  Clusters of galaxies are at the intersection of cosmic filaments and are
still accreting galaxies and groups along these preferential directions, but,
because of their relatively low contrast on the sky, they are difficult to
detect (unless a large amount of spectroscopic data are available), and
unambiguous detections have been limited until now to relatively low redshifts
(z<0.3). We searched for extensions and filaments around the thirty clusters of
the DAFT/FADA survey (redshift range 0.4<z<0.9) with deep wide field
photometric data. For each cluster, based on a colour-magnitude diagram, we
selected galaxies that were likely to belong to the red sequence, and hence to
be at the cluster redshift, and built density maps. By computing the background
for each map and drawing 3sigma contours, we estimated the elongations of the
structures detected in this way. Whenever possible, we identified the other
structures detected on the density maps with clusters listed in NED. We found
clear elongations in twelve clusters, with sizes reaching up to 7.6 Mpc. Eleven
other clusters have neighbouring structures, but the zones linking them are not
detected in the density maps at a 3sigma level. Three clusters show no extended
structure and no neighbours, and four clusters are of too low contrast to be
clearly visible on our density maps. The simple method we have applied appears
to work well to show the existence of filaments and/or extensions around a
number of clusters in the redshift range 0.4<z<0.9. We plan to apply it to
other large cluster samples such as the clusters detected in the CFHTLS and
SDSS-Stripe 82 surveys in the near future.
