Search for Pleiades T dwarfs .

We present our on-going project aimed at identifying Pleiades T-type planetary-mass members. An area of 0.82 deg2 was explored photometric and astrometrically with deep images taken in the J and H filters and separated by 9 yr. The survey limiting magnitude is J, H = 21 mag. The long time baseline allowed us to measure proper motions, since the cluster motion is quite distinctive. For a small fraction of our survey, methane images in the H-band are also available. To select our candidates we imposed the following criteria: H > 18 mag, J - H < 0.3 mag, and proper motions compatible with that of the cluster at the 1.5-sigma level. According to substellar evolutionary models, our exploration is sensitive to T-type Pleiads with masses in the interval 9-15 M_Jup. These observations will lead to the study of the planetary mass function in the Pleiades cluster. Confirmed Pleiades T-type dwarfs will have a well-defined age (120 Myr) and solar metallicity; they will thus become benchmark objects for our understanding of the ultracool dwarf population (both single and orbiting stars, including massive planets) of the solar vicinity.