Planetary Nebulae as Standard Candles. VI. A Test in the Magellanic Clouds

We have measured the [O III] λ5007 fluxes of the brightest planetaries in the LMC (102 objects) and SMC (31 objects) using narrow-band imaging at the CTIO 0.9 m telescope. Our fluxes agree to ~ 5% with photoelectric measurements available in the literature (31 objects); agreement is much worse for objects with only spectrophotometric observations. Using the fluxes for the complete sample of bright LMC planetaries, we derive a distance using the planetary nebula luminosity function (PNLF). If we adopt a foreground plus internal reddening of E(B- V) = 0.10 for the LMC, which is based on direct measurements of the Balmer decrement of several planetaries, and estimates from B stars, clusters, and H I measurements, we find the distance modulus to be 18.44 +/- 0.18. This agrees superbly with the Cepheid distance modulus of 18.47 +/- 0.15 (Feast and Walker) and estimates between 18.2 and 18.5 from RR Lyrae stars, Miras, OB stars, and clusters. Similarly for the SMC, we adopt E(B- V) = 0.06 and derive a distance modulus of 19.09^+0.25^_-0.32_. The excellent consistency between the PNLF distance to the LMC, which uses the bulge of M31 as its sole calibrator, and the Cepheid distance is very strong evidence that the method is insensitive to host galaxy Hubble type, color, or metallicity.