Testing the universality of star formation - II. Comparing separation
  distributions of nearby star-forming regions and the field
  We have measured the multiplicity fractions and separation distributions of
seven young star-forming regions using a uniform sample of young binaries. Both
the multiplicity fractions and separation distributions are similar in the
different regions. A tentative decline in the multiplicity fraction with
increasing stellar density is apparent, even for binary systems with
separations too close (19-100au) to have been dynamically processed. The
separation distributions in the different regions are statistically
indistinguishable over most separation ranges, and the regions with higher
densities do not exhibit a lower proportion of wide (300-620au) relative to
close (62-300au) binaries as might be expected from the preferential
destruction of wider pairs. Only the closest (19-100au) separation range, which
would be unaffected by dynamical processing, shows a possible difference in
separation distributions between different regions. The combined set of young
binaries, however, shows a distinct difference when compared to field binaries,
with a significant excess of close (19-100au) systems among the younger
binaries. Based on both the similarities and differences between individual
regions, and between all seven young regions and the field, especially over
separation ranges too close to be modified by dynamical processing, we conclude
that multiple star formation is not universal and, by extension, the star
formation process is not universal.
