Near-infrared [P II ] and [Fe II ] Emission-line Study of Supernova Remnants in the Magellanic Clouds

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Abstract We report findings from near-infrared imaging observations of 17 young and middle-aged supernova remnants (SNRs) in the Magellanic Clouds to examine the impact of SNR shocks on dust destruction and the possible detection of supernova ejecta. We have analyzed [P II] (1.189 μm) and [Fe II] (1.257 and 1.644 μm) narrowband images obtained with the InfraRed Survey Facility 1.4 m telescope at the South African Astronomical Observatory. We calculate the P/Fe abundance ratio, X(P/Fe), using the [P II]/[Fe II] line ratio, which provides valuable information on dust content and/or processing in the interstellar medium (ISM) because P is not depleted while Fe is a refractory species. Only 6 of 17 SNRs show emission features in both [P II] and [Fe II]. Among these, N49, N63A, and N206 exhibit X(P/Fe) ratios between 1.2 and 3.0 X ⊙(P/Fe), which are many times smaller than the general ISM ratio (e.g., Orion Bar ∼15 X ⊙(P/Fe)), suggesting significant destruction of dust grains by the shocks. In contrast, the remnants of SN 1987A, N157B, N158A, and the clump studied in N206 have P/Fe abundance ratios that are comparable to or higher than the general ISM. For SN 1987A, the high X(P/Fe) ratio may result from the lack of Fe in the gas phase, although the flux densities fluctuate constantly due to shocks. For N157B, N158A, and the clump in N206, many interpretations are being explored, including Fe atoms bound primarily to dust grains, material from supernova ejecta, and photoionization from nearby H II regions.

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