DEPENDENCE OF THE TURBULENT VELOCITY FIELD ON GAS DENSITY IN L1551
- Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8551 (Japan)
- Institute of Space and Astronautical Science/Japan Aerospace Exploration Agency, 3-1-1, Yoshinodai, Sagamihara, Kanagawa 229-8510 (Japan)
- Department of Astronomy, School of Science, University of Tokyo, Bunkyo, Tokyo 113-0033 (Japan)
- Nobeyama Radio Observatory, Minamimaki, Minamisaku, Nagano 384-1805 (Japan)
We have carried out mapping observations of the entire L1551 molecular cloud with about 2 pc x 2 pc size in the {sup 12}CO(1-0) line with the Nobeyama 45 m radio telescope at the high effective resolution of 22'' (corresponding to 0.017 pc at the distance of 160 pc), and analyzed the {sup 12}CO data together with the {sup 13}CO(1-0) and C{sup 18}O(1-0) data from the Nobeyama Radio Observatory database. We derived the new non-thermal line width-size relations, {sigma}{sub NT} {proportional_to} L {sup {gamma}}, for the three molecular lines, corrected for the effect of optical depth and the line-of-sight integration. To investigate the characteristic of the intrinsic turbulence, the effects of the outflows were removed. The derived relations are ({sigma}{sub NT}/km s{sup -1}) = (0.18 {+-} 0.010)(L/pc){sup 0.45{+-}0.095}, (0.20 {+-} 0.020)(L/pc){sup 0.48{+-}0.091}, and (0.22 {+-} 0.050) (L/pc){sup 0.54{+-}0.21} for the {sup 12}CO, {sup 13}CO, and C{sup 18}O lines, respectively, suggesting that the line width-size relation of the turbulence very weakly depends on our observed molecular lines, i.e., the relation does not change between the density ranges of 10{sup 2}-10{sup 3} and 10{sup 3}-10{sup 4} cm{sup -3}. In addition, the relations indicate that incompressible turbulence is dominant at the scales smaller than 0.6 pc in L1551. The power spectrum indices converted from the relations, however, seem to be larger than that of the Kolmogorov spectrum for incompressible flow. The disagreement could be explained by the anisotropy in the turbulent velocity field in L1551, as expected in MHD turbulence. Actually, the autocorrelation functions of the centroid velocity fluctuations show larger correlation along the direction of the magnetic field measured for the whole Taurus cloud, which is consistent with the results of numerical simulations for incompressible MHD flow.
- OSTI ID:
- 21455084
- Journal Information:
- Astrophysical Journal, Vol. 718, Issue 2; Other Information: DOI: 10.1088/0004-637X/718/2/1019; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
COSMOLOGY AND ASTRONOMY
ANISOTROPY
COMPUTERIZED SIMULATION
INCOMPRESSIBLE FLOW
LINE WIDTHS
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
RADIO TELESCOPES
STAR EVOLUTION
STARS
TURBULENCE
ANTENNAS
ELECTRICAL EQUIPMENT
ELECTRONIC EQUIPMENT
EQUIPMENT
EVOLUTION
FLUID FLOW
FLUID MECHANICS
HYDRODYNAMICS
MECHANICS
RADIO EQUIPMENT
SIMULATION
TELESCOPES