The study of binary galaxies is one the first steps towards understanding
the physics of interaction between galaxies. Many works have been done in
the past few years in order to understand the subtleties resulting from the
gravitational interaction between pairs of galaxies. It is likely that the
majority of these systems have approximately circular orbits with mean
eccentricity 
. Therefore, due to the dynamical friction they
should merge on a time scale of the order of 
(Karachentsev
1990). We remark, however, that these results rests on a sample
affect by selection biases, due to the isolation criteria, and an
oversimplified treatment of dynamical friction. On the other hand it is
well known that gravitational interaction stimulates star formation. For
instance, tidal distortions in interacting pairs could contribute up to
of the galaxy luminosity (Schombert et al. 1990).
Moreover, the mean star formation rate in physical pairs, measured from 
emission, can be three times larger than the observed rate on
non-interacting systems (see Kennicutt 1990 and references
therein). More recently CO observations suggest that more gas is available
in paired galaxies, resulting that the star formation is enhanced in these
systems (Combes et al. 1994). Reduzzi & Rampazzo
(1996) found that even a moderate interaction is able to constrain
the gas into nuclear regions and enhance the star formation and nuclear
activities in binary galaxies.
From the dynamical point of view, binary galaxies present several
indications of the damage caused by the interaction. In the case of disk
systems the classical work by Toomre & Toomre (1972) pointed
out very clearly that the interactions during direct encounters are far more
efficient than the retrograde orbits. Moreover, direct encounters tend to
form two spiral arms, while a single arm is favored on retrograde encounters
(Athanassoula 1990). Also, the formation of bars tend to be
stimulated; 81% of the binary galaxies are barred, while only 63% of the
spirals are barred in the general field. The dynamical interaction also
affects the interstellar medium of the objects favoring a more fragmented
distribution of clouds. As a result the star formation rate is temporarily
enhanced, reaching a maximum approximately 
after the
point of minimum separation.
In order to address some of these issues we begun a program to study binary
galaxies in the Southern hemisphere. As a first step we have built a sample
of isolated pairs extracted from the ESO-LV catalog (Soares et al.
1995). Statistical properties of this sample shows that the
luminosity function is very similar to the one found for a sample extracted
from the list of Karachentsev (1985) for the Northern
hemisphere (Xu & Sulentic 1991). Moreover, the 
test shows that our list is complete for the pairs having a primary
component brighter than 
.
However, several objects in our list do not have radial velocity measurements. Actually, out of 189 pairs only 30% of them have radial velocity published in the literature. Therefore, we began an observational program in order to complete the missing radial velocities, since this information is crucial in order to better understand the properties of this sample. In this paper we present the first results of these observations.