Improved prospects for the detection of new Large Magellanic Cloud planetary nebulae

TL;DR

This paper enhances the detection prospects of planetary nebulae in the Large Magellanic Cloud through improved optical and near-infrared surveys, discovering new faint PNe and estimating a larger total population.

Contribution

It demonstrates that advanced imaging surveys can identify previously undetected faint PNe, significantly increasing the known population in the LMC.

Findings

Discovered three new PNe via optical imaging.

Identified one PNe through near-infrared VMC survey.

Estimated up to 75 additional PNe in the LMC.

Abstract

The Large Magellanic Cloud (LMC) contains the nearest large extragalactic population of planetary nebulae (PNe). A shallow viewing angle and low interstellar reddening towards the LMC potentially means a larger, more complete flux-limited population can be assembled than for any other galaxy. These advantages appear to be reflected by the small gap between the catalogued ($\sim$700 PNe) and estimated ($1000\pm250$ PNe) population size. With more detailed multi-wavelength studies the catalogued number of LMC PNe may fall, potentially widening this gap. We demonstrate here that the gap can be further bridged with improved optical and near-infrared imaging surveys. We present three [O III]-selected PNe discovered from ESO WFI observations of the 30 Doradus region and one serendipitous discovery from near-infrared Vista Magellanic Cloud (VMC) survey observations. The WFI PNe have resolved [O III] and H$\alpha$ nebulae that verify their PN nature and their [O III] fluxes place them 6--7 mag ($m_{5007}=20$--21 mag) fainter than the bright-end of the planetary nebula luminosity function (PNLF). Their faintness, small angular size and surrounding complex emission-line background explains why previous H$\alpha$ surveys of the region did not select them. We estimate there may be as many as 50--75 similar PNe awaiting discovery in the central $5\times5$ degrees of the LMC. The VMC survey routinely detects PNe as red resolved nebulae that may allow some of this expected population to be recovered without traditional narrow-band imaging surveys. We demonstrate this potential with the first new VMC-selected PN which has a rare Wolf-Rayet [WC9]--[WC11] central star.