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FRACTAL DIMENSIONS OF INTERSTELLAR MEDIUM: II. THE MOLECULAR CLOUDS ASSOCIATED WITH THE HII REGION SH 156

  • 발행 : 2008.12.31

초록

We have estimated the fractal dimension of the molecular clouds associated with the Hii region Sh 156 in the Outer Galaxy. We selected the $^{12}CO$ cube data from the FCRAO CO Survey of the Outer Galaxy. Using a developed code within IRAF, we identified slice-clouds (2-dimensional clouds in velocity-channel maps) with two threshold temperatures to estimate the fractal dimension. With the threshold temperatures of 1.8 K, and 3 K, we identified 317 slice-clouds and 217 slice-clouds, respectively. There seems to be a turn-over location in fractional dimension slope around NP (area; number of pixel) = 40. The fractal dimensions was estimated to be D = $1.5\;{\sim}\;1.53$ for $NP\;{\geq}\;40$, where $P\;{\propto}\;A^{D/2}$ (P is perimeter and A is area), which is slightly larger than other results. The sampling rate (spatial resolution) of observed data must be an important parameter when estimating fractal dimension. Fractal dimension is apparently invariant when varying the threshold temperatures applied to slice-clouds identification.

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참고문헌

  1. Bazell, D. & Desert, F. X., 1988, Fractal structure of interstellar cirrus, ApJ, 333, 358
  2. Blitz, L., Lockman, E. J., & Tschope, R., 1990, Outer Galaxy. Lecture Notes in Physics No. 306, Springer-Verlag, Berlin
  3. Dickman, R. L., Horvath, M. A., Margulis, M., 1990, A Search for Scale-Dependent Morphology in Five Molecular Cloud Complexes, ApJ, 365, 58
  4. Falgarone, E., Phillips, T. G., & Walker, C. K., 1991, The Edges of Molecular Clouds - Fractal Boundaries and Density Structure, ApJ, 378, 186 https://doi.org/10.1086/170419
  5. Heydari-Malayeri, M., Testor, G., & Lortet, M. C., 1980, Interaction of hot stars and the interstellar matter. X - Morphology, excitation, and structure of the bright galactic nebula Sh2-156 /IC 1470/, A&A, 84, 154
  6. Heyer, M. H., Brunt, C., Snell, R. L., Howe, J. E., Schloerb, F. P., & Carpenter, J. M., 1998, The Five College Radio Astronomy Observatory CO Survey of the Outer Galaxy, ApJS, 115, 241 https://doi.org/10.1086/313086
  7. Isobe, T., Feigelson, E. D., Akritas, M. G., & Babu, G. J., 1990, Linear Regression in Astronomy, ApJ, 364, 104 https://doi.org/10.1086/169390
  8. Kang, M. & Lee, Y., 2005, A Study of Molecular Cloud Associated with the Hii Region Sh 156, JKAS, 38, 33
  9. Kramer, C., Stutzki, J., Rohrig, R., Corneliussen, U., 1998, Clump Mass Spectra of Molecular Clouds, A&A, 329, 249
  10. Lee, Y., Snell, R. L., & Dickman, R. L., 1990, Analysis of $^{12}CO$ and $^{13}CO$ Emission in a Three Square Degree Region of the Galactic Plane between l = $23^{\cdot}$ and $25^{\cdot}$, ApJ, 355, 536 https://doi.org/10.1086/168786
  11. Lee, Y., 2004, Fractal Dimensions of Interstellar Medium: I. The Molecular Clouds in the Antigalactic Center, JKAS, 32, 1
  12. Mandelbrot, B. B., 1983, The Fractal Geometry of Nature, San Francisco: Freeman
  13. Sanchez, N., Alfaro, E. J., & Perez, E., 2005, The Fractal Dimension of Projected Clouds, ApJ, 625, 849 https://doi.org/10.1086/429553
  14. Scalo, J., 1990, Perception of interstellar structure - Facing complexity in Physical processes in fragmentation and star formation, ed. R. Capuzzo-Dolcetta, C. Chiosi, & A, Di Fazio (Dordrecht: Kluwer), ASSL, 162, 151
  15. Scoville, N. Z., Yun, M. S., Clemens, D. P., Sanders, D. B., and Waller, & W. H., 1987, Molecular Clouds and Cloud Cores in the Inner Galaxy, ApJS, 63, 821 https://doi.org/10.1086/191185
  16. Stutzki, J., Bensch, F., Heithausen, A., Ossenkopf, V., & Zielinsky, M., 1998, On the Fractal Structure of Molecular Clouds, A&A, 226, 697
  17. Vogelaar, M. G. R. & Wakker, B. P. 1994, Measuring the fractal structure of interstellar clouds, A&A, 291, 557
  18. Williams, J. P., Blitz, L.,& McKee, C. F., 2000, Protostars and Planets IV (Book - Tucson: University of Arizona Press; eds Mannings, V., Boss, A.P., Russell, S. S.), p. 97. The Structure and Evolution of Molecular Clouds: from Clumps to Cores to the IMF

피인용 문헌

  1. Internal Structure of Stellar Clusters: Geometry of Star Formation vol.6, pp.S270, 2010, https://doi.org/10.1017/S1743921311000214