Calibrating Type Ia Supernovae Using the Planetary Nebula Luminosity Function. I. Initial Results

We report the results of an [O III] lambda 5007 survey for planetary nebulae(PN) in five galaxies that were hosts of well-observed Type Ia supernovae: NGC524, NGC 1316, NGC 1380, NGC 1448 and NGC 4526. The goals of this survey are tobetter quantify the zero-point of the maximum magnitude versus decline raterelation for supernovae Type Ia and to validate the insensitivity of Type Ialuminosity to parent stellar population using the host galaxy Hubble type as asurrogate. We detected a total of 45 planetary nebulae candidates in NGC 1316,44 candidates in NGC 1380, and 94 candidates in NGC 4526. From these data, andthe empirical planetary nebula luminosity function (PNLF), we derive distancesof 17.9 +0.8/-0.9 Mpc, 16.1 +0.8/-1.1 Mpc, and 13.6 +1.3/-1.2 Mpc respectively.Our derived distance to NGC 4526 has a lower precision due to the likelypresence of Virgo intracluster planetary nebulae in the foreground of thisgalaxy. In NGC 524 and NGC 1448 we detected no planetary nebulae candidatesdown to the limiting magnitudes of our observations. We present a formalism forsetting realistic distance limits in these two cases, and derive robust lowerlimits of 20.9 Mpc and 15.8 Mpc, respectively. After combining these results with other distances from the PNLF, Cepheid,and Surface Brightness Fluctuations distance indicators, we calibrate theoptical and near-infrared relations for supernovae Type Ia and we find that theHubble constants derived from each of the three methods are broadly consistent,implying that the properties of supernovae Type Ia do not vary drastically as afunction of stellar population. We determine a preliminary Hubble constant ofH_0 = 77 +/- 3 (random) +/- 5 (systematic) km/s/Mpc for the PNLF, though morenearby galaxies with high-quality observations are clearly needed.