The two aspect ratios of randomly oriented triaxial ellipsoids (representing isosurfaces of an

isotropic 3D random field) can be determined from a single 2D cross-section of their sample

using the probability density function (PDF) of the filamentarity F of individual structures

seen in cross-section (F = 0 for a circle and F = 1 for a line). The PDF of F has a robust

form with a sharp maximum and truncation at larger F, and the most probable and maximum

values of F are uniquely and simply related to the two aspect ratios of the triaxial ellipsoids.

The parameters of triaxial ellipsoids of randomly distributed sizes can still be recovered from

the PDF of F. This method is applicable to many shape-recognition problems, here illustrated

by the neutral hydrogen density in the turbulent interstellar medium of the Milky Way. The

gas distribution is shown to be filamentary with axis ratios of about 1:2:20.

Series:

Astronomy Unit Seminars

Speaker:

Prof. Anvar Shukurov (U. Newcastle)

Host:

David Tsiklauri

Date:

January 16th, 2015 at 14:30

Room:

GO Jones Room 610

Abstract: