A New Population of Planetary Nebulae Discovered in the Large Magellanic Cloud (IV): The Outer LMC

TL;DR

This study extends the planetary nebulae survey to the outer regions of the Large Magellanic Cloud, discovering 61 new PNe and confirming most previously known ones using advanced imaging and spectroscopic techniques.

Contribution

It presents the first spectroscopic confirmation of 61 new PNe in the outer LMC, expanding the known population with improved diagnostic methods and multi-wavelength validation.

Findings

Discovered 61 new planetary nebulae in the outer LMC.

Confirmed 98% of previously known PNe in the surveyed area.

Utilized multi-filter imaging and spectroscopy for robust identification.

Abstract

We have extended our PNe survey to the outer ~64deg^2 of the LMC using maps from the Magellanic Cloud Emission Line Survey (MCELS) and the UK Schmidt Telescope (UKST) H-alpha survey. Although the MCELS survey has poorer ~5 arcsecond resolution than both the UKST H-alpha survey and the original H-alpha median stacked map in the LMC's central 25deg^2, it has the advantage of additional narrow-band filters at H-alpha, [OIII] and [SII] providing improved diagnostic capabilities. Using these data to uncover new emission line candidates we have so far spectroscopically confirmed an extra 61 LMC PNe which we present here for the first time. We have also independently recovered and spectroscopically confirmed 107 of the 109 (98%) PNe that were previously known to exist in the outer LMC. The majority of our newly discovered and previously known PNe were confirmed using the AAOmega, multi-object fibre spectroscopy system on the 3.9-m Anglo-Australian Telescope (AAT) and the 6dF multi-object spectrograph on the UKST. These newly identified PNe were cross-checked against extant multi-wavelength imaging surveys in the near and mid-infrared in particular and against the latest emission-line ratio diagnostic plots for improved confidence in PNe identification.