We present the results of near-infrared imaging and spectroscopic observations of the young , core-collapse supernova remnant ( SNR ) G11.2–0.3 .
In the [ Fe II ] 1.644 \mu m image , we first discover long , clumpy [ Fe II ] filaments within the radio shell of the SNR , together with some faint , knotty features in the interior of the remnant .
The filaments are thick and roughly symmetric with respect to the NE-SW elongation axis of the central pulsar wind nebula .
We have detected several [ Fe II ] lines and Hi Br \gamma line toward the peak position of the bright southeastern [ Fe II ] filament .
The derived extinction is large ( A _ { V } = 13 mag ) and it is the brightest [ Fe II ] 1.644 \mu m filament detected toward SNRs to date .
By analyzing two [ Fe II ] 1.644 \mu m images obtained in 2.2 yrs apart , we detect a proper motion corresponding to an expansion rate of 0. ^ { \prime \prime } 035 \pm 0. ^ { \prime \prime } 013 yr ^ { -1 } ( 830 \pm 310 km s ^ { -1 } ) .
In addition to the [ Fe II ] features , we also discover two small H _ { 2 } 2.122 \mu m filaments .
One is bright and along the SE boundary of the radio shell , while the other is faint and just outside of its NE boundary .
We have detected H _ { 2 } ( 2-1 ) S ( 3 ) line toward the former filament and derive an excitation temperature of 2,100 K. We suggest that the H _ { 2 } filaments are dense clumps in a presupernova circumstellar wind swept up by the SNR shock while the [ Fe II ] filaments are probably composed of both shocked wind material and shocked supernova ( SN ) ejecta .
The distribution of [ Fe II ] filaments may indicate that the SN explosion in G11.2 - 0.3 was asymmetric as in Cassiopeia A .
Our results support the suggestion that G11.2 - 0.3 is a remnant of a SN IIL/b interacting with a dense red supergiant wind .