Detailed Structure of High Latitude Clouds

Details Detailed Structure of High Latitude Clouds Detailed Structure of High Latitude Clouds

Jan 1998

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998stin...9984013s&link_type=abstract

Nobeyama Radio Observatory Report, p. 9

Other

Molecular Clouds, Observation, Rarefied Gases, Carbon Isotopes, Collisions, Oxygen, Velocity Distribution, Telescopes, Stars, Spectral Line Width, Sensitivity, Scanners, Polar Regions, Mass, Cores, High Pressure

Scientific paper

To understand the detailed spatial and kinematical structure of molecular clouds in their early stages of evolution, we made extensive and sensitive strip-scan observations of MBM 32, MBM 54, and MBM 55 in C-12O J = 1 - 0 emission with the 15 sec.. (0.007 pc at 100 pc) beam of the Nobeyama 45 in telescope. The size of the smallest structure of low-density molecular gas traced by C-12O J = 1 - 0 emission was found to be approx. less than 0.03 pc. Clumps in these clouds tend to have larger line widths compared to those expected from the line width-size relation for low-mass cores. This may be due to high external pressure. In addition, we discovered a number of "pseudo-outflows" which are subparsec-scale outflow-like velocity structures probably not powered by young stellar objects (YSOs). They are well-separated in the position-velocity diagrams from other components, and are easily identified. They have a typical size of approx. 0.05 pc and a typical velocity gradient of approx. 40 km/ s pc. The small sizes and large velocity gradients suggest that these features are transient with typical dynamical timescales of approx. 2 x 104 yr. None of them seems to have YSO candidates in their vicinity. Our near-infrared follow- up observations failed to detect H2 upsilon = 1 - 0 S emission near the positions of pseudo-outflows. Considering these evidences and their narrow line widths (less than 1 km/ s), they are most likely weak shocks excited by collisions of clumps.

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