A Two-Component Power Law Covering Nearly Four Orders of Magnitude in the Power Spectrum of Spitzer Far-Infrared Emission from the Large Magellanic Cloud

TL;DR

This paper analyzes the power spectrum of far-infrared emission from the Large Magellanic Cloud, revealing a two-component power-law structure that reflects different physical processes at various scales.

Contribution

It identifies a two-component power-law in the LMC's emission spectrum and interprets the break as the disk's line-of-sight thickness, linking spectral features to physical processes.

Findings

Power spectrum exhibits two distinct slopes at different scales.

Break in the power spectrum corresponds to the LMC disk thickness.

Longer wavelengths show slightly steeper slopes, indicating smoother cooler dust emission.

Abstract

Power spectra of Large Magellanic Cloud (LMC) emission at 24, 70 and 160 microns observed with the Spitzer Space Telescope have a two-component power-law structure with a shallow slope of -1.6 at low wavenumber, k, and a steep slope of -2.9 at high k. The break occurs at 1/k ~ 100-200 pc, which is interpreted as the line-of-sight thickness of the LMC disk. The slopes are slightly steeper for longer wavelengths, suggesting the cooler dust emission is smoother than the hot emission. The power spectrum covers ~ 3.5 orders of magnitude and the break in the slope is in the middle of this range on a logarithmic scale. Large-scale driving from galactic and extragalactic processes, including disk self-gravity, spiral waves and bars, presumably cause the low-k structure in what is effectively a two-dimensional geometry. Small-scale driving from stellar processes and shocks cause the high-k structure in a 3D geometry. This transition in dimensionality corresponds to the observed change in power spectrum slope. A companion paper models the observed power-law with a self-gravitating hydrodynamics simulation of a galaxy like the LMC.