On the influence of resonant scattering on cosmic microwave background polarization anisotropies |
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| Authors: | C Hernández-Monteagudo J A Rubiño-Martín R A Sunyaev |
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| Institution: | Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, 19104-6393 Philadelphia, USA;Instituto de Astrofísica de Canarias, C/Vía Láctea, s/n, 38200, La Laguna, Tenerife, Spain;Max Planck Institut für Astrophysik (MPA), Karl-Schwarzschild Str. 1, D-85740, Garching bei München, Germany;Space Research Institute (IKI), Profsoyuznaya 84/32, Moscow 117810, Russia |
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| Abstract: | We implement the theory of resonant scattering in the context of cosmic microwave background (CMB) polarization anisotropies. We compute the changes in the E-mode polarization (EE) and temperature E-mode (TE) CMB power spectra introduced by the scattering on a resonant transition with a given optical depth τX and polarization coefficient E 1. The latter parameter, accounting for how anisotropic the scattering is, depends on the exchange of angular momentum in the transition, enabling observational discrimination between different resonances. We use this formalism in two different scenarios: cosmological recombination and cosmological re-ionization. In the context of cosmological recombination, we compute predictions in frequency and multipole space for the change in the TE and EE power spectra introduced by scattering on the Hα and Pα lines of hydrogen. This constitutes a fundamental test of the standard model of recombination, and the sensitivity it requires is comparable to that needed in measuring the primordial CMB B-mode polarization component. In the context of re-ionization, we study the scattering off metals and ions produced by the first stars, and find that polarization anisotropies, apart from providing a consistency test for intensity measurements, give some insight on how re-ionization evolved. Since polarization anisotropies have memory of how anisotropic the line scattering is, they should be able to discern the O i 63.2-μm transition from other possible transitions associated to O iii , N ii , N iii , etc. The amplitude of these signals are, however, between 10 and 100 times below the (already challenging) level of CMB B-mode polarization anisotropies. |
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| Keywords: | intergalactic medium cosmic microwave background cosmology: theory |
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