Stars and Planetary Nebulae in the Galactic Bulge


Planetary Nebulae are interesting objects for the study of the Galactic Bulge because they concentrate the energy of their central stars in the emission lines of their spectra, and can therefore be observed relatively easily at this distance. Furthermore the masses of their progenitor stars varying from 0.8 to 8M⊙, their ages span from 50 Myr to 25 Gyr, covering more than 95% of the possible ages in the Universe, and of course in the Bulge. The only stars with a similar ages range, that are reasonabely observable in the Bulge, are the Red Giants. They are actually the direct precursors of the Planetary Nebulae. Some elements have their abundances unmodified by the stellar evolution in Red Giants as well as in Planetary Nebulae. These elements keep the fingerprints of the chemical composition of the ISM when the progenitor star was born, and because of the span of their ages, they allow to follow its evolution over a very wide time range. One particular point of interest are the relative abundances of elements produced in type II and in type Ia supernovae. Type II supernovae explode very rapidely, after some Myr, e.g. quasi instantaneously on the Bulge evolution timescale, whereas type Ia supernovae explode after a period of the order of one Gyr. The relative abundances of type II and type Ia supernovae should thus allow to measure the timescale of the Bulge formation. On the other hand, elements produced during the lifetimes of the progenitor stars should allow to determine their ages at least statistically. In Planetary Nebulae, nitrogen is very easily detectable, and has its abundance modified in high mass progenitors, that are short lived. Nitrogen abundances in Planetary Nebulae should thus help to identify recent star formation.

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@inproceedings{Cuisinier2000StarsAP, title={Stars and Planetary Nebulae in the Galactic Bulge}, author={François Cuisinier}, year={2000} }