGs, 
).
This work is carried out in collaboration with
C. Benoist, S. Maurogordato (Obs. de la Côte d'Azure) and L.N. da
Costa (ESO).
In previous work on the Southern Sky Redshift Survey 2 (SSRS2;
Benoist et al. 1996; Cappi et al. 1998a,b; Benoist et al. 1999;
Cappi et al. 2001) it was shown that the clustering amplitude
of galaxies increases for galaxies with 
(with a non-linear
bias) and that VLGs
have a correlation length approaching that of clusters, even
if most of them are not in rich clusters; such results have been
confirmed by the 2dFGRS (see e.g. Norberg et al. 2001).
In our recent work (Cappi et al. 2003) we have analysed in more detail
the environment of a subsample of our VLGs
using partly our own spectroscopic observations obtained
at the 1.93m telescope at the OHP, and mainly the data for fainter galaxies
obtained from the 2dFGRS, selecting those
which are within 1.5h
Mpc from the VLGs. In this way it has been
possible to confirm that many faint objects previously detected
in the DSS images centered on VLG fields are at the same redshift of the VLG,
and that late-type VLGs appear indeed to be in poorer systems,
comparable to the Local Group.
Present work is focalised in the analysis of the new available
databases (the 2dFGRS final release and the SDSS), which will
allow us to build a more complete and homogeneous sample
of VLGs and to better determine their statistical properties.
We have also planned to perform H
observations of VLG groups
with the Wide Field Imager (WFI) at the ESO 2.2m telescope,
using filters centered on the VLG redshift,
in order to efficiently detect fainter candidate members,
and to study the star-forming galaxy population and the luminosity function
of the system.
The aim is to understand the evolutionary properties of this class of
poorly known systems.
As an example, one important issue is
the much debated overabundance of low-mass satellites in the Local Groups
with respect to simulations, and we would like to know if
this is a common property of other similar groups.