The luminosity and mass functions of the Pleiades: low-mass stars and brown dwarfs

COSMOS measurements of R and I Schmidt plates are used to determine the luminosity function and hence mass function of the Pleiades open cluster. Star counts are made in the cluster and the field star contribution, measured outside the cluster, is subtracted. The mass function is found down to 0.06 m⊙. A lower limit of 30 brown dwarfs is found; the mass function is flat at the lowest masses. The above are based on a Pleiades age of 63 Myr and theoretical models of D’Antona & Mazzitelli.