%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 }