Weak lensing survey of galaxy clusters in the CFHTLS deep

Aims. We present a weak lensing search of galaxy clusters in the 4 deg(2) of the CFHT Legacy Survey Deep. This work aims at building a mass-selected sample of clusters with well controlled selection effects. This present survey is a preliminary step toward a full implementation in the forthcoming 170 deg2 of the CFHTLS Wide survey. Methods. We use the deep i' band images observed under subarcsecond seeing conditions to perform weak lensing mass reconstructions and to identify high convergence peaks. Thanks to the availability of deep u*g'r'i'z' exposures, sources are selected from their photometric redshifts in the weak lensing analysis. We also use lensing tomography to derive an estimate of the lens redshift. After considering the raw statistics of peaks we check whether they can be associated to a clear optical counterpart or to published X-ray selected clusters. Results. Among the 14 peaks found above a signal-to-noise detection threshold v = 3.5, nine are secure detections with estimated redshift 0.1 less than or similar to z(1) less than or similar to 0.7 and a velocity dispersion 450 less than or similar to sigma(v) less than or similar to 700 km s(-1). This low mass range is accessible thanks to the high density of background sources. Considering the intersection between the shear-selected clusters and XMM-LSS X-ray clusters in the D1 field, we observe that the ICM gas in these low-mass clusters (T-X similar to 1-2 keV) is not hotter than the temperature inferred from shear, this trend being different for published massive clusters. A more extended weak lensing survey, with higher statistics of mass structures will be a promising way to bypass several of the problems related to standard detection methods based on the complex physics of baryons.