Infrared [Fe II] and Dust Emissions from Supernova Remnants

Abstract

The SNRs belonging to the former group are also bright in near-infrared H2 emission, indicating that both atomic and molecular shocks are pervasive in these SNRs. The SNRs belonging to the latter group have relatively small radii in general, implying that most of them are likely the remnants of SN IIL/b or SN IIn that had strong mass loss before the explosion. I also comment on the "[Fe II]-H 2 reversal" in SNRs and on using the [Fe II]-line luminosity as an indicator of the supernova (SN) rate in galaxies. In the mid-and far-infrared regimes, thermal dust emission is dominant. The dust in SNRs can be heated either by collisions with gas species in a hot plasma or by radiation from a shock front. I discuss the characteristics of the infrared morphology of the SNRs interacting with molecular clouds and their dust heating processes. Finally, I give a brief summary of the detection of SN dust and crystalline silicate dust in SNRs.

Near-Infrared Spectroscopy of Young Galactic Supernova Remnants

“…Fe II has 16 levels near the ground state that can be easily excited in the cooling region, and can emit strong NIR lines. In the NIR band, two strongest lines are 1.257 and 1.644 µm lines, and 10-20 (2011), Giannini et al (2014) lines are seen (Koo, 2014, and references therein).…”

“…[Fe II] line images of young SNRs show that [Fe II] line emitting regions are filamentary and spatially confined in contrast to radio or X-rays (see Fig. 4 of Koo, 2014). This is because they originate from different environments.…”

“…In shocks propagating into a medium of normal abundance, an extended temperature plateau region at T e ∼ 10 4 K develops in postshock cooling region, and this is where [Fe II] lines are emitted (Koo, 2014). In shocks propagating into SN ejecta, the temperature and emissivity profiles are very different because of strong cooling (Koo et al, 2013).…”

“…So NIR spectroscopy can probe the explosion dynamics, SN nucleosynthesis, and the late-stage evolution of progenitor star. Among young SNRs, G11.2−0.3, RCW 103, W49B, and Cas A are known to be bright in [Fe II] lines, and they are all small core-collapse SNRs that might be interacting with dense CSM (Koo, 2014 In this paper, we will first briefly summarize the characteristics and applications of NIR [Fe II] lines and then introduce our recent NIR spectroscopic study of Cas A where we detected strong [P II] lines.…”

“…So NIR spectroscopy can probe the explosion dynamics, SN nucleosynthesis, and the late-stage evolution of progenitor star. Among young SNRs, G11.2−0.3, RCW 103, W49B, and Cas A are known to be bright in [Fe II] lines, and they are all small core-collapse SNRs that might be interacting with dense CSM (Koo, 2014). We have recently completed a survey of the Galactic plane in [Fe II] 1.644 µm emission line, called UWIFE (UKIRT Widefield Infrared survey for Fe + ) survey (Lee et al, 2014a, see also the paper by Lee, J.-J.…”