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R. A. Shaw, L. Stanghellini, M. Mutchler, J. C. Blades (ST~ScI), B. Balick (Univ. Washington), G. H. Jacoby (NOAO), O. De Marco (AMNH)
We present images and slit-less spectroscopy from a survey of SMC planetary nebulae (PNe), which is now underway. These data, obtained with the Space Telescope Imaging Spectrograph, will quadruple the number of SMP PNe imaged with HST. The data permit us to determine the nebular dimensions and morphology in the monochromatic light of several emission lines, including those that have traditionally been used for morphological studies in the Galaxy (H\alpha, [N~{\sc ii}] 6583 and [O~{\sc iii}] 5007), plus others of varying ionization, such as [O~{\sc i}], He~{\sc i}, and [S~{\sc ii}]. The broad-band images will allow us to determine the central star magnitudes (for the brighter stars), which will yield the evolutionary state of the central stars. Our SMC sample, in combination with our published sample of PNe in the LMC (Shaw et al. 2001, see astro-ph/0010200), is ideal for studying the co-evolution of PNe and their central stars, in that the debilitating uncertainties of the Galactic PN distance scale and the selection effects of interstellar dust do not apply. The differing metallicity of the host galaxies makes our comparative study of the LMC and SMC PNe well suited to illuminating the question of Population effects on nebular and stellar evolution.
Although the total number of observed SMC PNe in this sample is still small, our data suggest that the incidence of non-symmetric nebulae (including bipolar and bipolar-core nebulae, which is an indicator of Population I ancestry) may be smaller than that reported for the LMC, and perhaps comparable to the Galaxy. However, there are a few cases where the morphology suggests the presence of a dusty torus. In addition, the onset of asymmetric features appears even in very young nebulae (<2000 yr), suggesting that at least the gross features of the nebular morphology are more directly tied to PN formation rather than subsequent shaping by the radiation field and wind from the central star.
Support for this work was provided by NASA through grant GO-08663.01-A from ST~ScI.
If you would like more information about this abstract, please follow the link to http://arXiv.org/abs/astro-ph/0010200. This link was provided by the author. When you follow it, you will leave the Web site for this meeting; to return, you should use the Back comand on your browser.
The author(s) of this abstract have provided an email address for comments about the abstract: shaw@stsci.edu