Planetary Nebulae as Standard Candles. VII. A Test versus Hubble Type in the NGC 1023 Group

We present the results of an [O III] λ survey for planetary nebulae in the NGC 1023 Group. In all, we detected 143 planetary nebula candidates: 110 in the SB0 galaxy NGC 1023 and 33 in the halo of the edge-on Sb spiral NGC 891. Using a statistically complete and homogeneous sample of planetary nebulae and the procedures described in previous papers in the series, we derive distances to these galaxies using the planetary nebula luminosity function (PNLF). After correcting for foreground extinction by using the estimated reddening values of Burstein and Heiles, we find the distance moduli for NGC 1023 and NGC 891 are 29.97 +/- 0.14 and 29.97 +/- 0.16, respectively. The similarity of these distances demonstrates the insensitivity of the PNLF to galaxy Hubble types and population age, and again confirms it as one of the best extragalactic standard candles.