Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Revealing the Spectral Properties of Galactic Interstellar Medium by Survey Observations

Ya-Wen Xiao, Jian-Fu Zhang, Alex Lazarian

Abstract

Based on multi-frequency radio polarization survey datasets, we investigate the spectral characteristics of the Galactic interstellar medium (ISM) using the polarization frequency analysis (PFA) method, referred to as polarization variance. By comparing this novel PFA technique with the traditional power spectrum approach, and by cross-examining data from two distinct surveys, we aim to reinforce the robustness of our findings. Our analysis reveals that the ISM scaling slope in the Galactic disk is steeper than the classic Kolmogorov slope, whereas the ISM scaling slope in the Galactic halo aligns with the Kolmogorov slope. We suggest a distinct turbulence cascade process operating in the Galactic halo compared to the Galactic disk.

Revealing the Spectral Properties of Galactic Interstellar Medium by Survey Observations

Abstract

Based on multi-frequency radio polarization survey datasets, we investigate the spectral characteristics of the Galactic interstellar medium (ISM) using the polarization frequency analysis (PFA) method, referred to as polarization variance. By comparing this novel PFA technique with the traditional power spectrum approach, and by cross-examining data from two distinct surveys, we aim to reinforce the robustness of our findings. Our analysis reveals that the ISM scaling slope in the Galactic disk is steeper than the classic Kolmogorov slope, whereas the ISM scaling slope in the Galactic halo aligns with the Kolmogorov slope. We suggest a distinct turbulence cascade process operating in the Galactic halo compared to the Galactic disk.
Paper Structure (10 sections, 10 equations, 4 figures)

This paper contains 10 sections, 10 equations, 4 figures.

Table of Contents

  1. Introduction
  2. Theoretical Considerations
  3. Synchrotron Polarization
  4. Statistical Methods
  5. Description of observational datasets
  6. Results
  7. Single Local Region from Galactic Disk and Halo
  8. Spectral Statistics of Multiple Local Regions of Galactic Disk and Halo
  9. Discussion
  10. Summary

Figures (4)

  • Figure 1: Maps of polarization intensities from STAPS (left) and GMIMS (right) corresponding to 1.65 GHz and 0.43 GHz, respectively. The images are in the Galactic coordinates with Plate Carrée projection. The colorbars are in units of $\rm{erg~ s^{-1}~ cm^{-3}~ Hz}$. The horizontal dashed lines represent the dividing line of $\pm 30$ degrees between the Galactic disk and halo. The squared symbols indicate randomly selected subregions located at the Galactic disk (orange) and halo (red).
  • Figure 2: Upper panels: polarization variance $\langle P^2 \rangle$ vs. the square of wavelength $\lambda^2$ from two subregions of the Galactic disk and halo. Lower panels: power spectra of polarization intensities corresponding to the two subregions in the upper panels, respectively. The used data cubes are from STAPS. The colorbars show the observational frequency in GHz.
  • Figure 3: Polarization variance $\langle P^2 \rangle$ vs. the square of wavelength $\lambda^2$ (upper panels) and the power spectra of polarization intensity $P$ (lower panels) obtained by GMIMS. The other descriptions are the same as those of Figure \ref{['fig: sub_STAPS']}.
  • Figure 4: Probability density function (PDF) of spectral indices of magnetized ISM corresponding to the Galactic disk and halo, using the polarization variance and power spectrum of polarization intensities, from STAPS (upper panels) and GMIMS (lower panels) data cubes.