  Using the NICMOS coronagraph, we have obtained high-contrast 2.0 micron
imaging polarimetry and 1.1 micron imaging of the circumstellar disk around AB
Aurigae on angular scales of 0.3-3 arcsec (40-550 AU). Unlike previous
observations, these data resolve the disk in both total and polarized
intensity, allowing accurate measurement of the spatial variation of
polarization fraction across the disk. Using these observations we investigate
the apparent "gap" in the disk reported by Oppenheimer et al. 2008. In
polarized intensity, the NICMOS data closely reproduces the morphology seen by
Oppenheimer et al., yet in total intensity we find no evidence for a gap in
either our 1.1 or 2.0 micron images. We find instead that region has lower
polarization fraction, without a significant decrease in total scattered light,
consistent with expectations for back-scattered light on the far side of an
inclined disk. Radiative transfer models demonstrate this explanation fits the
observations. Geometrical scattering effects are entirely sufficient to explain
the observed morphology without any need to invoke a gap or protoplanet at that
location.
