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

Abstract

We present the results of near-infrared imaging and spectroscopic observations of the young core-collapse supernova remnant (SNR) G11.2À0.3. In the [Fe ii] 1.644 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 northeast-southwest elongation axis of the central pulsar wind nebula. We have detected several [Fe ii] lines and a H i Br line toward the peak position of the bright southeastern [Fe ii] filament. The derived extinction is large (A V ¼ 13 mag), and it is the brightest [Fe ii] 1.644 m filament detected toward SNRs to date. By analyzing two [Fe ii] 1.644 m images obtained 2.2 yr apart, we detect a proper motion corresponding to an expansion rate of 0:035 00 AE 0:013 00 yr À1 (830 AE 310 km s À1 ). In addition to the [Fe ii] features, we also discover two small H 2 2.122 m filaments. One is bright and along the southeastern boundary of the radio shell, while the other is faint and just outside its northeastern boundary. We have detected the H 2 (2Y1) S(3) line toward the former filament and derive an excitation temperature of 2100 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 G11.2À0.3 was asymmetric, as in Cassiopeia A. Our results support the suggestion that G11.2À0.3 is a remnant of a SN IIL/b interacting with a dense red supergiant wind.

LARGE-AREA [Fe II] LINE MAPPING OF THE SUPERNOVA REMNANT IC 443 WITH THE IRSF/SIRIUS

“…Assuming T 4 = 1.2 and n e = 500, which were derived from the mid-IR [ and n e = 1 × 10 4 (e.g., Graham et al 1987;Koo et al 2007), M Fe + decreases by an order of magnitude, while if we adopt the gas density of only a few times 10 cm −3 which was suggested by H I (Lee et al 2008) and optical line observations (Fesen & Kirshner 1980), M Fe + increases by an order of magnitude. Accordingly the above Fe + masses can have such systematic errors.…”

“…A conventional idea is that the gas-phase Fe is produced by sputtering Fe-bearing dust grains, but we cannot rule out a possibility of supernova ejecta origins. Koo et al (2007) …”

UKIRT Widefield Infrared Survey for Fe+

“…The image is continuum-subtracted as described in section 3.3. The figure shows a comparison of our image with the [Fe II] image of the same target obtained with the WIRC onboard the Palomar Hale telescope (Koo et al 2007). Our UKIRT WFCAM image is basically identical to that of the WIRC, but shows more details that were not available in the WIRC image.…”

“…In the survey area, there are over 70 known SNRs mostly identified by radio and X-ray observations (Green 2009 (Koo et al 2007), W 28 (Reach et al 2005), G21.5−0.9 (Zajczyk et al 2012), 3C 391 (Reach et al 2002), 3C 396 ), W 44 (Reach et al 2005), and W 49B (Keohane et al 2007). In most cases, our [Fe II] images provide high-quality, wide-area views of detected SNRs, for which, sometimes, only parts of the area were covered by the previous observations.…”

Infrared [Fe II] and Dust Emissions from Supernova Remnants

“…Since the early days of NIR observations of SNRs, it has been known that there are SNRs with H 2 filaments lying beyond [Fe II] filaments, i.e., further out from the SNR center, which is not easily explained by shock models (Graham et al Infrared [Fe II] and Dust Emissionsfrom Supernova Remnants 219 1991;Oliva, Moorwood, & Danziger 1990;Burton & Spyromilio 1993). We now have more sources showing similar patterns, e.g., G11.2-0.3, W49B, and 3C396 (Koo et al 2007;Keohane et al 2007;Lee et al 2009). W44 in Figure 3 is another example.…”