High-Resolution Imagery of BD + 30degree3639 and Its Dusty Halo
The planetary nebula BD +30\arcdeg3639 has been imaged by the Hubble Space Telescope through nine narrow-band filters. A high resolution radio map has been obtained with the VLA. Comparison of Hβ , Hα and radio images allow us to derive the point-to-point variations in both the extinction and the ratio of total to selective absorption. The extinction shows (1) a gradient across the nebula, and (2) a large dust clump in the northeast and many small ( ~ 0farcs2 ) dust features. The ratio of total to selective absorption for this nebula is close to the normal ISM value, and can be modeled by a power law distribution of amorphous carbon grains. It is found that the optical images show a substantial halo due to light scattered by dust in the neutral envelope surrounding the ionized shell. Monte Carlo models indicate that such scattering could result from a dust halo with an optical depth of unity and an albedo of ~ 0.4. Such a high albedo is not consistent with pure carbon dust models. The halo images in [O I]lambda 6300 and [S II]lambda 6717,31 show anomalous structures not seen in the other lines, which seem to be in emission. The strongest [O I] feature is coincident with halo emission previously observed in the 1-0 S(1) transition of H_2. The [O I] and [S II] emission may indicate shock heating of the halo.
The Astronomical Journal
- Pub Date:
- June 1997