A Study of the Luminosity and Mass Functions of the Young IC 348 Cluster using FLAMINGOS Wide-Field Near-Infrared Images

We present wide-field near-infrared (JHK) images of the young, τ = 2Myr IC 348 cluster taken with FLAMINGOS. We use these new data to construct an infrared census of sources, which is sensitive enough to detect a 10MJup brown dwarf seen through an extinction of AV ∼ 7. We examine the cluster’s structure and relationship to the molecular cloud and construct the cluster’s K band luminosity function. Using our model luminosity function algorithm we derive the cluster’s initial mass function throughout the stellar and substellar regimes and find that the IC 348 IMF is very similar to that found for the Trapezium Cluster with both cluster IMFs having a mode between 0.2 − 0.08M⊙. In particular we find that, similar to our results for the Trapezium, brown dwarfs constitute only 1 in 4 of the sources in the IC 348 cluster. We show that a modest secondary peak forms in the substellar IC 348 KLF, corresponding to the same mass range responsible for a similar KLF peak found in the Trapezium. We interpret this KLF peak as either evidence for a corresponding secondary IMF peak at the deuterium burning limit, or as arising from a feature in the substellar mass-luminosity relation that is not predicted by current theoretical models. Lastly, we find that IC 348 displays radial variations of its sub-solar (0.5 − 0.08M⊙) IMF on a parsec scale. Whatever mechanism that is breaking the universality of the IMF on small spatial scales in IC 348 does not appear to be acting upon the brown dwarf population, whose relative size does not vary with distance from the cluster center. Subject headings: infrared: stars — open clusters and associations: individual (IC 348) — stars: luminosity function, mass function — stars: low-mass, brown dwarfs — stars: formation Department of Astronomy, University of Florida, Gainesville, FL 32611 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 European Southern Observatory, Karl-Schwartzschild-Strasse 2, 8574 Garching Germany Visiting Astronomer, Kitt Peak National Observatory. KPNO is operated by AURA, Inc. under contract to the National Science Foundation. present address: SIRTF Science Center, California Institute of Technology, Pasadena, CA 91125 USA