Power Spectra of JWST Images of Local Galaxies: Searching for Disk Thickness

TL;DR

This study analyzes JWST/MIRI images of nearby galaxies to examine their power spectra, finding no clear evidence of a transition in turbulence scale related to disk thickness, with implications for understanding galaxy structure.

Contribution

It provides the first detailed Fourier power spectrum analysis of JWST mid-infrared images of local galaxies, exploring turbulence and disk thickness effects.

Findings

Power spectra slopes range from -0.6 to -1.2 across wavelengths.

No evidence of a kink indicating a transition from 2D to 3D turbulence.

Sources and galaxy profiles influence the power spectrum slope.

Abstract

JWST/MIRI images have been used to study the Fourier transform power spectra (PS) of two spiral galaxies, NGC 628 and NGC 5236, and two dwarfs, NGC 4449 and NGC 5068, at distances ranging from 4 to 10 Mpc. The PS slopes on scales larger than 200 pc range from -0.6 at 21 microns to -1.2 at 5.6 microns. These slopes for one-dimensional PS are consistent with the PS slopes observed elsewhere using HI and dust emission. They are likely related to turbulence, but they may also be viewed as a hierarchical distribution of objects having a size-luminosity relation and size distribution function. There is no evidence for a kink or steepening of the PS at some transition from two-dimensional to three-dimensional turbulence on the scale of the disk thickness. This lack of a kink could be from large positional variations in the PS depending on two opposite effects: local bright sources that make the slope shallower and exponential galaxy profiles that make the slope steeper. The sources could also be confined to a layer of molecular clouds that is thinner than the HI or cool dust layers where PS kinks have been observed before. If the star formation layers observed in the mid-infrared here are too thin, then the PS kink could also be hidden in the broad tail of the JWST point spread function.