Intensity Mapping (IM) studies the formation and evolution of galaxies by statistically analyzing the collective emission at a given frequency contributed by all the radiation sources over large areas of the sky. The current theoretical framework and experiments have taken into account the overall amplitude of the signal, i.e., the total intensity, but I will present here the additional physical information on the sources and their surroundings that can be obtained by measuring the polarized components of the hydrogen Lyman-alpha (Lya) emission line. Lya polarization arises from the scattering of Lya photons off atomic hydrogen in the halo of star-forming galaxies, and because the polarization fraction increases with projected impact parameter, the power spectra of this quantity presents a sharp peak that signals the average extent of the scattering medium at a given redshift. Furthermore, the Lya polarization pattern can be decomposed into the E and B mode formalism used in cosmology, which in turn gives information about the anisotropy of the radiation field and the distribution of gas in the halos. I will discuss how these and other relevant physical parameters can be extracted from polarization but not from total intensity alone, and will present observational estimates that suggest that the signal is close to reach of current and near-future experiments and technology. Overall, the inclusion of polarization in Lya IM experiments boosts the amount of physical information retrieveable from the observations.

(based on https://ui.adsabs.harvard.edu/abs/2020PhRvD.101h3032M/abstract)

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