We present the results of wide integral-field near-infrared (1.0-1.8 μm) 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 μm 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 μm line images. This allows us to estimate the electron density (~4700-9400 cm-3) and extinction (A V ~ 16-20 mag) of the shell, including a detailed two-dimensional distribution of the properties in the brightest clump, as well as the discovery of a faint high-velocity (~ - 440 km s-1) component in the clump. Our SNR shock model calculations estimate the pre-shock number density of ~250-500 cm-3 and shock speed of ~80-250 km s-1 in the [Fe II]-emitting region of the SNR. The comparison between the observed and modeled 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.
