A Search for Intermediate Separation Low Mass Binaries in the Orion
  Nebula Cluster
  We present the results of a binary population study in the Orion Nebula
Cluster (ONC) using archival Hubble Space Telescope (HST) data obtained with
the Advanced Camera for Surveys (ACS) in Johnson V filter (HST Proposal 10246,
PI M. Robberto). Young clusters and associations hold clues to the origin and
properties of multiple star systems. Binaries with separations $< 100 $ AU are
useful as tracers of the initial binary population since they are not as likely
to be destroyed through dynamical interactions. Low mass, low stellar density
star-forming regions such as Taurus-Auriga, reveal an excess of multiples
compared to the Galactic Field. Studying the binary population of higher mass,
higher stellar density star-forming regions like the ONC provides useful
information concerning the origin of the Galactic Field star population. In
this survey, we characterize the previously unexplored (and incomplete)
separation parameter space of binaries in the ONC (15 - 160 AU) by fitting a
double-PSF model built from empirical PSFs. We identified 14 candidate binaries
(11 new detections) and find that 8$_{-2\%}^{+4\%}$ of our observed sample are
in binary systems, complete over mass ratios and separations of 0.6 $< $ q $< $
1.0 and 30 $< $ a $< $ 160 AU. This is consistent with the Galactic Field
M-dwarf population over the same parameter ranges, 6.5\% $\pm$ 3\%. Therefore,
high mass star forming regions like the ONC would not require further dynamical
evolution for their binary population to resemble the Galactic Field, as some
models have hypothesized for young clusters.
