NOAO >   Observing Info >   Approved Programs >   2006A-0327

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Proposal Information for 2006A-0327


PI: John Robinson, University of Missouri-St. Louis, johnr@newton.umsl.edu
Address: Department of Physics and Astronomy, 8001 Natural Bridge Road, St. Louis, MO 63121, USA

CoI: Bruce Wilking, University of Missouri-St. Louis
CoI: Michael Meyer, University of Arizona

Title: Unveiling the Low Mass Population Surrounding the Rho Oph Cloud

Abstract: We propose to observe 106 candidate association members in the vicinity of the Rho Oph dark cloud to complete our survey of the surface population. When combined with our previous lower resolution HYDRA observations for 130 stars, and our medium resolution HYDRA observations for 112 stars, we will have a large, unbiased sample of low mass association members that is drawn from our R and I band images and is complete for all objects above the hydrogen-burning limit with an age of 10 Myr or less and A_v < 2.5 mag. It extends into the sub-stellar regime for younger, less-extincted objects. Medium resolution spectra obtained with HYDRA from 6300-7700 \AA will enable us to; i) measure the Li equivalent width (6707 \AA) to identify association membership, ii) determine surface gravities using the CaH absorption band (6975 \AA), and iii) estimate spectral types (and thus photospheric temperatures) crucial for placing these objects in the H-R diagram and determining their ages and masses. From this we will establish the WTTS:CTTS ratio surrounding L1688 for comparisons with Upper Scorpius and explore the effects of environment on disk evolution. In addition, this combined sample can be used to estimate the fraction very low mass stars and brown dwarfs to higher mass stars, and when compared to that in the L1688 core and Upper Scorpius, investigate if the stellar environment has an effect on the IMF.


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