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Linke, R. A.

Publications and source records attributed to Linke, R. A..

9 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

A survey of the millimeter-wave spectrum of Sagittarius B2

More than 60 percent of the millimeter wave spectrum between 70 and 150 GHz of the giant Sgr B2 molecular cloud was surveyed with the Bell Laboratories 7 m telescope at a spectral resolution of 1 MHz. The observations and instrumentation are described, including beam efficiency and beamwidth as functions of frequency, frequency coverage, and rms noise. The catalog used to identify the 457 lines found is summarized, and the analysis of the data to determine column densities and rotational temperatures is discussed. The range of rotational temperatures obtained and their relation to the kinetic temperature, and their implications for the hydrogen density, are considered. More than 300 lines are transitions of 21 molecules, and the results for these are analyzed, giving excitation diagrams for most of them. A partly successful attempt is made to use ratios of the calculated abundances to predict abundances of as yet undetected species. Finally, the spectra for the entire survey are presented.

Cummins, S. E.↗
NASA NTRS1984

Identification of the SiCC radical toward IC +10216 - The first molecular ring in an astronomical source

In the radio spectrum of the envelope of the evolved carbon star IRC +10216, the fraction of lines from exotic molecules seldom or never observed in the terrestrial laboratory is exceptionally high. At least 20 lines have not been identified, and it is not known whether one, two, or a number of new molecules are involved. It is shown in the present investigation that nine of the previously unidentified lines in IRC +10216 are produced by SiCC, a radical long known to exist in stellar atmospheres. The true ground-state geometry of this radical has only been obtained recently on the basis of an elegant two-photon ionization experiment in a supersonic molecular beam. Information regarding the molecular geometry and lower rotational levels of SiCC is presented in a graph. The intensities of the SiCC lines confirm the assignments, yield new data on the temperature and density in the envelope of IRC +10216, and indicate that the amount of SiCC there is substantial.

Thaddeus, P.↗
NASA NTRS1983

The kinetic temperature and density of the Sagittarius B2 molecular cloud from observations of methyl cyanide

Observations of the K components of the CH3CN J = 4-to-3 rotational transition at 73.6 GHz, the 6-to-5 transition at 110.4 GHz, and the 7-to-6 transition at 128.7 GHz, yield a mean kinetic temperature value of 85 + or - 10 K and a mean H2 density of 110,000 + or - 50,000/cu cm for the central 2.0 arcmin of the Sgr B2 molecular cloud. Within the K = zero-to-4 ladders of CH3CN in Sgr B2, the populations of the radiatively coupled J levels are relaxed and exhibit a rotational temperature of about 16 K, which is similar to that of several linear molecules.

Cummins, S. E.↗
NASA NTRS1981

Three new 'nonterrestrial' molecules

Eight new interstellar lines have been detected from three molecules not previously observed spectroscopically in space or in the laboratory. One is a linear or nearly linear molecule with microwave constants B0 equals 21,337.15 plus or minus 0.06 MHz, D0 equals 21.4 plus or minus 1.5 kHz. This is the thioformyl ion HCS(plus), first identified because B0 and D0 are close to those calculated, and now confirmed by laboratory detection of one of the present lines (Gudeman et al.). The second molecule, also linear or nearly so, has microwave constants B0 equals 10,691,406 plus or minus 0.043 MHz, D0 equals 1.84 plus or minus 0.91 kHz close to those expected for the isoelectronic systems HOCO(plus) and HOCN; a choice between the two cannot be made on the basis of the available astronomical data. The existence of a third molecule is deduced from an unidentified line at 85,338 MHz that has been found in many sources, is fairly intense in several, and may be self-absorbed in Sgr B2.

Thaddeus, P.↗
NASA NTRS1979

Interstellar methyl mercaptan

Methyl mercaptan (CH3SH) has been identified in Sgr B2 from observations of six lines in its millimeter-wave spectrum. The CH3SH rotational temperature and column density in Sgr B2 are T(rot) = 9 plus or minus 3 K and N = 1.5 plus or minus 0.2 x 10 to the 14th per sq cm, respectively. The CH3SH/CH3OH ratio is apparently not greatly different from the cosmic S/O ratio.

Linke, R. A.↗
NASA NTRS1979

Interstellar isothiocyanic acid

Isothiocyanic acid (HNCS) has been identified in Sgr B2 from millimeter-wave spectral line observations. We have definitely detected three rotational lines, and have probably detected two others. The rotational temperature of HNCS in Sgr B2 is 14 plus or minus 5 K, its column density is 2.5 plus or minus 1.0 x 10 to the 13th per sq cm, and its abundance relative to HNCO is consistent with the cosmic S/O ratio, 1/42.

Frerking, M. A.↗
NASA NTRS1974

Kinematics of the Orion A molecular cloud

Examination of the velocity structure of J = 1 to J = 0 emission of CO in the Orion A molecular cloud, including a presentation of extended strip maps in both declination and right ascension intersecting at the position of peak intensity. The results in declination show evidence for large-scale rotation, while the right ascension maps show features which can be interpreted as gravitational condensations. The observed rotation is found to be sufficient to support a density equal to that estimated for the cloud (an H2 number density of about 2000 per cu cm).

Linke, R. A.↗