The Fractal Dimension of Projected Clouds

University of Zulia, Maracaibo, Zulia, Venezuela
The Astrophysical Journal (Impact Factor: 5.99). 02/2005; 625(2). DOI: 10.1086/429553
Source: arXiv


The interstellar medium seems to have an underlying fractal structure which can be characterized through its fractal dimension. However, interstellar clouds are observed as projected two-dimensional images, and the projection of a tri-dimensional fractal distorts its measured properties. Here we use simulated fractal clouds to study the relationship between the tri-dimensional fractal dimension (D_f) of modeled clouds and the dimension resulting from their projected images. We analyze different fractal dimension estimators: the correlation and mass dimensions of the clouds, and the perimeter-based dimension of their boundaries (D_per). We find the functional forms relating D_f with the projected fractal dimensions, as well as the dependence on the image resolution, which allow to estimatethe "real" D_f value of a cloud from its projection. The application of these results to Orion A indicates in a self-consistent way that 2.5 < D_f < 2.7 for this molecular cloud, a value higher than the result D_per+1 = 2.3 some times assumed in literature for interstellar clouds.

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Available from: Nestor Sanchez, Oct 01, 2012
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    • "This experimental method, and the light scattering technique in general, yields fractal dimension values related to the three-dimensional (3D) structure of the aggregate distribution, while direct imaging techniques usually deal with two-dimensional (2D) projected images of the actual threedimensional structure of the aggregate distribution. How the values of these 3D and 2D-projected fractal dimensions relate to each other is not an easy matter, but some progress in this direction has been done [26], and several possible relations have been theoretically found [27] [28] [29]. In this work we analyze the fractal dimension obtained by SALS for these aggregates of magnetic particles for different values of the concentration and amplitude of the external magnetic field. "
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