2002ApJ...578..523T

In this paper we present the mass functions in the substellar regime of three young open clusters, IC 348, σ Orionis, and Pleiades, as derived using the data from the Two Micron All Sky Survey catalog, which has a limiting magnitude of K_s∼15, and the latest version of the Guide Star Catalog, which has a limiting magnitude of F∼21.(4) Based on recent evolutionary models for low-mass stars, we have formulated the selection criteria for stars with masses below 0.5 M_☉. Using a statistical approach to correct for the background contamination, we derive the mass function of objects with masses ranging from 0.5 M_☉down to the substellar domain, well below the hydrogen-burning mass limit. The lowest mass bins in our analysis are 0.025, 0.045, and 0.055 M_☉for IC 348, σ Orionis, and Pleiades, respectively. The resultant slopes of the mass functions are 0.8±0.2 for IC 348, 1.2±0.2 for σ Orionis, and 0.5±0.2 for Pleiades, which are consistent with the previous results. The contribution of objects below 0.5 M_☉to the total mass of the cluster is ∼40%, and the contribution of objects below 0.08 M_☉to the total mass is ∼4%.