Infrared imaging and polarimetric observations of the pulsar wind nebula
  in SNR G21.5-0.9
  We present infrared observations of the supernova remnant G21.5-0.9 with the
Very Large Telescope, the Canada-France-Hawaii Telescope and the Spitzer Space
Telescope. Using the VLT/ISAAC camera equipped with a narrow-band [FeII] 1.64um
filter the entire pulsar wind nebula in SNR G21.5-0.9 was imaged. This led to
detection of iron line-emitting material in the shape of a broken ring-like
structure following the nebula's edge. The detected emission is
limb-brightened. We also detect the compact nebula surrounding PSR J1833-1034,
both through imaging with the CFHT/AOB-KIR instrument (K' band) and the IRAC
camera (all bands) and also through polarimetric observations performed with
VLT/ISAAC (Ks band). The emission from the compact nebula is highly polarised
with an average value of the linear polarisation fraction $P_{L}^{avg} \simeq
0.47$, and the swing of the electric vector across the nebula can be observed.
The infrared spectrum of the compact nebula can be described as a power law of
index $\alpha_{IR} = 0.7 \pm 0.3$, and suggests that the spectrum flattens
between the infrared and X-ray bands.
