Kinetic temperature in the interior of the zeta Ophiuchi cloud from Copernicus observations of interstellar C/sub 2/

Journal Article · Wed Mar 15 04:00:00 EST 1978 · Astrophys. J., Lett.; (United States)

DOI:https://doi.org/10.1086/182643· OSTI ID:7208086

Snow, Jr, T P

The Copernicus ultraviolet telescope-spectrometer has been used to carry out sensitive scans of the D/sup 1/..sigma../sub u//sup +/-X/sup 1/..sigma../sup +/ (0-0) transition of C/sub 2/ at 2312 A in the spectrum of zeta Ophiuchi. An absorption feature was detected at the 4sigma level of significance at the position of the R(0) line, implying a column density of 1.22 x 10/sup 12/ cm/sup -2/ for the J=0 level. An upper limit on the R(2) line of 2.6 mA, yielding N(J=2) < or =1.66 x 10/sup 12/ cm/sup -2/ implies a rotational temperature of at most 22 K, with a high probability that T/sub rot/< or =16 K. This represents the limit on the kinetic temperature of the ambient gas because radiative transitions between the rotational levels of this homonuclear molecule are forbidden. The total column density of C/sub 2/ is estimated to be at most 3.2 x 10/sup 12/, a factor of approx.4 below the abundance expected from a recent model calculation for the zeta Oph cloud. The discrepancy may be due to an incorrect branching ratio for the reaction CH)..-->..CH/sub 2/+H ..-->..+H/sub 2/, to the presence of greater depletion of carbon in the cloud core than assumed, to an underestimate of the photodissociation rate for C/sub 2/, or to an incorrect oscillator strength.

• Research Organization: Princeton University Observatory
• OSTI ID: 7208086
• Journal Information: Astrophys. J., Lett.; (United States), Journal Name: Astrophys. J., Lett.; (United States) Vol. 220:3; ISSN AJLEA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics &amp; Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CARBON
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
CHEMISTRY
COSMIC DUST
COSMIC GASES
COSMOCHEMISTRY
DUSTS
ELEMENTS
ENERGY-LEVEL TRANSITIONS
FLUIDS
FUNCTIONS
GASES
INTERSTELLAR SPACE
NONMETALS
SPACE
SPECTRA
SPECTRAL DENSITY
SPECTRAL FUNCTIONS
ULTRAVIOLET SPECTRA