A Multiplicity Census of Intermediate-Mass Stars in Scorpius-Centaurus
  Stellar multiplicity properties have been studied for much of the range from
the lowest to the highest stellar masses, but intermediate-mass stars from
F-type to late A-type have received relatively little attention. Here we report
on a Gemini/NICI snapshot imaging survey of 138 such stars in the young
Scorpius-Centaurus (Sco-Cen) region, for the purpose of studying multiplicity
with sensitivity down to planetary masses at wide separations. In addition to
two brown dwarfs and a companion straddling the hydrogen burning limit we
reported previously, here we present 26 new stellar companions and determine a
multiplicity fraction within 0.1"--5.0" of 21+/-4%. Depending on the adopted
semi-major axis distribution, our results imply a total multiplicity in the
range of ~60--80%, which further supports the known trend of a smoothly
continuous increase in the multiplicity fraction as a function of primary
stellar mass. A surprising feature in the sample is a distinct lack of nearly
equal-mass binaries, for which we discuss possible reasons. The survey yielded
no additional companions below or near the deuterium-burning limit, implying
that their frequency at >200 AU separations is not quite as high as might be
inferred from previous detections of such objects within the Sco-Cen region.
