Abundance of atomic carbon (C I) in dense interstellar clouds

Journal Article · Tue Dec 15 04:00:00 EST 1981 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/159494· OSTI ID:5426081

Phillips, T G; Huggins, P J

The abundance of interstallar neutral atomic carbon (C I) is investigated by means of its ground state fine-structure line emission at 492 GHz (609 ..mu..). Since this particular submillimeter line lies in a relatively opaque region of the Earth's atmospheric spectrum, the investigation was carried out from the 91.5 cm telescope of NASA's Kuiper Airborne Observatory. Atomic carbon is found to be very abundant in dense interstellar (molecular) clouds. Its column densities of about 10/sup 19/ cm/sup -2/ seem comparable to those for CO in directions towards the cloud centers. By contrast, current theories of carbon chemistry in dense clouds suggest that C I shoud be the dominant species only near cloud edges giving column densities of approx.10/sup 17/ cm/sup -2/, and should be a negligible constituent for deep regions where the UV field cannot penetrate. It is suggested that these observations of considerably greater column densities imply that the physical conditions in the clouds are not as simple as assumed in the chemical models. Some situations are discussed which would lead to large C I abundances, including the possibility that the chemical lifetimes of the clouds are relatively short (approx.10/sup 6/ yr).

• Research Organization: California Institute of Technology
• OSTI ID: 5426081
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 251:2; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABUNDANCE
CARBON
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CHALCOGENIDES
CHEMICAL COMPOSITION
CHEMISTRY
COSMOCHEMISTRY
ELEMENTS
EMISSION SPECTRA
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
FINE STRUCTURE
FUNCTIONS
GROUND STATES
INTERSTELLAR SPACE
NONMETALS
OXIDES
OXYGEN COMPOUNDS
SPACE
SPECTRA
SPECTRAL DENSITY
SPECTRAL FUNCTIONS