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CMB Polarization from Patchy Reionization

CMB Polarization from Patchy Reionization. Gil Holder. Outline. Patchy reionization CMB polarization Correlation with redshifted 21cm radiation Remote quadrupole measurements & Hubble volume 3D reconstruction. Patchy Reionization. First stars ``blow bubbles’’ in cosmic web

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CMB Polarization from Patchy Reionization

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  1. CMB Polarization from Patchy Reionization Gil Holder

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

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

  4. CMB Polarization quadrupoleanisotropy + Thomson scattering =polarization

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

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

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

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

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

  10. 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

  11. 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

  12. 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

  13. 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

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