Hubble Space Telescope NICMOS Polarization Observations of Three Edge-on
  Massive YSOs
  Massive young stellar objects (YSOs), like low-mass YSOs, appear to be
surrounded by optically thick envelopes and/or disks and have regions, often
bipolar, that are seen in polarized scattered light at near-infrared
wavelengths. We are using the 0.2'' spatial resolution of NICMOS on Hubble
Space Telescope to examine the structure of the disks and outflow regions of
massive YSOs in star-forming regions within a few kpc of the Sun. Here we
report on 2 micron polarimetry of NGC 6334 V and S255 IRS1. NGC 6334 V consists
of a double-lobed bright reflection nebula seen against a dark region, probably
an optically thick molecular cloud. Our polarization measurements show that the
illuminating star lies ~ 2'' south of the line connecting the two lobes; we do
not detect this star at 2 micron, but there are a small radio source and a
mid-infrared source at this location. S255 IRS1 consists of two YSOs (NIRS1 and
NIRS3) with overlapping scattered light lobes and luminosities corresponding to
early B stars. Included in IRS1 is a cluster of stars from whose polarization
we determine the local magnetic field direction. Neither YSO has its scattered
light lobes aligned with this magnetic field. The line connecting the scattered
light lobes of NIRS1 is twisted symmetrically around the star; the best
explanation is that the star is part of a close binary and the outflow axis of
NIRS1 is precessing as a result of non-coplanar disk and orbit. The star NIRS3
is also offset from the line connecting its two scattered light lobes. We
suggest that all three YSOs show evidence of episodic ejection of material as
they accrete from dense, optically thick envelopes.
