Brown dwarfs in the Pleiades cluster: Clues to the substellar mass function
Abstract
We present the results of a 6.4 square degrees imaging survey of the Pleiades cluster in the I and Z-bands. The survey extends up to 3 degrees from the cluster center and is 90% complete down to I ≃ 22. It covers a mass range from 0.03 M_⊙ to 0.48 M_⊙ and yields 40 brown dwarf candidates (BDCs) of which 29 are new. The spatial distribution of BDCs is fitted by a King profile in order to estimate the cluster substellar core radius. The Pleiades mass function is then derived accross the stellar-substellar boundary and we find that, between 0.03 and M_⊙, it is well represented by a single power-law, dN/dM ∝ M^(-α), with an index α = 0.60 ± 0.11. Over a larger mass domain, however, from 0.03 M_⊙ to 10 M_⊙, the mass function is better fitted by a log-normal function. We estimate that brown dwarfs represent about 25% of the cluster population which nevertheless makes up less than 1.5% of the cluster mass. The early dynamical evolution of the cluster appears to have had little effect on its present mass distribution at an age of 120 Myr. Comparison between the Pleiades mass function and the Galactic field mass function suggests that apparent differences may be mostly due to unresolved binary systems.
Additional Information
© 2003 ESO. Received: 4 November 2002. Accepted: 19 December 2002. We thank E. Bertin for allowing us access to PSFex before public release, E. Magnier for his help in the astrometric calibration of the frames, J. Adams and N. Hambly for providing us data in electronic form prior to publication, I. Baraffe for computing specific substellar isochrones for us and K. Luhman for providing his Monte-Carlo software program to estimate the effect of unresolved binaries on the mass function. We also gratefully aknowledge helpful discussions with X. Delfosse on estimating field star contamination from DENIS data, with M. Bate, C. Clarke, E. Delgado and M. Sterzik on the dynamical evolution of young brown dwarfs in clusters, and with G. Chabrier who brought our attention on the Galactic disk mass function and on the effect unresolved binary systems might have on the shape of the observed mass function.Attached Files
Published - aa3257.pdf
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Additional details
- Eprint ID
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- CaltechAUTHORS:20180228-114727540
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2018-02-28Created from EPrint's datestamp field
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2021-11-15Created from EPrint's last_modified field
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- Infrared Processing and Analysis Center (IPAC)