Planetary Nebulae as Probes of the Chemical Evolution of Early
Type Galaxies
M. Richer
Observatorio Astronomico Nacional, IA-UNAM, San Diego, USA
Bright extragalactic planetary nebulae have served as a probe of
the chemical evolution of several nearby dynamically hot systems
(DHSs: ellipticals, bulges, and dwarf spheroidals). There is a
pronounced symbiotic relationship between our understanding of the
evolution of planetary nebulae and their use to understand the
chemical evolution of their host galaxies. We have learned that
bright extragalactic planetary nebulae are similar to their Milky
Way counterparts and that they are useful probes of chemical
evolution, though the interpretation of their chemical abundances
is not necessarily simple. From the chemical abundances of the
planetary nebulae in DHSs, we have learned that DHSs follow a
metallicity-luminosity relation and probably did not evolve as
closed systems even while forming their stars. The
currently-available data, however, have yet to be fully exploited,
primarily because a quantitative understanding of the evolution of
planetary nebulae is lacking. Addressing this deficiency is
perhaps most easily done via observations of extragalactic
planetary nebulae themselves and will result not only in a better
understanding of planetary nebulae, but also of the evolution of
their host galaxies and of the role of planetary nebulae in
shaping that evolution.