Wide Integral-Field Infrared Spectroscopy of the Bright [Fe II] Shell in
  the Young Supernova Remnant G11.2-0.3
  We present the results of wide integral-field near-infrared (1.0-1.8 um)
spectroscopic observations of the southeastern shell of the young core-collapse
supernova remnant (SNR) G11.2-0.3. We first construct [Fe II] 1.644 um line
images of three bright clumps from the obtained spectral image cubes and
compare them with those of other transitions such as [Fe II] 1.257, [Fe II]
1.534 and He I 1.083 um line images. This allows us to estimate the electron
density (~ 4,700-9,400 cm^-3) and extinction (Av ~ 16-20 mag) of the shell,
including detailed two-dimensional distribution of the properties in the
brightest clump, as well as the discovery of a faint high-velocity (~ -440
km/s) component in the clump. Our SNR shock model calculations estimate the
preshock number density of ~ 250-500 cm^-3 and shock speed of ~ 80-250 km/s in
the [Fe II]-emitting region of the SNR. The comparison between the observed and
modelled radial profiles of the line intensities and their ratios reveals that
the shell is composed of multiple thin filaments which have been likely formed
in episodic mass loss processes of a progenitor star. The discovery of the
faint high-velocity component supports the interpretation that the southeastern
shell of G11.2-0.3 is mainly composed of circumstellar material with
contamination by supernova ejecta and also that its ejected material was
expelled primarily in the southeast-northwest direction.
