Revealing the nature of Bulge Planetary Nebulae
Abstract
We propose observing a sample of 11 bulge planetary nebulae using the IRS spectrograph on board Spitzer. The goal is to study their chemical composition and physical parameters in order to understand their nature and evolution. Because of their brightness bulge planetary nebulae are ideal to study the dynamics of the Galaxy and their abundances can be used to determine the metallicity gradient toward the Galactic Center. Despite their importance, the nature of these objects is still not well understood. For instance, do the bulge planetary nebulae belong to an old population or are they part of a population with recent star formation? One way to study this problem is by simply deriving the abundances of certain elements, like sulfur and argon. These elements are neither produced nor destroyed in the course of evolution and therefore represent the composition at the time of star formation. Abundance determination of these elements have been attempted but sulfur and argon emit most of their lines in the IR, and therefore optical or UV studies have been inconclusive. Spitzer posseses the ideal wavelength coverage to obtain accurate abundances for these elements and give a good insight in the evolutionary and nucleosynthesis properties of the stellar progenitors. Moreover, it's sensitivity allows one to observe these objects in very short integration times, and for the first time have a look into the dust of these objects in a metal--rich environment in our own Galaxy. In the same framework of study we have included in this sample a very interesting PN (NGC3132) which doesn't belong to the bulge but which shows very unusual characteristics. This unusual behavior should be studied in the infrared, both to study the dust and to account for unseen ions to derive accurate abundances. Spitzer's spectra will be of invaluable value obtain a consistent theoretical evolutionary picture of these objects.
- Publication:
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Spitzer Proposal
- Pub Date:
- May 2006
- Bibcode:
- 2006sptz.prop30550H