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Session 81 - Planetary Nebulae.
Display session, Wednesday, January 17
North Banquet Hall, Convention Center
We obtained high-resolution images of the planetary nebula BD+30\deg3639 using the HST WFPC2 instrument and the VLA telescope. Images were obtained in the emission lines H\beta, H\alpha, HeI\lambda5876, [O III]\lambda5007, [O II]\lambda3727, [O I]\lambda6300, [N II]\lambda6584, [S III]\lambda9532, [S II]\lambda6717,6731 and in the optically-thin radio continuum. These images reveal detailed structure not previously seen in this 7\arcsec\ diameter nebula, clearly resolving the rectangular-shaped shell.
In every emission line, significant flux is seen in a halo which extends, with exponentially decreasing brightness, to \sim 4\arcsec\ beyond the ionized shell. The fraction of light in this halo ranges from 0.12 to 0.25. Most of this light is apparently scattered from dust in the neutral halo; however, some small-scale structure seen in [O I] and [S II] emission may be due to other processes.
The H\beta and H\alpha images and the VLA radio flux map are used to calculate the extinction in the nebula and the quantity R=A_V/E_B-V. The reddening map determined from the Balmer decrement shows an east-west gradient across the nebula and reveals a large dust blob (c=1.2, twice the average value) superimposed on the northeast section of the shell. The VLA/H\beta map confirms a clumpy distribution of dust in the shell. There is a small gradient in R across the nebula and the mean value of R in BD+30 is found to be well below the standard ISM value of 3.1. Using theoretical dust models, we consider possible explanations for the anomalous extinction, such as a deficiency of large grains.
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