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Published February 1, 2009 | Published
Journal Article Open

Near-Infrared [Fe II] and H2 Line Observations of the Supernova Remnant 3C 396: Probing the Presupernova Circumstellar Materials

Abstract

We present the results of near-infrared [Fe II] and H2 line imaging and spectroscopic observations of the supernova remnant 3C 396 using the Palomar 5 m Hale telescope. We detect long, filamentary [Fe II] emission delineating the inner edge of the radio emission in the western boundary of the remnant in imaging observations, together with a bright [Fe II] emission clump close to the remnant center. There appears to be faint, diffuse [Fe II] emission between the central clump and the western filamentary emission. The spectroscopic observations determine the expansion velocity of the central clump to be ~56 km s–1. This is far smaller than the expansion velocity of 3C 396 obtained from X-ray observations, implying the inhomogeneity of the ambient medium. The electron number density of the [Fe II] emission gas is ≤ 2000 cm–3. The H2 line emission, on the other hand, lies slightly outside the filamentary [Fe II] emission in the western boundary, and forms a rather straight filament. We suggest that the [Fe II] emission represents dense clumps in the wind material from the red supergiant phase of a Type IIL/b progenitor of 3C 396, which have been swept up by the supernova remnant shocks. The H2 emission may represent either the boundary of a wind bubble produced during the main-sequence phase of the progenitor or molecular clumps left over inside the bubble. We propose that the near-infrared [Fe II] and H2 emission observed in several supernova remnants of Type IIL/b SNe likely have the same origin.

Additional Information

© 2009. The American Astronomical Society. Received 2008 July 13; accepted 2008 September 30; published 2009 January 28. Print publication: Issue 2 (2009 February 1). We thank Kristy Dyer for providing the VLA image of 3C 396. This work was partly supported by the Korea Science and Engineering Foundation through the Joint Research Project under the KOSEF-NSERC Cooperative Program (F01-2007-000-10048-0). D.-S.M. acknowledges the support from the Discovery Grant (327277) of Natural Science and Engineering Research Council of Canada. Facility: Hale (WIRC, HNA)

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