Proper motion Pleiades candidate L‐type brown dwarfs

We present results of an optical and near‐infrared (IR) 1.8 deg 2 survey in the Pleiades open cluster to search for substellar objects. From optical I ‐band images from the CFHT and J ‐band images from the 3.5m CAHA Telescope, we identify 18 faint and very red L brown dwarf candidates, with I > 20.9 and I – J > 3.2. The follow‐up observations of nine objects in the H ‐ and K s ‐bands confirm that eight belong to the IR sequence of the cluster and the proper motion measurements of seven candidates confirm that they are Pleiades members. A preliminary estimation of the substellar mass spectrum d N/ d M in the form of a power law M c – α provides α = +0.57 ± 0.14. We extrapolate this function to estimate the number of planetary mass objects that could be present in the cluster down to 1 M Jup . Sensitive searches combining far red and near‐IR observations may unveal these objects in a near future. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)