Joint Astrophysics Colloquium

Special Astrophysics Seminar

Gravitational Faraday rotation of the CMB by the large-scale structure

Björn Malte Schaefer

Institute for Cosmology and Gravitation
University of Portsmouth

I consider the effect of gravitomagnetic fields induced by rotating haloes in the large-scale structure on the polarisation of the cosmic microwave background, which manifests itself in coupling polarisation modes on different angular scales and in converting gradient to vorticity modes. In my model, the large-scale structure is assumed to be composed of haloes which acquire their angular momentum by tidal torquing with the important consequence of angular momentum coupling. The large-scale structure, the inertia of protogalactic objects and the tidal torques acting on them is modeled based on a joint Gaussian random process restricted to peaks in the density field. Working in the linear regime of structure formation and describing the tidal shearing in the Zel'dovich approximation, the angular power spectrum of the Faraday rotation angle and consequently the corrections to the angular power spectra of the CMB polarisation modes can be derived.