A new population of planetary nebulae discovered in the Large Magellanic Cloud - II. Complete PN catalogue

Abstract

This paper presents accurate homogeneous positions, velocities and other pertinent properties for 460 newly discovered and 169 previously known planetary nebulae (PNe) in the central 25-deg 2 bar region of the Large Magellanic Cloud (LMC). Candidate emission sources were discovered using a deep, high-resolution Ha map of the LMC obtained by median stacking a dozen 2 h Hα exposures taken with the UK Schmidt Telescope (UKST). Our spectroscopic follow-up of more than 2000 compact (i.e. <20 arcsec) Ha emission candidates uncovered has tripled the number of PNe in this area. All of the 169 previously known PNe within this region have also been independently recovered and included in this paper to create a homogeneous data set. Of the newly discovered PNe, we classify 291 as 'true', 54 as 'likely' and 115 as 'possible' based on the strength of photometric and spectroscopic evidence. Radial velocities have been measured using both weighted averaging of emission lines and cross-correlation techniques against high-quality templates. Based on the median comparison of the two systems, we define a measurement error of ±4 km s -1 . A new velocity map of the central 25 deg 2 of the LMC, based on results from the combined new and previously known PNe, is presented, indicating an averaged heliocentric velocity differential of 65 km s -1 perpendicular to the line of nodes for the entire PN population across our survey area. Averaged velocities of our PNe and molecular hydrogen (from the literature) across 37 x 37 arcmin 2 subareas are compared. The PNe are found to have a higher vertical velocity dispersion than the H i disc to a maximum of 10 times the spread of the Hi disc, in keeping with the findings of Meatheringham et al.. In addition, moving out from the main bar, we find that the PN population follows a plane which is somewhat warped in relation to the Hi disc. We estimate the total PN population of the entire LMC system, based on our R equiv Ha limiting magnitude of ∼22, to be 956 ± 141.