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Statistical signatures of interstellar turbulence in dust polarization maps

Ka Wai Ho, Ka Ho Yuen, Raphael Flauger, Alexei G. Kritsuk

TL;DR

This work presents a high-resolution ($2112^3$) MHD simulation of magnetized, multiphase interstellar turbulence in a $200$ pc volume, tailored to reproduce Planck observations of dust polarization. By computing synthetic polarization maps with optically thin dust emission, masking, and multiple line-of-sight projections, the study reproduces the Planck-like scaling of the $EE$ and $BB$ spectra, the $E$/$B$ asymmetry with $EE/BB\approx1.92$, and a significant positive $TE$ correlation, along with a polarization fraction PDF consistent with observations. Key results include $\alpha_{BB}=-2.38\pm0.01$, $\alpha_{EE}=-2.41\pm0.01$, $\alpha_{TE}=-2.40\pm0.02$, and $r_{TE}(k)=0.266\pm0.003$, with TB remaining undetected; these match Planck measurements in relevant sky regions and support turbulence-driven foreground modeling. The work highlights the physical origin of observed $E$/$B$ asymmetry and positive $TE$ signals, providing a physically grounded ISM-based dust foreground model for current and future CMB experiments.

Abstract

We present results from a high-resolution interstellar turbulence simulation and show that it closely reproduces recent $Planck$ measurements. Our model captures the scaling of $EE$ and $BB$ spectra, and the $EE/BB$ ratio in the inertial range. The probability density function of the dust polarization fraction is also consistent with observations. The $TE$ cross-correlation is in broad agreement with the $Planck$ sky. This simulation provides new insights into the physical origins of the observed $E/B$ asymmetry and positive $TE$ signal, facilitating the development of advanced Galactic dust emission models for current and future cosmic microwave background experiments.

Statistical signatures of interstellar turbulence in dust polarization maps

TL;DR

This work presents a high-resolution () MHD simulation of magnetized, multiphase interstellar turbulence in a pc volume, tailored to reproduce Planck observations of dust polarization. By computing synthetic polarization maps with optically thin dust emission, masking, and multiple line-of-sight projections, the study reproduces the Planck-like scaling of the and spectra, the / asymmetry with , and a significant positive correlation, along with a polarization fraction PDF consistent with observations. Key results include , , , and , with TB remaining undetected; these match Planck measurements in relevant sky regions and support turbulence-driven foreground modeling. The work highlights the physical origin of observed / asymmetry and positive signals, providing a physically grounded ISM-based dust foreground model for current and future CMB experiments.

Abstract

We present results from a high-resolution interstellar turbulence simulation and show that it closely reproduces recent measurements. Our model captures the scaling of and spectra, and the ratio in the inertial range. The probability density function of the dust polarization fraction is also consistent with observations. The cross-correlation is in broad agreement with the sky. This simulation provides new insights into the physical origins of the observed asymmetry and positive signal, facilitating the development of advanced Galactic dust emission models for current and future cosmic microwave background experiments.

Paper Structure

This paper contains 8 sections, 4 figures, 1 table.

Table of Contents

  1. Introduction.---
  2. Numerical model.---
  3. Statistics of developed turbulence.---
  4. Polarization maps.---
  5. The $EE$, $BB$ spectra and $E/B$ asymmetry.---
  6. $TE$ correlation.---
  7. Masking.---
  8. Conclusions.---

Figures (4)

  • Figure 1: Sample synthetic polarization maps, showing projections parallel (left) and perpendicular (right) to the mean field $\bm b_0$. The drapery texture generated using the LIC technique cabral.93 shows the POS magnetic field structure. Pseudovectors indicate the polarization direction (predominantly perpendicular to the field). Color shows the intensity in units of H i column density. These maps are built on full-resolution $2112^3$ numerical data smoothed with a low-pass box-car filter of length 5 voxels.
  • Figure 2: Compensated time-average $BB$ (left panel, top) and $TE$ (right panel, top) (co)spectra in arbitrary units, $EE/BB$ and $TE/EE$ spectral ratios (bottom). Dotted lines in the top plots show least-squares fits for projection along the mean field $\bm b_0$ in a range of $\log_{10}(k/k_{\rm min})\in[0.5,1.5]$. Horizontal dotted lines in the bottom plots indicate similar fits for the spectral ratios.
  • Figure 3: Polarization fraction PDF for projections along the principal axes $x$, $y$, and $z$ as well as the mean PDF for an equal mix of all three projections (left panel). Correlation coefficient $r_{TE}(k)$ (right panel). Horizontal dotted line indicates least-squares fit to $r_{TE}(k)$ for projection along $\bm b_0$ in a range of $\log_{10}(k/k_{\rm min})\in[0.5,1.5]$.
  • Figure 4: Effects of masking on the PDF of POS magnetic field fluctuations $\tilde{b}$.