Electron density measurements in NGC 6720.
Abstract
Spectral scans of NGC 6720 obtained with the Robinson-Wampler image-tube scanner on the Lick 3.0 m reflector have been analyzed to obtain electron temperatures from the [N ii] AA5755/6584 ratio and electron densities from the [S ii] AA6717/6731 and [Cl iii] AA55l7/5537 ratios. Comparison of these data with those obtained by previous observers for [0 ii], [0 iii], and [S ii] support the following model: The [S ii], [Cl iii], and presumably also the [N ii] radiation originates in filaments somewhat denser and cooler than the [0 ii] emitting region, while the [0 iii] radiation comes primarily from interior zones that are at least 1000 K hotter than the [N ii] emitting regions. It also suggests that the [N ii] and [S ii] emission observed near the center of the nebula is produced by outer shell material seen in projection. Subject headings: nebulae: individual - nebulae: planetary
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 1976
- DOI:
- 10.1086/154335
- Bibcode:
- 1976ApJ...205..798A