Planetary Nebulae in Galaxies Beyond the Local Group

Abstract

Planetary nebulae can be used to estimate the distances to galaxies and to measure stellar dynamics in faint halos. We discuss surveys which have netted a total of 665 candidate planetary nebulae in NGC 5128 (Cen A), NGC 5102, NGC 3031 (M81), NGC 3115, three galaxies in the Leo Group (NGC 3379, NGC 3384, NGC 3377), NGC 5866, and finally, in NGC 4486 (M87). Radial velocities of planetaries in M32 have shown that its halo velocity dispersion is most likely isotropic. Radial velocities of planetaries in M31 show that ∼ 2/3 of the nebulae with projected radii between 15 and 30 kpc are members of a rotating thick disk with slight asymmetric drift, while ∼ 1/3 belong to a slowly rotating halo. Velocities of 116 nebulae in NGC 5128 reveal pronounced rotation and a slowly declining velocity dispersion in the halo out to 20 kpc. The [O III] λ5007 luminosity functions (PNLFs) in NGC 5128, M81, and the three Leo Galaxies have the same shape over the first magnitude. The highly consistent distances derived from the brightnesses of the jth nebula and the median nebula in different fields in the same galaxy and from different galaxies in the same group lend strong support to the suggestion that planetaries are an accurate standard candle in old stellar populations. Comparison of theoretical luminosity functions to the observed PNLFs shows that there is a very small dispersion in the central star masses.