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 PNe in five galaxies that were hosts of well-observed SNe Ia: NGC 524, NGC 1316, NGC 1380, NGC 1448, and NGC 4526. The goals of this survey are to better quantify the zero point of the maximum magnitude-decline rate relation for SNe Ia and to validate the insensitivity of Type Ia luminosity to parent stellar population using the host galaxy Hubble type as a surrogate. We detected a total of 45 PN candidates in NGC 1316, 44 candidates in NGC 1380, and 94 candidates in NGC 4526. From these data and the empirical planetary nebula luminosity function (PNLF), we derive distances of 17.9(-0.9)(+0.8) , 16.1(-1.1)(+0.8), and 13.6(-1.2)(+1.3) Mpc, respectively. Our derived distance to NGC 4526 has a lower precision due to the likely presence of Virgo intracluster PNe in the foreground of this galaxy. In NGC 524 and NGC 1448 we detected no PN candidates down to the limiting magnitudes of our observations. We present a formalism for setting realistic distance limits in these two cases and derive robust lower limits of 20.9 and 15.8 Mpc, respectively. After combining these results with other distances from the PNLF, Cepheid, and surface brightness fluctuation distance indicators, we calibrate the optical and NIR relations for SNe Ia and find that the Hubble constants derived from each of the three methods are broadly consistent, implying that the properties of SNe Ia do not vary drastically as a function of stellar population. We determine a preliminary Hubble constant of H-0 = 77 +/- 3 (random) +/- 5 (systematic) km s(-1) Mpc(-1) for the PNLF, although more nearby galaxies with high-quality observations are clearly needed.