Standard Model Prediction for Cosmological 21cm Circular Polarization. (arXiv:2005.10250v1 [astro-ph.CO])

<a href="http://arxiv.org/find/astro-ph/1/au:+Ji_L/0/1/0/all/0/1">Lingyuan Ji</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kamionkowski_M/0/1/0/all/0/1">Marc Kamionkowski</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Inomata_K/0/1/0/all/0/1">Keisuke Inomata</a>

Before cosmic reionization, hydrogen atoms acquire a spin polarization

quadrupole through interaction with the anisotropic 21-cm radiation field. The

interaction of this quadrupole with anisotropies in the cosmic microwave

background (CMB) radiation field gives a net spin orientation to the hydrogen

atoms. The 21-cm radiation emitted by these spin-oriented hydrogen atoms is

circularly polarized. Here, we reformulate succinctly the derivation of the

expression for this circular polarization in terms of Cartesian (rather than

spherical) tensors. We then compute the angular power spectrum of the observed

Stokes-$V$ parameter in the standard $Lambda$CDM cosmological model and show

how it depends on redshift, or equivalently, the observed frequency.

Before cosmic reionization, hydrogen atoms acquire a spin polarization

quadrupole through interaction with the anisotropic 21-cm radiation field. The

interaction of this quadrupole with anisotropies in the cosmic microwave

background (CMB) radiation field gives a net spin orientation to the hydrogen

atoms. The 21-cm radiation emitted by these spin-oriented hydrogen atoms is

circularly polarized. Here, we reformulate succinctly the derivation of the

expression for this circular polarization in terms of Cartesian (rather than

spherical) tensors. We then compute the angular power spectrum of the observed

Stokes-$V$ parameter in the standard $Lambda$CDM cosmological model and show

how it depends on redshift, or equivalently, the observed frequency.

http://arxiv.org/icons/sfx.gif