A multi-transition study of the cyclic molecule cyclopropenylidene (C3H2) in the galaxy

Thesis/Dissertation · Mon Jan 01 04:00:00 EST 1990

OSTI ID:6032578

Madden, S C

Results of multi-transition observations and modeling of the hydrocarbon ring molecule cyclopropenylidene (C3H2) are reported. From a survey of the 1(sub 10)-1(sub 01) (18 GHz) and 2(sub 12)-1(sub 01) (85 GHz) transitions including cold, dark clouds, giant molecular clouds, the envelope of a carbon star, and diffuse clouds. Up to 10 transitions of C3H2 ranging in wavelength from 1.3 cm to 1.3 mm were observed in the dark clouds L1498, L134N, B335 and toward several positions in TMC-1. The Large Velocity Gradient (LVG) approximation was used to model the observations. Optical depth values of C3H2, estimated from 13-CC2H2 observations, are necessary to constrain the results since the range in excitation energies of the observed C3H2 transitions does not contrast sufficiently. The molecular hydrogen density in TMC-1 is estimated to be 3.7 x 10(exp 4)/cu cm, while the fractional abundance of C3H2 relative to H2 is 5.7 x 10(exp -9). Previous estimates assuming LTE conditions overestimate the abundance of C3H2. The abundance in the ridge component in Orion is estimated to be approximately 8 x 10(exp -10). Gas phase chemical models can reproduce the high C3H2 abundance found in dark clouds under assumptions such as steady state conditions with (C)/(O)/ is greater than 1.0, conditions of earlier evolutionary time, or optimistic rate coefficients. However, large deuteration ratios (0.05 to 0.15) create difficulties for gas phase models.

• Research Organization: Massachusetts Univ., Amherst, MA (USA)
• OSTI ID: 6032578
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CARBON STARS
CHEMICAL BONDS
COSMIC GASES
DATA
ELEMENTS
FLUIDS
GALAXIES
GASES
HYDROCARBONS
HYDROGEN
INFORMATION
MAIN SEQUENCE STARS
MATHEMATICAL MODELS
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
STARS
STEADY-STATE CONDITIONS
THEORETICAL DATA
VELOCITY