The Large Magellanic Cloud: A power spectral analysis of Spitzer images

TL;DR

This study analyzes Spitzer images of the Large Magellanic Cloud using power spectral methods, revealing a break at 100-200 pc that corresponds to the dust disk's scale height, supported by hydrodynamic simulations.

Contribution

It provides the first detailed power spectral analysis of FIR emission in the LMC and links the spectral break to the disk's physical thickness through simulations.

Findings

Power spectra show two distinct slopes at different scales.

The break scale (~100-200 pc) matches the dust disk thickness.

Velocity analysis reveals anisotropic large-scale motions and isotropic small-scale motions.

Abstract

We present a power spectral analysis of Spitzer images of the Large Magellanic Cloud. The power spectra of the FIR emission show two different power laws. At larger scales (kpc) the slope is ~ -1.6, while at smaller ones (tens to few hundreds of parsecs) the slope is steeper, with a value ~ -2.9. The break occurs at a scale around 100-200 pc. We interpret this break as the scale height of the dust disk of the LMC. We perform high resolution simulations with and without stellar feedback. Our AMR hydrodynamic simulations of model galaxies using the LMC mass and rotation curve, confirm that they have similar two-component power-laws for projected density and that the break does indeed occur at the disk thickness. Power spectral analysis of velocities betrays a single power law for in-plane components. The vertical component of the velocity shows a flat behavior for large structures and a power law similar to the in-plane velocities at small scales. The motions are highly anisotropic at large scales, with in-plane velocities being much more important than vertical ones. In contrast, at small scales, the motions become more isotropic.