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Published October 1, 2011 | Published
Journal Article Open

Hubble Space Telescope Observations of Field Ultracool Dwarfs at High Galactic Latitude

Abstract

We present a sample of 17 newly discovered ultracool dwarf candidates later than ~M8, drawn from 231.90 arcmin^2 of Hubble Space Telescope Wide Field Camera 3 infrared imaging. By comparing the observed number counts for 17.5 ≤ J_(125) ≤ 25.5 AB mag to an exponential disk model, we estimate a vertical scale height of z_(scl) = 290 ± 25 (random) ± 31 (systematic) pc for a binarity fraction of f_b = 0. While our estimate is roughly consistent with published results, we suggest that the differences can be attributed to sample properties, with the present sample containing far more substellar objects than previous work. We predict the object counts should peak at J_(125) ~ 24 AB mag due to the exponentially declining number density at the edge of the disk. We conclude by arguing that trend in scale height with spectral type may breakdown for brown dwarfs since they do not settle onto the main sequence.

Additional Information

© 2011 The American Astronomical Society. Received 2011 May 4; accepted 2011 July 14; published 2011 September 12. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. We thank the anonymous referee and Adam Burgasser for many insightful and helpful comments and suggestions. Support for this work was provided by NASA through grant numbers 11772 (for R.E.R), 11702 (for H.Y and M.R.M), and 11359 (for S.H.C) from the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555. R.A.W. acknowledges support from NASA JWST Interdisciplinary Scientist grant NAG5-12469 from GSFC. Facility: HST (WFC3)

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August 22, 2023
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