A search for supernova remnants in NGC 6946 using the [FeII] 1.64 μm line

Abstract

Shock models indicate and observations show that in the infrared (IR), supernova remnants (SNRs) emit strongly in [Fe II] at 1.64 μm. Here, we report the results of a search for SNRs in NGC 6946 relying on [Fe II] 1.64 μm line emission, where we employed an adjacent [Fe II] Off filter to accurately assess the local continuum levels. For this study, we used the WIYN High Resolution Infrared Camera on the WIYN 3.5 m telescope to image NGC 6946 in broadbands J and H and narrowbands [Fe II], [Fe II] Off, Paβ, and Paβ Off. From our search, we have identified 48 SNR candidates (SNRcs), 6 of which are coincident with sources found in prior radio, optical, and/or X-ray studies. The measured [Fe II] fluxes of our SNRcs range from 1.5 × 10 -16 to 4.2 × 10 -15 erg s -1 cm -2 and are among the highest of previously published extragalactic SNR [Fe II] fluxes. All of the candidates now need to be confirmed spectroscopically. However, the fact that we detect as many objects as we did suggests that [Fe II] can be used as an effective search tool to find extragalactic SNRs. © 2014. The American Astronomical Society. All rights reserved..