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M. Andersen, M. R. Meyer (Steward Observatory, The University of Arizona), L. E. Bergeron, M. Robberto, K. Smith, I. N. Reid (Space Telescope Science Institute)
Any successful theory of star formation must be able to explain the IMF and how it varies (if it does vary) as a function of the star formation environment. Because the stellar part of the IMF appears to be similar for clusters within 2 kpc (e.g. Meyer et al. 2000) we are compelled to expand the search to regions with more extreme conditions than nearby and to extend IMF studies well below the hydrogen burning limit. We present initial results from the analysis of HST/NICMOS 3 F110W and F160W band observations of the Orion Nebula Cluster (ONC) obtained through the HST Treasury Program by Robberto et al. The data were obtained in parallel with ACS observations of the ONC and provide non-contiguous coverage of the central 1 pc radius of the cluster. The main aim of our study is to constrain the brown dwarf and low mass stellar part of the IMF in the ONC as a function of radius in the cluster. We derive the ratio of the number of brown dwarfs (20-80 Mjup) to the number of low-mass stars (0.08-1 Msun) over the central parsec. We compare this ratio to the similar ratio derived for Taurus, Mon R2, and IC 348. Further, we discuss the radial variation of the ratio and the evidence for mass segregation.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.