New Probe of Cosmic Birefringence Using Galaxy Polarization and Shapes

Area of Science:

• Cosmology and astrophysics
• Particle physics
• Statistical methods

Background:

• Cosmic birefringence is a phenomenon that can indicate parity violation in the universe.
• Axions are hypothetical particles that could explain dark matter and influence cosmic birefringence.
• Measuring cosmic birefringence is crucial for understanding fundamental physics and the early universe.

Purpose of the Study:

• To propose a novel statistical method for measuring cosmic birefringence.
• To demonstrate the method's capability in probing parity violation caused by axions.
• To compare the method's potential with existing experimental sensitivities.

Main Methods:

• Utilizing an empirical correlation between integrated radio polarization direction and apparent shape of spiral galaxies.
• Devising an unbiased minimum-variance estimator for the rotation angle.
• Leveraging large galaxy samples from upcoming Square Kilometre Array (SKA) continuum surveys and optical shape catalogs.

Main Results:

• The proposed method can achieve an uncertainty of 5°-15° per galaxy.
• Future SKA surveys combined with optical data promise a rotation angle noise power spectrum comparable to or better than the Cosmic Microwave Background Stage-IV (CMB-S4) experiment.
• The method offers a complementary approach with different systematic uncertainties compared to CMB-S4.

Conclusions:

• The novel statistical method provides a powerful new way to measure cosmic birefringence.
• This technique offers a promising avenue for detecting parity violation and constraining axion properties.
• Large-scale galaxy surveys will enable precision measurements of cosmic birefringence, advancing our understanding of fundamental physics.