Frequency-dependent constraints on cosmic birefringence from the LFI and HFI Planck Data Release 4

Abstract

We present new constraints on the frequency dependence of the cosmic birefringence angle from the Planck Data Release 4 polarization maps. An axion field coupled to electromagnetism predicts a nearly frequency-independent birefringence angle, βν = β, while Faraday rotation from local magnetic fields and Lorentz violating theories predict a cosmic birefringence angle that is proportional to the frequency, ν, to the power of some integer n, βν ∝ νn. In this work, we first sampled βν individually for each polarized HFI frequency band in addition to the 70 GHz channel from the LFI. We also constrained a power law formula for the birefringence angle, βν = β0(ν/ν0)n, with ν0 = 150 GHz. For a nearly full-sky measurement, fsky = 0.93, we find β0 = 0.26° ±0.11° (68% C.L.) and n = −0.45−0.82+0.61 when we ignore the intrinsic EB correlations of the polarized foreground emission, and β0 = 0.33° ±0.12° and n = −0.37−0.64+0.49 when we use a filamentary dust model for the foreground EB. Next, we used all the polarized Planck maps, including the 30 and 44 GHz frequency bands. These bands have a negligible foreground contribution from polarized dust emission and we thus treated them separately. Without any modeling of the intrinsic EB of the foreground, we generally find that the inclusion of the 30 and 44 GHz frequency bands raises the measured values of βν and tightens n. At nearly full-sky, we measure β0 = 0.29°−0.11°+0.10° and n = −0.35−0.47+0.48. Assuming no frequency dependence, we measure β = 0.33° ±0.10°. If our measurements have effectively mitigated the EB of the foreground, our constraints are consistent with a mostly frequency-independent signal of cosmic birefringence.

Improved constraints on cosmic birefringence from the WMAP and Planck cosmic microwave background polarization data

“…The low frequency instrument (LFI [36]) maps of the Planck PR4 were included in the analysis of Ref. [37], which found β ¼ 0.33°AE 0.10°. The statistical significance exceeds 3σ.…”

“…Reference [37] also measured the frequency dependence of the signal by fitting a power-law model, βðνÞ ∝ ν n , finding n ¼ −0.35 þ0. 48 −0.47 .…”

“…These authors [33,35,37] initially ignored C EB;fg l in the analysis. As the foreground is dominated by polarized thermal dust emission at the HFI frequencies [38], they noted that the positive dust TB and TE correlations found from Planck [38] would suggest C EB;fg l ≃ C EB;dust l > 0, which would make the measured value of β a lower bound.…”

Isotropic cosmic birefringence from early dark energy

“…For comparison, the black line represents C EE l multiplied by a constant. We find that C EB l has a wide variety of shapes, which are different from C EE l commonly assumed in the data analysis [15][16][17][18]. One can understand the shape of C EB…”

“…Cosmic birefringence is a rotation of the plane of linear polarization of photons [11][12][13], which induces the cross-correlation between parity-even E and parity-odd B modes in the CMB polarization field [14]. A tantalizing hint of cosmic birefringence has been found by the recent analyses of the WMAP and Planck data [15][16][17][18]. The reported signal is isotropic and consistent with a rotation angle of β = 0.342 • +0.094 • −0.091 • (68% C.L.…”