The polarization of the 21-cm radiation from the epoch of reionization arises
from Thomson scattering of 21-cm photons from free electrons and provides
information that complements that from the intensity fluctuation. Previous work
showed that a direct detection of this signal will be difficult, and hinted
that the signal might be enhanced via correlation with other tracers. Here, we
discuss the cross-correlation between the cosmic microwave background (CMB)
polarization and the 21-cm polarization. We treat reionization using an
analytical model with parameters calibrated by semi-numerical simulations. We
then derive the cross-correlation angular power spectrum using the
total-angular-momentum formalism. We also provide a noise analysis to test
against two closely related, but subtly different, null hypotheses. First, we
assume no reionization as a null hypothesis, and determine how well this null
hypothesis could be ruled out by an observed 21cm-CMB polarization correlation.
Second, we determine how well the null hypothesis of no 21-cm polarization can
be ruled out by seeking the cross-correlation, assuming reionization is
established from the CMB. We find that the first question could be answered by
a synergy of ambitious next-generation 21-cm and CMB missions, whereas the
second question will still remain out of reach.
Description
Cross-correlation of the Polarizations of the 21-cm and Cosmic Microwave Backgrounds
%0 Generic
%1 ji2021crosscorrelation
%A Ji, Lingyuan
%A Hotinli, Selim C.
%A Kamionkowski, Marc
%D 2021
%K tifr
%T Cross-correlation of the Polarizations of the 21-cm and Cosmic Microwave
Backgrounds
%U http://arxiv.org/abs/2110.01619
%X The polarization of the 21-cm radiation from the epoch of reionization arises
from Thomson scattering of 21-cm photons from free electrons and provides
information that complements that from the intensity fluctuation. Previous work
showed that a direct detection of this signal will be difficult, and hinted
that the signal might be enhanced via correlation with other tracers. Here, we
discuss the cross-correlation between the cosmic microwave background (CMB)
polarization and the 21-cm polarization. We treat reionization using an
analytical model with parameters calibrated by semi-numerical simulations. We
then derive the cross-correlation angular power spectrum using the
total-angular-momentum formalism. We also provide a noise analysis to test
against two closely related, but subtly different, null hypotheses. First, we
assume no reionization as a null hypothesis, and determine how well this null
hypothesis could be ruled out by an observed 21cm-CMB polarization correlation.
Second, we determine how well the null hypothesis of no 21-cm polarization can
be ruled out by seeking the cross-correlation, assuming reionization is
established from the CMB. We find that the first question could be answered by
a synergy of ambitious next-generation 21-cm and CMB missions, whereas the
second question will still remain out of reach.
@misc{ji2021crosscorrelation,
abstract = {The polarization of the 21-cm radiation from the epoch of reionization arises
from Thomson scattering of 21-cm photons from free electrons and provides
information that complements that from the intensity fluctuation. Previous work
showed that a direct detection of this signal will be difficult, and hinted
that the signal might be enhanced via correlation with other tracers. Here, we
discuss the cross-correlation between the cosmic microwave background (CMB)
polarization and the 21-cm polarization. We treat reionization using an
analytical model with parameters calibrated by semi-numerical simulations. We
then derive the cross-correlation angular power spectrum using the
total-angular-momentum formalism. We also provide a noise analysis to test
against two closely related, but subtly different, null hypotheses. First, we
assume no reionization as a null hypothesis, and determine how well this null
hypothesis could be ruled out by an observed 21cm-CMB polarization correlation.
Second, we determine how well the null hypothesis of no 21-cm polarization can
be ruled out by seeking the cross-correlation, assuming reionization is
established from the CMB. We find that the first question could be answered by
a synergy of ambitious next-generation 21-cm and CMB missions, whereas the
second question will still remain out of reach.},
added-at = {2021-10-06T06:34:08.000+0200},
author = {Ji, Lingyuan and Hotinli, Selim C. and Kamionkowski, Marc},
biburl = {https://www.bibsonomy.org/bibtex/2acad09c0a12314e5e9bded3b4fc3feee/citekhatri},
description = {Cross-correlation of the Polarizations of the 21-cm and Cosmic Microwave Backgrounds},
interhash = {d13cdeed82812b8b325dfaa4f9bd5c1c},
intrahash = {acad09c0a12314e5e9bded3b4fc3feee},
keywords = {tifr},
note = {cite arxiv:2110.01619Comment: 9 pages, 3 figures},
timestamp = {2021-10-06T06:34:08.000+0200},
title = {Cross-correlation of the Polarizations of the 21-cm and Cosmic Microwave
Backgrounds},
url = {http://arxiv.org/abs/2110.01619},
year = 2021
}