A Narrowband Emission-Line Survey of the Large Magellanic Cloud


The Large and Small Magellanic Clouds provide sites to study the interstellar medium (ISM) and its components at all scales, from small to global. The University of Michigan / Cerro Tololo Inter-American Observatory Magellanic Cloud Emission-Line Survey (MCELS) is as a deep imaging survey of both of these nearby galaxies in the emission of Hα, [S II], and [O III]. These emission-line images are being used in detailed optical and multi-wavelength studies of planetary nebulae (PNe), H II regions, supernova remnants (SNRs), superbubbles, and supergiant shells. Here we present a deep and wide view of the ~104 K ionized gas in the interstellar medium of the Large Magellanic Cloud (LMC) using the MCELS data. We present large-scale flux-calibrated continuum-subtracted optical emission-line mosaics of the 8x8 square degree central region of the Large Magellanic Cloud created from the combination of thousands of observations taken over hundreds of nights, providing a detailed view of most of the gaseous extent of the galaxy. With these mosaics in hand we conduct a systematic analysis of the [S II] to Hα ratio of 59 known X-ray SNRs in the Large Magellanic Cloud. For 44 of these SNRs, Hα and [S II] flux values along with [S II] / Hα emission-line ratios have been derived. All derived [S II] / Hα emission-line ratios ≥0.4, strengthening their identification as true remnants. We compare our values to spectroscopic values in the literature. This work has uncovered at least one previously unidentified candidate supernova remnant, triggering an ongoing spectroscopic followup campaign.

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