13HCO(+) and CH3OH Line Observations of Pre-Stellar Dense Cores in the TMC-1C Region

Details 13HCO(+) and CH3OH Line Observations of Pre-Stellar Dense Cores in the TMC-1C Region 13HCO(+) and CH3OH Line Observations of Pre-Stellar Dense Cores in the TMC-1C Region

Jan 1998

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998stin...9945688t&link_type=abstract

Technical Report, NRO-456 Dept. of Astronomy

Astronomy and Astrophysics

Astronomy

Spatial Resolution, Radio Observation, Stellar Cores, Stellar Structure, Line Spectra, Spectral Line Width, Stellar Mass, Molecular Gases, Infrared Astronomy Satellite, Protostars, Star Formation

Scientific paper

We have mapped the whole TMC-1C region in 13HCO(+) (J = 1 - 0) and CH3OH (JK = 20-10 A+) lines at a grid spacing of 50" with the 45m telescope at Nobeyama Radio Observatory. We have also conducted high spacial resolution mapping observations at a grid spacing of 34" in both lines toward a 6' x 6' portion in the south and a 4' x 4' portion in the north of the TMC-1C region. We found that the structure of TMC-1C is filamentary in both molecular lines. The size and position angle of the filament are 0.75 pc x 0.17 pc and 135 deg, respectively. The filament consists of dense (approximately 105)/cc cores which are traced by either 13HCO(+) or CH3OH lines. We found that the distribution of cores seen in 13HCO(+) is quite different from the distribution of cores seen in CH3OH. The LVG analyses indicate that this difference is due to relative abundance variation between 13HCO(+) and CH3OH in the cores by about one order of magnitude. We have also carried out multi-transitional observations Of C3H2 (J(sub K prime, K double prime) = 21,2 - 10,1, and 31,2 - 30,3) at two positions in the same Cloud in order to estimate the molecular hydrogen densities for 13HCO(+) and CH3OH cores, and found that the density are around 105/cc for both cores. These starless cores (no IRAS source), considered to be pre-stellar cores, seem to be at chemically different evolutionary stages; the 13HCO(+) cores are more evolved and closer to protostar formation than CH3OH cores. On the other hand, we found no difference in physical properties, i.e., the size, line width, and mass, between 13HCO(+) and CH3OH cores; the averages are about 0.07 pc, 0.3 km/s, and 2 solar mass respectively.

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