[Feii] and H2Filaments in the Supernova Remnant G11.2−0.3: Supernova Ejecta and Presupernova Circumstellar Wind

We present the results of near-infrared imaging and spectroscopicobservations of the young, core-collapse supernova remnant (SNR) G11.2-0.3. Inthe [Fe II] 1.644 um image, we first discover long, clumpy [Fe II] filamentswithin the radio shell of the SNR, together with some faint, knotty features inthe interior of the remnant. We have detected several [Fe II] lines and HI Br-Gline toward the peak position of the bright southeastern [Fe II] filament. Thederived extinction is large (Av=13 mag) and it is the brightest [Fe II]filament detected toward SNRs to date. By analyzing two [Fe II] 1.644 um imagesobtained in 2.2 yrs apart, we detect a proper motion corresponding to anexpansion rate of 0.''035 (0.''013) /yr [or 830 (310) km/s]. We also discovertwo small H2 filaments. One is bright and along the SE boundary of the radioshell, while the other is faint and just outside of its NE boundary. We havedetected H2 (2-1) S(3) line toward the former filament and derive an excitationtemperature of 2,100 K. We suggest that the H2 filaments are dense clumps in apresupernova circumstellar wind swept up by the SNR shock while the [Fe II]filaments are probably composed of both shocked wind material and shockedsupernova (SN) ejecta. The distribution of [Fe II] filaments may indicate thatthe SN explosion in G11.2-0.3 was asymmetric as in Cassiopeia A. Our resultssupport the suggestion that G11.2-0.3 is a remnant of a SN IIL/b interactingwith a dense red supergiant wind.Comment: 30 pages with 10 figures, To appear in the Astrophysical Journa