Topology in Synthetic Column Density Maps for Interstellar Turbulence

Putko, Joseph
(
University of Wisconsin-Madison; Middlebury College
);
Burkhart, B. K.
(
University of Wisconsin-Madison
);
Lazarian, A.
(
University of Wisconsin-Madison
)
show affiliations
American Astronomical Society, AAS Meeting #221, #349.03

Published in Jan 2013

We show how the topology tool known as the genus statistic can be utilized to characterize magnetohydrodyanmic (MHD) turbulence in the ISM. The genus is measured with respect to a given density threshold and varying the threshold produces a genus curve, which can suggest an overall ‘‘meatball,’’ neutral, or ‘‘Swiss cheese’’ topology through its integral. We use synthetic column density maps made from three-dimensional 512_{3} compressible MHD isothermal simulations performed for different sonic and Alfvénic Mach numbers (M^{s} and M^{A} respectively). We study eight different M^{s} values each with one sub- and one super-Alfvénic counterpart. We consider sight-lines both parallel (x) and perpendicular (y and z) to the mean magnetic field. We find that the genus integral shows a dependence on both Mach numbers, and this is still the case even after adding beam smoothing and Gaussian noise to the maps to mimic observational data. The genus integral increases with higher M^{s} values (but saturates after about M^{s} = 4) for all lines of sight. This is consistent with greater values of M^{s} resulting in stronger shocks, which results in a clumpier topology. We observe a larger genus integral for the sub-Alfvénic cases along the perpendicular lines of sight due to increased compression from the field lines and enhanced anisotropy. Application of the genus integral to column density maps should allow astronomers to infer the Mach numbers and thus learn about the environments of interstellar turbulence. This work was supported by the National Science Foundation’s REU program through NSF Award AST-1004881.
(c) 2013: American Astronomical Society