1. CMB Polarization from Patchy Reionization Gil Holder

3. Outline Patchy reionization CMB polarization Correlation with redshifted 21cm radiation Remote quadrupole measurements & Hubble volume 3D reconstruction

4. Patchy Reionization First stars ``blow bubbles’’ in cosmic web Strongly inhomogeneous Bubbles growing, becoming more numerous, range in bubble sizes… Furlanetto et al

5. CMB Polarization quadrupole anisotropy + Thomson scattering =polarization

6. Polarization from Patchy Reionization Very small scales Very small signal Dore et al

7. CMB Pol. & Patchy Reionization Unlikely to be a problem for inflation B modes Mainly confined to single Stokes component Dore et al

8. Thomson optical depth/21cm anti-correlation Holder, Iliev & Mellema Mass density Thomson optical depth 21 cm emission (slice dz~1; 100 Mpc on a side)

9. Some equations… 21 cm fluctuations Optical depth Optical depth fluctuations 21 cm - (optical depth) anti-correlation

10. Thomson optical depth/21cm anti-correlation Holder, Iliev & Mellema Early times: blowing bubbles (ionize and awe) Late times: last throes of neutral overdense regions

11. The benefits of alien collaborators at z~10 Surface of last scattering at z=10 has little overlap with ours More than 1/2 of signal from “dark ages” Good enough data over large patch of sky allows reconstruction of “initial conditions” for most of Hubble volume Needs polarized 0.1 uK on arcminute scales and mK redshifted 21 cm

12. Comparison with Galaxy Clusters Z~9 : mean density x1000, comoving 10 Mpc=1 Mpc At z=0, this is a galaxy cluster! Remote quadrupoles with galaxy clusters suggested by Kamionkowski & Loeb –Z=10 has less overlap with z=0 CMB –Optical depth from 21cm instead of ??? –No galaxy cluster in the field (radio halos, AGN, CMB lensing) SZ Image by Laurie Shaw

13. How hard is this? Need 100 nK in CMB polarization on arcminutes scales (basically 100 times the collecting area of APEX) Need few mK at wavelengths of few m (likely needs SKA) Radio point sources will be particularly nasty Big bubbles around largest sources could have 10x larger signal and detectable with current technology

14. Summary Fine-scale polarization measurements allow new cosmological insights Redshifted 21cm emission well anti- correlated with CMB polarization Cross-comparison allows measurement of quadrupoles at z~10 (but signals are small) –21cm gives you optical depth –CMB polarization=optical depth * quadrupole –mK radio signal and 100 nK CMB pol on 1’ scales