Frequency-Dependent Constraints on Cosmic Birefringence from the LFI and HFI Planck Data Release 4

J. R. Eskilt

doi:10.1051/0004-6361/202243269

paper

Frequency-Dependent Constraints on Cosmic Birefringence from the LFI and HFI Planck Data Release 4

arXiv:2201.13347 · doi:10.1051/0004-6361/202243269

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, $β_{ν} = β$ , 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 $n$ , $β_{ν} \propto ν^{n}$ . In this work, we first sample $β_{ν}$ individually for each polarized HFI frequency band in addition to the 70 GHz channel from the LFI. We also constrain a power-law formula for the birefringence angle, $β_{ν} = β_{0} (ν / ν_{0})^{n}$ , with $ν_{0} = 150$ GHz. For a nearly full-sky measurement, $f_{sky} = 0.93$ , we find $β_{0} = 0.2 6^{\circ} \pm 0.1 1^{\circ}$ $(68% C.L.)$ and $n = - 0.4 5_{- 0.82}^{+ 0.61}$ when we ignore the intrinsic $E B$ correlations of the polarized foreground emission, and $β_{0} = 0.3 3^{\circ} \pm 0.1 2^{\circ}$ and $n = - 0.3 7_{- 0.64}^{+ 0.49}$ when we use a filamentary dust model for the foreground $E B$ . Next, we use all the polarized Planck maps, including the 30 and 44 GHz frequency bands. These bands have a negligible foreground contribution from polarized dust emission. We, therefore, treat them separately. Without any modeling of the intrinsic $E B$ of the foreground, we generally find that the inclusion of the 30 and 44 GHz frequency bands raises the measured values of $β_{ν}$ and tightens $n$ . At nearly full-sky, we measure $β_{0} = 0.2 9_{\circ - 0.1 1^{\circ}}^{\circ+ 0.1 0^{\circ}}$ and $n = - 0.3 5_{- 0.47}^{+ 0.48}$ . Assuming no frequency dependence, we measure $β = 0.3 3^{\circ} \pm 0.1 0^{\circ}$ . If our measurements have effectively mitigated the $E B$ of the foreground, our constraints are consistent with a mostly frequency-independent signal of cosmic birefringence.

11 pages, 9 figures, 3 tables. (v2) References added. Accepted for publication in Astronomy & Astrophysics

Frequency-Dependent Constraints on Cosmic Birefringence from the LFI and HFI Planck Data Release 4

Abstract

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