We present the results of a high-resolution imaging survey of 22 brown dwarfs and very low mass stars in the nearby ( \sim 145 pc ) young ( \sim 1-2 Myr ) low-density star-forming region Taurus-Auriga .
We obtained images with the Advanced Camera for Surveys/High Resolution Channel on HST through the F 555 W ( V ) , F 775 W ( i ^ { \prime } ) , and F 850 LP ( z ^ { \prime } ) filters .
This survey confirmed the binarity of MHO-Tau-8 and discovered a new candidate binary system , V410-Xray3 , resulting in a binary fraction of 9 \pm 5 \% at separations > 4 AU .
Both binary systems are tight ( < 10 AU ) and they possess mass ratios of 0.75 and 0.46 , respectively .
The binary frequency and separations are consistent with low-mass binary properties in the field , but the mass ratio of V410-Xray3 is among the lowest known .
We find that the binary frequency is higher for very low mass stars and high-mass brown dwarfs than for lower-mass brown dwarfs , implying either a decline in frequency or a shift to smaller separations for the lowest mass binaries .
Combining these results with multiplicity statistics for higher-mass Taurus members suggests a gradual decline in binary frequency and separation toward low masses .
The implication is that the distinct binary properties of very low-mass systems are set during formation and that the formation process is similar to the process which creates higher-mass stellar binaries , but occurs on a smaller scale .
We combine the survey detection limits with models for planetary-mass objects to show that there are no planets or very low-mass brown dwarfs with mass > 3 M _ { J } at projected separation > 40 AU orbiting any of the Taurus members in our sample , implying that planetary-mass companions at wide separations are rare .
Finally , based on fits to the optical and near-infrared spectral energy distributions , we identify several BDs with significant ( \gtrsim 1 mag ) V-band excesses .
The excesses appear to be correlated with signatures of accretion , and if attributed to accretion luminosity , may imply mass accretion rates several orders of magnitude above those inferred from line-profile analyses .