  The paper presents results from a small survey of 22 young, nearby stars that
was designed to detect substellar companions and ultimately giant extrasolar
planets down to Jupiter masses. The targets are members of the Tucana and Beta
Pictoris moving groups apart from the somewhat older star HIP 71395 that has a
radial velocity trend suggesting a massive planet in large orbit. The survey
was carried out in the L-band using adaptive optics assisted imaging with
NAOS-CONICA (NACO) at the VLT. The chosen observation wavelength is well suited
to search for close companions around young stars and delivers unprecedented
detection limits. The presented technique reaches some of the best
sensitivities as of today and is currently the most sensitive method for the
contrast limited detection of substellar companions that are cooler than about
1000K. The companion to 51 Eri, GJ 3305, was found to be a very close binary on
an eccentric orbit. No substellar companions were found around the target
stars, although the method permitted to detect companions down to a few Jupiter
masses at orbital distances of typically 5 astronomical units. A planet with a
mass >1 M_Jup at distances >5 AU around AU Mic can be excluded at the time of
our observations. The absence of detected planets sets constraints on the
frequency distribution and maximum orbital distance of giant exoplanets. For
example, a radial distribution power law index of 0.2 in combination with a
maximum orbital radius exceeding 30 AU can be rejected at a 90% confidence
level.
