2011ApJ...739...83R

We present a sample of 17 newly discovered ultracool dwarf candidates later than ∼M8, drawn from 231.90 arcmin² of Hubble Space Telescope Wide Field Camera 3 infrared imaging. By comparing the observed number counts for 17.5 ≤ J₁₂₅ ≤ 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.