  We report the outcome of a deep multi-wavelength study of the IC2391 young
open cluster. We aim at uncovering new low-mass and sub-stellar members of the
cluster and identifying new debris disk objects. A 30*30 square arcmin area in
IC 2391 was observed using the wide-field imager at the ESO 2.2m telescope. The
completeness limits of the photometry at 3 sigma level are V=24.7, Rc=23.7 and
Ic=23.0, faint enough to reveal sub-stellar members down to about 0.03 solar
masses. Our membership criteria are based on the use of our optical data, in
combination with JHKs magnitudes from the 2MASS catalog. We also estimate the
physical parameters of the selected candidates. Debris disk candidates are
identified on the basis of their infrared excess emission using near- and
mid-infrared photometry from the Spitzer Space Telescope. Our optical survey,
which has a limiting magnitude at 3 sigma level 1-2 mag fainter than previous
optical surveys conducted in IC2391, revealed 29 new low-mass member candidates
of the cluster. We estimate the contamination to be at least 50%. We constrain
the fraction of sub-stellar objects in the range 8-15% and discuss possible
explanations for the deficit of brown dwarfs in this cluster. We also
identified 10 candidates in the cluster showing IR excess emission consistent
with the presence of debris disks.
