An Examination of Galactic Polarization with Application to the Planck TB Correlation

Abstract

Angular power spectra computed from Planck HFI 353 GHz intensity and polarization maps produce a TB correlation that can be approximated by a power-law (Planck Collaboration XI 2018). Whether the observed TB correlation is an induced systematic feature or a physical property of Galactic dust emission is of interest both for cosmological and Galactic studies. We investigate the large angular scale E and B-mode morphology of microwave polarized thermal dust emission, and relate it to physical quantities of polarization angle and polarization fraction. We use empirical models of polarized dust to show that dust polarization angle is a key factor in producing the TB correlation. A small sample of both simulated and observed polarization angle maps are combined with 353 GHz intensity and dust polarization fraction to produce a suite of maps from which we compute TB and EB. Model realizations that produce a positive TB correlation are common and can result from large-scale (> 5 • ) structure in the polarization angle. The TB correlation appears robust to introduction of individual intensity, polarization angle and polarization fraction model components that are independent of the 353 GHz observations. We conclude that the observed TB correlation is likely the result of large-scale Galactic dust polarization properties.

The Origin of Parity Violation in Polarized Dust Emission and Implications for Cosmic Birefringence

“…These measurements are independent of the Planck polarization angle calibration. The K-band data probe polarized synchrotron emission while the starlight is largely polarized by the same dust grains probed in the far infrared emission; either way, Weiland et al (2020) find evidence for a positive T B correlation, and conclude that measurements of T B > 0 are real, rather than spurious.…”

“…XLIX (2016), derived from pre-launch measurements described in Rosset et al (2010)). Weiland et al (2020) report a significant nonzero T B signal for T 857 B 353 and T 545 B 353 computed with the PR3 data. We confirm that result using the NPIPE Planck maps (Figure 1).…”

“…We confirm that result using the NPIPE Planck maps (Figure 1). Weiland et al (2020) also measure a nonzero T SFD B 353 correlation, where T SFD is a dust intensity map derived from IRAS and COBE data (Schlegel et al 1998), and thus independent of Planck. This constitutes evidence that the nonzero T B is not an artifact of Planck systematics, except for the global polarization angle miscalibration discussed above.…”

“…This constitutes evidence that the nonzero T B is not an artifact of Planck systematics, except for the global polarization angle miscalibration discussed above. Weiland et al (2020) further substitute B 353 for B derived from either Wilkinson Microwave Anisotropy Probe (WMAP) K-band data (Page et al 2007) or a template map described in Page et al (2007) that is derived from optical starlight polarization data (Heiles 2000;Berdyugin et al 2001Berdyugin et al , 2004Berdyugin & Teerikorpi 2002). These measurements are independent of the Planck polarization angle calibration.…”

New physics from the polarised light of the cosmic microwave background

“…Polarised thermal emission of dust grains is the dominant foreground at the Planck HFI frequencies. The Planck collaboration also detected intriguing correlations between the dust intensity and Eand B-mode polarisation, C T E,dust and C T B,dust , respectively 147,148 . This is also confirmed by an independent analysis using the distribution of filaments of neutral hydrogen atoms 149 .…”