[11.12] Constraining the Distribution of L \& T Dwarfs in the Galaxy

AAS 205th Meeting, 9-13 January 2005
Session 11 Brown Dwarfs and Exoplanets
Poster, Monday, January 10, 2005, 9:20am-6:30pm, Exhibit Hall

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[11.12] Constraining the Distribution of L & T Dwarfs in the Galaxy

R. E. Ryan Jr., N. P. Hathi, S. H. Cohen, R. A. Windhorst (Arizona State University)

We address the distribution of L- & T-dwarfs as a function of Galactic coordinates to study their contamination in high redshift galaxy surveys which employ the dropout method. A Monte Carlo simulation was used to exponentially distribute 10¹⁰-10¹¹ points in both vertical scale height and radius, while constraining the local number density to a published value. Then, by assuming a radial scale length of 2100 pc for the Galaxy and an offset location of 8000 pc in radius and 30 pc above the disk for the Sun, the models are created as a function of their scale heights varying from 100-500 pc. At a given latitude and longitude, a power-law trend between the model surface density and vertical scale height is found. Using 16 Hubble Space Telescope Advanced Camera for Surveys deep parallel fields, a vertical scale height based on 30 L- & T-dwarfs candidates is calculated. When neglecting fields with extreme contamination by dust (fields more than 20 deg from the Galactic plane) and immeasurably low surface densities, we find an average scale height of 340 ± 84 pc, similar to the thick disk. This work was supported by a NASA Space Grant Fellowship and HST Grant GO.9793.0*.

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