Neutral atomic carbon in the globules of the helix

We report detection of the 609 μm ³P1 → ³P0 line of neutral atomic carbon in globules of the Helix Nebula. The measurements were made toward the position of peak CO emission. At the same position, we obtained high-quality CO(2-1) and ¹³CO(2-1) spectra and a 135″ × 135′ map in CO(2-1). The velocity distribution of C I shows six narrow (1-2 km s^-1) components, which are associated with individual globules traced in CO. The C I column densities are (0.5-1.2) × 10¹⁶ cm^-2. C I is found to be a factor of ∼6 more abundant than CO. The large abundance of C I in the Helix can be understood as a result of the gradual photoionization of the molecular envelope by the central star's radiation field. © 1997. The American Astronomical Society. All rights reserved.

Duke Scholars

Author Ken H Young Pathology