Planck dust polarization power spectra are consistent with strongly supersonic turbulence

Understand

The polarization of the Cosmic Microwave Background (CMB) is rich in information but obscured by foreground emission from the Milky Way's interstellar medium (ISM).

• To uncover relationships between the underlying turbulent ISM and the foreground power spectra, we simulated a suite of driven, magnetized, turbulent models of the ISM, varying the fluid properties via the sonic Mach number, $\mathcal{M_S}$ and magnetic (Alfv\'en) Mach number,$\mathcal{M_A}$.
• We measure the power spectra of density ($\rho$), velocity ($v$), magnetic field ($H$), total projected intensity ($T$), parity-even polarization ($E$), and parity-odd polarization ($B$).
• We find that the slopes of all six quantities increase with $\mathcal{M_S}$ Most increase with $\mathcal{M_A}$, while the magnetic field spectrum steepens with $M_A$.