Planetary Nebulae as Standard Candles. XII. Connecting the Population I and Population II Distance Scales

Abstract

We report the results of [O III] λ5007 surveys for planetary nebulae (PNe) in six galaxies: NGC 2403, NGC 3115, NGC 3351, NGC 3627, NGC 4258, and NGC 5866. Using on-band/off-band [O III] λ5007 images, as well as images taken in Hα, we identify samples of PNe in these galaxies and derive their distances using the planetary nebula luminosity function (PNLF). We then combine these measurements with previous data to compare the PNLF, Cepheid, and surface brightness fluctuation (SBF) distance scales. We use a sample of 13 galaxies to show that the absolute magnitude of the PNLF cutoff is fainter in small, low-metallicity systems, but the trend is well modeled by the theoretical relation of Dopita, Jacoby, & Vassiliadis (1992). When this metallicity dependence is removed, the scatter between the Cepheid and PNLF distances becomes consistent with the internal errors of the methods and independent of any obvious galaxy parameter. We then use these data to recalibrate the zero point of the PNLF distance scale. We use a sample of 28 galaxies to show that the scatter between the PNLF and SBF distance measurements agrees with that predicted from the techniques' internal errors, and that there is no systematic trend between the distance residuals and stellar population. However, we also find that the PNLF and SBF methods have a significant scale offset: Cepheid-calibrated PNLF distances are, on average, ∼ 0.3 mag smaller than Cepheid-calibrated SBF distances. We discuss the possible causes of this offset, and suggest that internal extinction in the bulges of the SBF calibration galaxies is the principle cause of the discrepancy. If this hypothesis is correct, then the SBF-based Hubble Constant must be increased by ∼ 7%. We also use our distance to NGC 4258 to argue that the short distance scale to the LMC is correct, and and that the global Hubble Constant inferred from the HST Key Project should be increased by 8 ± 3% to H 0 = 78 ± 7 km s −1 Mpc −1 .

Molecular gas in the inner 0.7 kpc-radius ring of M 31

“…The prompt SNIa component (which represents 50% of the SNIa population) discussed by Mannucci et al (2006) (2000) observed several high-ionisation "clouds" in this area. These authors discussed that the intensity of 3 of these sources is much larger than those of planetary nebulae detected in M 31 by Ciardullo et al (2002). However, in this central region, it might be possible that these sources are multiple.…”

Modelling the cosmic ray electron propagation in M 51

“…In Sect. 3 we present the observational data used in this work, the Very Large Array (VLA) maps at 1.4 GHz and 4.8 GHz Fletcher et al (2011), LOw Frequency ARray (LOFAR) map at 151 MHz (Mulcahy et al 2014), and our new GMRT map at Tully (1974); (b) Ciardullo et al (2002); (c) Bigiel et al (2010).…”

Planetary Nebulae as Probes of Stellar Populations

“…The first of these is a "dip" in the luminosity function which starts ∼ 2 mag below M * . This feature is not present in every galaxy: in M31, the faint-end of the PNLF is well described by the simple Henize & Westerlund (1963) exponential, which is expected from an ensemble of uniformly expanding spheres ionized by non-evolving central stars (Ciardullo et al 1989(Ciardullo et al , 2002. However, as Figure 2 illustrates, star-forming systems such as the Small Magellanic Cloud and M33, have a factor of ∼ 2 fewer PNe than predicted from the exponential law (Jacoby & De Marco 2002;Ciardullo et al 2004).…”

“…For example, PNe in the Milky Way exhibit a wide range of excitation, with [O III] λ5007 to Hα emission line ratios (R) ranging from ∼ 4 to ∼ 0.1. However, when one studies extragalactic PNe, a pattern emerges: the brightest PNe all have R > 2, regardless of their parent stellar population (Ciardullo et al 2002). In fact, the best way to analyze the bright emission lines from a homogeneous PN dataset is through a differential, multi-dimensional analysis.…”