NOAO >   Observing Info >   Approved Programs >   2003A-0139

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Proposal Information for 2003A-0139


PI: I. N. Reid, STScI, inr@stsci.edu
Address: 3700 San Martin Drive, Baltimore, MD 21218, USA

CoI: K. Cruz, U. Pennsylvania
CoI: J. Liebert, Univ. of Arizona

Title: Meeting the cool neighbours: covering the sky

Abstract: Over the past two years we have undertaken the first systematic, large-scale survey for nearby ultracool dwarfs, using 2MASS data covering 50% of the sky to search for late-M and L dwarfs within 20 parsecs of the Sun. Our goal is a definitive determination of the luminosity function for late-M and L dwarfs, and hence a statistically robust derivation of the mass function across the hydrogen-burning limit. We have identified over 90 L dwarfs and more than 120 M7 to M9 dwarfs. However, only 50 ultracool dwarfs fall within our 20-parsec limit, barely sufficient numbers for an accurate luminosity function determination. With the release of the entire 2MASS database, we propose to double this sample by extending coverage to the full sky. Based on our experience, we have refined our search criteria and anticipate identifying ~250 new candidates, of which 80% are expected to be \sl bona-fide ultracool dwarfs. We will use intermediate resolution optical spectroscopy to determine accurate distances and luminosities, besides characterising the level of chromospheric activity.


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



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